Journal of Oil Palm Research Vol. 11 No. 2, December 1999, p 72-88 MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENT FOLLOWING REPLANTING OF AN OIL PALM PLANTATION Keywords: carbon mineralization, nitrogen mineralization, aerobic incubation, anaerobic incubation, soil respiration, carbon dioxide evolution, oil palm replanting, zero burning. KHALID, H*; ZIN, 2 Z* and ANDERSON, J M** * Palm Oil Research Institute of Malaysia, P.O. Box 10620, 50720 Kuala Lumpur, Malaysia. ** Department of Biological Sciences, University of Exeter, U.K. D uring oil palm replanting, substan- tial amounts of the above-ground oil palm residues were available which contributed about 577 kg N ha-’ and 40 t C ha-’ and the root materialsproducedabout 65 kg N ha-’ and 8 t C ha-‘. These materials were the main sources Q~C and N which would affect the mineralization ofC and N in the soil. In this study, the potential mineralizable N, the mi- neralization of organic C through soil respira- tion and CO2 evolution with different residues management practices were estimated. The results of C mineralization study showed that the carbon fluxes due to crop residues inputs contributed about 7.7 t CO, ha-’ yr-’ which was mineralized from the soil. However, the mine. ralization rate of C from the light fraction organic matter which accumulated on the top soil surface was found to be about 20 times higher than that in the soil under the organic layer. The CO2 fluxes might largely reflect mic- robial activity from different residue treatments. Nitrogen mineralization due to the inputs of crop residues could significantly increase the availability of N to the young palms of which about 428 kg N ha-’ yr-’ were mineralized from the mineral soil and made available to the palms. In contrast, the N mineralization from the plots without crop residue inputs only con- tributed about 312 kg N ha-’ yr-’ which probably came from decomposed roots of the previous crop. Thus, the fluxes of about 109 kg N ha-’ yrl was transferred to the soil as a consequence ofleaving crop residue above the ground during replanting of the plantation. A large amount oflv was in the
Transcript
Journal of Oil Palm Research Vol. 11 No. 2, December 1999, p 72-88
* Palm Oil Research Institute of Malaysia, P.O. Box 10620,50720 Kuala Lumpur, Malaysia.
** Department of Biological Sciences, University of Exeter, U.K.
D uring oil palm replanting, substan-
tial amounts of the above-ground
oil palm residues were available
which contributed about 577 kg N ha-’ and
40 t C ha-’ and the root materialsproducedabout
65 kg N ha-’ and 8 t C ha-‘. These materials were
the main sources Q~C and N which would affect
the mineralization ofC and N in the soil. In this
study, the potential mineralizable N, the mi-
neralization of organic C through soil respira-
tion and CO2 evolution with different residues
management practices were estimated.
The results of C mineralization study showed
that the carbon fluxes due to crop residues inputs
contributed about 7.7 t CO, ha-’ yr-’ which was
mineralized from the soil. However, the mine.
ralization rate of C from the light fraction
organic matter which accumulated on the top
soil surface was found to be about 20 times
higher than that in the soil under the organic
layer. The CO2 fluxes might largely reflect mic-
robial activity from different residue treatments.
Nitrogen mineralization due to the inputs of
crop residues could significantly increase the
availability of N to the young palms of which
about 428 kg N ha-’ yr-’ were mineralized from
the mineral soil and made available to the
palms. In contrast, the N mineralization from
the plots without crop residue inputs only con-
tributed about 312 kg N ha-’ yr-’ which probably
came from decomposed roots of the previous crop.
Thus, the fluxes of about 109 kg N ha-’ yrl was
transferred to the soil as a consequence ofleaving
crop residue above the ground during replanting
of the plantation. A large amount oflv was in the
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
bile pool of the light fraction organic matter
hich accumulated on the top soil surface and
hich, when mineralized, was six to seven times
&her than that in the soil under the organic
yer.
INTRODUCTION
Y oil organic matter (SCM) plays a major role3 in terrestrial ecosystem development andmctioning by forming both a source and sinkfnutrients. This buffers the nutrient availabi-ty to plants and reduces losses from the systemallowing disturbance at time of replanting.‘emperate and tropical soils are known to haveimilar concentrations of SOM, averaging 3%-% (Buol, 1973; Sanchez, 1976) but with wideariations between ecosystem types according3 plant inputs, climate and soil texture. With5% of soil nitrogen (N), 40% of soil phosphorusP), and 90% of soil sulphur (S) located in theoil organic matter fractions, the balanceletween SOM formation and turnover is criticalDT plant growth (Smith et al., 19%).
