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SOIL AND LAND�§URVEY OF PAR�_QE_1HE DAWSON VALLEI� ,9UEENSLAND.
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c 0 N T E N T s. ----------Summary
Locali ty Plan
In t roduct ion • • t/,'
Clima t e of' the R egion
Physiography and Geology ..
1. Phy s iography . . .
2. Geology . . .
Vege tat ion of the Region
Cla s s ification and Descript ion of'
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the Soils . . .
1. Mapping Techn' i que and Class ificat ion
2. Descript ion of' the Soils . . . • • •
Soils in Relation t o . I rr igated Crops and Pas tures
1. A s s e s sment of Irrigation Po ten tial of Soils
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21 Classification of the So ils as to �ui tab 111 ty for Irr igation Developme nt • • • I I I 0 I I
C onclusions and Recommenda t ion s . . .
Acknow ledgmen t s . . . . . . . . . . . . . . . .
1. SGil A s s oc iat ion Map p Dawson Valley Regionp Queens l and.
2. Map showing Lan d U s e Groups for Irrigation Deve lopmentg D awson Val ley Regionp Queensland.
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An area of 760 square miles in the Dawson River Valleyg Queenslandg has been investigated in a reconnaissance survey to determine the irrigation potential of the various soils. This regiong lying adjacent to the.river between Baralaba and Theodore has a sub-tropical climate with an average annual rainfall of 28 inchesg 70 per cent. of which falls during the summer months of October to March1 inclusive. At present considerable areas are subject to flooding.
The climate1 physiography� geology and vegetation of the region are briefly discussed and the soils have been mapped into 18 associations which are largely defined at the great soil group level. The most important soils from the viewpoint of irrigation potential are alluvial types developed on the river floodplain but a considerable area of solodized-solonetz soils occur on Elightly higher land bordering the floodplain, It is thou�ht that this group of soils can also be suitably utilised under irrigation. Other soils occurring in large areas include
• dark grey and brown self-mulc)1ing calcareous clays that are · . developed on an undulating landscape underlain by Permian sedi
mentary rocks. At present mdny of these soils are utilised for dry land agriculture. Finally9 the most extensive group of soils in the region consist of grey and browh clays that possess a very strongly developed gilgai microrelief. It is considered that these soils are entirely unsuited for present irrigation development.
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Provided that the flood hazard can be overcome it is estimated that a gross area of some 1509000 acres of land can be readily utilised under irrigation. At least half of this area should be suitable for a wide range of crops and pastures. Previous irrigation experience. is available for some soils but on certain others trials would be desirable to determine their best means of utilisation • .
Scale: I lnch�30 Miles Loca1itJr pla-n showing sur>veyed area.,
Dawson V:alley, Queensla.nd
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§OIL AND LAND USE SURVEY OF PART OF THE DAWSON VALLEY�UEENSLAND •
.Q.y R. ·F. Isbell.
I. INTRODUCTION •
A reconnaissance soil and land use survey has been made or ·an area or 760 square miles in the lower Dawson Valley with a view to evaluating the irrigation potential or the various soils. The survey has been concerned with a strip of land adjacent to the Dawson River extending upstream from Baralaba to the mouth of Orange Creek - some 25 miles above Theodore. This embraces a straight-line distance of about 80 miles with the greater portion of the area situated on the right banlc of the river. Below ·Moura the proposed irrigation area extends up to 1 2 or 13 miles away from the river but upstream from this area it narrows considerably 1 only averaging 3 to 4 miles or le·ss from the river. The area si tuate.¢1 on the left bank normally does not exceed 3 miles in width and is freQuently much less.
The soils of certain parts of this area have previously been surveyed in some detail although the results were not published. In particulary the soils of the Thr:·odore Il'rigation Area ( 3 1 5 00 acres) and the Moura Irrigation Area ( 2�300 acres) were examined and mapped ·
by G. ·D. Hubble of .the C.S.I.R.O. Division of Soils as part of a war-· time need to expand cotton production while officers of the Department
.of Agriculture and Stock later examined the soils of small areas to the north of the Moura Irrigation Area and in the vicinity of Wandoa Station. P. J. Skerman9 form�rly of the Bureau9 also made a b�ief ' reconnaissance report on certain soils in'the Baralaba-Harcourt region. In this present report certain relevunt information has been included from these earlier surveys.
The proposed irrigation area is served by a railway which connects Baralaba9 Moura and Theodore.9 the former town being 91 miles by rail from the coast at Rockhampton9 and the latter 148 miles. The right banlc area is reasonably well supplied with roads but all are unsealed and many unformed. Traffic disabilities - both road and rail - are common during the wet season months due to flooding from the river and local streams. The chief towns in the region are Theodore (population 595 -.figures are those of the June 1954 census) and Baralaba ( 433 ) . ·
At presen'b9 apart from the small irrigation settlements at Theodore and Moura9 the greater part of the area is devoted to grazing9 mainly beef cattle9 but with some dairying9 particularly around Baralaba • • Dry land agricultural activities have extended in recent years, with wheat and grain sorghum being increasingly cultivated in certain areas not subject.to flooding. Cotton is also grown9 but the yearly acreages which are planted fluctuate somewhat.
Survey Procedure:
A period of some 9 weelcs was spent in the field examining representative soil profiles and plotting soil unit boundaries on aerial photographs9 of which a full cover at a scale of approximately 1 inch = 30 chains was available for use in the field. The aerial photograph interpretation was· supported by as many ground traverses as was �ossible. All available roads were traversed as well as those areas about which there was some doubt as to the nature of the soil. After the soil unit boundaries had been delineated on the aerial photographs1 they were transferred to the base maps of the Queensland Lands Department 2 Mile Serie • In most cases representative profiles were sampled and analysed for each soil group
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delineated. Two maps are presented, one showing the actual distribution of ·the soils, and the other showing the various soils combined into land use groups.
II. CLIMATE OF THE REGION.
The climate of the region may be broadly described as sub-tropical1 with long hot sumners duril� which the greater part of the rainfall occurs, and short mild winters which are normally dry •
. The region lies within the 25-30 inch rainfall isohyets summer maximum temperatures are high? frequently exceeding lOOoF. During the winter months of June, July and August9 frosts are common and may be fairly severe.
1 . Rainfall Data.
Average monthly and annual rainfall figures for available stations ( Banana is situated ju&t to the east of the surveyed area ) are set out in Table lp while Table 2 shows the seasonal dist�ibution of rainfall. Figures for Biloela are included for comparison.
�ab1�--.l.:. Mogth1x_Q1stribution of Rainfall (inches)�
Station Jan. ;Eeb. Mar. Apr!.. Ma;y Jun. Juh Aug!.. Sep!.. Oct. Nov!.. Dec. Year.
From Table 1 it will be seen that January and February are ·normally the wettest months when monsoonal, or occasionally cyclonic., .influences produce rain groups extending over a period of days. Pre-January rains are usually the result of thunderstorms which may produce local heavy falls. The mean intensity of precipitation is fairly high ( 0. 5 inches per ·wet day for Banana ) ; this is largely a consequence of the heavy storm rains. As shown in Tab.le 2 1 70 per cent. of the rainfall occurs during the summer months, the winter rainfall is unreliable, with August and September being the d riest months of the year •
2 . Temperatur�_gnd HU@1di1;y_�g1a.
The nearest hlimatological station is at Biloela9 which is approximately 30 miles to the east of the surveyed.region. For
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Theodore temperature datn are only available for a period of five years and the records are incomplete. However, a comparison of these fig-
. ures shows that there is probably little significant difference between the temperature regime of Biloelu and Theodore, so that the following tables ehow1ng ta�pOrAtu�s aatQ fo� S1lDelQ mQ¥ b@ PeBDPdad as also being fairly typical for Theodore: -
:J:able __ .l:_ Mean Monthly Maximum anQ. Mini!}llim_S£!:een_:£§.!!:!12§..tQ1l!!:�.C..::tl
gnd_B§.1Q11Y£_Bum1di1K-I��f2£�11£ela�
Maximum
Minimum
Relative Humidit;y ( 9 a.m. )
92.5 89.4 87.9 83.1 77.5 71.2 70.9 75.4
67.5 66.3.62.6 54.3 48.3 43.4 39.8 40.6
80.7 85.6 89.4 91.4
46.4 54.7 60.8 64.6 ...
66 69 69 69 72 77 73 68 61 59 60 61
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Number of Years Record: 30-year period to 1955.
During the hot summer months of Decef)lber, January and February 1 maximum temperatures in excess of 100 F. al'e common and successive occurrences give rise to heat wave conditions which may adversely o.ffect such crops as cotton and grain sorghum. In TabJ.e 4 heat wave .data for Biloela is set out, showing the distribution over ', the period 1926-1950 (Data from Skerman 1953+).
ti§.Q1_Way£_:QQ!Q.t._!21loela�
December
2 consecutive days with maximum tenperature 100°F. or higher .
3 do. do.
5 do. do.
7 do. do.
2 consecutive days with maximum temperature l05°F. or higher
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Although data arc not available for Theodore 9 l'L·csts are quite common dur·ing th::; winter months� and it is likely that the frost data for Biloela will give a good indication of the general occurrence. in the region surveyed, Data from Foley (l945)X· are presented for Bi·loela in Tables 5 and 6 and show the occurrence of. first and last frosts, average frost free period and frost frequency. A scroon
+ Skerman, P.J. (1953) - "Some Agricultural features of the Central Highlands Region of Q'ld.''· Q' ld. Agric. Jour. , LXA'VI, Pts. 3, L�.
x. Foley 9 J. C. ( 1945) - "I•\:Post in the Australian Region"• Commonw. Met. Bur. Aust. Bull. No. 32.
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temperature of 33°F. -36°F. i s cons idered to repres ent a light fro st and 32°F. or under a severe fro s t . Data are based on t he ten-ye ar period 1930-1939.
THble '). O c���_Qf_Fi£�!_ang_�as t Er��ts_gnd_1y�ra�_Eros t
Pr�LPeriQ.Q_fQL!2ilo�la. Fir s t and Las t Fro s t s - Head ings.
1 . Average date of fi rs t/last occurrence ( ten-year period 1930-39) .
2 . Mean deviation from average date ( days ) .
3. First/las t recorded date of oc currence ( ten-year period 1930-39) .
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Average fro s t free �eriod ( 36°F. )
252 days. May 23 �pl 22 Jun 2��Ma;-;:; ::; 2� F4- Oc� 5 ;ep -;:;-r�;;;-;-5
Ave rage numb er0of days per month of minimum sc reen temperature of 32 F. or under ( Based on period 1930-39) .
Ave rage No . of days. 0 . 6 4.6
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5 . 7 0. 6 0. 1 18 . 4
Reliable evapo ration figures are not available for Theodore · but it is likely. that conditions would be similar to those obtaining
at Biloela where the me an annual evaporation i s 75 inche s • .
The s omewhat meandrine cours e of the . Daw s on River has bui l t u p a n irregular floodplain w i th some a s soci a ted minol' levee-type depo s i t s . This floodplain vari e s cons iderably in width , the larger
· areas u sually b eing found on t he right b ank side of the r iver. In the Moura-Harcourt sect ion where the floodplain has i t s gre atest development it may range from 5 t o 6 mi les in width. There i s no rmally a general fall o f from 4 to 6 f e e t from t h e river baruc t o the lower lying level area s a t the s id e s of the valley. The flood plain has also b een partly built up by tribu ta�ie s which enter from the s id e s of the valley, more particularly f rom the r ight bailie s ide • .
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A notable f0ature of the floodplain is the frequent occurrence of old drainage l ines� swamps and billabongs 9 s ome at J.east of ·
w�ich probably mark former courses of the river. These drainage l1ne s are mo stly non-functional except at very high river levels� but some9 such as west of Baralaba9 ar•e true an(Lbranches which do not stop flowing until the river has subsided to l'elatively low levels . 'l'he fairly widespread occurrence of these drainage lines9 together with the general fall away from the r iver ban1c� often results in flooding b eing most accentuated at some distance from the river rather than in its·immediate vicinity. This away from the river flooding may be further increased by tributaries enter ing from the valley s ide s .
Although the river. itself cannot b e classed a s a permanent stream, it flows throughout the year in all but extremely dry period s. The stream bed cons i s ts usually of a chain of elongated waterholes separated by shallow stretches . The se may contain rocky bars but are more often merely s ilty� s andy or gravelly depo sits containing more than one channel. In the region concerned the general fall of the river i s. some 2 to 3 feet per mile.
The s ide s of the •valley in most areas r i se gently.from the floodplain but sometimes this occurs in the form of two terrace-ljJcc steps. The lower terrace , where present� is frequently not w ell defined and may be' only some 10 feet above the floodplain level. However� from thi s terrace there is.normally a fairly marked r i se to the higher, maturely d i s s ected areas of Cainozoic or Palaeozoic
·sediments, such a ris e giv ing slopes of up to 6 per cent. or occas ionally greater. This relatively sudden descent from the valley s ides to the floo r, with sub s e quent s light change in tributary stream gradient, has p�obably b een re sponsible for the fact that some tributaries on reaching the valley floor d o not pursue a d irect course to the r iver but tend to run parallel to it for a s hort distance before jo ining the main stream. The slight fall away from the actual l'iver banks i s doubtles s also a contributory factor .
North from Kianga, the higher land bordering the floodplaj.� commonly cons ists of a maturely d i s s ected, s crub covered landscape which has b een derived from deeply weathe red Cainozoic sediments. Except near the dis sected margins slopes are usually gentle with s ome relatively small flat areas. To the south of Kianga the higher land i s d eve loped on more re s i stant les s deeply weathe red Permian sediments and in thi s area slopes are normally greater and there are occurrences of bare rock outcrops as well as relatively more strongly d i s s ected areas . The more res istant Upper Bowen s andstones extendir� north and south of Kaloola Siding have resulted in the relatively elevated Malakoff Range.
There are throughout the region numerous and often extensive flat forested areas that have a strongly developed gilgai microrelief. These areas are almo st invariably topographically lower than the undulating Cainozoic o r Permian landscape and a characteristic feature is their often pronounced lack of surface drainage. In mo st cases rainfall run-off merely collects in the often deep depre s s ions and does not find its way to a recogni sed drainage l ine.
The Dawson Ri�er in the region surveyed flow s approximately parallel to the north-north-we sterly trend of the e astern margin of the Bowen synclinal bas in. However, not ever�vhere are Permian s equences exposed, in many instance s they are covered by later Tertiary and Quaternary deposits, e specially by the Recent alluvi al floodplain depo s its of the river . Vi rtually the only rock outcrops in the region ( with the notable exception of Mt. Ramsay) are tho s e of .the Permian formations, the Cainozo ic sed iments normally are deeply weathered o r altered by lateritic influence s . Brief account s of the geology of the region have been e arlier published by Reid (1945 )+,
+Reid, J. H�l945)--'' Th;-D;;;;;-Ri;;;-�;;;�-Q1ld�-G�vt�-Min�
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XLVI,296. ''Baralaba Coalfield". Q'ld. Govt. Min. J.,XLVI,;>5Lt.,;
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(a ) Th�__!:erm_;hgg_§�.9.l!Q�:
Although the Lower Bowen Vo lcanics are the oldest rocks present in the surveyed area they are only to be found in two very small localities on Oxtrack and Delusion Creelcs at the eastern margin of the r egion. The fos siliferous marine Middle Bowen Series has a slightly more widespread distr ibution; to the s outh of Theodore the westerly dipping sediments - l imestonES at the base, s iltstones , mudstones and calcareous felspathic s andstones , have a probable thicknes s of some 5, 600 ft. (Unpubl ished information supplied by Australian .O i l Exploration Ltd. geologists ) . In thi s area the Daws on River approximately follows the boundary between the Middle and Upper Bowen Series. �urther north to the east and s outh-east of Baralaba the Marine Series is aga in exposed but here the sediments are highly folded and their thicknes s has not been establi shed. In thi s area they extend east and south-eastwards from Kalewa S iding.
South from Theodore the overlying conformab le Upper Bowen Series (non marine) mainly outcrops on the left bailie of the r iver and its thicknes s has been estimated'at 13, 000 ft. by oil company geologists . In this region the sediments cons ist of greenish to grey siltstones and tuffaceous s ediments at the base, followed by cong lo• meratic and felspathic sandstones with a very thick upper member consi sting of the typical olive green mudstones, s iltstones and sandstones with plant remains. Further north the lower members of the Series outcrop extens ively on the right bank of the r iver in the Kaloola-Nipan area but north f rom here the Series only outcrops sporadically on the eastern margin of the surveyed area. North of Wandoo Station the only outcrops are limited to small areas in the vicinity of Mt. Ramsay, just west of Kalewa, and in the river at Baralaba. At thi s latter locality there i s a much disturbed coal; measure sequence (sandstones, shales and anthracitic coa l ) which i s worked a t the township.
(b ) Qai�;h£_!2QY��Q.Q@�t s :
The prominent peak of Mt. Ramsay i s an alkaline trachyte which intrudes Upper Bowen sediments, but other than it being p ostPermi an there i s no evidence of its age. · In the past (Reid 1945 ) it has been refer:.t.•ed to a s being of Tertiary age.
To the west and south-west of Baralaba there are outcrops of sub-hori zontal Tertiary (? ) mudstones , sandstones and grits which in places have been strongly l ateri ti sed.. It i s likely that these are to be related to the Tertiary Duaringa Formation which has a much wider di stribution to the north and north-west.. Certain more elevated laterite exposures on lJenby Holding further so.uth may b e lateritised Clemati s Sandstone (Trias s ic) rather than altered Tertiary sediments .
Extending south from Baralaba almost continuous ly to Kianea on. the right bailie s ide of the r iver there i s a scrub covered, deeply weathered formation that is probably of l ate Tertiary or early Quaternary age. Outcrops are almost non-exi stent but deep s o i l borings and gravel pit excavations together with an outcrop north of Kianga have revealed that the deep so ils of thi s region have been derived from whitish to pale ·browni sh weakly cemented sandstones and coarse g rits which sometimes have rusty b rown mottled patches. In some areas.such as in the vicinity of Moura� there are depos its of unconsolidated conglomerates in which ''b illy" is common. Billy pebbles have also been found in the more cemented s andstones north of Kianga. These depos its have occas ionally been affected by lateritic influences� g iving deep red s oils with an underlying weakly developed mottled zone. Such i solated occurrences are lar?ely confined to higher portions of the landscape. As Reid (1945) has pointed out, the general uniformity of s o i l s developed from these sediments would suggest a horizontal formation� however9 no evidence of thi ckness i s ava ilable although it i s doubtful if the formation would exceed · 50 feet.
