AGFACTS AGFACTS AGFACTS Getting the best from old man saltbush Agfact P2.5.43, First edition Brett M Honeysett, Research Agronomist, Peter L Milthorpe, Senior Research Agronomist, Margaret J Wynne, Clerical Officer, Agricultural Research & Advisory Station, Condobolin ORDER NO. P2.5.43 AGDEX 136/10 INTRODUCTION Awareness is growing of the need for perennials to be re-introduced into the landscape, to stem, or reverse, the rate of land degradation. However, reintroduction of perennials into agriculture will not occur unless they have the potential to provide positive financial returns or demonstrate significant positive environmental benefits. Forage shrubs are a group of plants that offer this potential, particularly old man saltbush (OMSB). Conflicting perceptions about the value of OMSB to the pastoral and farming industries have developed in recent times and these need resolution. Disappointing experiences with OMSB usually stem from unrealistic expectations of the potential of OMSB or the level of management that prevailed. This Agfact outlines the potential of OMSB for each of the different functions that it can fulfil in its capacity as an environmental or productive plant. It is important that the reader is focussed on their reason (or reasons) for wanting to establish plantings well before commencing operations, particularly if cost recovery is important.
Transcript
AGFACTSAGFACTSAGFACTS
Getting the bestfrom old mansaltbushAgfact P2.5.43, First editionBrett M Honeysett, Research Agronomist,Peter L Milthorpe, Senior Research Agronomist,Margaret J Wynne, Clerical Officer,Agricultural Research & Advisory Station,Condobolin
ORDER NO. P2.5.43 AGDEX 136/10
INTRODUCTIONAwareness is growing of the need for perennials to bere-introduced into the landscape, to stem, or reverse,the rate of land degradation. However, reintroductionof perennials into agriculture will not occur unless theyhave the potential to provide positive financial returnsor demonstrate significant positive environmentalbenefits. Forage shrubs are a group of plants thatoffer this potential, particularly old man saltbush(OMSB).
Conflicting perceptions about the value of OMSB tothe pastoral and farming industries have developed inrecent times and these need resolution. Disappointingexperiences with OMSB usually stem from unrealisticexpectations of the potential of OMSB or the levelof management that prevailed.
This Agfact outlines the potential of OMSB for eachof the different functions that it can fulfil in itscapacity as an environmental or productive plant. It isimportant that the reader is focussed on their reason(or reasons) for wanting to establish plantings wellbefore commencing operations, particularly if costrecovery is important.
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BACKGROUNDHistorically, the �saltbush� country has been held in highesteem by pastoralists, especially the sheep graziers(Figure 1). However, recent research using shrubsgrown on saline land has cast doubt on the value ofshrubs such as OMSB as a fodder. Forage shrubs havea multi-functional role and their many attributes, bothpositive and negative, need to be considered carefullyin assessing their potential. Some of the attributes ofOMSB are listed in Table 1.
requires an addition of a high-energy feed source tothe diet if maximum production is to be achieved,especially if the leaf has a high salt content. This canbe in the form of good quality grass pasture or grain.
ABOUT OMSBSuitable growing areasOMSB appears highly suited to a broad regionthrough central NSW (Figure 2). It is unlikely that �onfarm� plantation development of shrubs will takeplace in areas receiving less than 300 mm annualaverage rainfall unless there is supplemental wateravailable due to unreliability of rainfall and lowproduction potential. Hence the 300 mm isohyet isseen as the approximate western limit for plantationstands. The eastern limit for plantations is about the350 metre altitude line, which roughly follows thebreak between the slopes and tablelands. Above thisaltitude the winters are too cold and long, and thesoils become less suitable. Plants are usually dormantfrom late May to late August as little growth is evidentwhen mean daily temperatures drop below 13°C.Optimum growth occurs between 30�35ºC. OMSBwill grow on most soil types, although production ispoor on heavy clays and the plants prefer alkaline soils.They do not tolerate highly acid soils (pH<5). Theplants are very drought tolerant and provide a sourceof green feed year-round with no loss of feedincurred through trampling. Growth is driven by therainfall received as plants respond to wet periods bycontinuing growth at a steady rate well into the nextdry period. They will tolerate shallow, intermittentflooding, but not deep or prolonged inundationduring the summer.
Competitive abilityOMSB is a poor competitor as a seedling and itsnatural distribution is restricted to those soils where itis able to establish sufficiently to maintain itspopulation. When establishing the seedlings it isimportant to realise that they are non-competitive withother species and must be protected from nearbypasture and weeds during the establishment phase.Cropping lands are ideal areas to establish stands asthey are often free of weeds and stumps. Also littleadditional machinery is usually required by farmers forestablishment and management of shrubs.
It is extremely salt tolerant and will grow in mostsaline environments (<25dS/m), but the rate ofgrowth declines as salt levels rise. Production in thesesituations is usually markedly lower than in similarnon-saline areas where good pasture or crops are ableto be established.
Figure 1. A remnant stand of OMSB that has persisteddespite grazing by rabbits and domestic stock. Noterecent recruitment of young plants and excellent pasturecover.