Nitrogen is a major nutrient element and is‘equired by plants in substantial quantities asompared to other nutrients such as P whichs often present in suboptimal concentrations”ditrogen produces the greatest responses tonorganic fertilizers applied in oil palm planta-#ion even though economic responses to phos-chorus fertilizers are often obtained (Corley!t al., 1976; Hartley, 1988). Soil is the majorsource of nitrogen for plants, where the concen-oration usually ranges from 0.05% to 1.00%:Bremner, 1968). Tropical soils vary widely intheir reserves of N but in humid tropical lowlandforest more than half the total N capital maybe found in the soil (Anderson and Spenser,1991). In topsoils more than 90% to 95% of thetotal N usually occurs in organic compounds,while inorganic N forms a very small pool at anyone time (Wild, 1988). Understanding the con-trols of the processes of N mineralization istherefore important in managing N supplies toplants from organic materials.
73
Most plant-available N in soils is derivedfrom microbiological mineralization of N boundin soil organic matter or detritus (Alexander,1977). The term ‘nitrogen mineralization’ iscommonly used to describe the conversion oforganically bound nitrogen into plant-availableinorganic forms such as ammonium and nitrate(Harris, 1988). Mineralization of organic Ncompounds is brought about by micro-organ-isms to meet their energy and nutritionalrequirements through the initial process of“ammonification’ which is the conversion oforganic nitrogen into ammonium (NH,+) byheterotropic micro-organisms and ‘nitrification’which is the conversion of ammonium (mainly)by autotroph bacteria into nitrite (NOz-) andnitrate (NOX-).
The development of microbial biomass insoils requires critical Ievels of available C andN for growth and maintenance. If N is in excessof C for the microbial population, mineral N willbe mobilized, but when carbon is in excess theN will be immobilized and conserved in micro-bial tissues until the excess C has been respiredoff. The thresholds at which N immobilizationand mineralization take place vary within andbetween groups offungi and bacteria, and, whenother factors are limiting decomposition. Inbroad terms,. plant residues with C:N ratio<50:1 will decompose rapidly while materialswith C:N ratio >lOO:l will decompose moreslowly by undergoing an extended period of Nimmobilization before net N mineralization”During the immobilization phase, micro-organ-isms may sequester N from exogenous sourcesin the soil or other organic materials. This isa well recognized phenomenon associated withcrop residue management in arable agricultureand can be used to manipulate the timing of Nmineralization in relation to crop demand (Myerset al., 1994).
The rate controls of N mineralization areessentially the same as those regulating decom-position (Jenkinson, 1981) and are principallycontrolled by temperature, moisture, soil distur-bance and the quality of soil organic matter asmicrobial substrate. Soil CO2 production is asimple measure of these controls on microbialprocesses which can be determined under labo-ratory or field conditions (Anderson, 1982).
Most research on mineralization for estima-
JOURNAL OF OIL PALM RESEARCH 11(2)
tion of mineralizable soil nitrogen are based onlaboratory or field incubations using disturbedsamples. Assessment of management includingchanges in N-supplying capacity can also bemade using the paired core technique of in situmeasurement of N mineralization in the field(Raison et al., 1987). However, the problem withthe method is that in humid tropical regionsthe soil in the cores can be very wet at the timeof sampling, or flooded by heavy rains duringincubation, resulting in anaerobiosis anddenitrification, or leaching of mineral N. Inaddition, the rapid decomposition of cut rootsin the core can immobilize N. The method ofin situ incubation is also prone to soil compactionfrom the sampling.
Thus, the potential mineralizable nitrogenis normally estimated through biological methodof aerobic and anaerobic incubation in thelaboratory. Measurements of N mineralizationunder controlled laboratory conditions providean estimate of the pool of mineralizable N atthe time of sampling. Biological methods deve-loped to provide an index of plant available soilN generally involve measurement of inorganicN released during short term (7-25d) incubationunder aerobic or anaerobic (water-logged) con-ditions (Keeney, 1982). Even though we recog-nize the problem of disturbance causing aggre-gate disruption, including ‘light fraction’ soilorganic matter being in the mineral soil, at leastconditions are standardized for comparing treat-ments, thereby enabling process controls to bestudied even if plot level fluxes are difficult toestimate.
The anaerobic (water-logged) N mineraliza-tion method initially developed by Waring andBremner (1964), and later modified by Keeneyand Bremner (1966; 1967) and others, hasseveral advantages over aerobic incubationmethods: (i) only NH+ need be measured afterincubation, (ii) there is no need to establish anoptimal soil water content, and assessment ofwater loss during incubation is avoided, (iii)more N is mineralized in a given period thanunder aerobic conditions, (iv) higher tempera-tures, and hence, more rapid mineralization,can be used because field temperatures fornitrification do not need to be maintained, and(v) smaller soil samples can be used (Keeney,1982). The amounts of NH+ produced anaero-
bically have been found to be highly correlatedwith amounts of inorganic N produced duringaerobic incubation (Waring and Bremner, 1964;Smith, 1966) and with plant uptake (Keeneyand Bremner, 1966; Ryan et al., 1971).