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South of Kianga occurrences are more re stricted 9 be ing·. found only in fai rly close proximity to the river9 particularly in the large bends between Theodore and Nipan9 but there i s a smaller occurrence jus t to the south-east of Theodore. This general as sociation with the river leads to the suggestion that these depo�its may represent old terrace-like coarse levee mate�ials that were deposited -at a time when the river was capable of carrying much more coarse detritus than i t i s to-day. The occurrence of b illy pebbles in the sed iments sugge sts that they are later than the main period of lateritisation which has affected T ertiary sediments in the general area while the fact that they a re sometimes weakly lateritised themselves suggests a furthe r later period of lateri tic action. It might be mentioned als o that e s sentially s imilar depo s its occur ad jacent to the Mackenzie River north of Dingo and in the vicinity of the Isaacs River junction.
Occurring throughout the region but especially north of Moura9 there are flat densely forested areas of clay so ils with a strong gilgai microrelief. It is evident from deep so il borings that these clay sheets have,not ·:b een formed in s itu from underlying Permian sediments which elsewhere fo·rm clay s oils on we a the ring. Quite often these gilgaied clay soil sheets occur in close as sociation with the abovementioned Cainozoic s ediments but almost always at topographically lower levels. Deep so il borings to 17 feet in the s e clays have r evealed that the lower levels are extremely acid and ofter are QUite strongly mottled although the pattern is d ifferent to that in the normal mo t tled zone of a laterite profile. There is really no evidence of the age of these depo s its but it i s thought that t�ey are probably Pleistocene. Po s s ibly they formed contemporaneously with (but more likely later than) 9 the coarser Cainozoic sed iments and represeht fine materials depos ited in �onded surface waters
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similar to present day lalces f!,nd swamps.
Finally9 there are the unconsolidated clays9 s ilts and sands that constitute the Dawson River floodplain. These are likely to be quite deep to judge from lirrli ted bore logs 9 at least 80 feet might be expected in many areas and this could als o indicate the po ssib ility of useful underground water supplie s.
lY�----�Ym��!�T.lQ�_QE_T.HE_gEGJQN. Plant communi ties in the region range :!:'1�om small areas of
almost true gras sland to dens e softwood scrub. As a whole much of the a rea i s heavily timbered with a large part of the non-floodplairt area be ing covered with dense brigalow and other mixed forest types. There i s often a correlation between the vegetation and the nature of the supporting so ils although on most of the clay so ils b rigalow tends to be a ubi quitous species. No attempt has been made to study the vegetation in any detail. In general only natural communi tie s are cons idered9 even though cons iderable areas are now ringbarked or cleared.of timber and sown with Rhode s grass: To facilitate description four broad structural formations of forest9 scrub 9 woodland and parkland (savannah) have b een cons idered.
At leas t 40 per cent. of the surveyed area was originally cove red by forests and9 although extensive areas have b een cleared 9 there still remain cons iderable stands 9 the .chief cornmuni ties b e ing thos e dominated by brigalow (Acacia_har£ophylla) •
( a) Br1galo�-Be1ah_Co���11�es:
_ Brigalow-belah communities are widespread throughout the surveyed area especially away from the r iver floodplain. It i s estimated that, o f the total area surveyed (nearly 500,000 acrei) , communities dominated by brigalow would occupy at least 1709000 acre
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In almost all instances the brigalow (f1_<?acia_hari?£Phylla) is greatly ,· dominant over belah (QQ.§.��£l£Q_;),�J2lS!2.I?hl£i.Q). This is rather in
contrast to many of the bri[�alow-belah areas further south in Queensland. Associated species invariably include blackbutt or Dawson gum (f:g£.Q1.YI?.!:\JJL£Qt:!)Qag§.§l!)..€! ) v wilga (Q,S!,;j.j�£lLE.SU.:Y1.L!:£r.S1.l and sandalwood (]_r��Qphiil !:Qit£liell_H.l� while in some areas yapunyah (Euca;L�us t_hozeti_ana ma;y be common. A low shrub stratum of currant bush �Carissa ovata)� wild holly (tlet�_rode�Qron dive.r�1fQlium) and
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BQ.Qgodia� is co®nonly present. The ground cover in most forests _is sparse� consisting chiefly of the brigalow grasses ;eas.ealidiU!!! �ae.§.J21tosu�_and E�_g£QCile� Bas�ia�tracuspis and the creeping saltbus A tril2.1ex_Q§_mi bacc Q ta.!.
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'.rhe soils of these brigalow-belah communi ties are normally the strongly gilgaied grey and brown clays9 but brigalow (with belah
·absent) may also be the dominant species on the undulating soils of the brown and black earth associations where bauhinia (Bauhinia hookeri) is its normal associate.
A feature of the Dawson Valley region is the predominance of eucalypt species in some of the brigalow communities (Plate 1). In these occurrences the surface sGils are lighter in texture (clay loam or sandy clay loam) and the profiles tend to be solodic or solodized-solonetzlc in 1norphology. Gilgai microre�ief is normally absent. In these mixed forests brigalow is not often the dominant species. Belah� Dawson gum and yapunyah are frequently more prominent while poplar box (!!;ucaly�us_]:2QJ2�lnea) may .also be present. Wilga and sandalwood are common as lower storey associates and bottle tree (Q£Q£QY£hiton_£�12�st_ri_�) and tree pear (Qpuntia S£12�) are often present. 'l'he ground flora may be somewhat denser than in the more typical brigalow communities.
In the immediate vicinity of the Dawson River and its larger tributaries there is normally a fringing forest of v ariable depth. This may consist of merely a narrow fringe of tall trees or a somewhat wider zone where a broad lower river terrace is present. The chief' species are typically coolibah (E. microtheca) and blue gum (E. tereticornis). However� on some stretches of the river there may be-welr-developed stands of the palm bivistona sp. (Plate 3).
2 . Softwood Scrub Communities.
Softwood scrub co1nmunities� although usually fairly small in extent� are rather widely distributed throughout the re�ion. Most often they o c cur on the deeper sandy low humic gley soils \Plate 2) but they are also found in some areas on the lateritic red earths� the sandier surfaced solodized-solonetz soils and some brown clay loams. Th8se scrubs are dense with much undergrowth and tall trees are restr1.8ted to blackbutt� poplar box� yapunyah9 brigalow and belah which� however� only occur sparingl;y. The chief scrub species are bottle tree (���2hK£.hiton_rgQestrie)� red ash (Alphitonia excelsa)� scrub wilga ( Qeijera salicifoliar;-scrub olive (Notolaea microcarpa), myrtle (Ma_2g humilis) g Ca_Q�ll_i§_l?�ntis_!Y],is � ElQCODdend£2�L£\:!S tralie, l<'lil}Q�r..sia_§_:£!_ and occasionally quinine u:�talo�_!,;j.gma_Q_)J£��cens}. A low dense undergrowth is normally present, consisting chiefly of currant bush (Ca£i.§.sa OV£ta)� wild holly (Heterodendron dive_rsifolium) and CrQ_tog_i�sularis. Tree pear (QQgntia §1212.!.) may be common in some scrubs. The ground cover is sparse, consisting mainly of species of ;§;.r£BfOStis and h£1Sti_Q� .
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Plate 1 . Mixed fores t con@unity of brigalow1 Dawson gum, box,yapunyal wilga and sandalwood on s ol?,dized-s olonetz soil near Wonbindi •
Plate 2. Fringing fores t of coolibah with Livistona s p. on flooded land adjacent to the Daws on River near Delu�CreelC junction •
Plate 3. Softwood scrub with bottle tree prominent on sandy low humic gley soils t mile north of Kianga Siding.
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�---�ood1anQ_Q�nun1�ie�
Woodland cowmuni ties are wides pl'ead throughout the region but they show considerable variation in species composition and spatial distribution of the trae species. In general� the river floodplain and the higher undulating areas a re characteris ed. by woodland communities in which there is no prominent shrub s tratum.
(a) §11ve_r-1.£§�L1£Q.nb�rk =-�Q:Qla_r_]Q�Comr.D�n.1�.Y.!. ·A community domina ted by s ilver-leaf ironbarlc (E. melano
Eh1oi�) and poplar box (E�_Eopulgea) is characteris tic of the-medium textured alluvial soils tunit 2) that have a wide dis tribution throug out the river floodplain. It appears that soil texture and d rainage largely determines which of thes e two s pecies as sumes dominance. Silver-leaf ironbark is normally dominant on the more freely drained soils with A horizons of a sandy loam to s andy clay loam texture (Plate 7)P while poplar box dominates the les s freely drained s oils · with· a s urface texture of a loam or clay loam. Ass ociated s pecies are als o largely dependent on s 'oil conditions; on s ome freely draine deeper s andy soils Moreton 'Bay ash (E. tess eDaris )� grey bloodwood · (��-cor.�bos�)P and occas ionally blue gwn (E._tereticornis) and cabba gum tm�-���) may be prominent. In shallow drainage lines or on clay loam s oils which are dominated by poplar box there may be a considerable proportion of s andalwood in the community.
Much of this woodland on the river floodplain has been cleared by ringbarlcing and s ubsequent burning s o that the ground cove is s omewhat variable. However, the chief s pecies are normally black spear (Hetero o bn contortus )p fores t blue (Bothriochloa intermedia), desert blue B. ewartian�pitted blue (�. decipi�) and golden-beard grass Ch�s opogQn falla�, together with species of Chloris2 Aristid_g and §r.agrostis .
A much spars er woodland colTh11Unity dominated by silver-lea! ironbark occurs on the s hallow and often s tony clay s oil.s which are developed on the undulating landscape derived from Permian s edimental rock13. The largest occurrence is in the vicinity of Wanooo Station with sm\:l],ler areas east of Baralaba, s outh of Kaloola and ups tream from Theodo�e where there is only a no��ow floodplain oevelo�ment. The chief as sociated species is s till poplar box but red bloodwood (�_9ichromophloia) may als o be prominent1 less often cabbage gum ( E. papuana). Sandalwood may also be common while on s tony outcrops dead finis h (Albizzia bas altica) is s ometimes characteristic. A dens e ground cover of black-spearp des ert and forest blue gras s es is present.
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(c) Poplar Box=Sand.@:lW.QQ9_Co!!.@�git�:
This community is characteristic of' areas with a s omewhat restricted s urface drainage and the soils are chiefly solodic: or solodized-s olonetz types with clay loam A horizons. Thes e soils frequently tend to be 11spewy11 when wet due to the impeded internal drainage. The only other tree s pecies likely to be found are silve leaf' ironbark and very occasionally coolibah (���1croth�). The ground cover is normally des ert and forest blue gras s es with some Ch12£iS and §ragros ti.§. s pecies.
(d) More _1.QD_Bai }lsh-G£�Y2�_o_qd!"OOd,-:.�l.:':��=1�§f_J.£Q:QQ££!LQQ[!)ill�:Qi ty:
This rather taller woodland cormnunity occurs in fairly we defined areas on rather deep sandy soils with restricted internal drainage (Unit 17 ) . The chief' areas of occurrence are the undulati lands in the vicinity of Moura (Plate 11) and tho high country in th large bends of the Dawson River immediately downstream from Theodore The community is also present on·s ome of' the more freely drained s an
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soils (Uni't 1) that occur in small areas throughout the river floodplain. Blue gum (E._te£����Qrnis) and poplar box are commonly associated tall tree species while a lower storey consisting mainly of quinine (E���1Q§tigma�Qesc�ns) and occasionally red ash (A!Qbl�QQia_��£�1sa} may be prominent in certain areas. The ground cover is dominated by black spear grass and species of Aristida and �!�SEO�tia. --------
g� ___ Pa£tl�D£ Co�un�1���-L§�y�nn�hl·
The term parkland is used to refer to certain formations which may be quite treeless and approach true grasslands but which usually possess scattered trees or clumps of timber. In the region surveyed9 these comnunities are small in extent although they have a fairly wide but irregular distribution.
���!QW-�auhin��=�l��-Q�ss Coir���i1ies:
There exist throughout the region areas of grey and brown clay soils with little or no �irnber cover. True grasslands are small in extent and limited·in,occurrence as normally there are scattered clumps of brigalow and bauhinia (�aub�Di�_QQOk�£1) througbout9 giving a typical parkland formation. In lower lying situations there may be scattered stands of coolibah (E. microtheca). These
· parkland communi ties often r::a ss abruptly into-the -typical brigalow forests (Plate 4 ) . The ground cover is a fairly dense stand of Queensland blue grass (���b�ntb���-§ericeum), forest blu€ (�Q�h£�QQhloH intermedia) , early spring grass fEriochloa�.)9 fani�um_�.9 and less c01mnonly9 desert blue (B. ewartianaL so that this parkland is most valuable for grazing purposes.
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Mention must also be made of the numerous .artificial coimnuni ties that are now present throughout the region as a result of extensive land clearing. 'rhe woodJ.and on the river floodplain has been extensively ringbarked but improved pasture species have not been planted. However9 on much of the cleared softwood scrub and mixed forest areas that have been cleared Rhodes grass has been·exten sively sown so that in many areas the ground cover consists almost entirely of this species. Normally the bottle trees are left standing for shade purposes and as a fodder reserve (Plate 5). Many brigalow-belah forest areas have also been cleared and sown to Rhodes grasi but in some cases a dense brigalow regrowth has occurred and largely nullified the results of the original clearing (Plate 6).
Plate 4, Undulating black earths (Unit 6 ) 5 miles east-south-east of Theodore. The brigalow-bauhinia parkland community often passes abruptly into a brigalow forest.
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Pla te 5. Cleared s oftwood ·S C J:!Ub 3 miles south-s outh-ea s t or Theodore. The bottl� t rees have been left s tanding for shade . and fodder purposes .
Plate 6. Cle&.red brigalow rorest near Mt. Rams ay9 now with a dens e regrowth . Gilgai depress ion in roreground rilled with water.
_;),_. __ Mapping_Techni_g}:!e and_Qla s s i.f_!ca:tk2.D·
In all s oil s urveys the s elect ion of an appropri ate mappi; uni t i s. bas ed on s everal cons iderations . In a reconnai s sance s urve; (s uch as the pres ent one)9 each t axonomi c s oil uni t di s tinguishable on t he ground nat urally cannot be us ed as a single mapping uni t . This is becaus e of limi t a t i ons impos ed by the s cale o f the rinal map and the impracti cabili ty of delineat ing many s uch uni ts with any degree or accuracy. As aerial photographs are extens ively used i n reconnais s ance s oil surveys , a further condit ion i s us ually i mpos ed i n that s oil uni ts recogni s able on the ground mus t als o be i dent ifia on t he aerial photogra phs so that their boundar i es may be plot ted. In effect this us ually means that t he fi nal mapping unit i s a combin tion of perhaps s everal taxonomi c s oil uni t s which 9 however9 normall occur in a definable proport ional pattern and are more or les s regula ly as sociated geographically. This is the concept of the soil a s s oci ation which is almos t universally used in all but detailed s oi mapping.
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An a s so cia tion� then� normally has ma jor and minor cons t i t\. ent soils a s soci ated in some def'inite pattern and quite frequent ly thE minor member of one as sociat ion is the' ma jo r consti tuent of' ano ther. In general� in reconnai s sance surveys i t has been found convenient to select the association member s at the great . s oil g roup level� but where a survey i s carried out primarily to es tablish the land use potential of the soils of a region� s ome modification i s often neces s ary . Thus i t i s often e s s ent ial t o map separately� if pos s ible � two s oils which belong to the s ame great soil group but which may have qui te impol'tant difference s from the viewpo int of utili s ation9 especi ally under irrigated condit ions . Another consideration that may assume importance i s the relat ive areas of the soils in quest ion. If a s o il i s suf'ficiently di s t inct from the aspect · of' both morphology and potent ial utilisation to be cons idered as a pos s ible mapping unit , consideration may well have t o b e given to i t s actual areal � i s tribut ion before a decis ion can be made. On the actual soil map it i s usually good policy t o map individually a s many of the distinctive a s sociations os pos s ible� for even though some of. the se may have an i dentical ut ili sation pot ent ial 9 such so ils can later be readily · combined into land use grou�s . ··
This i s the procedure tha t has' been adopte·d in the present survey. The mapped a ssociations have9 in general , been chos en at . the great soil group level9 but w i th further subdiv� s ion wher·e such a course was both des irable and feas ible. As an instance of this the alluvial so ils have been subdivided into s everal a s sociat ions. To give a clearer picture of the po s s ible utilis at ion of t he so ils a further map has b een prepared showing land use groups which are comb inations of' those soil a s socia tions which are thought to b e very s imilar fr.om the viewpoint of land use under irrigated conditions .
Table 7 show s the rel ationship of t he mapping unit associations and their appropriate or mos t nearly related dominant great ' s o il group cons tituent, togethe r- w i th their areas and relative di stribution
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Unit 1. Coarser Textured Alluvial Soil Associat ion
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2. Medium Textured Alluvial Soil Assoc iation
3 • . Finer Textured Alluvial Soil Associat ion
4. Mis cellaneous Alluv i al Soil Assoc i ation
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Gro ss Area IT�oo�r ac s )
7 . 2
57 . 4
39 . 4
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3. 6
I I 5. Dark Grey C lay Assoc iat ion 22 • . 2
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6. Black Earth As sociation
7. Brown Clay Associat ion
8 . Brown and Dark Grey Clay Catenary Association
9 . Shallow Solodic S o i l As s oc iation
10. \Veakly Solod ized-Solorietz As soc iat ion
�1. Solod ized-Solonetz-Low Hum� c Gley Assoc iation
1 2 . Gr�y G i lg a i od Olay As soc ia tion ·
13. Brown Gilgaied Clay Assoc i ation
14. Red-Brown Gilgaied Clay A� soc iation
15. Later i t i c Red Earth Association
16. Lateritic Podzolic Associat i on
17. Gleyed Podzolic As soc iation
18. Shallow S tony Soil Assoc iat ion
24. 6
50. 6
14. 3
i 2 . 1
20. 9
59 .7
135 . 1
4. 0
2 . 2
2 . 0
6 . 8
17, 1
19 . 9
;;£_of Total are o..
1. 5
ll. 7
8 . 1
0. 8
Alluv ial soils which · ofi show varying degrees of profile development -usually of a podzolic 0 1 solodic nature,
4. 5 l 5 . 0
Related t o Black Earths ,
10. 4
2 . 9
0. 4
4. 3
12 . 2
27 . 7
0. 8
0. 4
0. 4
4. 0
Brown Soil of Heavy Texture.
Brown soil of Heavy Texture 9 Black Earths .
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Solodic .
) Related to Solodized) So lonetz and So lod i c ,
� Solod ized-Solonetz 9 Low Humic G;Ley.
Closely related to Grey and Brown Soils of Heavy Texture.
� Lateri tic Red Earths.