TTTTTab le 1 . Some potent ia l uses o f OMSB when grown onab le 1 . Some potent ia l uses o f OMSB when grown onab le 1 . Some potent ia l uses o f OMSB when grown onab le 1 . Some potent ia l uses o f OMSB when grown onab le 1 . Some potent ia l uses o f OMSB when grown on
non-sa l ine and sa l ine so i l snon-sa l ine and sa l ine so i l snon-sa l ine and sa l ine so i l snon-sa l ine and sa l ine so i l snon-sa l ine and sa l ine so i l s
A t t r i bu teA t t r i bu teA t t r i bu teA t t r i bu teA t t r i bu te Non- sa l i neNon- sa l i neNon- sa l i neNon- sa l i neNon- sa l i ne Sa l i neSa l i neSa l i neSa l i neSa l i ne
so i l sso i l sso i l sso i l sso i l s so i l sso i l sso i l sso i l sso i l s
Productive capacity Moderate Low
Environmental benefits Moderate-High High
Suited for grazing with pasture Yes N o
Extends feed availability High Low
Value as sole drought fodder Marginal N o
Management needs Critical Not socritical
As well, OMSB grows more slowly than annualpastures, but offers a more consistent supply of feed.The quality of feed it supplies makes it suitable for usein a production ration rather than as droughtsustenance as the concept of using forage shrubstands as living haystacks has little appeal with mostlandholders. Rather they see stands as requiring diligentmanagement and are best used as part of a wholefarm management strategy. Stands need to be grazedregularly to maintain plant vigour as well as keepingthe plants within grazing height of the animals. Thehigh protein, moderately digestible nature of OMSB
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AttributesOMSB is a woody perennial shrub that grows toabout two (2) metres tall and four (4) metres indiameter in its natural environment. It is extremelydrought and salt tolerant and is long-lived (greaterthan 100 years). Part of its drought tolerance is due toits ability to accumulate salt in its leaves as it extractswater from the soil, consequently leaf material is veryhigh in salt compared to most other pasture species.Once established, the plants provide shelter and highprotein forage for animals. Off ground feed in theform of green leaf is available to animals overconsiderable periods, often extending into prolongeddry or drought periods.
Ener g yResearch has shown that saltbush grown on non-salinesoils still has a high non-digestible componentpredominantly consisting of ash. Energy is calculatedon a dry matter basis, which incorporates ash, whichactually contains zero energy. Energy needs to becalculated on the dry matter portion minus the ash(Table 2). The ash content of most saltbush on nonsaline areas may vary between 10�30% (average 15%)
depending on soil characteristics, and may be as highas 40% on highly saline areas. Accordingly energyfigures calculated on dry matter which includes ash areactually only 70�80% of the figures shown.
ProteinAlthough saltbush has similar crude protein content tolucerne (Table 2), approximately 50% of this exists asNon-Protein Nitrogen (NPN) which can only beconverted to digestible protein when there is a goodsupply of energy available. Saltbush has a protein levelwhich can exceed 20%, but due to a lack of energysupply when fed as a full ration, approximately sixtypercent (12�13% crude protein) is utilised.
SaltThe high salt load of saltbush (>10%) compared tonative pasture (3�6%) plays a major role in its poorutilisation. It is suspected that the high salt content ofsaltbush reduces the absorption of Volatile FattyAcids (VFA � a major source of energy) in therumen, possibly due to either impairment ofmicrobial activity or shorter residence time of feed inthe rumen due to higher water intake(Weston et al, 1970).
Figure 2. Area suited to plantation establishment of OMSB � west of the 350 metre elevation (above sea level) to thewestern edge of the main cropping area.
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The need for a mixed dietSheep can tolerate approximately 150 g of salt a day(cattle less) (Master et al 2001) before productivitydrops. At a concentration of 15% salt, their maximumintake would be reached after eating 1 kg of saltbushdry matter, 0.5 kg below their feed intakerequirement. This also assumes the other dietarycomponents are salt-free and illustrates the need toprovide other sources of feed with saltbush to dilutesalt intake to achieve optimum production.
Production potential in non-saline soilsProduction patternsProduction following establishment of woodyperennials is often more rapid than that experiencedover a longer production period. This is due to theuntapped nutrient and moisture supply deep in the soilprofile beyond the reach of annuals. It usually takesabout four years for the stands to utilise this resource,resulting in an inflated production from the stand.This may be extended if seasonal conditions havebeen above average or the area flooded, but once theresource is depleted production then becomes afunction of incident rainfall. On most soil types ediblematerial produced is about 4 kg of leaf and twig permillimetre rainfall per hectare. For example, annualaverage production from a stand (of 2500 plants/ha)in a 400 mm rainfall zone would be about 1.6 t/ha.However, this would vary depending on the patternof distribution and intensity of rainfall eventsreceived. Prolonged heavy rainfall that wet deep intothe profile promotes the greatest response, especiallyif the rainfall is in summer and conditions are humid.
By comparison, lucerne inthe same environmentproduces about 7 kg/mmrainfall/ha.
As the stand ages,production may drop asmore wood accumulates inthe stand and has to bemaintained by the plants aswell as an increasedlikelihood of nutrientdepletion.
Rapid estimates of feedon handGood management requiresthe ability to quickly assessthe amount and quality offeed that is on hand at anytime. When using OMSB aspart of the ration it is alsoessential that the amount of
pasture available to be used with OMSB is alsoknown. This section describes some quick techniquesthat can be adopted to assist in getting a betterestimate of the amount of feed on hand for bothpasture and shrub.
� PasturesQuick estimates of how much feed is on hand can bedone in several ways. The most accurate and timeconsuming method is by cutting quadrats andweighing the samples. But, they say a guess is the bestmethod if it is right and a lot quicker. The method weuse is not far removed from that. There is no need toknow production to the last kilogram so we have abroad-based approach where we estimate productionon a square metre basis and convert it to tonnes perhectare (Figure 3).
Figure 3. Divided metresquare quadrat used toestimate pasture production.The shaded section selectedas the most representative ofthe pasture.
One hundred grams (100 g) of production per squaremetre is equivalent to one tonne per hectare. A goodhandful of dry pasture weighs about 25 g, but if thepasture is green some adjustments are needed to thecalibration.
Using the Prograze method of throwing a squaremetre quadrat and selecting the most representative
Table 2. Nutritive values of selected feed stocks.
Species Metabolic Energy Crude Protein Digestibility(MJ / kg DM) (CP%) (DMD%)
Annual grasses (dry) 4–6 4–7 44–80
Perennial grasses (dry) 7–9 8–12 51–60
Medic pasture 7.5–11 16–20 50–77
Wheat 13 12 86
Oats 10.5 10.5 73
Lucerne hay 8.5 17 63
Oaten hay 9.3 5.8 54
Saltbush 8–11a 15–20b 55–70
a – energy calculated on total dry matter minus ashb – Up to 50% of N exists as non–protein nitrogen which is not readilyutilised without adequate energy
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quarter is a good method to adopt. The first step is toestimate how many handfuls there are in the selectedsquare (the shaded area in Figure 3). That will tell youthe pasture on hand, for example, 3 handfuls wouldbe 300 g/m2 (4*25*3) or 3 t/ha.