This paper reports results for the minerali-zation of organic C and N from soils incubatedunder standard conditions (i.e. for 14 days at26°C f 2°C) and in situ measurement of COZevolution from a field. In addition, mineraliza-tion of N under anaerobic conditions to derivea N availability index was also studied. T h eobjectives were to estimate the potentialmineralizable nitrogen and the mineralizationof organic C through soil respiration and measure CO2 evolution from a field with differen Itresidue management practices. The relationships between carbon mineralization or bass 11soil respiration (CO2 evolution) and N mineralzation under aerobic and anaerobic conditionsare also discussed.
MATERIALS AND METHODS
The experimental plots were set up at thl ePORIM Research Station, Kluang, Johor on aI 1inland Ultisol of the Rengam series following thlfelling of a 23-year-old oil palm plantation ofirst rotation. Four treatments of residue m a nagement namely, complete removal (C/R), chipping and shredding (C/S), chipping and pulverization (C/P) and partial burning (P/B) wenestablished. The measurements were madeduring the experimental period from October1994 to February 1996 from each treatment andon the old avenues (O/A) and old frond piles(O/FP). Further details of the site and treat.ments can be found in Khalid Haron (1997).
Nitrogen Mineralization Potentials
An initial attempt was made to measure Nmineralization in situ using a modification ofthein situ incubation method of Raison et al. (1987).The theoretical advantage of this method is that,by sampling paired soil cores, variation in theestimated rates of N mineralization due to thespatial heterogeneity can be reduced to someextent.
Pairs of plastic tubes, approximately 35 cm
74
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
in length and 7 cm internal diameter, weredriven into the soil to a depth of 30 cm with5 cm of the tubes projecting above the soil sur-face. One of the tubes was removed immediatelyfor determining initial mineral N concentration(at timeo) and the other was left intact with acover to protect it from the rain. This core wasremoved after two weeks (time,> and the in-crease in mineral N concentration determined.
After first series of incubation, it was ob-served the method was prone to soil compactionand some samples became water-logged as aconsequence of local ponding of surface waterduring rain. Removing of compacted soil fromthe tube was also very laborious given the highclay content of the soil.
The results obtained from the first series ofN mineralization in situ showed only 10% of thesamples gave positive and acceptable results,and the field measurements were discontinued.
Aerobic Incubation
Nitrogen mineralization was measured attwo-month intervals during the experimentalperiod. In aerobic incubations mineralizable Nwas determined from a 14-day laboratory incu-bation. Sub-samples from bulk soil cores fromtwo sampling depths, O-15 cm and 15-30 cm,were incubated separately to enable detectionof differences between treatments. Samples of40 g soil were extracted with 100 ml 0.5 MK$04. After 30 min shaking, followed by filtra-tion, the filtrate was analysed for NOa--N andNHi-N by calorimetric method (Anderson andIngram, 1993). A further 40 g of sub-sampleswere incubated in 200 ml glass jars (pluggedwith cotton wool) at room temperature(26”C+2”C) for 14 days. The weight of the jarswere checked periodically and corrections madefor water loss. After 14 days, the incubated soilswere extracted for exchangeable NOZ--N andNH$-N. The difference in exchangeable inor-ganic nitrogen during the 14-day period wasconsidered net N mineralization and expressedas pg N g-l dry soil 14 days-l.
Anaerobic Incubation - N MineralizationIndex
The anaerobic method involves the incuba-
tion of soil samples under water-logged condi-tions in an enclosed container. Soil samples of40 g were incubated in airtight plastic bottlescontaining 50 ml deionized water with as littlehead space as possible. The samples were placedin an incubator and incubated at 40°C for sevendays. After seven days, the samples were trans-fered to clean containers and added with 50 ml2 M KCl. After 30 min shaking, followed byfiltration, the filtrate was analysed for N&+-Nusing calorimetric method. The amount ofN&+-N in the soils before incubation (time,) wasdetermined by the same procedure by extractingwith 1 M KCl, and mineralizable N was calcu-lated from the difference in the results of theseanalyses as below:
Anaerobic N mineralization rate(pg N g-’ dry soil day-l)
= [(time, NIL+-N) - (time0 NW-N)]/7 days.
All laboratory incubations were performedon soils at the moisture content prevailing atthe time of collection.
Mineralization of C and N from LightFraction C
In addition to soil samples, the light fractionC accumulated on the top soil surface under thedebris in the C/S and C/P treatments were alsosampled for measurements of mineralizationrate of C and N at 12 and 18 months after thetreatments were established. Light fraction Cis defined as the C not bound to the mineral litterin the soil and represents the organic materialas yet undecomposed. The reactivity of the lightfraction C will depend on the quality of theorganic inputs.
Soil Respiration
The studies of soil respiration involved labo-ratory incubation and measurements of CO2evolution from soil in situ. The laboratoryincubation, which is a measure of substratequality under standardized conditions of tem-perature and moisture, was carried out toinvestigate microbial activity in the soil ofdifferent treatments and in relation to mine-
75
JOURNAL OF OIL PALM RESEARCH 11(2)
ralization of nitrogen. The measurements of CO2evolution in the field were intended to provideinformation on climatic controls on microbialprocesses.