� Lateritic Podzo lic
Meadow Podzolic or Lo'c Humic Gley.
Litho sols .
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g!.--· -�gripti on,_Qf the So_ils!..
Unit l � Coarser Textured Alluvi al Soil Assoc iation. --------------Gross�rea-7-2oo-acre�---------------
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The c o arser textured alluvial soils of thi s as soc i a tion have only a rather limi ted d i s tribution on the river floodplain where they often occur as old � slightly elevated levee depo s i t s . Becaus e o f their limited ex tent i t was not always po s s ib le to map e a ch are a ind iv idually s o that many o f the smaller occurrences have b e e n includ• in the nex t assoc iation ( Uni t 2 ) . Also inc luded in thi s coar s e r textured a s s oc i at ion are the small alluvial depo s i t s o n Oxt rack and De lus ion Creeks.
The s o ils are somewhat var iable � as might b e e�pe ct ed from the nature of the ir oc currenc e � but as u rule they po s s e s s rather d e e ( 18 to 30 ins. ) � very freely draine d A horizons that range from a loa s and t o a s andy. loam and occas i onally a loam in texture . Co lour i s usually b rown t o light brown. A clay l o am o r clay B horizon i s present and i s of ten s omewhat gleyed due to the restricted internal d ra inage caused by thi s ho�izon. The de eper s ubso ils are somewhat : variable but are normally not heavier than a light clay in t extur e . Thes e s o i l s are s imi lar i n mo st respe c t s t o tho s e de s cribed by G . D . Hubble as Type s 2 and 3 i n t he Moura Irriga t ion Area.
The following profiles are repre s ent ative of the s o ils o f this a s sociation: -
( i ) Profile l mile e a s t of t he Dawson River anab ranch nea r Baralaba.
A1 0- 20 in. Brown loamy s and , loo s e , s ingle grain9 merge s int1
A2 20-36 in.
B2 36-48 in.
Light brown loamy s and � s l ightly compac ted � fairl; sharp break to
Greyish brown s andy c lay loam w i th s light grey mo ttling � c ompac t , s l ightly pla s t i c when we t .
( i i ) Profi le � mile west of Dawson R iver at Baralaba .
A1 0-15 in.
A2 15-22 in.
BC 30-38 in.
Brown fine s andy loamy very weak blocky, soft y merges into
L ight brown s andy lo amy very weakly b leache d , ma s s ive , fairly sharp bre ak t o
G re y i s h brown s andy light clay, s t rongly mot tled o range and gre y � v e ry firm to s lightly plas t i c , rather ma s s ive 9 merg e s into
Light re dd i sh brown l ight clay� friabl e , merges :
C 38-60 in. Yello� i s h b rown l ight c l ay w i th s ome greyish s ane patche s .
An�1x�i£�1-�a t�
The se s o i ls were no t s ampled during the pres ent survey b data ar e avai lable for very s imi lar s oils from the Moura survey conduct ed e arli er by G . D . Hubble . In thi s area the A horizons are v s lightly a c id to neutral, the B hor iz ons are neutral but t he d e eper sub s o i l s may become moderately alkal ine . Calc iwn is t he d ominant exchang e able met al cation in t he clay B horiz ons with exchange ab le sod ium very low. Chlor ide and t o tal soluble sal t s are very low throughout the profile. Tot al ni trogen is very low in the s andy A ho rizons 9 while available pho spha te - i s als o low . The s andy horizc of thes e soils have a low moi s ture ho ld ing capac ity.
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The vege tation of the se s o i l s i s typically a tall woodland communi ty of More ton Bay ash 9 grey bloodwo o d and s i lver-leaf ironbark •
. The ground flora i s frequently dominated by black spea r gra s s .
Ming£_��sociateQ_§Q il��
On the crests of s ome of the higher levee-like terraces the soils may .b e a s and or loamy s and t o depths great er than tho s e indicated above . Towards the marg ins of these occurrenc e s t h e A horizons become shallower in depth and fine r in t exture unt il they merge int o the typic al soils of Unit 2 .
Uni t 2 . Medium Tex tuPed Alluvial So il A s s oc i a t ion. ------------ Qross-Area-�l.l+oo=�cr�i�--------------This important a s s o c i ation occupi e s the ma jor por tion of
the Dawson R iver floodplain d owns tream from Theodore with i ts great e s t d evelopment in the. Kianga-Harcourt section. The land s c ape: is e ither flat or with very s light s lope s but a fe ature of the terrain is the frequent pres ence of old drainage line s 9 swamps o r s lightly d epre s sed areas which r e.:tain water fo llowing heavy rainfall. That por tion of the floodplain occupied by this a s s oc iati on is subj e c t to flood ing but such inundation only oc curs during very high floods and t he d epth of water i s s e ldom great .
Although fo r purpos es of descript ion the s e soils have b een classed as alluv i al 9 there i s normal ly a profi le d evelopment with dis t inc t A and B hor izons . Prof ile morphology tends t o show podzolic o r s o lodic feature s but usually i s not suffic i ently t ypical t o warrant a class ification as such. The d ominant soil of this a s s o c i a tion i s gene rally s imilar t o t hat described a s Type 5 by G . D . Hubb le i n his Moura survey.
The A hor izons range in thickne s s from 8 to 15 inches 9 but c ommonly average 8 to 10 inches with c olour a shade of g reyish b rown, grey or grey-brown. A s lightly bleached A2 horizon is
. o ccas ionally developed 9 espe c i a lly in les s well drained s i t e s . A horizon texture s range from s andy loam t o c lay loam but a loam o r s andy clay lo am i s probab ly the mo s t common. The s e A horizons have a fairly s t ab le s t ruc ture al though a c ompacted s lightly platy surface may b e pres ent . The med ium clay or s andy clay B horizons 9 brown or grey-brown in co lour 9 are ra the r sharply d emarc ated from the A but appear to b e sufficient ly fre ely dra ine d s o as not to c ause any prolonged perchtng of water on top of t he c lay. An occas ional dull orange and grey mot t ling in t he s e horizons ind i cates some slight gl eying effec t s but largely the c l ays are relat ively permeable w i t h an angular b locky s t ruc ture and a re hard when d r y and rather plas t i c when wet. Small carbonate nodul e s may b e pres ent i n the B hori z ons but no rmally o ccur lower in t he prof ile. ' · Be low the B hor iz ons there i s a mor� fri ab le l ight brown calc areous l ight c lay t o 6 feet but ' b elow thi s 9 s t rat ification become s evi dent and the texture rather variable , In s ome profi�es b elow 8 feet there may be loo s e po rous s ands at least 4 fee t in thi ckne s s .
The fo llowing profiles illu s t rate the chief characterist i c s of the maj o r s o i ls of thi s association : -
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( i ) Profile 1 mil e north of Mungi Sid ing.
BO
0- 6 in. Grey-b rown to greyi sh brown s ilt loam-c lay lo am1 weak b locky, sl ightly hard 9 me rges into
6- 9 in. Grey to browni sh grey c lay lo am, mas s ive and s lightly porou s , fai rly sharp b reak t o
9- 1 8 in. Light brown med iwn clay w i t h s ome dull orange al grey mo t t ling , s tiff and sl ightly plas t i c , me rge s into
18- 28 in. Bright brown to redd i s h b rown med ium c lay , more fri ab l e , merge s into
28- 36 in. Light b rown light c lay with t race o f c arbona t e , friable , me rg e s into
C 36-48 in. Yellowish._. b rown l ight clay, friable , merg e s intc .
0 48- 70 in. Light yellowish brown light c lay-clay loam, very friable.
( i i ) Profile at Harcourt S i ding·�
0- . 8 in. Greyish brown fine s andy c lay loam, weak blocky, friable , d i s t inct change to
8- 15 in. Brown med ium c lay w i th s light grey ahd reddieh mo t t ling 9 angular b locky, hard , merges into
15- 36 in. Bright brown to redd i s h b rown med ium clay w i th s light greyi sh mo ttling , angular, b +ocky and hard , merge s into
BO · 36- 48 in. Brown light c lay with mod era t e carb onat e nodules
0 48- 60 in. Light br own l ight c lay , friable.
C 60- 72 in. Yellowish b rown f ine s andy c lay l o am, friableo
0 72-100 in. Yellow i s h b rown f ine s andy l ight c la y 9 friable .
0 100-150 in. Light brown loamy s and-sand, loose and uncemente
Below 36 inche s a ll boundar i e s are very d iffuse 9 each horizon gradually merging into the next .
hnalytical Dat a : I n t he upper level s o f t he profile the s o i l s are s l ightly
acid t o . neutral and b elow thi s they r emain neutral except for a mod erately alkaline hori zon c orre R�ODd ing to the zone of carbonate accumulation. Calc ium is the dominant exchR ngeable me tal c a tion in b o th the A and B hor i z ons with exchange able s o d ium very low. Exchang e ab l e pota s s ium is pre s ent in relatively high amounts . Chloride s ( expre s s e d a s NaCl ) and t o tal soluble s alts ( expre s s e d in terms of spec ifi c conduct ivi t y ) are relat ively low in the upper leveJ of the profile ( up to 0. 02 per c ent. NaO l ) but show a sl ight accumulation b elow 36 inche s ( up to 0. 13 . per cent. NaOl) . Tot al ni trogen is s omewhat low in the A horizons ( 0. 06-0. 1 per c ent . N) . "Ava i lab le" pho spha te in the A hori zons i s very fair to h igh , ranging from 70 to 150 p. p. m. P205 . In the B horizons of some profi les value s may fall b elow 5 0 p. p . m . The moi s ture holding c apa c i ty of the l o am or c lay loam surfaced soils should be reas onab ly good but would no t b e s o favourable on s o i ls of coarser texture than thi s . Be t t e r c ondi t ions should obtain in all sub s o i l s .
Plate 7 . SilYer-leaf ironbark-poplar b ox wood l and on the med ium textured alluvi al soils 1 mile north-w e s t of Baralaba •
The vege tation of the s e s o i ls i s a wood land comnuni ty o f s ilver-leaf ironbarl< and poplar b ox ( Plate 7 ) � the former spe c i e s usually b eing dominant o n the s o i l s w i th a deeper coar s e r t extured A hori zon and the la t t e r when the A ho riz ons are slightly shallower w i th a clay loam t exture . A mixed gramineous ground c over is a.tways pre s ent . ·
Mil}QL�.§.§oc_!atesi_§Qi1.£ :
In the s hallow d rainage l ine s o r b road s lightly depre s s e d are as that are fairly crnmnoh i n thi s a s s o c i at ion s o lod iz ed-solone t z soils very s imilar to tho s e o f Unit 1 0 may occur. Th�se have rather shallow ( 6 inches or less ) clay loam A horizons overlying a t ough impermeable heavy c lay. On s l i ghtly elevated s i t e s which p in s ome cas e s g repres ent o ld levee d epo s i t s the deeper c oars er textured s o i ls that form the ma j o r c omponent of Unit 1 may occur.
Unil_}_. __ E_!ner T��1�re�_A!!�v ig1_2o i l A�.§_oc_!at_!Qg. Q£QS S_�reg�22�QQ_acre�
In many areas imme d i ately ad j ac ent to t he river there i s a s t rip o f land o f variable extent that i s sub j e ct to very frequent inundat ion. Often this land is in the form of somewhat low terro::t c e s but o ccasionally the s e lower lying areas may extend some d is t ance away from the r ive rp more part i cula rly where t ri bu tar ies or othe r drainage line s approach the main s tream . In o ther ins tanc e s there are areas of lowlying land whi ch may or may not oc cupy the s it e of o ld ma jor drainage lines but ye t are characterised by regular s easonal flood ing. Nearly all of the se are a s cont ain only a limited ex tent o f land which is not d i s s e c ted to s ome ext ent by dra inage lines . The soils of such occurrenc e s as the s e compr i s e this a s s o c i ation of finer t extured soils • .
The chief feature �f the s e s o ils i s the lack of any pro -. nounced horizon d evelopment. They are usuall;y- grey or greyish brown in colour and the texture i s a clay loam or clay which i s often r a ther s i l ty. . The surface of t he s e s oi ls is not s e lf-mulching but t end s to b e s omewhat compac ted. The s tructure of the upper levels of the prof ile i s . inclined to be uns t able and might be expected to de teriorat fur the r if d i s turbed by cult ivation. Cond i t ions improve with d epth where there may be small amount s of carbona te pre s ent .
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. The s o i l s immediately no rth and north-we s t of the township of Theodore ( mapped a s Type 3 by G, D� Hubble ) have also been ·
included in thi s as s o c ia t ion. Howeve r9 the s e soils have a rather mor e s trongly deve loped dens e c lay B horizon •
The fo llowing pro f iles illus t rate the e s sent i al features of thi s group o f s o i l s : - ·
( i ) Profile 1 mile nor·th-we s t of Harcourt S i ding .
0-14 in. Grey b rown s i l ty clay, weak b lo cky , rather b r i t t l � , grad e s into
14-34 in. Greyi s h brown med ium clay , sl ightly s i l ty, b lo cky t o mas s·ive , firm t o hard , merge s i nto
34-48 in. Ye llowi s h brown light c lay , fr iable , t race of carb on- · ate •
'·' ( i i ) Profile on lower rive� t errace i mile south of Baralaba .
0-12 in. Brown c lay loam, weak b locky , rathe r bri ttle , me rge s into
1 2-20 in. Bro wn med ium clay, mod erate blocky tend ing mas s ive , fairly hard , me rge s into
20-48 in. Light b rown l ight clay, friable.
Deep b oring in the area immed iately north of Theodore ( G � D . Hubble ) has shown that w i th depth the se profile s may c ontain fairly thick horiz ons of rathe r loos e sandy clay · loam, c layey sand o r s and.
No ana�l.yoes of t he s e s o i ls have b e en obta ined during the present s11rvey but s o,;,.:, :la '!;a are ava i lable for Hubble ' s Type 3 and i t i s b e li eved that these would g ive a fairly good indi c a tion o f this group of s o i l s in gene ral . Thus for Type 3 the surface s o i l reac tio� may b e s Ught ly a c :i, p 9 peutral o r weakly allcali;ne b11t t he sub s o i ls are modGX'6\tel.y a. llta l 1no , C�lo �um ;i. s tne uom1nan·c exchange ab le metal c at ion w i th the o ther met al i ons pre s ent in normal amount s . ChloridE and t o t a l s olub l e s al t s s how s ome accumulation in the sub s o i l but not in harmful quant it i e s . · The surface so ils are reason�bly w e l l supplied with ni trogen and t h e pho sphate status i s very g ood . The moi s ture hold ing c apac i t i e s of thes e s o i l s , parti cularly the s ub s o i l s , should b e modera tely high.
·
y��l!.!ion:
Coolib ah and po�lR r box are normally dominant on the s e s o i l s but i n s ome are A R there li•.J.�' l) p C! l nmps of brigalow a nd o c c R.A ionally b auhinia�
Minor As soc i a��.c!_J3oi 1.12. : The chief a s R o c i ated soils of thi s unit inc lude s ome
mis c e l laneous alluv ial s o i ls of variable texture but w i thout any horizon d eve lopment . 1'hus in s ome s i t e s deep coarse t extured
· depo s i t s exis t while in swampy areas the s o i ls may be a med ium to heavy clay thr�ughout the prof ile.
Uni t 4. Mi sce llaneous Alluv ial Soil As s o c i a tion. ��o ss-Area_3�Q acres . -----------
1'here :i. s a small ex tent of very variable alluvial s o i l s in the vicinity and jus t to the e a s t of Goo l ar a S iding , approxima t e ly
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3 mi les north of Theodore . In this loc ality Cas tle C reek c e a s e s t o flow i n a defined channel for a short d i s tance and cons e quently an irregular pa t t ern of shallow d i s tr ibutary channel s and as soc i ated variable textured alluvia ha s been built up. : The whol e area i s . sub ject t o local flood ing and the rathe r complicated s o il patt e rn also extends further up Cas tle Creek even where i t is confined to an e n.trenched bed.
S o il chang e s are fre quently so rapid and uniformi ty of cond i tions so small that this area � be ing as a whole rather l imi ted in extent 9 has b een treated as a single unit . It is d i ff i cult to give any other than a gene rali sed de s c ript ion of t he soils a s s ome rathe r diverse types o c cu r � frequently in c lo s e proximi ty. In part icular � textural change s may b e marked even over a dis tanc e of several yard s . Coarse t extured very freely dra ined s o i ls may o c cur on slight ly elevated l evee b ank type s i te s � more part icularly in proximi ty to Cas tle Creek or one of its d i s tr ibutary channels . The follow ing profile is typical of thi s type : -
. 0- 6 in. Fairly coarse b rown s andy loam� loo s e � me rge s into
.
6-20 in. Coarse light greyi sh bl"OWn loamy s and , single grain, also contains s ome po cke t s of brown s i lt loam, merge s int o
2 0-30 in. Brown loamy s and with pocke t s of d ark b rown s i l t loam • .
30-48 in. Dark brown silt loam� friable • .
O n flatter s it e s o r i n the b o t tom of shallow d rainage lines f iner t extured s o i ls usually o ccur. The following profi l e 9 2 00 yards away from the c reek, is typic al : -
0-10 in. Brown c lay l o am9 weak b locky, friable 9 me rges into
10-20 in. Light b rown s i l t loam, very weak b l o cky , soft , merg e s into
20-36 in. Dark brown to grey-b rown l ight clay, med ium blocky , friable.
I t i s not t o b e thought that the s e are the only s o i l s o c curring in thi s a s soc iat iony all gradations exi s t b e tween c o a r s e textured s o i ls and me dium clay s . However , a feature common t o all is the la ck of any hor izon deve lopment and the frequent pre s enc e of s trat if ication.
.6D�lii:t��ta :
No s ample s of t he s e s o i ls were submit ted for labo ratory examina tion but i t might b e . expe c t ed that all exc ept the more s andy · soils s�ould b e of . reasonab ly high fert ility. ·
y�getati2]l!.
Most of the area was originally covered by a tall and s ome t ime s rather d ens e woodland c ommuni ty of More ton Bay ash , b lue gum an s i lver-leaf ironbark. The ground cover is usually dominated by b lack spear and for e s t blue gra s s e s .
�g!!_2• Dark Grey_Cl��-A��oc iation� Q:ro s!L_Area�QO a�.
In some low lying s i tuat ions throughout t he r iver floodplain that are sub j e c t to inundat ion by h igh floo d s t here are areas of deep d ark grey heavy clay s o i l s which have a s t rongly developed s elf-mulching surface and which crack d e eply when dry. Mos t of the s e so ils have ,close affini t i e s wi th· the black e ar t hs and could
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pe rhaps b e regarded as hyd romorphic e quivalent s 9 b eing l e s s well dra ined than the typical Que ens land black e arths . The s oi l s included i n thi s a s s o c i ation resemble c lo s e ly tho s e mapped and described at Theodore by G. D. Hubble as Type s 2 1 5 and 6 .