� OMSBThe simplest and best method for estimating availablefeed of plantation stands of OMSB is by measuringthe diameter of the plant. This is closely correlated tothe amount of edible forage. You will need tomeasure at least 15�20 typical plants in the paddockand calculate the average diameter from these. If thereis a lot of variability in plant size, it is a good idea tomeasure in a few locations around the paddock.When measuring the diameter ignore single brancheswhich protrude. If you want to get an idea ofproduction over time measuring the same markedplants each time may be an option.
This method can be applied to plantation stands ofOMSB provided the following management criteriahave been adopted:
1) plants are grazed at least once annually and thenspelled until fully re-leaved.
2) plants between 35 cm and 250 cm in diameter arewithin the range which this method is effective.
Plants which have grown above sheep grazing height(> 1.5 m high) can have a substantial amount of leafmaterial at the top of the plant (up to 300 kg/ha) andif it is not removed by slashing or pruning it willreduce total production especially in the lower portionof the plant and give a misleading estimate.
Estimating yieldEstimating the yield of edible forage can be achievedby one of two methods once average plant diameterand stand density (plants per hectare) have beencalculated. Plant diameter is estimated by taking aseries of measurements (say 10) from typical plantswithin the stand and averaging.
� Refer to Table 3 for appropriate diameter andplanting density (no need for calculations), or
� By using the following equations:
Edible Dry matter (g/plant)= 9.5 x (diameter in cm ) – 340
The next step is then to multiply that value by theplant density of the stand.
Edible dry matter (kg/ha)= (g/plant x planting density)/1000
e.g. if plant density = 2000/ ha and average shrubdiameter = 1.10 m
9.5 x 110 � 340 = 705 g/plantto calculate kg/ha, multiply by planting density anddivide by 1000
= (705 g/plant x 2000)/1000= 1410 kg/ha
A correction may be needed periodically to accountfor deaths.
Criteria for stock removalNot all of the edible material should be utilised andgrazing should cease when there is 5�10% remaining(Figure 9). This will ensure rapid recovery by theplants and it is vitally important that leaf is retained inautumn grazings to assist plants to get through thewinter dormant period. Repeated severe defoliationswill result in plant deaths.
Fertiliser needsNitrogen is likely to become the first nutrient to limitgrowth as there is a big demand due to the highprotein content of OMSB leaves. Phosphorus mayalso need to be added to maintain potential growth,particularly on acid soils where plant available P levelsare low. To ensure that growth is not limited by lackof nutrients, it is possible to monitor leaf nutrientlevels and add fertiliser as required. It is also importantto be mindful of the underlying pasture and itsnutrient needs. A dense actively growing pasturesward can seriously deplete availability of nutrients toOMSB and restrict growth. At Condobolin, a pasturesward of 1 t/ha that grew during the spring periodcompletely inhibited any OMSB growth in newlyplanted seedlings.
IS OMSB THE RIGHT PLANT FORYOU TO GROW?When introduction of forage shrubs is contemplateda complexity of issues need to be considered by thelanduser. Potential users need to understand theattributes that forage shrubs bring and how thebenefits, or limitations affect not only the short-termproduction goals, but also the long-termenvironmental well being of the landscape. Asummary of the many attributes of OMSB is listed inTable 4.
Integration with other farming practicesThe presence of OMSB can have a positiveenvironmental impact on the whole property if it ismanaged wisely. Tactical grazing strategies that useforage shrubs as feed sources to allow spelling ofother paddocks at critical flowering and seeding timescan result in greater diversity and/or improvement in
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Tabl
e 3
. E
stim
atio
n of
OM
SB y
ield
(kg/
ha o
f ed
ible
leaf
and
twig
s) u
sing
ave
rage
pla
nt d
iam
eter
(cm
) and
pla
ntin
g de
nsit
y (p
lant
s/ha
)
Num
ber
of p
lant
s /
hect
are
Dia
met
er (c
m)
15
00
10
00
15
00
20
00
25
00
30
00
35
00
40
00
50
0.1
39
69
13
92
08
27
83
47
41
64
86
55
5
60
0.2
34
11
72
34
35
14
69
58
67
03
82
09
37
70
0.3
30
16
53
30
49
56
59
82
49
89
11
54
13
19
80
0.4
25
21
34
25
63
88
50
10
63
12
76
14
88
17
01
90
0.5
21
26
05
21
78
11
04
11
30
21
56
21
82
22
08
3
10
00
.61
63
08
61
69
24
12
32
15
40
18
48
21
56
24
64
11
00
.71
23
56
71
21
06
71
42
31
77
92
13
52
49
02
84
6
12
00
.80
74
04
80
71
21
11
61
42
01
82
42
12
82
53
22
8
13
00
.90
24
51
90
21
35
41
80
52
25
62
70
73
15
93
61
0
14
00
.99
84
99
99
81
49
71
99
62
49
52
99
43
49
33
99
2
15
01
.09
35
47
10
93
16
40
21
87
27
34
32
80
38
27
43
74
16
01
.18
95
94
11
89
17
83
23
78
29
72
35
67
41
61
17
01
.28
46
42
12
84
19
26
25
69
32
11
38
53
44
95
18
01
.38
06
90
13
80
20
70
27
60
34
49
41
39
19
01
.47
57
38
14
75
22
13
29
50
36
88
44
26
20
01
.57
17
85
15
71
23
56
31
41
39
27
21
01
.66
68
33
16
66
24
99
33
32
41
65
22
01
.76
28
81
17
62
26
42
35
23
23
01
.85
79
29
18
57
27
86
37
14
24
01
.95
39
76
19
53
29
29
25
02
.04
81
02
42
04
83
07
2
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composition of the pasture paddocks. This isespecially beneficial if the tactics result in a greaterproportion of perennials in the pasture.
Its presence also provides an opportunity forimproving overall feed quality as well as availabilitythroughout the year. This may allow a change ofenterprise to provide greater economic returns whilemaintaining vegetative stability. For example, withprime lambs reared on lucerne and natural pastures,problems of feed availability can occur in extendeddry periods as a result of leaf drop by lucerne.OMSB supplies a similar quality and quantity of feedas lucerne and can overcome these problems.