Laboratory Incubation of Soils
Soil, respiration was also measured at two-month invervals during the experimental pe-riod. Soils from the bulked soil samples of eachplot at O-15 cm depth were used for incubation.The bulked samples were initially sorted toremove stones and root material. Samples of150 g were then incubated for CO2 mineraliza-tion in plastic bottles (7 cm diameter and 12 cmheight) for a 24 hr period to check whether thevolume of KOH was enough to absorb the totalCOZ evolved in one week. A 25 ml beakercontaining exactly 25 ml 0.1 M KOH, was placedinside each plastic bottle to trap the CO2 re-leased from the soil.
After 24 hr, the beakers were removed fromthe containers, 2 ml of saturated barium chlo-ride added to the KOH and then titrated with0.1 M HCl to a colourless end point usingphenolphthalein indicator. The soils were thenincubated for a further six-day period with newaliquots of 0.1 M KOH to get a total incubationperiod of one week. On each measurement, soilmoisture content was estimated gravimetricallyfrom bulked soil samples. All estimations weredone using duplicate soil samples.
Total COZ absorbed in 0.1 M KOH wasmeasured by titrating 25 ml aliquots of KOHwith standardized 0.1 M HCl to a colourless endpoint using phenolphthalein indicator. The CO2evolved from the soil was calculated from thefollowing formula:
Total COZ (mg C g-l soil) =(VII - V,) x 2.2
ws
where V, and Vo are the volumes (ml) of HClused to titrate KOH contained in the sampleand empty incubation (blank) respectively.W, is the oven-dry weight (g) of moist soilin each bottle. The amount of absorbed CO2was calculated on the basis that lml of 0.1M HCl is equivalent to 2.2 mg absorbed CO2(Anderson and Ingram, 1993).
Field in situ Technique for Measurementof Soil CO2 Evolution
Techniques for measurement of COn evolvedin a known time from a known area of soilsurface in situ are either ‘static’ (using a chemi-cal absorbant) or ‘dynamic’ (analysis by IRGAin a gas stream flushing the system).
A ‘static’ technique (Anderson, 1982) wasused in this experiment. Metal boxes of 23 cmwidth (square) and 35 cm height with one sealedend were used as chambers to collect or trap theCOn produced at the soil surface.
A week before the first measurements wenmade, sites for the respirometers were selecteeat random in the planting row approximatel!2 m from the palms and cleared from livingvegetation and mulch at the soil surface. At thetime of sampling, the CO2 traps were preparecin screw-capped small plastic jars with 8 endiameter and 9 cm height containing exact1125 ml 1M KOH which were placed on metatripods about 2 cm above the soil surface. Tbmetal boxes were immediately placed over thlalkali traps and pressed into the soil to abou2 cm depth by cutting the soil with knife at thlperiphery and additionally sealed with soil athe edge around the lower margin. The boxewere shielded from heating by direct sunlighby covering them with an appropriately size,sheet of plywood.
After 24 hr exposure, the exposed MO1samples were removed, sealed with air-tight lidand returned to the laboratory for analysi:Controls for the amounts of CO2 in air consisteof jars of KOH placed in the metal boxes whitwere closed using plywood lids and sealed witbinding tape.
In the laboratory, the exposed KOH sampleswere titrated with 1 M HCl after addition of2 ml saturated BaCL and a few drops ofphenolphthalein indicator. Absorbed COZ wascalculated on the basis that 1 ml 1M HCl isequivalent to 22 mg COZ and results expressedas mg COzm-2 hr-1 (Anderson and Ingram, 1993).Four replicate measurements were made ineach plot. A mean value was taken for the fourdeterminations in each plot.
The amount of CO, evolved from the soil (mgCO* m-* hr-’ ) was calculated using the function:
76
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
con = [Vc-(Vtz-Vt*)] x 22 x t x10 000
24 area of chamber ( cm2)
where Vc and 0% - Vt,) are the volumes (ml)of 1 M HCI needed to titrate the KOH fromthe control boxes or the KOH samplesexposed to the soil surface, respectively.
RESULTS AND DISCUSSION
Carbon Mineralization from LaboratoryIncubation
Figure I shows the C mineralization pat-terns of different treatments obtained from oneweek laboratory incubations. The C minerali-zation rates varied over time because of differ-ences in substrate availability in the soil sam-ples and soil moisture during sampling. Treat-ment effects were fairly consistent while thetime trends in C mineralization were similar forall the treatments. The rise and fall of C
0.08
0.07-7$u2 0.06z?-0
k 0.05
(v8E 0.04
aIP.z 0.03z4c!