Normally the �eneral topography is flat but t he land may b e d i s s ected to s ome extent by d rainage line s . The s oi ls themse lve s may exhib i t a very s light gilgai microrelief but the vert ical interval between puff and depre s s ion would s e ldom if ever exc eed 6-8 inche � The surface s o i l po s se s s e s a s trongly developed moderately coarse granular s elf-mulching s truc ture and i s ·grey to d ark grey in colour. 'l'his loo se surface may pers i s t for s everal inche s b efore the clay gradually as sumes a med ium then coarse blocky s truc ture whi l e s ti ll re ta ining a dark wey or grey-brown co lour. This may extend t o depthf ranging from 3 to 5 feet before merg ing int o a greyish brown or brown clay · whi ch is more . fri able. Carbonate may b e pr e s ent throughout the
. profile , usually in only sl ight amount s in the upper levels but increas ing w i th depth. Gypsum has also b een recorded in the s e s o i l s a t Theodore.
The fo llow ing prpfiles show the charac te r i s t i c feature s o f the s e so ils : -
( i ) Profile 1 mile east o f Coo.�um Stat ion, 2 mi les we·s t of Baralaba.
( i i )
0- 2
2-1 2
12-20
20-30
30-50
in.
in.
in.
in.
in.
Grey heavy c lay w i th s trong granular fairly coarse s elf-mulching s truc ture '· grades into
Dark grey heavy clay, med ium blocky , hard , t race of c arbonat e , merges into
Grey heavy clay, coarse b locky , ha rd when d ry and pla s tic when wet , slight carbona t e , merge s into
Brownis h grey to ' greyi sh brown heavy clay ( trans itional ) , s�ight carbona t e , me rge s into
D ark brown t o b rown med ium clay, firm, c arbonate increas ing , merges int o
·50-66 in. Brown med ium clay with abundant c arbonate nodule s , fri able .
Profi le north- e a s t of Theodore railway s t at ion ( descr iption from G . D . Hubble ) .
0- 6 in. Blaclc he avy c lay with a browni sh t inge , g ranular s truc ture .
6- 24 in. Black heavy clay, loos e granular s truc ture , very s light c arbonate.
24: 40 in. Dark grey to black heavy c lay , very s l ight c arbona t e nodule s .
40- 5 1 in. Grey-black heavy clay , sl ight t o light c arbonate nodules and very slight fine crys talline gypsum.
5 1- 64 in. Dark grey heavy clay with slight to light c arbona t e nodule s .
64- 80 in. Grey c lay with a yellowish t inge going t o yel low-g rey heavy c lay with slight carbonate .
Below 80 inche s i s a ' yellow and yellow-grey fr i ab le clay with c arbonate d ecreas ing and yellow colour bec oming s tronger t o 10 feet depth.
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�yt ical Data ( Supplemented by data from G. D . Hubble repo r t ) :
The upper hor i z ons of the se s o i l s contain 55-70 per cent . c lay but the parent ma ter ial alluvium �t depth falls t o ab ou t 50 per cent . clay. The upper 6 inc he s of the profi le i s neutral to moderate ly a ll\:o.line but b elow thi s modera t e ly alkaline cond i t i ons prevai l . The soils have a h igh total exchangeab l e metal ca tion content w i th exchangeable c a lc ium d ominant throughout . Exchangeab le s od ium is normally low . Chloride and t otal s o lubl e salt content are low in the upper levels of the prof i l e ( up to 0. 016 per cent . NaC l ) but may show a s l ight accumula tion i n the 5 t o 6 f t . zone ( up t o 0. 15 per cent . NaC l ) . The surfa c e 6 inche s has a to tal ni trogen content r anging from 0. 08 to 0. 1 2 per c ent. N. Avai lable phos �hate in the upper levels of the profile i s very fair ( 75 p. p. m. P205 ) . It is expected tha t these heavy clay soils would have a high moi s ture hold ing capac i t y •
.Y�p;e ta_:tion : '·'
Thc �o clay s o i l s . support a vege tat ion of br igalow ? b auhiniE and cool ibah 'il i , ich may occur as s c at te red c lumps or d ens e r s tands 1 · howeve r small areas of open gra s s land s ome t imes occur.
In s ome areas mo re prone t o flood ing the s o i l s may los e their s elf-mulching surface and approach thos e d e s cr ibed in Unit 3 while in b e t ter d raine d s i te s the s o i l s clo s e ly r e s embl e tho s e -de scribed a s black earths in the next as socia t ion ( Unit 6 ) . I n s ome localit ies there rna� b e small development s of the typic a+ gilgaied grey c l ays ( Uni t 12 ) .
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D ark grey o r grey-b rown c lay s o i l s that are s hallowe:ii . and be tter drained than the pre ced ing group of heavy clay s o i l s occur sporadic ally throughout the r eg i on and are mos t ly d eve loped on Permia sed imentary ro cks. Thes e s o i l s are in many res pec ts very s imilar to b la cl,J: earths' 1 al though the c olour may not b e as dark as in the mo re typi cal Queens land examples of this group of so ils . They are typica ly deve loped on a gently undulat ing landscape ( Plate 4) bu t flat area .a l so occu�1 part icularly on .wide valley floo rs. Some of the oc currenc e s may be on s lopes of up t o. 5 per cent . or slight ly grea t e r and there may b e a prominent l inear gilgai d evelopment.
Depend ing on t h e t o pography the s o i l s may vary i n thi ckne s from about 15 inche s t o 4 f e e t . The surface s o il h a s a loo s e med iurr granular s elf-mulching s t ructure which becomes med ium t o coarse angul blocky wi th d epth. Co lour may range from dark grey to grey-brown. In s ome · areas there may b e numerous smooth rounded ma s se s of billy u� to 3 or 4 inches in d iameter sca ttere d on the surface and through the upper levels of the profil e . _ Carbonat e nodule s o ccur a s a rul e throughout the prof ile .
The fol low ing pr ofiles i llus trate the fea ture s of the s o i l s . ( Type l d e s cribed by G . D. Hubble at . Theod o re i s to be included in thi s s o i l as sociat ion) : -
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( i ) Prof i le 1 mil e east of the road c ro s s ing of Lone some Creek1 north of Theodor e . S ite on the crest of a broad low r idge .
0- 8 in. Dark grey to grey br own med ium c lay ? granular . s elf-mulching surface 9 then medium b loclcy and hard 1 sl ight c arbonate nodule s , merges into
8-36 in. Dark g rey heavy clay , coarse b lo cky 1 hard p s l ight t o mod era te carbonate 9 merges into
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( i ) contd .
36-44 in. Greyish b rown c lay with moderat·e carbonate � t rans iti onal to
41+..:.56 in. Brown to light b rown medium c lay w i th mod erate large carbonate nodule s .
· 5 6 in. + Decompos ing c al c areous s and s tone .
( i i ) Profile o n cre s t of high r idge 3 mi les eas t-nort h-east o f Theodore.
0- 6 in. Grey-brown heavy c lay � g ranular surface then med ium b locky � hard 9 s l ight c arbonate � merges into
6-15 in. Dark grey-b rown c lay with t races of decomposing ye llowi sh c alcareous s ands tone .
' 15 in. + Decompo sing ye llo\Vi sh calc areous sand s tone . ' Analyt ical Dat a :
The upper ho rizons o f the se soils have a s omewhat lower clay c ontent than the preced ing g roup of d ark grey s o i l s ( 43-50 per cent . clay ) . The surface s o i l is neutral to mod erately a lkaline but lower horizons are all mod erat e ly alkaline . Total exchangeable me tal c a ti ons are high w i th exchangeable c alc ium be ing greatly dominant . Exchangeable sod iwn is very low . Chlor i de and to tal s o lub le sal t content s are low in the upper part of the profile and only s how a slight increase with dep th. Total nitrogen is rathe r
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vaPiab le but may b e reasonably high in s ome s amples ( G. D . Hubble data ) Avai lable pho spha te i s a l so rathe r var i ab l e 9 ranging f rom 3 0 to 60
p. p. m. in the upper 6 inche s but is less than 40 p. p . m. in the 6-12
inch zone. ·
yegetation:
Small ar eas of true gras s land occur but mo s t con�only qn the s e s o i ls there are s c a ttered c lumps of br igalow and b auhinia w ith occas ionally denser st and s of the former specie s . The gra s s e s are domina ted by Queens land � fore s t and d e sert blue 9 toge ther with �riQch1Q§_�. and Pani crun sp •
Mi:gor AssQc i a ted_S oils ...:_
The s e dark grey and grey-brown clays frequent ly me rge into the typical brown clays that are described in the next as s o c i a t ionp ( Unit 7 ) , mor e par t i cularly on the c r e s t s of higher r i d ge s . In s ome of the intervening valleys w he re surface d rainage i s s omewhat re s tricted p the deeper heavier dark g rey clays described in Unit 5 may o ccur.
Unit 7. Brown cla� a s s o c i ation. ---�!:o s s-A£. e a_5�£55 -�£res.-
Calcareous brown c lays are rathe r ex tens ively developed to · the sou th of Nipan with some smaller o ccurrenc e s further no rth. The s e soils have qeve lope d from Permi an c alcareous s and s t ones and sha l e s on a lands cape that i s mod erately to fairly s trong ly undulat ing . The soils on t h e c re s t s of the r idge s are oft e n s hal low and po s s e s s a . clay loam surface 9 d own the s lope s they d e epen and become darke r in colour, thus forming a c a tenary s e quenc e 9 whi le in s ome valley floors the s o i l s approach the b lack e ar ths in mo rpho logy, Slopes range from 2 or 3 per c ent . to occasionall y over 5 per c ent . and on some a very s l ight l inear gilgai microre l i e f may b e pre sent . Some waterworn b i lly i s s omet ime s s c a t t ered o n the surface and throughout the upper
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leVels of �he profi l e .
O n the cre s ts of the higher ridge s 1 e spec i ally tho s e carrying a softwood scrub vege t a t ionv the upper 6-inch hor j.zon i s often a fri ab le br own o r even sl ightly reddish brown clay lo am but more commonly the surface s o ils ·are s elf-mulching b rown clays which become darke r in colour and heavier in t exture down the s lope. The sub surface brown clays have a med ium to coarse blocky s truc ture and are quite hard when d ry. Carbonate i s normally pre s ent b elow 12 inches and may o ccur throughout the profile . Decompo s ing parent material i s enc ountered a t depth s r anging from 2 to 4 feet •
The fo llowing profiles illus trate many of the features of this group of s oi l s : -
( i ) Profile 1 mile we s t of Woodle igh turn-off 1 21 mil e s s outh of Nipan. Site on the c re s t of a fairly high ridge.
0- 4 in. Light brown c lay· loam with s ome i s ola ted waterworn gravel on the surfac e 9 weak blocky t o mas s ive 1 hard , · fairly d i st inc t from
4-14 in. Dark b rown c lay 9 med ium to coarse b locky1 hard p merge s into
14- 24 in. Brown clay 9 coarse blocky1 s lightly friable 1 s light c arbona t e ? me rge s into
24-46 in. Yel low ish b rown light s and y clay w i th s ome decompos ed calc areous s and s t one ma terial 9 very friable.
46-60 in. Yellow-b rown c lay with de compos e d mud s t one.
( i i ) Profil� i mile no rth of Wil lawa on upper to mid- s lope pos i t � on. ·
0- 6 in. Brown clay1 f ine granular surface then med ium blocky and har d , slight to moderate carbonate 1 me rges into
6-18 in. Dark b rown clay 1 c oars e blocky 9 somewha t friab l e when mo i s t 1 moderate c arbona t e 1 merge s into
18-36 in. Yellow i sh brown light s andy clay , soft and very fri ab l e w i th abundant soft carbonate and s ome d ecompo s e d calcareo.us s ands tone.
�§.lyt ical_Qat a :
Chemi cally the s e s o i l s a r e very s imilar to the black e arths . Clay content average s 50 per cent . , react ion of the surface s oils i s neu tral o r mod erat e ly alkaline with alkaline cond i t i ons c ontinuing w ith d epth. Calc ium is the dominant exchangeable met a l cation w t th exchangeable sodium ins ignificant. Chloride and total soluble salt c ontents are low. Available pho s phate in the upper 6-inch later shows much variation with values ranging from 20 to 120 p. p. m. The 6-1 2 inc h zone rang e s from 20 t o 50 p . p . m.
yeget a tion:
O n the cres ts of some high ridges where the surface s o i l i s a c lay lo am a sof twood s crub vege tation i s c ommon but normal ly
· these s o i ls support a br igalow-bauhinia parkland coinmuni ty w i th s ome sandalwood and poplar b ox a s s o c i ated. The r e are also s ome small open gras sland a reas . The ground flora i s mos tly dominated by Queensland blue gras s .
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Min9.r As soc iated Soi l s :
The chief mino r s o i ls of thi s a s s oc i at ion inc lude s ome · · trans i t i onal d ark grey-brown c lays tha t clo s ely resemb le the b lack
ear ths described in Uni t 6 and occur in the lower flat s i tuations . The cre s t s of s ome hich r idges may oc casiona lly have shallow s tony skele tal so ils that are d e s cr i b ed els ewhere ( Uni t 18 ) .
Qni�_§�---�ro�Q_§Qd D§��-g£�l_Q1�l_Q��eng£y_��i a t iQ� �ro��ArQQ_1�2QO a££�£�
Thi s a s s o c i at ion i s of limi ted extent and i s found on Pe rmi an s e d iment s - shule s 9 muds tone s and c alcareous s and s tone s 9 in rather res tric ted areas . The chief o ccurrenc e s are t o the e a s t of Baralaba and in t he vicinity of Wandoo S t a t ion9 w i th s ome smaller development s s outh of Theod or e . The s o i ls have developed o n an undul at ing lands cape 9 slopes commonly ranging up to 3 or 4 per cent. although flat or g ent ly s loping areas d o occur. The s e t opographi c c ircums tanc e s have l e d to the format ion of catenary s o i l s e quenc e s with the s o i ls on the cr e s t s of the r idge s often being qui t e d ifferent t o t ho s e of the lower s lopes or leve l s it e s .
O n the ridge c r e s t s the s o ils are frequently shallow and po s s e s s a brown clay loam o·r l ight clay s urface which over lies a redbrown c lay. The s e s o i ls have affini t i e s w i t h the red podz o l i c s and red s olod i c s . The fo llow ing profile from a ridge crest near Wando o S t ation i s typical : -
A1 5-14 in.
B2 5-14 in.
14 in. +
Light brown to brdwn c l ay loam - l ight clay9 ve ry weak b lo cky t o ma s s ive 9 fairly hard 9 merge s into
Red-b rown clay9 med ium blocky9 fairly hard with s ome fragment s of weathered tuffaceous sand s t one.
We a the red tuf faceous mud s tone .
. Down the s lopes the s o ils are a darker shade of brown w i th a heavier textured surface and the redd ish colour i s lacking in the sub s o i ls . Again they ' may be shallow as the following pro f il e from the s ame locality ind i c ate s : -
0-10 in. Brown medium clay 9 slight granular surface then med ium bloclcy and hard 9 merge s into
10-22 in. Dark brown to grey-b rown med ium c lay9 medium b lo cky9 hard .
2 2 in. + Decompo s ing browni sh tuffaceous s ands tone
On t he lower slope s 9 flat valley floors or any s l ightly depre s s ed " area s 9 de eper dark g rey clays very s imila r t o the black e ar ths o ccur. A very s light gilgai microrelief may be pre s ent on level s i t e s and on s ome s lope s a linear gilgai s tructure is d eveloped. Thes e clays a re d ark grey or g rey-b rown in co lour9 pos s e s s a granular se lf-mulching surface and c ontain c arbonate in the profi l e . The follow ing �ofile on Wandoo Hold ing of a s o i l formed on a wide valley floor is charac teri s t i6 : -
A1 0-24 in.
AC . 24-3.6 in.
Dark grey to grey-brown heavy c lay9 g ranul ar s e lfmulching s urface then med ium b locky9 t race of c arbona t e at lower level s 9 me rges int o
Yellow i s h grey-brown to yellowish b rown med ium clay9 slight to mod erate carbonat e 9 oc c a s i onal weathered shale fragments and s ome small waterworn gravel .
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·"'
I
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Thi s ca tenary sequence as des cribed above i s no t always_ pre sent. On s ome lower ridge cre s t s the b rown mid-slope member de scribed above may oc cur and black earth type soils may extend a c onsiderab le d i s t ance up many of the les s er s lope s •
.hEQ1Yt ic_§ l DatlU
These s o i l s were no t s ampled dur ing the pre s ent survey but re sul ts are ava i lable for s ome s imilar s o i l s which were examined during an e arlier survey of Wandoo Hold ing by officers of the Department of Agri cul ture and S tock.
The shallow brown so i l s have horizon w i th the B neutral to alkaline . dominant exchangeable me tal cat ion w i th ing s ignificant levels . The pho sphate
a s l ightly ac id t o neutral A Magne s iwn i s s ome t ime s the
exchangeable sod ium approachst a tus of the se s o i ls i s low .
The d eeper grey and grey-b rown s o i l s are alkaline throughout the prof i l e 9 calc iwn i s t he dominant exchangeable metal cation with exchangeable sod ium low, Chlor ide and total s o luble salt s show : a slight accumula tion in some s ub s o i l s . Tot al ni trogen i s low t o fair w i th organi c carbon s l ightly greater than one per cent. C/N ratios range from 10 t o 16. In the s e soils avai labl e phos pha te i s low throughout ( 20-30 p. p . m. P205 ) . ··
On the shallower brown s o i l s 9 e spe c ially on the ridge cre s t s the vege ta tion i s a woodland of s andalwoo d 9 poplar box and s ilver-leaf ironbark. Elsewhe re t he two lat ter spe c i e s occur as dominant s in a parkland c ommuni ty 9 the ground f lora be ing mainly Que ens land 9 d e s ert and forest b lue gras s e s but with black spear prominent in many localit i es .
M1D2£ . AssociatQQ_§oil s :
. Sc a t tered 9 usually small 9 clumps of d ens e br igalow oc cur. in some locali t i e s and t he s o i l s a re greyi s h b rown clays with often- · a strong gilgai microre lief. Thes e are e s s ent i ally s imilar t o tho s e describ ed i n Uni t 1 2 . I n t opographic s i t e s charac terised by a re s tr icted surface d ra inage 9 small areas of the we akly so lod i z edso lone tz s o i ls of Unit 10 occur. '
Uni t 9. Sha l low Solodic Soil A s so c i at i on. Qros�-�£e a 2 .1QO aC£Q��-----
------
The soils included in thi s as s o c i a t ion are of v ery restric ted occurrence 9 be ing found to the eas t of Kalewa near the northern l imit of the surveye d region. They are s hallow s tony types derived from Permian shales and mud s tone s . The land s c ape i s undulat ing with some rock qut crops on the cre s t s of the r idg e s .