Potential productive usesThe ability to turn off finished products is probablythe best way to minimise the adverse impact of ourvariable climate. OMSB can help this ability. Standscan readily be assessed to see how much green feed isavailable and management can be adjusted accordingly
without the need to rely on regular rainfall. Howeverstands need to be managed correctly and inconjunction with other available dry or green fodder.To achieve this, strategic placement of stand/s on theproperty is important in the planning stages to ensurethat the right mix of feeds can be provided.
When considering the introduction of OMSB thereare several factors that should be taken into account,apart from the initial high cost of establishing a stand.The first is how best to utilise the feed source in termsof its quality and quantity and the second, how to bestmanage it to obtain the greatest benefit. OMSBprovides greatest nutritional value when grazed inconjunction with other pasture species or othersupplementary sources (e.g. grain). Hence, there is aneed to identify where and how OMSB can beincorporated into an existing grazing managementstrategy in order to complement and enhance pastureand livestock production.
Table 4. Complexity of attributes that need considering when planning to establish forage shrub stands.
Environmental – permanent planting – cool temperature dormancy
– deep deep-rooted – acid soil intolerant
– ideal for dryland salinity control – unsuited to waterlogged soils
– wind protection – may provide harbour for rabbits
– sink for carbon sequestration
Stock management – provide year-round feed – slow growth
– reliable supply – moderate digestibility
– feed not wasted or fouled – needs high energy supplement
– high protein – animals need to be trained
– high quality product potential – needs good quality water
– not favoured by native or feral animals – potential Ca:Na imbalance in stock
Plantation – able to access feed on hand – ties up land from other usesmanagement
– fills seasonal feed gaps very well – expensive to establish
– head-up grazing – less worms – needs good management
– greater flexibility in stock type – can’t handle pasture competition
– a tool to improve pastures in – needs fertiliserother paddocks
– possible high Na, N and oxalate %
– needs a high quality or value productto be profitable
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A number of use options include:
Maintain shrubs as a drought reserveThe concept of utilising OMSB as a �living haystack� isnow considered to be of little value as other feedsources are better suited as drought forage and oftenmuch cheaper to provide. Oats is a good example ofa better drought feed option as it is cheap to produce,easy to store and has saleable utility if not required onfarm. We would not advocate this �living haystack�option unless there are extensive plantings of OMSBon the property and adequate grain supplements areavailable.
To obtain the greatest production from OMSB theplants need to be grazed on a regular basis irrespectiveof seasonal conditions, as opposed to keeping themas a drought reserve where grazing occurs only insevere feed shortages. As this may be only once every3�5 years, plants grow out of reach of stock, becomewoody and leaf material becomes unpalatable duringthe intervening period. Furthermore, stock need toadjust to them over a period of time, and thiscoupled with the high cost of establishment ofOMSB warrants greater levels of utilisation to achieveeconomic benefits.
Managed to overcome seasonal or short-term feed gapsAreas with seasonal rainfall (summer or winterdominance) have a period of low rainfall andsubsequent feed shortage at some period during theyear. OMSB provides a source of high protein greenfeed that can be grazed on an annual basis toovercome these seasonal feed gaps. The establishmentof OMSB to overcome seasonal feed shortages andmaintain nutritional quality, usually with a grain orpasture supplement, is presently the most commonutilisation strategy. An example of the benefit ofmaintaining nutritional supply throughout the year isprominent in the wool industry�s target of consistentfibre strength. As autumn feed gaps are commonplacein much of the southern area planning to incorporateOMSB as part of an extended feed supply would bemost useful. Longer exposure to animals by rotatinggrazing through several small blocks improvesefficiency. In the northern parts, a winter-spring feedgap more commonly needs to be filled (see section onanimal management).
As part of an integrated production systemThe incorporation of OMSB into a holisticmanagement approach to property management haspotential for wider application. The utilisation ofOMSB as a grazing tool to provide managementflexibility and sustainability also benefits other farmenterprises. For example, utilising 75% of the bush to
bridge the feed gap each year, and maintaining 25% asa drought reserve, overcomes annual concerns such asfull ration grain feeding as well as providing thesecurity of a drought reserve if the seasonal breakdoes not come. Indirectly, there may be other benefitsto those pasture paddocks that are rested whilst stockare predominantly grazing saltbush.
Used as a pasture spelling toolThe use of shrub stands as a spelling tool has similarprinciples as managing for seasonal feed-gaps,however the objective here is the enhancement ofother pastures with more desirable species by spellingthem at crucial times. This indirectly benefits livestock.By identifying favourable pasture species and knowingtheir growth cycle, graziers are able to remove stockat critical periods to allow selected species to flower,set seed and establish. OMSB is capable of carryinglarge numbers of stock in a limited area for shortperiods without serious detriment to stock, allowinglarge areas of land to be rested. Again for best results,an extended period of grazing OMSB (that is, stockmoved serially through several paddocks) will givebest results, especially if a grain supplement is alsoprovided to satisfy metabolic energy requirements.Spelling of grass paddocks following new plantrecruitment is also an important consideration toallow new plants to become firmly established and setseed.
Set-stocked natural standsThis is the most common method employed in thedrier pastoral zones of NSW and South Australia. It isalso used in other areas such as along the lowerreaches of the Bogan River and in the Riverina. Someof the best remaining saltbush and bluebush countryhas been set-stocked since settlement and it appears tobe the most stable method of grazing, provided thestocking rate is correct (Figure 1). This method relieson conservative stocking rates and a managementphilosophy of maximising output on a �per animal�rather than on a �per area� basis. Lambing percentagesare usually greater than 100%. Management optionsemployed by some managers include skipping amating during droughts or double lambing inexceptional seasons. Some producers have takenadvantage of this natural system and have been ableto market their product as �Organic� as reliance onchemicals can be avoided.