. - $ 0.02
0
0.01
mineralization rates between months 8 and 12were mainly due to changes in soil moisturestatus for each treatment during sampling asaffected by the rainfall. As mentioned earlier,laboratory incubation is a measure of substrateavailability and the effect of different treat-ments on C mineralization was observed through-out the experimental period. During the earlyperiod, the O/FP location showed higher Cmineralization compared with other treatmentsand this was maintained for 8-10 months. Thisindicates that the O/FP location had greatermicrobial population or activitiy resulting fromprevious input of residual materials of cutfronds which accumulate significant amount oforganic matter and this was paralleled with thehigher initial concentration of organic carbon inthis area.
An early effect of labile carbon in palmresidues on C mineralization was observedduring the early stages (4-6 months) in theC/P and P/B treatments in which C minerali-zation in the C/P and P/B treatments was
\\+ Complete removal (C/R) I+ Complete removal (C/R) I
+ Chipped/shredded (C/S)+ Chipped/shredded (C/S)
+ Partial burning (P/B)+ Partial burning (P/B) ’’
U Chipped/pulverized (C/P)U Chipped/pulverized (C/P)
e Old avenue (O/A)e Old avenue (O/A)
+ Old frond pile (O/FP)+ Old frond pile (O/FP)
2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0
Time (month)
Figure 1. Effects of various treatments on C mineralizationdetermined in laboratory incubations over seven days.
77
JOURNAL OF OIL PALM RESEARCH 11(2)
significantly higher (PcO.05) compared with theI C/S and C/B treatments and O/A location. This
could be attributed to significant amount oforganic C entering the soil system due to thefaster rate of decomposition in the C/P treat-ment and the slower release of organic C fromburned materials in the P/B treatments.
The C mineralization rates at six months.ranged from 0.017-0.038 mg 602 g-’ dry soilday’, highest in the O/FP location and lowest inthe O/A location and intermediate in the C/Streatment with a value of 0.025 mg CO, g’ drysoil day’. The O/FP location, P/B and C/P treat-ments showed significantly higher (PcO.05) ratesthan the C/S and C/R treatments and O/A loca-tion.
The carbon mineralization rates reachedtheir peak at 12-14 months for all treatments.At 12 months, the C mineralization rate in theC/S and C/P treatments were significantly higher(PcO.05) compared with the other treatmentsand positions. The C/S and C/P treatments hadmean values of 0.067 and 0.062 mg COZg-l drysoil day-’ respectively and the other treatmentsvalues ranging from 0.027-0.041 mg COZg-l drysoil day”. The high C mineralization rates at12-14 months appeared related to the high meansoil moisture for all treatments and locations of29.47%. Similar observations were also made bySingh and Gupta (1977) who reported that soilmoisture was positively correlated with CO2evolution. Unlike temperate regions, soil tem-perature is not a seasonally limiting factor inthe tropics for microbial activity, and soilmoisture is of greater significance in controllingthe release of COZ from the soil. Even at 18months, the C/S and C/P treatments still hadhigher values of C mineralization rate amongother treatments although the level tended todecrease significantly.
It was observed that much of the palmresidues decompose above-ground, hence, thecarbon mineralized reflected the carbon of dis-solved and particulate materials entering thesoil and also carbon from decomposing roots.Thus, the measurement of C mineralizationthrough soil respiration did not quantitativelyreflect the carbon mineralized from residuesinputs above-ground. By substracting the Cmineralized from C/R treatment or from theO/A location (without crop residues inputs), we
can estimate the carbon mineralized in the soildue to transfers of dissolved and particulatematerial from above-ground. For example, atthe peak of 12 months the mean value of C mine-ralization rate in the C/P and C/S treatmentswas 0.065 mg CO2 g’ dry soil day-l and the meanvalue of C mineralization rate in the C/B treat-ment and O/A location was 0.032 mg CO2 g-l drysoil day-“. The difference of 0.033 mg CO, g-l drysoil day-” was from the carbon inputs of cropresidues entering the soil. It was estimated at 12months that about 49.5 kg CO2 ha-l day-l or18.07 t CO1 ha-l yrp enter the soil at the top of15 cm in the plots which received crop residuesinputs. The mean value of C mineralized in theplot that received no crop residue inputs (C/Rtreatment and O/A location) was 0.023 mg C!OZg1 dry soil day’ whereas the mean value ofC mineralized in the plots that received cropresidue (C/S and C/P treatment) was 0.037 mgCO2 g-l dry soil day-l. Hence, the flux of COZ dueto residues inputs was 0.014 mg COn g-l dry soilday’. This amounts to about 21 kg COZ ha-’day’ and is equivalent to 7.7 t CO2 ha-’ yr’(to adepth of 15 cm).
Overall the mean C mineralization ratesdecreased in the rank order: C/S = C/P = O/l?P> P/B > C/B = OfA throughout the study period.This suggests the lack of substrate in the areawithout crop residue inputs (C/R treatment andO/A location) except decomposed roots andinsignificant input from legume covers.