The A hor izon o f the s e s oils i s a fairly shallow grey i s h brown c lay loam o r light clay which i s s ome t imes s l ightly bleached at the base and cont a ins numerous small irons tone nodul es . Thi s overlies a tough brown c lay B horizon which may o r may not c onta i n c arbonate i n i t s lower lev�l�. W�a thered rock i s encountered b etween 18 and 24 inche s .
The following profile i s charac t er i s t i c o f these s o i l s :
( 2 mil e s s ou th of Kooemb a Siding ) -
0- 5 in. Greyj;sh b rown c l ay loam - l ight c lay9 very weak b locky to mas s ive 9 firm t o fri ab le 9 oc cas ionally b le ached a t the b as e 9 numerous s mall ir ons tone nodul e s 9 fairly sharp break t o
i I I I . I I
I I I I I ! .
I , '
B21 5-10 in.
B 2 2 10-17 in.
17 in. +
-27-
Brown medium clay 9 medium bloclcy 9 f airly tough9 s ome ironstone nodule s in upper s e c t ion1 gradual change t o
Greyi s h t o y e l l ow i s h b rown med ium o lay 9 med ium blocky tend ing mas s ive , very s light carbona t e .
Weathered shales and muds tone s .
•:
Plate 8 . Shallow solod ic s o i l 2 miles s outh o f Kooemba Siding , e a s t of Baralaba. The parent rocks are Permian shales and muds tone s .
�Balyt1Q�l_��t a :
Laboratory d ata confirm the s olodic nature of the s e s o i l s . The A ho rizon i s med ium ac id, the B2 1 s l ightly acid t o neutral and the B22 alkal ine. Magnes ium is the dominant exchangeable met a l cation i n the B ho rizon w i th exchangeabl e s od ium approaching s ignif icant l evels ( 9 per cent . of the tot al metal i ons ) . · Chloride and total s o lubl e salts are mod erat e ly high throughout the profil e ; available pho sphate is low.
Wattle is often the dominant vege tat ion o f t hese s o i l s w i th bo th s i lver-leaf and narrow leaf ironb ark also prominent. The ground flora chiefly cons i s t s of b lack spear , Qh12£i��1£Ul�ri s and s ome Kang aroo gra s s .
MinQ£_���££1�}�Q_§Qil� : A l s o occurring in thi s a s s oc ia tion a re small areas o f
brown o r ·g reyi sh brown c lays with a slight g i lgai microrelief . · Thes e s o i l s support an oft en dens e s tand o f brigalow and are s imilar t o tho s e des cribed i n Uni t 13.
Unit 10. Weakly Solodiz ed-Solone tz A s s o c i a t ion. ----------Gr.Qi�:=h:£� a -.gQ:;:�.QO-a££es-. ------·-·�
Throughout the r egion9 but mo re part icularly on the river ' floodplain9 there are numerous areas whe re surface drainage is rather res tric ted . On such s it e s s o i l s with an impeded internal d r ainage have d evelope d ; the ir profile morpho logy c ommonly d i sp lays s o lodizeds o lonetzic or solod i c feature s , a lthough fre Quent ly the s e are only weakly expre ssed . S o i l s s imil ar t o these are very c ommon in Queensland ( for inst ance the O �ky-Dow ie s o i l s of the Burdekin region are . closely related ) and s ince this general group of s o i ls has recently b e en more extens ively s tud ied in s outhern Queensland ( Goondiwindi-Tara
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I i
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I I
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region ) i t i s propo s e d to refer to them as weakly solod i z ed-solonetz s o ils to ma intain tm:i.fol�mi ty of nome nc lature.
On the river floodplain they o c cupy flat o r s l i g h t ly depl' C s sed s i te s that act as shal low d rainage l ines fo llowing heavy rainfa ll . Els ewhere the s o ils also charac ter i s e ar eas that pos s e s s s omevrha t res tricted surface drainag e . Mo rphologi cally , a prominent feature of the s e s CJ i ls is a dens e imperme ab l e c lay B horizon v1hich restricts int ernal c.1rainage and cau s e s waterlogged cond i t ions t o prevail i n the A hori zons fol low ing he avy ra infall ; this fac tor i s the explanation o f the 1 ' spewey 1 1 nature of . the s o i l s when we t .
The A hori zons are o f variable thickne s s , ranging from 3 to 10 inches but m� s t commonly averaging 4 to 6 inche s . The texturE is normally a c l ay loam but c oarser textured vari ant s do occur. Colour is usually a shade of greyish brown. A bleached A2 ho rizon i s often pres ent , moro part i cularly associated with the d eeper surfaced s o i ls but the occurrence of thi s horizon also appe ars partly related to the drainage c ondi tions of the s i t e , be ing more prominent in the les s well draine�1 n·reas . The se A hor i zons have an uns table s truc ture , be ing very bri t t le and tend ing to powdel� when d i s turbed.
The tough , dense clay B hor izon - grey-brown, brown or d ark gl'BY in colour , i s sharply d emarcated from the A, but c olumnar or pr i smat ic s t ruc ture i s o nly very weakly d eve loped , if at all . Mos t ly the s truc ture of the B hor izon is coarse blocky or mas s ive . Carbonate nodule s may b e present but more often o ccur deeper in the profile.
The s o i l s of thi s a s s oc i a t ion are very s imilar to tho s e d e scribed by G . D . Ht::.bblc 2. r:: 'l'ype s 6 , 7 and 8 at Moura , and Type s 9 and 10 The6dore . The fo llowing prof iles i llus trate their ma j or feature s : -
( i ) Profile appr ox ima t e ly 2 mil e s e a s t-south-east of Baralaba on Coolmn r oad �
A;�,. 0- · L� in • . Light grey i sh b rown c lay loam 9 s l ight platy , to ma s s ive , o r i t t l e p sharp change t o
Grey-brown heavy c la,;y2 ma,s $ ive and toue;P., g �'ad e s �. nto
·
Grey-brown heavy c l ay with s light carbona t e , f irm t o hard , grades into
BC 24-36 · in. Brown clay� moderate carbonat e 9 fri ab l e .
( i i ) Profile o f T�pe 7 of Moura Irrigation Area ( Description by G . D . HubbJ.e ) ···
Al · 0- 3
A2 3-:- 6
B21 6-18
B2 2 l. P. - : �
3 6-70
i:c..
in.,
in.
�--1
in.
Browni sh grey lo am.
Whit i s h g re�r J.oam to sandy loam.
Dark grey to black intrac table he avy c l ay.
� ark grey t o black heavy c lay with ve ry s l ight c a :�h ona t e .
D 2-rl�o: gre�r he 3.vy clay wi Jch s light c a rb ona t e .
Belc':: 70 inc�es the c lay i s l ighter in t exture and become E b rown t o yel low brown in colou r 9 from 110 to 120 inches is yel low clayey sando
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These soils were not sampled dur ing the pr esent survey as ade quate d ata were ava ilable from previous laboratory examinations. The A ho r i z ons a re norma l l y s l ightly uc i d , the B21 i a s l igh t l y a c i d to neutral, and the B2 2 and lower horizons mod era tely alkaline. Calcium· is the dominant exchange able metal cation throughout these soils� but in some B hol� izons exchange able sod ium may range up to 13 per cent. bf the tot a l .exchange able metal ions. Chloride may show s ome accumula t ion in the B horizons but values are not unduly high. Available phosphate in the upper levels of the profile is variable but is often high.
Vegetatio:g :
These soils are almost invari ably character ised by the prominence of sandalwood in the plant communi t ies. Associ ated speci es are chi efly poplar box with some coolibah or si lver-leaf ironbark.
'·'
MinQr Aee££iated_§£i1e :
The ch i ef minor so ils occurr ing in this associ ation as mapped are better drained types that are transitional or ·similar to the med i um textured alluv i al soils of Unit 3. In some more swrunpy areas grey clays with little or no horizon development may be present.
Extend ing northwards from the vicinity of Kiang a , there is a slightly e levated , d iscontinuous belt of d e eply w eathered Cainozoic sed iments that in most are as deline ates the margin of the river floodplain. These sed iments have g iven r i se to two quite distinct groups of soils , e ach of which possess a d ense timber cover. These two d istinctive soils can be r e a d i ly recognised on the ground bu t the i r irregular d istribution and fre quent lack of any d istinctive pattern on aerial photographs� together w ith their often inaccessible nature due to the dens e vege t ation , prevented the ir separation as two d istinct mapping units. Thus these soils were mapped as a single associ ation but the ir d i stinctive characteristics may be descri be d separately.
Solod ize d -Solon£��-Me0ber.
Solod ized-solonetz soils occupy the gre ater part of the associ ation, possi�ly some 70 per cent. They are formed on flat to mod erately sloping land , the latter chiefly occurring as the d issected margins of the unit where slopes of up to 5 or 6 per cent. are fairly c.ommon. In some localities a d istinct microreli ef is pre-sent , some of which is analogous to the typical g ilga i format ion ; in other cases d eepe r d epressions are of the sink hole type . However, this microrelief is not wid espread. Morpholog ically the ma j ority of the soils are typical solod ize d -solonetz types but consid erable vari ation may occur.
The A1 horizon is 5 to 8 inches thick 9 brown or grey-brown in colour and a sandy loam or sandy clay loam in texture. Its structure appe ars to be fa irly stable . Rathe r surprisingly , th ere is seldom a well d eveloped bleached A2 hor izon , but there is a ·
gradual lightening of colour of the Al with d epth with some rather more ble ache d material capping and lylng betwe en the d omed columns of the B horizon. Sharply demarcate d from the A horizons are the clay or sandy clay B horizons 9 the B2 1 often possessing a well d eveloped . columnar structure with domed columns up to 10 inches in d i ameter. (Plate 9 ) . Colour is grey-brown and the clay is hard
c · --. ,"'1
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and r athe r tough when dry and s t iff and plas tic when wet . The B2 horizon clay in some prof ile s i s QUite s trongly mo t tled orange and grey. The B 2 2 ho rizon i s a s a rule more s andy and i s l e s s hard and t ough ; s light carb onate s ome t imes occurs and increas e s w i th d epth. The deeper sub s o ils are a greyish brown to ye llowi sh b rown s andy clay wh ic h c ont a ins c a r b o nat e 1 o f t on to c ons iderab le depth. In one d e e p profile examined a fairly c o a r s e s andy c l a y loam t o clayey s and occurred b elow 8 feet .
Plate 9 .
•:
Solod ized-Solone t z s o il w i th colmnnar s t ru cture , 2t mil e s north o f Kianga S id ing.
The fo llowing profile 2. 8 mile s no rth of Kianga S id ing repres ent s a fairly t ypical s o lod ized-solone t z : -
B22
BC
c
0- 5 in. Darl( b rown s a n:'ly clay l o am, weal( blocky 9 hard when dry 9 sharply defined from
5- 12 in. Grey-b rown med ium c lay, slightly s andy , fairly .tough, co lumnar s t ruc ture with b road domes two inche s high and 10 inc he s di��e ter . Grade s into
12- 20
20- 48
48- 84
84- 96
96-144
in.
in.
in.
in.
in.
Browni sh grey s andy light clay 1 slight c arbonate , s omewhat fri ab le 1 merge s into
Greyish brown sandy med ium clay with abundant c arbonate 1 grad e s into
L ight greyi sh brown s andy med ium c lay9 fa irly t ough.
Light greyish brown to l ight brown s andy med ium c lay, trans i t i onal to
Light brown t o yellowish brown s andy clay loam tend ing clayey s and w i th depth, s ome ye llowish mot tling and occas i onal waterwo rn peb ble s .
144-180 in. Light brown coars e clayey s and w i th fairly numerous wat erworn pebble s .
In . s ome profiles t h e charac t eris t i c s olodized- solonetz mo l'phology is not y{e l l developed , there b e ing no s ign of any bleaching at the ba s e of the A horizon, a B1 horizon may be pre sent and there i s no c olurnnar struc ture in the B2. The following profile on the Moura-Baralaba road half a mile north of the Wonbind i turnoff i llust rates this type : -
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A1 0- 5 in.
B1 5-12 in.
B21 12-l8 in.
B22 l8-26 in.
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Brown clay loam� w eak blocky� f i rm to s lightly hard � grades into ·
Grey-b rown clay loam-light c lay 1 rather mas s ive , firm. moderately sharp change to
Grey c lay , slight ly sandy, ' coarse blocky to ma s s ive � hard and tough , grad e s into Greyi sh brown clay, sl ightly s andy � slight carbonate p s omewhat fr iable , merge s into
BC 26-36 in. Light grey i sh brown s andy clay with abundant soft c a rbona t e .
In the mo re t ypical solod ized-solone t z s o i l s the A hor i zons are sl ightly ac i d to neu tra l , the B21 hor i zon i s neutral with lower horizons moderately 'alkaline . In the Kianga profile des cribed above the ma terial below 60 inches becomes very s trongly acid. In this feature i t r e s embles many of the s t rongly g ilga i e d soils of Uni ts 1 2 and . l3. Calc ium is t h e d ominant exchangeab l e me taJ cation in the A horizons but in t'he B2 ma(Snes ium is often dominant , particularly in profiles w i th a s trongly deve lope d co lumna r s t ruc ture . Exchangeable sod ium may r ange u p to 20 per cent. o f the t o t a l met a l i ons i n the B2 1 hor izon. Thes e s o i l s are low i n chloride and total soluble s alt s . Ava i lable pho spha te in the A ho rizon i s variable but i s often qui te high. In the B hori zons it is low.
Y.2g�.'J!.§.ti2.!f..:_ The se solod ized-solone t z s o i ls support a mixed fores t
communi ty ( Plate l ) in which the chi ef speci e s are belah, brigalow ? poplar box , Dawson gum and yapunyah. Bo ttle tree and tree pe ar are commonly a s s oc i ated while small patche s of s oftwood s crub are s ometimes pr es ent.
12�_li��i c_Q1£�_Me�£££�
Deep s andy surfaced soils with s trong ly gleyed lower horiz ons oc cur t hroughout the unit although normally in small areas on s light ly higher por tions of the land s c ape . Thes e soils have been tentative ly referred to the low humic gley c ategory and i t is probable that they have forme d on coarser textured parent mate rials than the so lodized-so lone t z member . Thes e soils may o c cur on level s i te s but more commonly they are found on s l ight s lopes o r low ridge cre s t s . The ir int ernal d ra inage i s poor and the upper horizons o f the s o i l
· b e c ome s a turat e d fo l lowing he avy ra infa l l ; th i s cond i t ion i s a c c entuated on sloping s it e s due to lateral water movement from higher portions of the landscape.
The A hori zons are thick ( 20 to 30 inche s ) , and range in · texture from a loo s e sand or loamy sand to a s andy c lay loam. The lov1er part of the A horizon is weakly ble ache d and may be r egarded a s an A2• This i s sharply demarcated from an underlying sandy clay hor iz on which is s trongly gleyed ( mo t tled yellow , grey and red ) . This mndy clay i s very hard when dry and s tiff and plas t i c when mo i s t and evidently serve s as a barriel' to downw ard water movement. The .lower horizons are mo re fri able and may c ontain free c arbonate ; w i t h inc reas ing d epth the texture become s coa rs e r and waterworn gravel may be c orrunon. The fo llow ing profile 2 miles south-east of Baralaba i llustrates the fea tures of these soils : -
A1 0- 18 in. Brown to light b rown loamy s and , very weal( blocky, s o ft , merg e s into
A2 JB- 3 0 in. Light grey i sh brown fairly coarse loamy s and- sandy loam, mas s ive and s oft � sharp change to
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G1 30- 38 in.
G2 · 38- 50 in.
5 0- 80 in.
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Greyish brown s andy clay, strongly mot t led yellow and grey, st iff' and plastic , small black manganiferous c onc r e t ions up t o i inch d i ameter. Grad e s into
Ye llowi sh bl'OWn s andy clay 1 fairly s trong ly mo tt led dull yellow and grey1 s tiff' and plas t i c 1 nume rous black manganife rous s tains and flecking s 1 s ome small waterworn quartzose pebble s 1 Grades into
Ye llow-brown s andy· clay as above , s l ight t o moderate carbonate 1 grades into
80-100 in. Rathe r c oars e light browni sh grey sandy c lay with greyi sh and rus ty mot t ling 1 nwnerous b lack mangani� ferou s areas 1 slight c arbonate, moderate waterworn grave l.
6��1i c�1-��!� ...
The A horizons and uppe r part of the s trongly gleyed ho rizon are neutral with modera tely alkaline condi t ions below thi s . Calc ium i s the dominant exchangeable metal c ation throughout , with exchangeable sod ium very low. Chloride and salt valu e s are low in all horizons . The s e s oi ls may huve a fairly high available pho spha te cont ent in spit e of the s andy nature of the surface horizons .
Almost eve ryw he r e thes e s o i l s are charact e r i s ed by a dense softwood s crub vegetation in whi ch there i s much low d ense und e rgrowtl: ( Plate 3 ) . C' s c B. 8 'i.onal2y the.t'e are more open areas in whi ch quinine and 'bloodwood are the domi nant spe c i e s .
iwinO£_AS§OC igte£_§Q�l§ :
Sinc e thi s unit i s �ather a b ro ad one it i s only t o b e expect ed that int ermediate type s o i l s occur which d o not fall read i ly into e i ther of the c ategories d e s c ribed above . Some o f the s o lod i z ec so lone t z soils tend to grade into the g i lgaied grey c lays of Unit 12 · in certain areas while the l e s s s t rongly gleyed so ils may approach the so ils of Uni t 1 .
This is the mos t extens ive soil group in the surveyed region and occupi e s 27 per c ent. of the total area . The larg e s t and mos t uniform occu�"rences extend s outhwards from Baralaba t o Moura o n b o t h s ides of the river ; south of Moura they are mo re res tricted . The se grey or greyish brown c l ay soilu a re d eve loped on a virtua lly fla t landscap e 1 there frequently being no drainage outl e t s for ra inf'all runoff so that exc e s s water merely collects . in the deep gilgai depr e s s ions. The s e s o i ls are often c lo s e ly a s s o c ia-ted with tho s e of the previous unit but in ne arly all ins tances. occur at topograph ically low e r leve l s .