Environmental benefitsWhen assessing the merit of changing managementstrategies on a farm it is usually only the direct cost ofimplementing the change and the immediate dollarbenefits received that are considered. Incorporating,
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or increasing the proportion of forage shrubs on afarm can result in other indirect benefits. Thesebenefits are difficult to assign a dollar value to, butthey can provide an overall long-term benefit to theproperty that is also in the �public� good. Agriculturehas become well aware of the importance ofenvironmental stability and the impact that poormanagement options can have in the long-term. Thethreat of dryland salinity as a result of pursuingagricultural products based on production fromannual crops and pastures is now being realised,particularly in areas with undulating topography andshallow, sandy-textured topsoils. The introduction ofperennials can enhance landscape stability bymodifying many environmental attributes.
OMSB has several environmental applications themost common being its establishment in saline areasto reduce watertables and revegetate salted land. Beinga salt accumulator OMSB is able to grow in areas ofextreme salinity, gradually altering conditions allowingother pasture species to establish. OMSB alsoprovides excellent shelter and in hedge formationsprovides an excellent windbreak. Although it is notrecommended as a forage plant in these situationssome foraging may be possible as total vegetativecover and production will be enhanced compared tothe do nothing option. As well as its use in colonisingsaline land, saltbush can also be planted to stabiliseerodable surfaces such as scalded gullies and dunecrests.
Water balance� Increased water useDetailed information on timing and pattern of wateruse in the soil profile is not readily available for mostof the native forage species. Some information isavailable for other woody and semi-woody speciesgrown in the western agricultural parts of the regionwhich can be used as an interim guide. These are allsummer growers with a similar growth period to theforage shrubs. Fast growing species like lucerne andblue mallee are able to exploit stored soil moisturedown to at least 3.5 m depth in the second year afterestablishment, whereas slow growing species likejojoba take 3 years to reach the same amount of leafcover and water use. The water use ability of OMSBappears to be intermediate to the two species above.
� Increased moisture retentionIt is believed that areas with good shrub covergenerally intercept and retain more rainfall than doshrub-free areas. This increase in percolated wateroccurs as a result of a cut in overland flow of waterafter heavy downpours, greater debris on the surface
to trap moisture and to a major reduction in the windcrossing the soil surface and evaporating water fromthe topsoil. The increase in net water intake at thesurface does not mean a greater deep-drainagecomponent as all the water will be utilised by theshrubs before it escapes down the profile.
� Lowering of watertablesSome plants have the ability to lower watertables andhave been widely promoted for that function. OMSBhas been widely used in irrigation areas and on sandysoils where shallow watertables are a common featureof the landscape. Its effectiveness in loweringwatertables depends largely on the salinity of thegroundwater and on soil texture. Where thegroundwater is highly saline its effectiveness is greatlyreduced as little water is transpired. Further, the forageproduced is high in salt content and not suitable asstock feed, but the plant provides importantenvironmental benefits.
Wind reduction� Increased protection to soil against erosionShrub stands offer increased protection from windand water erosion. Natural stands offer betterprotection against wind erosion than do plantationstands because of the random distribution of plants.Plantations established using curved rows providebetter protection than ones established with straightrows. The level of protection afforded against watererosion depends on the amount of pasture cover andlitter allowed to accumulate, slope of land and line ofplanting. Generally plantations aligned across thecontour will give greatest protection against overlandflow of water, particularly if there is a good littercover.
� Increased animal protectionSmall clumps or 2�3 rows of OMSB planted in alleysystems provide good protection to stock from coldwinds, while extensive plantings provide excellentprotection. The greatest protection is afforded toewes and lambs, or to off-shears, during cold changesin the weather. Mustering stock is generally not aproblem in either natural or plantation stands.
The downside of this is a potential increase in flystrike in sheep under certain climatic conditions. Therehas been a report from a landholder who hasexperienced severe fly problems in a flock that wasgrazing a dense stand of OMSB during a bout ofhot, humid and stormy conditions in summer. Heattributed the problem to lack of wind and a build upof humidity within the plantation. Stock on otherparts of the property did not have the same problemat that time.
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STARTING A PLANTATIONPlanning layoutsIt is important to assess the role and needs of OMSBalong with the existing property layout well in advanceof planting. It is important to ascertain how muchOMSB needs to be planted to meet the needs ofstock and where plantings on the property should bemade to facilitate best management and obtaingreatest returns. The extent of plantings on each farmis difficult to estimate here but usually 10�15% offarming area is the maximum area required. Goodstock management is the key in obtaining best resultsfrom OMSB and these are discussed later. Plantingscan either be as blocks of plants in small paddocks orin alleys (several rows of OMSB in strips across largerpaddocks).
Planting Configurations� Block plantingsThe advantage of blocks is that the area of bush isconfined to small areas freeing up the management ofother land and fencing is kept to a minimum (Figures4 and 5). Independent access to several adjoiningpasture paddocks is also possible, increasingmanagement flexibility. Subdivision of the block intosmall areas also increases managerial control ofproviding better diet mixes of saltbush and pasture.
� AlleysThese on the other hand, provide a better mix ofshrub and pasture for stock and still permit croppingof the intervening areas, but grazing of bush isrestricted during the cropping periods (Figure 6). Thealley system has potentially greater environmentalbenefits for drying the soil profile as well as providinggreater protection to pastures and stock from winddamage. The close proximity of pasture to shrubsmakes it easier to provide a well balanced ration forstock. The down side is that at times options forshrub management may be curtailed by lack of accessto the paddock, e.g. during cropping.
Planting densityThe nominal planting density for block plantings isabout 2500 plants/ha, commonly planted in rowsspaced 3.0 metres apart with intra-row plant spacingsof 1.2 metres. Variations to this often alternate wideand narrow row spacings (e.g. 4-2-4 m) as thispermits easier access to the paddock for musteringand weed control. The same procedure is adoptedfor alley plantings, however the width of the plantings(usually 3 or 4 rows) and the alley width may varyconsiderably from place to place.
Some evidence suggests that lower planting densities(about 2000 plants/ha) are nearly as productive (andcheaper to establish). However, if this is adopted it isadvisable to maintain intra-row spacing and broadenthe row spacings as this helps to make planting andweed control operations more efficient and cheaper.OMSB with planting densities as low as 400 plants/haare feasible, especially where no grain supplementationis contemplated but the proportion of pasture needsto be increased.