Soil CO2 Evolution under Field ile sitlaConditions
The efflux of CO, from soil in the fieldtheoretically represents an integrated measureof root respiration, soil fauna respiration andcarbon mineralization from all the differentcarbon pools in the soil and crop residue. In thecase of this study, however, respiration fromliving roots was not a significant source of COZbecause most above-ground biomass was clearedto establish the new plantation. The develop-ment of the cover crop will have contributed toroot respiration during the experimental periodbut this was likely to be small in relation to COZmineralization from litter and soil organic matter,However, with the uniform growth of legume inall treatments area, the effects of differences in
78
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
treatments can be observed.CO2 evolution provides a sensitive measure
of the response of microbial activity to diurnalvariations in temperature and moisture, theeffects of wetting and drying following rainfallevents, and differences in plot treatments.
Figure 2 shows the patterns of CO2 evolutionfrom field in situ measurements made overperiods of 24 hr. The COZ flux varied during thecourse of the experimental period. In general,the COZ fluxes increased with time over the 18months study period. Over the first two months,there were no significant differences betweenthe treatments. This was probably due to theeffect of disturbance in all plots after felling andclearing of the old stand. After four months, asignificantly higher (PcO.05) rate of CO, evolu-tion was observed in the O/F’P location comparedwith other treatments except the P/B treatment.At six months after treatments, the CO2 flux inthe C/R treatment and O/A location were sig-nificantly lower (PcO.05) compared with the
other treatments. The C/S, C/P and P/B treat-ments and O/FP location showed no significantdifferences in COZ evolution rate between eachother. The CO2 flux at 8 and IO months mea-surements gave low values for all treatmentsdue to low temperature in the afternoon (cloudyweather) and rain at night. Similarly, the 12 and14 months measurements also gave low valuesfor all treatments, attributed to the low tem-perature (cloudy weather) during the whole day.Several workers (Reiners, 1968; Schwartzkopf,1978; Buyanovsky et al., 1986) have stressed the \importance of soil moisture, soil temperature,and/or wind velocity at the soil surface asenvironmental factors that dramatically affectthe rates of CO2 evolution
Measurements conducted at 16 and 18months showed high rates of CO2 evolution asthe air temperature was higher. At 16 months,the CO2 flux of the C/P and C/S treatments andOLFP location were significantly higher (PcO.05)than the C/R and P/B treatments and O/A
8 0
6 0
-i> Chipped/shredded (C/S)
+ Partial burning (P/B)
“J- Chlppedlpulverized (C/P)
a Old avenue (O/A)
-& Old frond pile (O/FP)
2 4 6 8 IO 12
Time (month)
1 4 1 6 1 8 2 0
Figure 2. Effects of various treatments on CO2 evolution determinedfrom field measurements (in situ) over 24 hr periods.
79
JOURNAL OF OIL PALM RESEARCH 11(2)
location. By this period, some of dissolvedorganic carbon and particulate organic carbonhad entered the mineral soil from decomposingresidues”
The mean CO2 evolution rate for all treat-ments during the study period ranged from104.57-146.61 mg CO2 m-2 hr-’ with the O/FPlocation $at the highest end of the range and theO/A location at the lower end of the range. TheCO2 fluxes for the C/S and C/P treatments werecomparable with mean values of 141.58 and145.39 mg COZ m-“hr.’ respectively. This reflectsthe same amount of crop residue inputs in theseplots and similar transfer of labile carbon to thesoil in the two treatments. The mean value ofthe fluxes of carbon as affected by crop residuesinputs during the study period was obtained bysubtracting the mean value of CO2 evolved ofC/R treatment plots and O/A location. Thus,107.93 mg CO, m-2hr-1 was subtracted from themean value of C/S and C/P treatment plotswhich had a value of 143.49 mg CO2 m-2 hr-’ andthe fluxes of carbon due to crop residue inputswas estimated to be approximately 35.56 mgCOZ m-“hr.‘, This amounts to about 8.53 kg CO2ha-” day” or about 3.12 t COZ ha-’ yr-’ producedfrom soil respiration due to crop residues inputsThe value was about 50% the value obtainedfrom laboratory incubation. This could be attri-buted to the flush of COZ during early stage oflaboratory incubation and soil disturbance. Alsothe field measurements of COZ evolution wereaffected by seasonal effects, especially of soilmoisture (Singh and Gupta, 1977) and tempera-ture fluctuations during the day (Bandara,1991) which significantly affect the CO2 evolu-tion rate. In addition, the value of CO2 producedfrom laboratory incubation was calculated using15 cm soil depth and the value would be lowerwhen using soil with less than 15 cm soil depth.In this case, we cannot determine the effectivesoil depth which affects the flux of CO2 evolutionfrom field measurement. Soil depth of less than10 cm would narrow the value of 602 producedby the two methods. Another possibility wasthat some losses of CO2 at the edge of the metalboxes might have occurred.