The mos t charac t e ri s t ic and st riking feature of the s e . clay so ils i s t he i r pronounced gilgai mic rorel i ef 1 the vert i ca l
interval be tween the t o p of t h e puff or b ank and the bot tom of the ·depres s ion may be as great as five fee t but commonly average s two to three feet ( Plate 10 ) . In the d eeper depre s s io ns water may pers i s t fo r s everal months fo llow ing heavy rain. Bo th puffs and depre-
m ions may be separate or cont inuous and although they are often sub� c ircular in outline j.rregular elongate forms are also common.
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,,· Plate 10. Greyish brown q lays with a s trongly d eveloped gilg a i
microrelief � 2 mile s e a s t of Gib ihi . Here the depre s s ions may range up to 5 feet in d epth. A brigalow fore s t is a s soc iated wi th t he s e s o i ls ; they become s t rong ly acid a t shallow depth s . ·
The so ils thus have t o b e considered in terms of puff and depress i on profi le s . The surface of the puff i s a grey or g reyish brown clay which may b e slight ly platy to medium granular selfmulching . Thi s quiclcly p a s s e s into a greyi sh brown o r g rey heavy c l ay which i s hard and tough when dry and s t iff and plas t i c when moi s t . It po s s e s s e s a coarse bloc�y s t ructure which b ecomes mas s ive or lent icular with depth. Clay skin surfac e s are often prominent. F ree carbonate may occur in the upper levels of many profiles and fine gypsum cry s t als may also be pre s ent i,n s ome s o ils .. The s e heavy clays extend to cons iderab le depths � at l e a s t 17 feet in o ne deep profile examined . Qui t e .often a pronounced orange or red and grey mo ttling become s evident in these lower l eve ls .
The surface s o i l o f the d epre s s ions i s fre q_uent ly a darker .grey o r grey-brown c olour due t o an ac cumula tion of organi c mat ter , s ome of which has been wa shed in from the surround ing higher puff s . Thi s surface soil often h a s a coarser granular s tructure t han t hat of the puff and wi th depth b e come s c o arse b loc k y . · The deeper subs o i ls are g enerally s imilar to tho s e of the puff. Fre e carbona t e and gypsum may again b e pre s ent in the upper levels of the profile. When dry the so ils of both puff and d epre s s i on c rack d e eply.
The following profile s i llus trate the chief fea tures of the s e s trongly g i lgaied clay s o i ls : -
( i ) St rong ly g i lgaied soil 2 miles ea s t of Gib ihi -. Puff prof ile ( s t rongly ac i d b elow 36 inche s ) .
0- 6 in. Browni sh grey heavy clay w i th sl ight pla ty surface then med ium b lo ckyp hard and toughp s light c a rbonate . Merg e s into ·
6-24 in. Greyish brown to brown heavy c lay� coar s e blocky , har d 9 slight c arbonate � mode rate gypsum cry s t a l s p merge s into
24-36 in. G:.."eyish brown he avy c lay w i th s ome i ll-defined rus ty mo ttle s and moderate clay skin development. Grade s into .
3 6-60 in. Brownis h grey clay w i th lent i cular s t ruc tural unit s and s trong clay skin deve lopment.
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Depres s ion profile - 3 to 4 feet lower $ 15 feet dis tant .
0- 18 in. Grey brown he avy clay9 s l ightly sandy with s ome organic matter, g ranular s urface then medi um t o coa r se blocky� merges into
18- 72 in. Grey to browni sh grey heavy clay9 s l ightly s andy , . tough cons i s tence.
·
( i i ) Puff profile 4 mile s north of the Baralaba turn-off on the Ivloura-Baralaba road. ( Soil s trongly acid below 24 inches ) -
0- l in. Grey heavy clay with weakly developed coar s e g ranular s t ructure9 g r ades into
1- 24 in. Grey heavy clay, coar se blocky9 hard9 t rac� of carbonate9 merges into
24- 48 in.
48- 60 in.
Browni s h grey heavy clay, sl ightly friable, merges . into •·
Greyi sh brown medium to heavy clay w i th s l i ght clay skin development , grades into
60-1 20 in?. Brown to light greyi s h brown medium to heavy clay with infre quent ye l low i sh and rus ty mot t ling becoming s t ronger· w i th depth. S t ronger clay skin development .
Below 1 2 0 inches and extending to 17 feet i s a l ight browni s h gr·ey medi'.lm to heavy cJ.ay which is prominently mot t led w i th reddi sh orange or rus t y colour s . C l ay skin development i s s t rong with some shear planes al so present . A t the lower leve l s a pronounced whi te s peckling i s common.
Mechanical analyses show tha t these soi l s range in clay cont ent from 45 to near ly 60 per cent . ; there may be an increase in cl ay content w i th dep th. F ield textures would often indicate a higher clay content than that revealed by analys i s . The react ion values of these soi l s are mo s t interes t ing. In common with s imilar soils examined elsewhere in Queens land , although the upper leveln of the ii:rofile are usualJ.y alkaline the clays generally become ext remely acid w i th dep th9 pH value s a s low as 4. 0 �ay be encountered a t depth s in the v icini ty of 2L� inches . Les s commonly the puff soils a re acid throughout $ a lthough only s l igh t ly so a t the s urface. However react ion values as low as pH 5 . 5 at 6 inches have been recorded. In the deep prof ile examined and described above pH va lues were les s than 4. 0 below 36 inches and reached the ext remely low va lue of 3 . 4 a t 17 feet.
Ei ther cal cium or ma�nes ium may be the dominant exchangeable metal cat ion in the upper ( alkaline ) sect ion of the profi le but with dep th a:n(} under acid condi t ion s magnec ium i s always dominant w i th exchangeable calcium often very low . Exchangeable s odium in these soils is often high and may rang e up to 25 per c ent . of the total exchangeable met a l j_ons. Chloride and tot al soluble s a l t s a1�e high ( up t o 0. 5. pe r cent . NaC l ) in some subsoil horizons , but in the upper levels of the p rofi le values are normal ly low. Ava i lable phos phate in the upper 6 inches of the puffs i s l:�w ( 30 to 40 p . p. m. P2o5 ) , although s ome higher values have been recorded. In the 6-12 ��h zone or below thi s values are mos t ly les s than 30 p. p. m. In the depres s ions and in areas s ub j ect to flooding higher levels of available phosphat e obta in.
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The s e c lay s a i l s everywhere support an dften d ens e brigalow fore s t . A s s o c i ated spec i e s inc lud e be lah, w i lga and s andalwood whi l e in some areas Dawson gum and yapunyah are common.
Minor�s so2_iated So;h!§..i.
The more impor t ant a s so c i a ted s o i l s includ e s ome type s wi thout gi lga i whi c h are trans i t i onal to the solod i z e d-s olone t z s o i l s o f the prev ious uni t . I n some flooded a r e a s t he re a r e much le s s s trongly gilg a i ed darke r grey c lays which are s imilar to tho s e of Uni t 5 . O c c as ional ly ther e are small areas o f the b rown g i lgaied clays too small t o map s eparately.
·
gD�1_12_. ___ �£Q�g_�!1gai�d_Q1QY-6££22.!g1!on� Q£Q�§_A rea_g�QQQ_gcr��� Brown c l ay s o i l s w i th a s trongly developed gi lga i mi cro
relief are not comnon in the region and o c cur only in one area to the no rth-eas t of Moura. Apart from their d i st inct ive c o lour the s e so i ls are in �o s t r e s p e c t s very s imi lar to the grey g i lgaied c lays al though in some areas there are v ar iable amount s of waterwo�n b illy and o ther grave l on the surf ac e and throughout the upper level s of the prof ile .
Gilgai mic ro relief i s a gain strongly deve loped , the depre s s ions ranging up to 3 feet in depth. The s o i ls have a b rown c lay surface which i s medium granular in s tructure . W i th depth a red-brown or redd ish eo lour p r evails and in the lower levels of s ome profiles a d i s t inct red and gl'ey mo t t ling i s evid ent . Carbonat e may b e pres ent in the upper hori z ons .
The follow ing puff profile 3i miles north-ea s t of Moura illus trates the chief fe ature s of thes e s o i ls : -
0- 12 in. Brown med ium clay, slight platy to med ium granular surface the n med ium blocky , s t iff and s l ightly plas t i c when mo i s t , t race of c arbonate , g.rad e s into
12- 24 in. Light brown med ium clay, s light to moderate soft carbona t e , c o a r s e blocky and hard when dry, s t iff and pla s t i c when moi s t , grad e s int o
24- 36 in. Light r e d d i s h brown heavy c l ay w i th lent icular s tructura l uni ts and f airly prominent clay skin deve lopment , trace of carbonate , grad e s into
36- 60 in • . Ligh t red to light b rownish red heavy clay , s t i ff and s l ightly plas t i c , grad e s into
60- 7 2 · in. Light red to o range he avy c lay w i th s ome red and greyi sh mo t t l ing and slight c lay skin deve lopment , merg e s i nto
72- 84 in. Light red d i sh brown med ium clay w it h i ll-defined redd i s h and g rey mo t t ling , slight clay skin development and o c c a s ional smooth shear fac e s , fairly d i s tinct change to
84-120 in. Grey to l ight g rey med ium c lay w i th red and rus ty mo t t l i ng . Frequent siriall mud s t one fragment s o c cur that are grey i sh ot b rowni sh in colour but oft en pos s e s E a light grey c lay coat ing . Clay skin d evelopment i s only weak.
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An�1xt ic§1_Q� ta :
In the above prof i l e the clay cont ent ranges from 50 p er cent. in the upper horizons to 60 pe r cent . in the 6-7 feet horizon. React ion valu es follow a similar patt ern to those of the grey clays with s trong g i lga i in tha t the soi l becomes strongly to extremely acid at relat ive ly shallow d epths ( below 36 inches ) . Ca lcium is the dominant exchangeable metal cat i on in the alkal ine horizons but magnesium becomes dominant w i th d enth. In these soi ls exchange abl e sod ium aga in reaches high l evels � { 14 per cent. of the tot al me tal ions in the 1 2-24 inch horizon� 35 per cent . in the 60-72 inch horizon ) . Chlor ide and tot a l soluble sa lts are also modera t e ly high in the subso i ls . These brown clays appear to have a be t te r avai l abl phosphate status than those of the prec ed ing group.
Ve�Q,!ion :_
These soi ls also support a dense briga low forest vege t a t io with assoc i ated wilga and sand alwood but eucalypt species only rare ly occur .
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M inor Associated Soi ls :
· In some areas th e brorm soi ls merge into the typical strongly g i lgaied grey clays whi'le in othel' inst ances there is l i t t le or no g i lg a i deve loped and the soi ls are simi lar to the brown clays of Uni t 7.
The s e unusual soi ls occur only in very l im i t e d areas� be i� restricted to near the nor th-east corner of the surv eyed are a . The topography is a ga in leve l or very slightly slopi ng but here the soil E are some t imes in fairly close proximi ty t o later i t ic residuals. ·
Red -brown clays with a s trong g i lga i microre l i ef ( here the depressio1 may be 4 feet d e ep ) do not appe ar to be a t all · co1mnon in Queensland and have not prev iously been d escr ibed .
The puffs ar e usually broad and leve l and the ir surface soi l is a red-brown fr iable clay loam or l i ght clay which ext ends t o approximat e ly 1 2 inches before merging into a red-brown light clay. Wi th d e pth � a redd ish brown to yellowish brown colour becomes prominent and the texture is apprec i ably he avier. Sma l l ironstone nodules may be pr·esent throughou t the prof i le and sca t t ered on the surface. The . d epressions have a re dd ish brown ur yellowi sh brown granular clay surface and this colour persists w i th depth. The texture of the upper horizons of the d epressions is heav i er than tha of the upper puff horizons.
The following puff prof i l e 7 mi l es sou th of Kokotunga i llust�at es some of the fea tures of these soi ls -
0-10 in. Red-brown clay loam- l i g h t clay9 we ak blocky � fairly soft and fri able � slight ironstone gravel and small concre t ions� merges into
10-24 in. Red-brown l i ght cl ay � med ium biocky 9 trace of ironstor nodules � merg e s into
24-50 in. Redd ish brown l ight clay , fa irly fri able � trace of ironstone nodules � merges into
5 0-70 in. Light redd ish brown to yellovJ ish brown med ium clay� fa int dul l red mot tling and numerous black manganifer· ous stains and flecks decreasing with d epth. Isolat • small ironstone nod ules.
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Analyt ical Da ta :
The above profi le showed s ome unusual fe atures on laboratory examinat ion. Reaction values are med ium acid to 18 inche s , neutral t o 50 inches and be low this s trongly ac id. Magnes ium is the dominant exchangeable metal cation throughout t he profi le 9 ( 70 per cent. of the total exchangeable metal i ons in the 10-18 inch horizon9 90 per cent . in the 66-70 inch z one ) . Exchangeable calc ium is ex tremely low a t depth. Exchangeable s od ium only reache £ moderate levels throughout the profi le ( 10-14 per cent . of the t otal exchangeable me tal cat ions ) . Chlor ide and total soluble salt leve l£ are moderately high in lower horizons .
Vegetation :
The se s o i ls support a brigalow fore s t ; belah o nly occur s sporad ically but wilga and s andalwood are common. Yapunyah i s ofte! prominent and there may a l s o be small area s of s oftwood s c.rub s pecie £ on the lighter textured more f,riable s o i l s .
Minor As soci ated Soils :
The chi ef s o ils associated with the s e gilgaied clays are lateritic red earths ( no gilgai 'mi crorelief ) whi ch have a somewhat s imilar profile but wi th a much g reater accumulat ion of irons tone nodules in t he upper. levels of the profile and a deepe r A hor i z on. Towards the i r wes tern margin the red -brown gilga ie d clays become brown in colour b efore merging int o the typical grey or greyish browi gilgaied clays of Uni t 12.
Uni t 15. Lateritic Red Earth Assoc iation. Gro s s Area 2.000 ac re s .
Lateri tic red earths o ccur only i n small loc ali s e d areas :!..n the surveyed region w ith the large s t s ingl e o ccurrenc e s i tuated ea s t of Mungi S id ing on the Moura-Bara laba road . The o ccurrenc e s appear to repre s ent are as of fairly c o a r s e Cainozoic s ed iment s that have b e en affe c t ed by later i t ic inf luenc e s . In general wher e under· lain by Cainozoic sed iment s they ar·e conf ined to the higher portions of the landscape .
The s o i l s are deep very freely drained red s andy c lay loams which may show a textural increase to a light clay with depth. In the vicini t y of 10 feet there may be a thin z one of red and grey mo ttled clay which show s s imi lari ty to the mo t tled zone material of a laterite prof ile . In o ther ins t anc e s the red fr i ab le materi al may be underlain by a much more indura te d light coloured s andie r material that displays only a very oc cas ional small red mot tling.
The fo llowing profile on the Moura-Baralaba road jus t s outh of the Mung i turn-off i s characteri s t i c : -
0-10 f t . L:ight r e d s andy c l a y lo am t end ing a l.Li_-;ht clay with depth9 weak b lo cky and friable 9 some waterworn pebbles g �a irly sharp change t o
10-12 ft . Red and light grey mo t tl ed light clay 9 fairly soft and s l ightly plas t i c 9 grades into
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12-14 ft . Light redd i sh brown clayey sand 9 fairly coar s e and uncompacted w ith waterworn grit . This is probably parent material .
14-16 ft . Light redd ish brown f airly coarse loamy sand 9 loo s e but w i th some wat erwo rn grit and quartz pebbles 9 s ome hardpan-like c emented ferruginous mat er ial and an occasi onal faint rus ty-brown mot t ling.
16 f t . + . Hardpan� evidently the c emented ferruginous ma terial ab ove .
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· These s o i l s were no t sampled but field t e s t s ind i c ate that the upper section of the profile i s neut ral to s lightly acid.
Vegetation :
The lateri t i c red earths support a woodland communi ty of grey bloodwood and s ilver-leaf ironbark with wattle and ouinine prominent in some local i t i e s . Occas ionally� as in the occurrence s north-we s t of Theodore � a softwood s c rub community may b e pre s ent.
Minor Associa t ed So ils :
Towards their marg ins the s e so ils lose the ir red co lour a! develop s trongly gleyed horiz ons at shallow depths , thu s approaching the s trong ly gleyed s andy s o i ls of Uni t 17 •
Uni t 16. Later i t i c Podzolic As s o c i at i on. -------- Q££��=Erea §�QQ-a�res_-. ---------
,.
Later i t i c podzalic soils are found only in an area sout�we s t of Baralaba on the left balli< side of the Daws on River. In t h i 1 region there a r e surface outcrops o f lateri t i c materials , more particularly to the west of the . region surveyed . The soils have formed on low s loping ridges and a prominent feature is their poo r internal drainage. Fo llowing rainfall a shallow p erched wat ertable develops and per s i s t s fo r cons iderable period s ; on the lower s lope s the re are often wide spread s ee page are as due to lateral water movement from highe r portions of the landscape.
The s o i l s are qui t e typical late ri t i c podzolic s such as aJ commonly d eve loped e l s ewhe re in Queens land ; they are similar to sucl soils developed on the c oas tal lowlands to the north of Bris b ane . The Al horizon i s a brown or dark b rown loam to s andy clay loam that norma:}.ly does no t exce ed 6 inche s in thickne s s . It grades into a lighter coloured A2 hor i z on9 light brown or ye llowi sh brown in colouJ but with. a s imilar t exture , and may be up to 12 inche s t hick. The A2 grades int o a yellowi sh brown B1 horizon which has a clay loam to light clay texture and may c ontain s ome small s oft irons tone nodule s , Thi s B1 grade s rather more rapid ly into the B2 horizon which is a yellow-brown light c lay and s trongly mot tled red , yellow and grey. Soft irons tone nodule s b ecome much more abundant and increas e with depth. In the vicini ty of four or five feet there is an abrupt change to a red and grey mot t led l ight clay which al though fairly soft when wet i s mo re indurat ed than the overlying horizons . Thi s mat eri al i s identi ca l w ith the red and grey mot tled clays that under · lie mo s t laterit i c podzolic s o i ls els ewhere in Que ensland.
The fo llowing prof ile 1 mil e west of Coolum s tation ( appr1 ximately 4 miles wes t of Baralaba ) was d es cribed from near the base of a low s loping ridge and al though no rain had fallen for over a month a perc he d watertable was pre s e nt at 36 inche s .
Al o.:.. 4 in.
A 2 4-16 in.
B l 1 6-24 in.
B21 24-50 in.
B2 2 50-66 in.