It is important to consider the likelihood ofsubsequent recruitment of new plants as well asdeaths of those originally planted. When planting atthe lower densities it may be wise to considerincreasing the initial number of plants to allow for anyloss in numbers during the establishment phase andduring the first few years of production.
Establishment methodsThere are some general requirements for successfulestablishment. These involve ensuring adequate weedcontrol and soil moisture levels, at least during theestablishment phase. There are two methods ofestablishing stands; by direct-seeding or bytransplanting seedlings.
Direct seedingThis method has been used extensively on sandy soilsin South Australia and Western Australia with mixed
Figure 4. Block planting of OMSB with good pasturegrowth in access area.
Figure 5. Good regrowth from well-managed OMSB blockplanting.
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success. The technique relies on the ability to scalp thesoil of weed seeds at sowing followed by a reliableperiod of favourable rains to firstly germinate theseed then allow it to establish quickly. Much of thewheatbelt of NSW appears unsuited to this techniqueas many soils are too heavy in texture and rainfall istoo unreliable to get consistent soil moistureconditions to allow germination and thenestablishment of seedlings, hence it is regarded as ahigh risk operation here.
SeedlingsThese can either be �bare-rooted� (Figure 7) orsupplied as a �speedling� (a seedling raised in thenursery and supplied with a small plug of soil aroundthe roots). Detailed descriptions of the methods of
establishing stands of OMSB are given in an Agfacttitled Establishing shrubs and trees in the central-west ofNSW or Bare root seedling production, a fact sheet fromPrimary Industries, SA. Speedlings are normallyproduced and supplied through commercial nurserieswhile bare-rooted plants are normally produced �on-farm�.
PLANTATION MANAGEMENTOnce stands of OMSB have been established it isimportant to consider the welfare of both the plantsand the stock in the subsequent management of thefarm. There are many aspects to be considered tooptimise production from OMSB. Initially, size or ageof bush is important. Plants are usually large andstrong enough to graze at 9�12 months. The firstgrazing (Figure 8) should be carefully monitored toensure that the plants are defoliated to the desiredlevel quickly and that no damage is done to the mainbranches. It is suggested that about 15% of leaf beleft at the first grazing to ensure rapid recovery.
On subsequent grazings, defoliation can be down to5% of leaf in most instances (Figure 9), however ifgrazing is near the onset of winter, then it is advisableto defoliate only to the 10% level. In all cases, theduration of grazing should not exceed 21 days as
Figure 6. Alleys of OMSB used in conjunction withcropping and grazing.
Figure 7. Nursery of �bare rooted� seedlings ready for planting.
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continual grazing weakens plants and there is a riskthat new growth will be removed before plantreserves can be restored.
There are a number of reasons why OMSB needs tobe grazed regularly and undertaken irrespective ofseasonal conditions. If seasonal conditions are goodand plant growth is rapid the plants can quickly growto a height where stock can not reach the tips, makingthe feed unavailable. There will then be a need toprune or �top� the plants (Figure 10). Regular grazing,even with sheep, keeps plants within �bite height� ofthe animal and reduces the need to prune. Plants canbe pruned or topped mechanically by usingreciprocating or rotary mowers. When pruning it isadvisable to cut the sticks as low as possible, initiallyabout 60 cm above ground, and gradually raise theheight at subsequent events as the plantation ages.Where cattle are run, they can be used to reduce plantheight. Grazing should take place at 6 to 12 monthintervals and certainly no longer than every 18 months.Some evidence shows that better utilisation of bushoccurs when grazing is at closer intervals.
Paddock size is also important, irrespective ofplanting configuration. Management should aim atproviding the correct balance (OMSB and pasture or
grain) in the ration for the animal�s need as well ascompleting the grazing in a period of less than 3weeks. The flock or herd sizes normally run on theproperty need to be considered when determiningsubdivision and paddock size. Four to eight paddocksof OMSB to rotate stock through are needed ifoptimum production is to be obtained. Access towater and water quality also needs carefulconsideration.
PESTSImpact of pests and diseasesObservations made from field trips and a literaturereview shows that a wide range of plant and animalpests affect the growth of shrub stands. Some of themain impacts are from:
WeedsThe presence of pasture cover (including weeds) at,or following, planting is a major impediment tosuccessful establishment and subsequent growth of astand. It is well known that OMSB is unable tocompete with fast growing annuals for nutrients andwater, particularly during the cooler months andyoung plants are subsequently shaded out. Therefore itis important to understand critical levels ofcompetition to maximise total production. Theimpact that weeds may have at various stages of standdevelopment are summarised below:
� At establishmentThe survival and growth of speedlings planted atCondobolin in autumn 1997 was severely affected bya pasture growth of about 1 t/ha in the followingspring compared to plants that were kept weed freefor the same period (Figures 11 & 12). This is a majorimpact that cannot be ignored and highlights one ofthe reasons why direct seeding is often unsuccessfuldespite apparently good seasons.
Figure 9. Same shrub with 5% leaf remaining aftergrazing.
Figure 8. Typical shrub fully leafed prior to grazing.
Figure 10. Poor management has led to excessive top-growth occurring between grazings.
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� Moths and butterfliesDefoliation of OMSB by several species of caterpillar(larval stage of moths and butterflies) during springbecomes particularly evident during periods whenthere is a shortage of green feed. The larvae of thePasture day moth (Apina callisto), the Weed web moth
(Achyra affinitalis) and theChequered blue butterfly(Theclinestes serpentata)(Figure 13) are three ofthe more common andwidespread species whichattack saltbush. Theimpact of these pests onsaltbush production in acommercial scaleplantation is not likely tobe large in most years(Figure 14).
Figure 12. Impact of pasture/weeds on establishment �compare poor growth of plants in mid-ground with thosein background.
0
20
40
60
80
100
120
140
160
180
Autumn 97 Winter 97 Spring 97 Summer 98 Autumn 98 Winter 98 Spring 98 Summer 99
Dia
met
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cm)
Summer grassesWinter grassesNil
Figure 11. Impact of summer and winter growing pastureson young OMSB growth as shown by changes in plantdiameter.