The overall increasing trend of COZ produc-tion through soil respiration indicated that moreorganic carbon, especially labile organic carbonand particulate materials from decomposing
crop residues and roots material, enter themineral soil over time.
The values obtained in this study were quiteclose to the value obtained by Henson (1993)who reported the CO, evolution from the soilwithout root respiration under mature oil palm.IIenson (1993) gave a value of 0.100 g CO2m-2 hr-’ in the avenue or interrow location anda mean value of 200 mg COZ m-2 hrP from thevarious locations in the plantation. Andersonet al. (1983) reported the mean CO2 efflux ratein lowland rain forests in Gunung Mulu Na-tional Park, Sarawak ranging from 186-307 mgCOZ m.2hr-1. A higher rate of CO2 evolution wasobtained by Ogawa (1978) from tropical forestsoil at Pasoh, Malaysia ranging from 476-709mg CO2 m-2 hr-I. Thus, the CO2 evolution ratesmeasured in this study are in the same orderbut significantly lower than those obtained fromtropical forest.
The CO2 evolution rates in the field weresignificantly correlated with the CO2 productionrates in the laboratory incubations (Table 1).The CO2 evoPution rates in the t?ePd werecalculated based on I5 cm soiP depth and usinga bulk density of 1.00 g cm-3. The mean valueof CO2 evolution rates for all treatments in thefield was highly correlated with the mean valueof CO2 production rates in the laboratoryincubations over one week (E = -0.02 + 2.5F withr = 0.989, P<O.OOl) throughout the study period.It was found that the average CO2 productionrates in the laboratory incubations over oneweek 2.5 times higher than the CO, evolutionrates in the field. This suggests that the ob-served CO2 fluxes do reflect the microbial ac-tivity from different treatments with differentsubstrates quality and crop residues inputs. Theflush due to disturbance of soil aggregatesincreased the microbial activity during labora-tory incubations
Nitrogen Mineralization
N mineralization rates over the 18 monthsstudy period showed significant differencesbetween different treatments (Tables 2 and 3).In the early stages (first four months), all thetreatments and positions showed an early flushof N mineralization The early flush was ex-pected as a consequence of soil disturbance after
MlNERALlZATlON OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
TABLE 1. REGRESSION EQUATIONS FOR RATES OF COz EVOLUTION IN THE FlELDPLOTS (F) OVER 24 HOURS (mg CO1 g-l dry soil day-‘) AND CO* PRODUCTION
(mg COz g-l dry soil day-‘) FROM SOILS FROM THE SAME TREATMENTS INCUBATEDIN THE LABORATORY (L) AT 25°C FOR SEVEN DAYS
Months aftertreatment Coefficientestablished Equation Cd Significance
2 L = -0.03 Y 2.9F 0.942 <0.0054 I, = -0.04 9 3.OF 0.967 <0.0056 L = -0.04 + 2.7F 0.887 <Q.O28 L = 0.02 -I- Q.9F 0.808 <O.lO
10 L = 0.01 + 1.3F 0.972 <0.00512 L = -0.02 + 3.8F 0.920 <O.Ol14 k = -0.09 -I- 7.2F 0.938 <O.OP16 L = -0.03 c 2.lF 0.987 <Q.OOl18 E = -0.01 + 1.8F 0.959 <0.005 ____-
TABLE 2. NET NITROGEN MINERAL~~ATI RATES FOR TREATMENTS AND PLOTLOCATIONS IN SOIL AT O-15 em AND 15-30 cm DEPTHS DETERMINED BY TWO WEEKS
TABLE 3. NET NITROGEN MINERALIZATION RATES FOR TREATMENTS AND PLOT LOCATIONS IN SOILAT O-15 cm AND 15-30 cm DEPTHS DETERMINED BY ONE WEEK ANAEROBIC LABORATORY INCUBATION
time1 = after seven days incubation periodtime0 = before incubation.
land clearing. The aerobic mineralization rate At six months, the WFP location, and C/S,of the WFP location (0.15 cm soil depth) was P/B and C/P treatments showed significantlysignificantly higher (P<O.O5) than all the other higher (P < 0.05) N mineralization rates thantreatments except the C/P treatment in the first the C/R treatment and O/A location. The mine-two months (Z’abk 21, and maintained the ralization rates for all treatments and locationshigher rates for 10 months. The nitrogen min- generally increased at 12 months. This mayeralization potential was reflected by the high have been the consequence of higher decompo-initial total soil N in the O/FP location, sition rates and microbial activity in mineral
Similarly the P/B treatment also showed soils associated with continuously moist condi-high initial rates of mineralization, which were tions in the month during sampling. The meanmaintained until six months. The effects of soil moisture for all treatments and locations atburning on mineralization were transient. Singh 12 months sampling was 29.46%.et al. (1991) reported the mean annual N Moisture was one of the limiting factorsmineralization was 20% higher and the pool of influencing the mineralization rate throughoutavailable N 54% higher in the burned treatment the experimental period and the soil moisturein a dry tropical savanna compared with the values tended to fluctuate following the rainfallprotected treatment. The N mineralization rates distribution pattern recorded during the study.in dry tropical savanna ranged from 1.8 to 30.6 For example, the mean N mineralization ratepg N g-l dry soil day-’ within an annual cycle. for all treatments and locations from aerobic
82
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
incubation at 10 months (O-15 cm soil depth) was0.39 pg N at a mean soil moisture content of25.79%. In contrast, at 12 months the mean Nmineralization rate was 0.53 pg N g-l dry soilday’ at a mean soil moiture content of 29.46%.In addition, it was observed most of the residuematerials such as the trunks, rachises and rootshad lost more than 50% of initial mass by 12months and substantial amounts of N (c. 320kg N ha-l) would have been lost from thedecomposing material.