Dark brown to brown loam to s andy clay loam� very weak blocky , s of t , grade s into
Light b rown s andy clay loam, very weak b locky , soft , grad e s into
Yellowish b rown clay loam-iight clay , v.ret and s ligh tly plastic with s ome small soft i rons tone nodules � grade s more qui ckly into
Yellow-brown light c lay with red , yellow and greyi sh mo t t lj_ng and s oft irons tone nodule s becoming more abundant with depth� w e t and plas tic � fairly sharply separated from Red and grey mo ttle d l ight c lay with some hard ire s tone nodule s . Wet and slightly plaG tic ( grey por t ion) but much f i rms r than overlying horiz on.
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The s e s o :i l c a P e s l ight l y t o me d ium a c i d thr oughou t the pro f i l e and have 2 very low t o t a l c ont ent o f exchang e ab l e me t al c a t i on� . . C al c: ium i � d ominan t in the A1 h o r i z o n b u t b e low thi s magne s lum J. s the do:mno!l t exchang e a b l e me t al i o n w i t h e x c hang e ab l e c a l c ium v ery low.
Chlo.ridG and t o t al s o luble s a lt s are v e r y low and ava i l a b l e -pho s ph a t e r a r:8 e s from l ow to very low.
The s e s o i l s oupport a wood l and communi ty of s i lv e r - l e af i ronb arlc w i t h b l acl� s p e a r the d ominant gr a s s s p e c i e s .
I n s ome s l i g ht ly d e pr e s s e d a r e a s w i th a r e s t r i c t e d surfa c E d r a inage th ere m<:<y b e m:1a l l oc,c;:urr e nc e s o f typi c a l s o l o d i z e d - s o lone t � s o i l s w i th s h a l J.orr A hO l' i z,o ns ov e r l y ing a t ou gh dense c lay. The s e are as soci ated w i th B bull o a k v eg e t a t io n . O n the c r e s t s o f s ome high e r � � a g e s ��e re b e t t e r i nt ernal d ra inag e cond i t i o ns prev a i l l a te r i t i c r e d e a r t h s c ommonly o c c ur in smalJ. are a s .
I n 'G l1•:: l•C:ou.rG.-·G :i.. hihi r·e gi on and t o tho no r t; h -w e s t of The a d o pe s t ::: • o :c..:..,; l �' gJ.ey<:::d :J 8.1� :5 y s ur f a c e d s o i l s are deve l oped on a mo d e r a t <
· l y t o s ·tro::J[(LJ t;:r..l: :.'. j . <J. t L .-:�; J.and n c ape ( Pl a t e 1 1 ) tho t h a s forme d on r a the r c o et ri3 8 ·; ;'3;cl;\:j: ·c��, C & �. ;.�o z o :i.. c s e d 1ment s . A l t hough in mo s t s i t e s external G0G.inaJe is ��od ( s lope s may r a ng e u p t o 5 o r 6 p e r c ent , o r o c c a s i onally c r e a t c r ) -i�t..� :Ln"c e l'::'l.al d r a inage i s impe d e d b y a s t r o ng ly gleyed c lay hol":i.. z on r:!1 :L c h �i' t e n oc cur s a t f a i rly sha l l o w depths .
· A pe r·cheJ l'i a t e :, t a o l e �. s t1Y�i.3 often pr e s ent and s e epag e a r e a s f r e qu ently o c c1:. :• O!l s orr..e of t ho lo?r e r s l ope s .
'F' l ::tt e 1 1 . .:: : .1· • .::. <> .3 L\ rL, .::: 0 -:i f:S ::_ 0 ,y <:.d t.:;od z o l i c .:; o i l s 1 :nil::, ,, e s t o f M o u r a . T h e s o i l s a r e d ev e l o p e d on an undu l a t ing land s c ape and suppo r t ::t v c t; e c a t i o n of iv! o re toa Bay ash9 g rey b l o o d w o o d and s i �v e r - l e ar i ronbark.
The A ho r i z � nG are a light b r6wn to l i ght greyi s h b r own s and o r l o amy s £ m d r: �::·� .;h is c ome t im e s c o a r s e . 'l'he lovt e r pa rt o f the A ho r i z on � s �e 8��Y b ]. A o � hed and c ou l d b e r ega rd e d a s an A 2 • Thi s :� :' o h ar:>:l_y c>;:::�.:· c a ·c e d fl'Om a s t ro ngly gleye d c lay or s andy
· c l ay ho ri ;; w n w '--.. :1 c; �l i s mo t t led yellow and grey and o c c a s i onally b lu i s h grey " w i ·:: ;" r:i 8%> rl'. G ty ar e a s along ro o t chnnneJ. s , Thi s c lay i s hard Yths.t'l (i�y and s U :'f and pl::ts t i c whe n w e t·.
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The se general pPofile features ind i cate that thi s s o i l i s a member o f the me adow podzoJ. i c o r low humi c gley group. Howeve1• 9 i t is normally more s t ro ngly g leyed than the s o i l d e s c ribed in Uni t l as a low humi c rrley and fPe quently pos se s s e s a much thinner A hor izor.
. Thus to avo id confus ion thi s pr e s ent s o i l w i l l be :r.efel•.red t o o. s a gleyed pod z o l i c . The fol low ing prof i le % of a mile we s t o f Moura ne ar the top of a fairly high ridge is char acter i s t ic : -
. Al 0-12 in, Brown to greyi sh brown loamy s and 9 single grain and loo s e but with a s ligh tly compac ted s urfa c e 9 grade s into
A2 12-18 in. Light b rown loamy s and , s ingle grain9 loo s e 9 s harpl defined from
Gl 18-24 in. Yel low i sh g rey-brown c la y 9 s t rong ly mot tl ed ye llow , grey and some blu i sh grey with rus ty roo t channels 9 s t iff and plas t i c , grad e s into
G2 . 24-36 in. Ye llow ish brtnvn sa1idy clay9 les s s t rong ly mot tled and t end'ing to b e fri ab l e when mo i s t .
sna lyJ! i c .§!.LJ2�.:t.�!. The A ho rizons of these s o i l s are s light ly ac i d and the
mor e s trongly gleyed horizons are med ium a c i d . Calc ium i s the dominant exchangeable metal cation in the B horizon. The s o ils are low in chloride and salts and avai lable pho sphate is also low •
.Y�et.§j!;i.QQ :
The s e undulat ing s andy s o i l s support a tall wood land communi ty of More ton Bay a ch9 grey bloodwood 9 poplar box 9 s i lver- leaf ironbark and blue gum with s ome areas in which quinine and red a sh are prominent. O c cas ionally the1•e are pat ches of s oftwood s c rub.
M i!:J:QLS.�.§..Q.QJ.:Q.t.�.g_§Q;E.Q :
drainage o c cur. approach
On certain h igher port ions of the landscape where better c ond i t ions ob tain, small areas of lateritic red earths may Els e·Nhe re the s o i l s may become l e s s s trongly gleyed and tho s e des c ribed in Uni t 1.
:Q:!}_t:L.�-"--�.t).Q]:low §ton;r Soil :£>:�o c i at io!:!.!_ Q£.Q£>S _Are a_1.2...z.9_QQ ac re§.�
Th is i s a broad uni t c reated to inc lude tho s e s o i l s whict po s s e s s e it her a vel'Y thin s o lum or much s tone throughout the shallov prof i le . . The s e . shallow s tony s o i l s usually occupy the higher parts of the lands c ape and bare 1•o ck out crops are common. I t i s d ifficuli to g ive any gene ral des cript ion of the so i l s 9 in mo s t c a s e s they are clay lo'am to· c lay in textUNl but colour i s qui t e variable.
The so i l s · have fo rmed on a varie ty of p·arent rna te rial s b\ Permian s e d hnentary rocks are mo s t common, On the left b anl<: s ide oj the river d owns tre am from Moura sor.1e lat e :e i t ic s c arps and mesas have b een inc luded in this UDit as the s o ils a re very s hal low and ove rlie indura t e d ferruginous l a t e r i t i c material.
L ikew i s e qui t e a wide range of plant conununi ties o ccur 0 1 the s e �ke le tal s o i l s and it is not p o s s ible to give a gene rali s e d descript ion.
In general the . irriga tion potent i al of an are a of s o i l will depend largely on the fo llow ing cons iderat i ons . ( Not nec e s s ar i l
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arranged in order of importanc e ) .
( a ) Ti lth and s tab i lity of the upper 3 to 4 inch layer o f s o il.
( b ) (i:'htl g�no.N�l o O l'l.c'l i 't:. i o 'ft o :t t h tl m�;�, i :n P ti X't <::>f' t h o p .r- o t :t l ill QQWn to 4 or 6 feet.
( c ) Chemi cal aspect s of the s o i l .
( d ) The actual and po tent ial ground water s i tuation.
( e ) The g eneral nature of the land surface .
( f ) Clima t i c fac tors •
Factors other than the se may also b e of importanc e . Thu the d iff i culty of c learing exis ting vege tation may have to be cons id ered , as well a s the commandability of t he are a w i th r egard to i rr igation water. However in mo s t instanc e s the fac tors l i s t ed above are of ma j o r importance �and the s e may be bri efly d i s cu ssed . . . .
( a ) !J).. th nn.Q_ . .§tabili t:v Qf t h�]:!J2��L2_1Q_!±__inch_!:!g,y§_.r._of_§..Qi l :
I t has been d emons tra ted by exper i enc e in irriga tion area tha t one of the mo s t impor t ant cons iderat ions whi ch d e c ides whe ther a s o i l can be succes sfully irrigated or no t is based on the charac-
_ teri s ti c s of the upper part of the profiJ. e , which frequently corres pond s to the A ho rizon in nany S Q i l s . The import ant thing here i s the pe rmeab i l i ty under w ater und the har\lnes s or otherw i s e when dry. The d e s ir able sta te i s a stab l e 9 permeable 9 loo s e . cond i t ion and the oppo s ite , an impermeable very hard state 9 i s prohi b i t ive of any suc c e s sful i rriga t i on. These condi tions may b e .as s e s sed i n terms o f texture � s truc ture and c ons i s tence .
Light e r textured s o i l s have a g·reater range over which they are l e s s dependent on phys i c al propert i e s such as cons i s tence and s truc ture , but for clay loam and clay surfaced s o ils a d e s i ra bl e phys i c a l state o f the surfac e i s a primary requi s i te . Unde s i ra ble surface phys ical cond i t i ons preclude or rende r d iffi cul t suc c e s sful irr iga tion b ecaus e of s everal r e a s ons . The mo st important i s water pene trat ion9 a po or surface phy s i cal cond i t ion w i ll no t permit adequ water penetration into the s o i l . Also import ant i s the fact that w undes irable surface phys i c a l cond i t ions germina tion and plant e s tablishment prob lems ari se .
( b ) 1h�_Q�§.�!_Con.Qi1i9.!}_Q[_ih§._�gin_�Q£i_Qf_1h�Pro file :
I f i t ha s b een d ec ided after an examination of the surfac s o i l c ondi t ions as ind i cated above that a soil c an be irrigated 9 in general it is the nature of the s ub s o i l that de termines wha t crops can b e grown. Sub soil phys i ca l cond i tions a re important in that th cietermtne permeability9 root penetrat ion9 aerat ion, e t c . 9 and variou crops have differing toleranc e s to the s e cond i t ions . Some time s , however � sub soil c ond i t ions may be such a s t o prec lude the succ e s sfu growth of any c rop und e r irr iga t ion.
( c ) .Qhemi_£al �£l2�c t s_.Qf__:!!he SQil :
Undes irable chemical feature s in a soil are normally less impor t ant in irriga t i o n prac tice than phys ical fac tors be cause a s a rule they c an be corre c t ed more r e ad i ly. Often how ever an und e s irabl e chemi c al fenture i s d irec t ly reflected in the phys ical c ond i t io u well known ex�mple b eing the adver s e phys ical proper t i e s tha t ar0 imported to a so il by high amounts of t he s odium ion on the exchangE complex.
Pe rhaps the mo st important chemi cal aspect of a potent ia: irrigation soil is its salt c ont ent bu t again this is usually c l o s e :
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rela ted to such physical f actors as permeability and the pre sence O J ab s enc e of a watertab le . Exper i ence ha s shown that the gre at ma j o J ity o f s al t troubles a r e clo sely assoc iated with undes irabl e ground
. water movement � i . e . high w at ertab le development . If s o i l water movement is g enerally down and uway then the likelihood of s al t prob lems i s remote. I t h a s a l s o b een found . that impermeable s o i l s are much l e s s prone t o surfac e s al t ac cumulat ion than perme a ble s o i l s � thi s i s mainly due to the rate of c apillary r i se f rom a wate1 tab l e be ing related to b o th soil texture and soil permeabil ity.
To prevent s al t accumulat ion therefo re it i s e s s ent i a l tc preserve a desirable water balance , that is the ne t movement of water ( and t hu s also s al t s ) mus t be d ownward. However it mu s t b e remembered t h at exc e s s ive downward movement o f water may eventually
· lead to a high watert ab le and thus d efeat the original o b j e c t ive .
( d ) �he A£1�Ql_anQ_Po ten1i�1_Gr�un£_��ter_§i1�ation :
Because of its importance t o such facto rs as s a l ting and waterlogging of the plant· roo t z one the ground water cond i t ions of the s o i l have to be cons idered . This que s t ion has to be approachec from a much wider viewpo int � often a r egional appl'Oach i s nec e s s ary. Normally i t is the po tent ial gr..ound wa ter d evelopment tha t is go ing to be of import ance s ince the land s c ape i s going t o be m1,1ch wetter after i rriga tion than it w a s before and thus i s mus t be able t o accommodate and dispo s e of the extra water which i s going t o b e a6ded t o i t . The b e s t s i tuat ion i s one w i th a good s lope and an extens ive outfall.
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The burden which will b e plnced on the hydr aulic sys t em c the landsca:r;>e will d epend on ( i ) the proport ion of the l and to b e irrigated 1 ( ii ) the permeability of the s o i ls , and ( i i i ) the me thod by which the land is i rrigateg ( this also emb ra c e s the unwise u s e of irrigation w a t er ) . Regions of low pe rme� b i l i ty will no t need the underground drainage po tent i a l that a more permeable region would require and from the ind ividual s o i l point of v iew experience has shown that i t is almo s t invariably in the mor e permeable s o i l s that fre quent prob lems of high gr•ound water have been encountered .
( e ) The Gen�r�1_Tig1�r�of th�_Land_§�rfg� :
The mo s t impor tant aspects here are the s lope and evennes of the land and how extens ive the uniformit y of cond i t i ons . I t i s obvious ly des irab le t o have large expans es of even-surfaced, evenly� grad e d land . A s teep slope will make a relatively impermeable s o i l qui te usele s s , which however , would b e quite sui table in a fla t te r s i tuation. O n t h e o the r hand a highly permeable s o i l in a f l a t s i tua t i on would almos t certainly be overwatered. The amount of grading �equired is an import ant factor in t he s ucc e s s of an irr iga-tion pro j e c t .
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Land surface cond i t ions are also very important f rom the surfac e drainage point of view. It i s almo s t axiomatic that d i s pos of exc e s s surface water is e qually a s impor t ant a s its applic a tion. This a s sume s ma jor importance in regions characteri sed by high rainfall intens i tie s .
( f ) Clinm ti£ __ Q���id�r�t i£��
At tention mus t also b e paid to c l imat i c factors when a s s e s s ing the irrigation po tential of nn area of s o i l . R aini'all ( bo th amount and intens i ty ) , t empe rature and huri"ii d i ty have an obviou importanc e in decid ing wha t c rops a s o i l may grow if cond i t i ons are o the rw i s e sui table . Cert a in s o i l s whic h are sui table for a part ie� lar plant under one s e t of e nvi ronment al cond i t ions may not nece s s a.r ily be sui table under a d ifferent s e t of cond i t i ons . It ha s t o b e rememb ered tha t whi le the minimum water r e qui rement s fo r a c rop in E irrigation area c an be me t the contro l ove r exces s ive amount s of wai is much more d i fficult .
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The general principles on which are based any as ses s ment of soils for irrigation h ave been br iefly d i s cus sed . It now remains to cla s s ify the s o ils of the s urveyed area into various categories that indicate their irrigation potential. However ? s ince actual irr igation experience i s only available for s everal soils in the reg ion thi s mus t be largely induct J.ve. This h a s been attempted and i s s hown in Table 8 p in which the various soils hove b een comb ined into categor ies - lnnd use g roup s ? based on the variou s factor s that determine their i rr igation potential. Table 8 i s a s ummari sed cla s s fication of the various soils , a more complete discu s s ion to include some aGditional factor s i s now presented.
The soils a s s igned to t h i s category are confined to one a s s oc iation, the medium textured �lluvial soils (Unit 2 ) . These soils have succes sfully grown yarious crops and pastures in the Moura Irr igation Area and it is ,thought that little difficulty should be exper ienced in their succe s s ful utili sation. In most areas clear i-n!? <.>nd levelling problems w ill not be very great and many of the d raino.& lines tha t travers e these soils s hould be able to be utili sed to di s pose of exces s water. Wate� penetration s hould be good as most c the s urface soils have a fai rly s table structure p w ith the pos s ible exception of some clay loam s u rfaced types. On the lighter texture� soils however rather· frequent water ing of s hallow rooted plant s peciE may be neces s ary. Although clay sub soils are present field evidencE indicates that internal drainnge i s quite good and root penetration should not be af�ected. The presence of porou s s and beds at depth in some areas w ill have to be kept in mind as with exce s s ive use of i rr igation water thi s could lead to a high watertable development an< consequent danger of s alting problems although these soils ar'e not inherently s alty.
Initially at lea s t these soils s hould not require fertili· sat ion and it is con s idered that they should be suitable for a w ide range of crops and pastures. However p crops w ith rather s peciali set phy s i cal re quipemen t s such a s tobacoo and pos s ibly citrus may not be f3Ucces sful� ·
Again one soil a s soc i ation only i s as s igned to thi s category , the dark g rey clays (Unit 5 ) . 'l'hese soils have= been s ucces s fully irr igated at Theodore s o that exper ienc � i s available for thei bes t uti l i s ation. Although these soils have a v e ry heavy texture their structure i s good and adequate water penetration is po s s i ble if due attention i s paid to i rr igation methods. A feature of thes e s o il s i s a very slight g ilgai microrelief and thi s � together w ith the fact that they occupy rather lower portions of the lands cape and are thus subject to some pend ing of surface w ater ? neces s itates very careful levelling and g rading to ensure that follow ing irrig ation or heavy rainfall water does not lie on the s urface for any length of t ime 1 s ince when wet the internal drainage of these clays i s very slow . It also appear s that if these soils are put down under permanent pasture the slight g ilga i microrelief may again become evident after a pe riod of years even though carefully levelled in tr f i r st instance.