� On mature plantsRows of OMSB were established by fallowing theland 1 metre either side of the planting row prior toplanting and then keeping it weed-free for 12 monthsfollowing planting to allow establishment. Treatmentsthen allowed pasture to encroach onto the fallow onhalf the plots, but kept bare on the other half. After18 months the difference in growth between thetreatments amounted to 50% improvement with noweeds.
Being native to Australia, OMSB provides food andshelter for many potential predators and there areoccasional reports of severe damage to natural stands.The significance and impact of these attacks tends tobe episodic and dictated by seasonal conditions.Insect, mammal and fungal attacks have all beenreported as causing periodic large scale damage.
Insects� Scale (Pulvinaria maskelli)Attacks the stems and shoots of OMSB and bladdersaltbush draining moisture causing widespreaddieback and can result in death. Forty hectares ofOMSB near Carinda has been reported as destroyedfrom a heavy scale infestation.
� Leafhoppers (Austroasca merredinensis)These insects attack the leaves and green stemsdraining moisture from the plant, resulting in a distinctyellowing of leaves and reduction in growth andvigour of plants.
� BorersLarvae of some weevil species have been found inOMSB that attack the older wood by burrowing upthe centre of stems, resulting in dieback. They appearto have an annual impact and are most noticeable eachautumn-winter. They do not appear to be a majorproblem in well managed stands.
Figure 13. Chequered bluebutterfly, a potential pest inOMSB.
Figure 14. Complete loss of grazing caused by insectattack on established seedlings.
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VertebratesDuring establishment hares and birds, particularly thesulphur-crested cockatoo regularly destroy manyplants by biting the young plants off just aboveground level. Rabbits are capable of similar damageon mature plants during extremely dry periods andhave been observed ringbarking OMSB. Feral goatswill graze OMSB but are more than likely attracted tothe rested pasture growing between the plants,kangaroos are also fond of the pasture but seem toavoid the bush if pasture is available.
Fungal DiseasesIt is difficult to estimate the impact of these diseaseson saltbush as identification of a causal pathogen isnot easy. The widespread dieback of saltbush(predominantly bladder saltbush) that occurred on theRiverine plain in the late 1970s and early 1980sinitiated a detailed study to determine if fungal florawere responsible for this phenomenon. This researchidentified 70 fungal pathogens associated withsaltbush, none of which could be identified as thecausal link responsible for the dieback, nevertheless theimpact was significant.
ANIMAL MANAGEMENTStock familiarisationThis is clearly the area least understood with regard tomanagement of OMSB. Although production datafrom prolonged grazing of bush using large mobs ofstock is being collected, further, more detailed studiesare required.
The most efficient livestock production from OMSBoccurs when stock are acclimatised to eating it andwhere it constitutes a portion of the diet for extendedperiods. Initially, stock need to become familiar withthe plant and learn to browse it in conjunction withgrazing pastures. An acclimatisation period is alsonecessary to allow the stomach flora of the stock toadapt to digesting the plant. These processes will takeseveral weeks and care needs to be taken to ensurethat stock are not �starved� and productioncompromised during this period. Once stock arefamiliar with OMSB they readily browse it on returngrazings after a break from bush, but they will stillrequire a short acclimatisation period for theirstomachs to adjust. Continuous supply of OMSB forlonger periods by moving stock through severalpaddocks of OMSB gives best results. �One-off �short-term grazings often give poor responses asanimals are poorly equipped to handle the bush.Young stock will need to be trained to browse thebush by older stock.
Starved breeding or growing stock are particularlysusceptible to do poorly if introduced to saltbushwhen in poor condition and where there is an absenceof pasture. There have been several reported cases ofbreeding animals aborting and lactating stockabandoning their young. Animals such as these, withan increased metabolic requirement, will need to beheavily supplemented with a high energy source whenintroduced to saltbush, especially in the absence ofpasture.
Prescribing a rationAnimals have difficulty in handling OMSB as the solefeed source due to the high salt intake. Further, aproportion of the protein component of OMSB willbe wasted due to the animal�s inability to digest itunder these circumstances. The optimum amount ofOMSB in the diet appears to be about 30% of dailyfeed intake, with the remainder being pasture orstubble. Good quality dry pasture or stubble make anexcellent fill for the animals as well as increasing theefficiency of production. Poor quality straw orstubble hay should be supplemented with grain if thisis the only available fill for stock. Where grain is fed tosheep optimum production is reached with dailyintakes of about 200�300 grams.
Setting paddock sizesWhen planning the layout of plantings it is importantto consider how the plants are intended to bemanaged. When block plantings are contemplated,care needs to be taken to allow access to adjoiningpasture paddocks simultaneously.
Stock managers need to consider duration of grazingand match this with other available feed (pasture orgrain), flock or herd size and availability of goodquality water and how it relates to paddock size. Thecost of sub-division fencing and new watering pointsare points to consider here. Number of stock in aflock or herd will be largely dictated by whole farmsize and enterprise mix, as well as which group/s willhave access. Grazing times of about three weeks perpaddock before moving to the next paddock appearsoptimum. Therefore the number of paddocksplanted to OMSB will depend on the length ofcontinuous grazing that is planned, remembering thatreturn grazings are likely to be at 6- or 12- monthlyintervals.
General managementWhat also needs to be considered is how the standswill be managed during an extended period of goodgrowing conditions. It is most important that theplants are not allowed to put on excessive growth asthis will result in poorer quality feed ultimately being
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available to stock as well as necessitating the addedcost of pruning to bring plants back to a size thatanimals can graze.
Water supplyThe consumption of water by sheep may increase by2�3 times (up to 12 litres/day in summer) whenplaced on a diet high in saltbush: whilst for cattle, theirwater consumption will increase to 70�140 litres/day.Water quality is also an important consideration whengrazing livestock on saltbush. Generally, salt levelsbelow 12,500 ECe (8000 ppm) for sheep, and 7500ECe, (4800 ppm) for cattle are considered adequatefor stock on grass pastures. However, when grazingsaltbush salt levels in water below 1600 ECe (1000ppm) are required for maximum saltbushconsumption.