It i s not expected that watertable or s alting problems w : be encountered in thes e soils and from exper ience a t T.heodor•e they s hould be suitable for a fairly w ide ro.nge of crops and pastu res. The heavy· texture ensures a high water holding capacity so that the soils should not need to be w atered as frequentlY as those of Group
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The soils a s s igned t o this category are tho s e of the solodi zed-solonetz - low humic gley associat ion ( Uni t 11 ) . Two rathe r different soils are thus pre sent and although only one - the
· s o lodized-solonetz , i s c ons idered suitable for irrigation1 i t ocoup11 po s s ibly 70 per cent. of the assoc iat ion. No ac tual experience i s available as t o how thi s s o i l will behave under irr igat ion but d ry land agricul tural crops and pas tures have been grown successfully. The surface hori zons of these soils pos s e s s a relatively stable s truc ture and although a dense clay B horizon with columnal' s tructur1 is present field evidenc e t ends to indic ate that the int ernal d ra'inage is rather be tter than might be expected . However , the clay horizon does cause some t empOl'ary water logging and e specially on any · low er slopes lateral water movement may c ause s eepage areas .
The successful irrigation of these so ils w ill depend largely on the provis ion of adequate drainage 1 more especially on . sloping land . With this provis ion the s o il s shoul d be well sui ted fo r pastures and those crops which are tolerant of a wide range of sub soil condi tions . Experience with cotton at Theodore has shown tha t roo t development may be re s t ric ted by dense clay subsoils so th trials with this c rop may b e ne cessary b efore i t could be s afely recommended. I t i s doubtf'ul if' the soils would be sati sfactory for lucerne .
The other member of the associu tion9 the J.ow humi c gle;y soils , are characterised by a deep sandy horizon ( 20 to 30 inches ) which overlies a s trongly mottled ( gleyed ) s andy clay which badly impedes internal d ra inage . Thi s soil would be d ifficult to manage under irriga tion, very frequent light waterings , poss ibly by spray method s , would probab ly be neces s ary and the fertility status is r·ather low. At thi s · s tage i t s us e for irrigation is not rec()mmendE
I t may als o be mentioned that all soils in thi s category support a dense fore s t or s crub vegetation and thus c learing c o s ts are l ikely to be cons iderab le. In some areas the s olodized-solone1 soils pos s e s s a gilgai-like microrelief but this is not extens ive .
This c ategory includes the co arser t extured alluvial so� : assoc ia tion ( Uni t 1 ) and the lateritic red earths ( Unit 15 ) . The former soils are very fre ely drained s andy types that have been uti l ised to a certain extent at Moura. Their chief d i s advantages are the ir high water duty and rather low fertility. The soils hav• a low mois ture hold ing capac ity and frequent waterings would probab : be ne cess ary. Often the s e soils occur in the form of levee-like terraces but where found in flat s i tuations overwatering could lead to high watertable deve lopment . I t i s likely that only certain hi value crops could b e economically justified on the se soils 9 some t y should b e suitable for tobacco and c itrus but a t Moura luc erne has no t d�ne well on these soils .
The lateritic red e arths : only occur in very small are a s 1 s ome o f which may not b e c o�nandable. Phys ically these s o i l s are a ttrac t ive but again their ferti li ty would probably be low and the i water requirements rather high.
Three s o i l a s soc iations may be included in this categor;y the finer textured alluvial soils ( Unit 3 ) , the mi s cellaneous allu\ soils ( Uni t 4) and the weakly so1odized-solonetz a s s oc iation ( Unit 'l'he mo st important of the s e are the fine textured al luvial soils 1 these oc cur ad j ac ent t o the river and a t pres ent a re sub j e c t t o s e1 flooding, s ome of which i s due to local s treams and run-off and wi : not be easily contro lled . Drainage line s � swamps and depres s ion areas are prominent . Although many of the soils s hould be of hi�
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ferti l i ty often they are c lay loam or s i l ty c lay type s whi ch appe a r to po s s e s s a r u ther uns t ab l e s t ruc ture . Thi s would be expected t o d e terj, ora t e und er cul t iva t io n ahd J ead t o w a t e r pene t r a t ion and pl ant
· gorini na tion d ifficul t i e s . Thi s :� ; c q;parent in a s omewhat s imi l ar so i : which i s b e ing i rrigated a t the The odore expe r imenta l f arm. However some use could c e r t a i nly be mad e of the s e so i ls p rovided the f l o o d hazard were el iminated .
The mi s c e l l ane ous al luvial s o i l as s o c iat ion c ompr i s e s a very small area of rather v ariable s o i l s ju s t nor t h of The odore • .
Somewha t s imi lar r ema rks to the above a l s o apply he re .
The weakly so lod i z e d - s o lone t z s o i l s are clay loam surf� c ed types almo s t invar i ably cha ra c t e r i s e d by a vege t a t ion o f sandalwo o d . The s u rface hori z ons have a ve ry uns table s t ruc ture 9 b re aking d own t o a f in.e powd e r when d i s turbed and puddling when w e t . The .d ens e c lay sub s o ils impe de int e rna l d ra inage and pro b ably would r e s t r i c t rpo t development . Thi s has b een d emons t r a t e d w i t h c o t t on plants . Many . of t he s e s o i l s o c cur in s li ghtly d epre s sed areas in whi ch surface runoff co llect s . Exper ienc e hro s hown �hat s o i l s such as the s e are very d i fficul t to manage under irrigated c ond i t i ons and the ir u t i l i s a t ion a t th i s s t age i s no t re commend e d .
Thi s ca tegory inc lud e s thr e e a s s o c ia t ions 9 the b l ack e ar t hs ( Uni t 6 ) , the brown c lay a s s o c i a t ion ( Uni t 7) and the b r own and dark grey c lay c a t enary a s s o c i ation ( Uni t 8 ) . The s e t h r e e have many fea tur e s in c ommon. All are d eve loped o n an undul ating land sc ape with s lopes tha t may r ange up to 5 pe r cent . or o c c a s ionally gre a t e r . The t exture of the so i l s is nea r ly always a c lay and inte rnal d rainage i s somewhat slow. Thus on many of the s lop ing s i t e s it may be d ifficul t to ob t a i n a d e qu a t e water pene t l'a t i on, po s s ibly such i rr iga t ion ' ·
me tho d s a s the c ontour d i t ch may have t o b e applied on s ome of the s lope s , many of which p o s s e s s a s light l inear g i lg a i m i c roreli ef. Ad e qua t e d rainage will b e nec e s s ary for the low e r areas a s ' they are su b j e c t to surface wat e r ac cumu l a t i o n fol low ing he avy rainfall. Certain r idge cre s t s po s s � s s s o i l s t ha t are s hallow .
L i t t le expe rienc e i s ava i l ab l e for the u t i l i s a t io n o f heavy textured s o i l s w i t h slow interna l d r ainage on s loping s i t e s and t ri a l s may be nec e s s ary b efore the s e s o i ls c an b e s u i t a b J. :,.· u t i l i sed for i rrigat ion. I t may b e ment ioned that many of t he s e s o i ls a re a t pre sent u t i l i s ed for dry land agr i cu l ture .
This category includ e s the three s t rongly g i lg a i e d c lay soi l a s s o c iat i ons ( Uni t s 1 2 � 13 and 14 ) tha t suppor t a dens e fo re s t o f b r igalow and o ther s pe c i e s . The ma j or d i s advant age o f the s e s o i ls i s the exc e s s ive amount of leve l l ing and g rading that is ne c e s s a ry ( fo llowing clearing ) t o prepare the land for irr iga t i on. Becau s e of the i r v ery slow inte rna l drainage c a reful leve l l ing and grad i ng is a nec e s s i ty but exper ience has shown that after a pe r iod of ye ars the g i lg a i mi cror e l i ef t e nd s to r e appe ar unl e s s f r e quent cul t iv a t i o n i s pr& c t i s e d . The re i s al so a po s s i b i l i ty of br igal ow regrow th prob lems being exper ienc e d .
Chemi c a lly many of t he s e s o i l s a l s o pos s e s s und e s i r a b l e fe atur e s . F r e quently they b ec ome s t rongly t o ex t r. eme ly a c i d ( pH 5 . 0 or le s s ) at sha llow depths and fol low ing levelling operat ions t h i s ac id , infe r t ile , i nt r a c table c l ay would b e expo s e d a t t h e surfac e . O b s e rv a t i o ns a t G i b b e r Gunyah near The o d o r e where s imi lar s o i l � have b e e n lev e l l ed s how that e s tabli s hment of natural gra s s es i s def init e ly inh i b i t e d on such expo sed are as � even t hcmh here the sub s o i l s are no t a c i d . Al though many of t he sub s o i l s are high in s al t i t i s not likely that thi s wou ld be a pro b lem as on t he s e ra the r impe rme a b l e s o i l s high w a t e r t a b l e d evel opment would b e unlikely.
Fert il i t y medium to good. Ho o nlt dnn-gal' if w i s e ly 1 r l'1ijll t o d .
F e r t i l i ty medium �o goo d . Little o u l t dang o r .
Solodized-Solonctz aoilo are of mod 1um £ert i l i ty , othero would be ra thor low.
Fer t i l i t y �ay bo rather law.
Fer t i l i ty probably 1•ather low.
Fairly s table ourru c e , oub o o i l o of mod erato water holding capacity.
Heavy texture rendero cultivntion d i fficult but o t �ucturo i o good . High I'IU tor holding capacity.
S o lodl zed-Solonetz l1uvu dense c luy eubo oi l o but our£aco s t ruotul'E> io i'n i rly s table. Low humic glcyo unattractive phys i c ally.
Uppor horizons have very low mo i o ture hold ing capa c i ty.
A t trac t i\ o phyoi cally b u t mo i o ture capacity probably rather low.
Remarks on Land U s e .
Shaul� b e ouitable for puo turc o and a
·,yidc
runue of c ropo ( oxoopt t o\;,,Qa<,, � 11<1 \'>O ij o lhl ;.< o 1truu ) . Adoqunto surface drainage ar.<1 'uniform grading o r. � c ntial. Should
be oui tnbltl for fuirly wiclo range of o ropa und puo turo n .
Solod izcd-Solonetz sui ted for puo turco and loao faa tid iouo crapo , but low humio glcys generally unoui tablo for irriga-tion. ( Ad oquute dra ina�c nccoo oary on olope o ) . Do th thooe ooilo o upport 11 denoo fo r o o t or o o rub vegetation.
Theoe o o 1 l o �ould have a 'high nater duty with opecinliaod irrigation pructico no ceaenry. Probably only c e rtain high vuluo c rops could be cons idered.
Orten d i s sected b y d rainage l inea and O\Tampo .
D i s o e c ted b y ohullo'o'1 d r ainage chunnol·o .
Frequent ohallo,·: drainage l i nen nith ao aoo iated flooding.
Gently undulating, some flat arena. Linear gilgai on some a lopes .
Gently to moderately undulat ing.
Gently to modera tel y undulating. . Some flat nreao. Linear gilgni o n some elopeo .
Very flat bu t w i th o xtrome gilga1 microrelief in mo a t nre o.a ; ( depress-ions may range u p · to 3 or . 4 feet in depth ) .
Gently eloping.
J.lny be s trongly undulat ing.
Undulating
Usually steep elopes and dissected.
Mo o t areas oub j e c t to oovere flood ing from river and local a t reruno . Sub j ect to flooding by local a troam o .
Surrnce drainago often r e s tricted. Internal d ra i nage usually impeded.
Surface d rainage goocl except for some pending in lovr arona. Internal drainage usually slow.
In mas t arona sur-faoo run-orr collecto in depre s s i ons. Internal drainage very s lovt.
:t::··V>rnal drainage b ,,,ily imped e d .
Internal d rainage badly impeded.
Internal drainage reotricted.
Normally good
Should b e medium to high fertility.
Should b o of medium fert i l i ty.
Medium t o low fert i l i ty.
Fe r t i l i ty medium to good but phosphate s t a tus appeara rather variable and may 'be low.
1\edium to lo;r ; fer-t i l i ty except for oome flooded arena. Sub s o i l s s t rongly acid , often at shallow depths. Sub-surface salt often high. i
Low fertility! I
Low f ertili tyl
Probably of low rertility
Variable.
Phya i c n l cond i t i o n ort o n p o o r w i t h unotnble s t ructure.
Rnvid c'hang e o from ve1•y rrce to poor drainage duo to textural vari a t ion. Una tab lo au1•face s tructure , dense impermeable auboo il.
Heavy texture but g e nerally good otruc ture . Moderate to high mo i s ture 'hold ing cnpnoity. Soils on ridge create may be ehnlloYI.
Tho heavy c layo are usually dense and afton poorly a truo-tured • 1fo i o ture holding capacity moderate to high.
A t tractive but sub-ooil wa terlogging common.
Loose sandy surface · vti th tough dense
clay sub s o i l s .
Struo turnlly un-attractive.
Normally with s tone / . throughout. profile.
Limited ouitab i l i t y for pnotureo and oomo crops i f flood hazard c an be controlled. Limited ouitab i l i ty due to flood ing and o o i l variat ion.
Unsuitable for mo st crops and pastures due to poor p'hyo ionl prope r t i e s .
Heavy tex ture, low . permeability and degree
or o lope will nec e s s i t a t e spec inli oed irrigation methods but otherwise would be ouited for c e rtain o ropa and pas tures. Much of thio land is nt present u s ed for dry land agriculture.
The gilgai microrelief and other und e s irable p'hys ionl and chemical featuroo makes these soils una t tractive for uoe under i rrigation. Most arena ·are densely foreo ted •
These are unattractive i rrigation soils duo to their ouecep t ib i li ty to wat erlogging, low fertil i ty and und e s i r-able oub o o i l phyo ioal cond i tion.
These aoilo canno t b e considered due to the w nhallow a tony naturo. Much of the area i o not cotrurulndnb l o .
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In view of the above problems it is recommended . that these so ils should no t b e c ons idered for irrigation at pre sent 9 certainly · no t until further experience of handling them i·s available from the pre sent development a t Gibbe r Gunyah.
The laterit ic podzolic soils ( Unit 16 ) and t he gleyed podzolic s � ils · ( Unit 17 ) may b e �ons idered toge ther. Both are charac terised by a badly impeded internal drainage which renders . them part icularly susceptible to waterlogging even though they occu r on sloping s i tuat ions . The rather loose s andy nature o f the A horizons of the gleyed podzolics would make efficient watering difficult. The se so ils frequently occur on moderate slopes with areas of flat land rather limited . ·
Both soils have a low fertility s tatus and their irrigation development is no t recommended .-
This category compr ise s tho se soils which are e ither too shallow or t oo s tony for any form of agricultural development. Many of the occurrenc e s are not cornmandable and slopes in some areas may be s teep.
The soil and land us e reconnaissance has shown that in the surveyed reg i on the re is probably a gro s s area of at least 1509 000 acres that could be read i ly utili sed for irrigation. Of thi s at lea s t ha l� should be land on which l ittle trouble would be experienced ! in irrigat ing a wioe range of crops and pas ture s . These are gros s I areas however and ab tual areas will nece s s arily be s omewhat les s . · l
I
The d i stribu t ion of the better class land is a fac tor of I some importance and may b e briefly considered. . From a s tudy of the maps i t is apparent that the b e t ter so ils 9 in particular Group A ( Unit 2 ) 9 are confined to the r iver floodplain and Group A has i t s grea test development . in the Kiunga-Harcourt s e ct ion. The s o ils of ·
Group C ( Unit l l ) are also prominent in t his region but occupy higher land away from the river floodplain. If it were not for this group there would be l i t tle advantage in diverting from the or iginal scheme of utili s ing only the r iver floodplain.
One d i sadvantage i s the remo tenes s of the bet ter land from · the ac tual s torage s i te . Ups tream from the vicinity of Kianga 9 and in particular ups tream from Theodore 9 ther0 are only limi ted areas . of land that warrant consid erat ion. · A pro blematical group of soils has a wide spread occurrence in the Nipan-Oxtrack Creek se6t ion9 these are the undulat ing clay s oil s of Group 1.<' 7 many of which are at present cult ivated extens ively for dry land agriculture and may not wa1•rant I development for irrigation on e conomic grounds .
A s tudy of the maps reveal certain o ther fac t s . I t i s obvious tha t there i s l i t tle land worth developing o n the left bank s ide except immediately ups tream from the present Moura Irrigation Area. Also there is l i t tle to be gained from the proposed extens ion of the commandable area toward s Banana as thi s region is largely occupied by the s trongly g ilgaied clay soils which are cons idered ent irely unsui tab le for irr iga t ion.
Mention must also be made of the flood hazard. I t c an be accep ted tha t cons t ruc tion of a s torage s i t e will largely prevent any flooding from the river i t s elf9 a t lea s t as far downstream a s Mimo s a Creelc · june t ion7 below which there may be some doubt . . How ever local f'looding from such tributarie s as Boam9 Castle 9 Lonesome and
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Kianga C reel<s will have to be cons idered and 'prevent ative measures may b e neces sary.
If it i s decided to proceed with the proposed irrigat ion scheme it is recommend ed that e a rly cons id erut ion be given to the e s tablishment of experimental trials with various irriga ted crops and pa s tures on cert a in soils which will occupy . the mos t prominent par t in the scheme . In thi s regard i t i s unfortunate that the pres ent experimental area at Theodore i� situated on a s o i l that is far from be ing charact eri s t ic of a large propor t ion of the area that will · be irrigated .
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Finally 9 . a referenc e may b e made · to the purpo se of the a c c ompany i ng maps . The accuracy of the soil unit boundaries is rel�t ive to the s c ale of the map . The soil map is meant to be a reconnaissance interpretation showing the d i stribution of the various ma jor s o ils and a s such is no t to be used as a basis for farm de s ign ·
by inflating the s c ale and transferring the present boundarie s .
I t i s d e s ired t o acknowledge the a s s i s tance of those personE and orGanisat ions who readily c o-operated in this work. The Irrigat i o n a nd Wat er Supply Commi s s ion made available ael'ial photographs and any nec e s sary maps or plans . 'rhe Department of Agriculture and Stock ( Plant Nut rition Section) conduc t ed the s o il analyses and thank s are : due to those officers 9 Mes srs . I . Fergu s 9 J. Hughe s and E . Rose 9 who 9 . under the leadership of Mr. c . R . von St ieglitz were respons ible for the analytical worl< and helpful comment s and c rit ic i sms of the data. · . . Mr. A . Nagle of · the Department accompanied the writer on cine inspectio:r: of the area and gave freely of his knowledge and experienc e of irrigat- ·
ed agriculture in the region.
Mr. G . W . Tweedale of the Geological Survey a s s i sted the writer in the interpre ta t ion of some of the geological problems 9 and climatological data w ere readily made availab le by the Queensland Divis ion of the Commonwealth Me teorological Bureau and the Irr igation and Wa tel' Supply Co:mnis s ion.