Health issuesThe main health issues with OMSB are oversupply ofsalt and protein if the diet is not balanced with anadequate energy source from pasture or grain and orgood quality water supply. However, there areindications that other health issues may arise wherestands are grown on acidic soils, resulting in calciumdeficiencies in stock. At this stage this issue is notwidespread and can be addressed if observed.
� Other Compounds in SaltbushNitrates � Nitrate poisoning of young stock has beensuspected as the cause of death after young hungryanimals were allowed to graze a OMSB plantingdevoid of a pasture understorey. In these situations itis likely that much of the nitrogen is not converted toprotein in the rumen and is absorbed directly into theblood stream.
Oxalates � These cause precipitation of insolublecalcium in the rumen and the kidneys. Theconsequence is kidney damage, rumen stasis,gastroenteritis, calcium deficiency and possible death.Poisoning in sheep and cattle has been reported whenpastures contain 7�8% oxalate. Many saltbushescontain levels approaching the toxic threshold,3.3�6.6%, however reports of toxicity are rare.Possibly because high oxalate concentrations lowervoluntary feed intake of the offending plant material.There are reports that 3% oxalate levels will depressfeed intake significantly.
Tannins � When present, from 2�4% in the dietprotect protein from rumen degradation and increasethe absorption of essential amino acids whereas athigh levels (4�10%) it depresses voluntary feed intake.Atriplex spp. have been reported to contain low levelsof tannin <1%.
ECONOMIC RETURNSIn 2000, a study was completed that evaluated theinvestment in a forage shrub plantation as a droughtpreparedness strategy for landholders in the central-west of NSW compared to the existing tactical grainfeeding for drought management. A representativefarm was established and a partial budgetingprocedure was used in a benefit-cost analysisframework to compare alternatives. Proposals werenot only assessed for the change in expected returnsfrom the introduction of OMSB but were alsoassessed considering the impact of climatic variabilityfor the central west of NSW. In the analysis threemethods of establishment were considered. The costsof establishment of stands (at 2500 plants/ha) were$190 for direct seeding; $203 for bare-rooted, and$550 for speedlings respectively. No increase incarrying capacity of the property was expected, ratheran increase in reliability of finishing animals and gain inbest market price is expected, or alternatively thelanduse could confidently change to prime lambproduction because of a more reliable feed supply.
It was found that landholders could potentially benefitfrom the introduction of a forage shrub plantation,establishing two and a half percent of the propertyusing the bare-rooted technique, when compared tothe existing strategy of tactically grain feeding.However, when the area of saltbush was increased to5 percent of the property the existing tactical grainfeeding strategy was desirable. In all cases, it wasfound that the existing tactical grain feeding strategywas desirable when compared to the speedling anddirect-seeding alternatives.
Since that study was completed commodity prices forlivestock products have increased dramatically and are-appraisal of the initial study has been undertaken.The value of wool has increased by about 100%, andewes and lambs from between 35 and 40% from2000 values. Feed grain was also costed out at 25%higher than in 2000. The net result is a huge increase inlivestock gross margins. These have increased byabout $30 per ewe for wool sheep. By introducingOMSB and/or changing to prime lamb productionfurther increases can be made, with per ewe grossmargins increasing to over $53 for prime lambs whichare run in conjunction with OMSB. The environmentalbenefits have not been costed into these returns asthey are not easily assessed in �$� terms.
A detailed economic analysis can be obtained byreferring to the Integration of alternative forage sources indrought management final report referenced below.
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CONCLUSIONWhen considering the merits of introducing OMSBonto a farm it is readily seen that there are many issuesthat need to be addressed before a final decision canbe soundly made. The most important points are tobe sure that you are growing it for the right reasonsand that the projected returns match the cost ofestablishment. It is hoped that the points raised herewill assist the reader to arrive at the right decision, aswell as assist management of the stands once they areestablished. The section on stock response andmanagement on OMSB is grossly deficient of soundinformation, but these matters are priority issues forfurther research.
FURTHER READINGNSW Agriculture (2003) Prograze, profitable sustainablegrazing. NSW Agriculture and Meat and LivestockAustralia.
Barrett-Lennard, E.G. and Malcolm, C.V. (1995)Saltland pastures in Australia � a practical guide.Department of Agriculture, Western Australia.
Lamont, H. (1996). Old man saltbush as a potentialvegetation option in unreliable rainfall, cereal/pasture systems.Working papers � Farming systems developments pp153�154.
Martin, B (1997). Bare root seedling production. Fact sheetFS26/97 Primary Industries, South Australia.
Masters, D.G., Norman, H.C. and Dynes, R.A. (2001).Opportunities and limitations for animal productionfrom saline land. Asian-Aust. J. Anim. Sci. (14)199�211.
Milthorpe, P.L. and Yee M, (in press) Establishing shrubsand trees in the central-west of NSW. Agfact NSWAgriculture.
Milthorpe, P.L., Honeysett, B.M., Patton, D.A. andWynne, M.J. (2000) Integration of alternative forage sourcesin drought management. Final report for the DroughtRegional Initiatives Program, Program 6. NSWAgriculture.
Weston, RH., Hogan, J.P and Hemsley, J A. (!970).Some aspects of digestion of Atriplex nummularia(saltbush) by sheep. Proc. Aust. Soc. Anim.Prod. (8)517�21.
AcknowledgmentThe photo in Figure 13 was supplied by Ross Field,DPI Victoria.
Disclaimer
The information contained in this publication is based onknowledge and understanding at the time of writing (May 2004).However, because of advances in knowledge, users are remindedof the need to ensure that information upon which they rely isup-to-date and to check currency of the information with theappropriate officer of New South Wales Department ofAgriculture or the user�s independent adviser.
Always read the label
Users of agricultural (or veterinary) chemical products mustalways read the label and any Permit, before using the product,and strictly comply with the directions on the label and theconditions of any Permit. Users are not absolved fromcompliance with the directions on the label or the conditions ofthe permit by reason of any statement made or omitted to bemade in this publication.
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Edited by Bill NoadInformation Delivery ProgramDubbo, May 2004Agdex 136/10Job No. 4921