The mineralization rates at 12 months ob-tained from aerobic and anaerobic incubationsof the C/S treatment at O-15 cm depth (Tables2 and 3) were significantly higher (PcO.05) thanthe other treatments and locations except theC/P treatment. The C/S and C/P treatments atO-15 cm soil depth mineralized about 0.60 ygN g-l dry soil day’ and the C/R, P/B, O/A andO/FP treatments 0.50, 0.51, 0.47, 0.53 pg Ng-l dry soil day’ respectively from aerobic incu-bation (Tuble 2). Higher rates of N minerali-zation in the C/S and C/F treatments may haveresulted from the build up of readily-minera-lizable organic N in the soil over the 12 monthsof oil palm residue application.
The mineralization rates at 18 months ob-tained from aerobic and anaerobic incubationsof the C/S, C/P and P/B treatments were sig-nificantly higher (P < 0.05) compared with theC/R treatment and O/A location at both soildepths. The mineralization rates for the OLFPlocation were slightly lower compared with theC/S, C/P and P/B treatments.
The mean aerobic mineralization rates forthe plots which received crop residues (C/S andC/P treatments) and the plots without residues(C/R and O/A treatments) were 0.41 and 0.31pg N g-l dry soil day1 (at O-15 cm soil depth),0.36 and 0.26 pg N g’ day-’ (at 15-30 cm soildepth) respectively. It was found that the mi-neralization rates of N from the plots whichreceived crop residues (C/S and C/P treatments)and the plots without residues (C/R and O/Atreatment) were 224 and 170 kg N ha-’ yr-’ atthe top O-15 cm soil depth respectively. Themineralization rates of N at 15-30 cm soil depthfor the plots (with and without residue inputs)were 197 and 142 kg N ha-l y-r-l respectively.Thus, the total N mineralization rates to adepth of 30 cm for plots with and withoutresidue inputs were 421 and 312 kg N ha-l
y-r’. The difference due to crop residues inputwas about 109 kg N ha-’ yr-l~
In all cases, mineralization rates were sig-nificantly higher at the O-15 cm in the soil profilethan at 15-30 cm soil depth which possibly dueto lack of transport of dead organic carbon. Thisreflects the increasing stability of soil organicmatter down the soil profiles but the relativelyhigh mineralization rates at 15-30 cm are incontrast with results from undisturbed naturalforest soils.
The cumulative N mineralization rates of allthe treatments and locations at O-15 cm and ’15-30 cm soil depths obtained from aerobicincubation over 18 month periods reflects theoverall profile of N availability to the youngpalms. The trends were quite similar but weredifferent in magnitude. The O/FP location hadsignificantly higher tP < 0.05) cumulative netN mineralization rates\ than soils in the othertreatments and decreased in the order: O/FP >C/P = C/S > P/B > C/R > O/A. The mean Nmineralization rates at O-15 cm soil depthobtained from aerobic incubation for all treat-ments and locations over 18 months periodranged from 0.31-0.45 pg N g-l dry soil day-l inwhich the highest value in the O/FP location andthe lowest value was in the O/A location. Thismay be related to the availability of soil carbonand organic N in these areas and was found tobe parallel with soil respiration results.
It is difficult to compare the rates of Nmineralization found in this study with ratesfound for other systems because of differencesin incubation conditions. As reported by Scholesand Sanchez (1989), most temperate forest soilincubations have N mineralization rates ofaround l-2 pg N g-l dry soil day-’ and typicalrates for tropical forest soils range from 0.1 to6 Fg N g1 dry soil day’. Their work on Nmineralization studies, using an in situ metho-dology of incubation of undisturbed Ultisol soilunder forest in Yurimaguas, Peru, showed Nmineralization rates in the range of 0.3-0.7 pgN g’ dry soil day-l. These values were quite closeto those obtained in this study.
The mean mineralization potential or ‘Nmineralization index’ obtained from anaerobicconditions during the study period rangedbetween 0.53-0.86 Kg (O-15 cm depth) and 0.48-0.79 pg g-’ dry soil day-’ (15-30 cm depth) inwhich the highest value was in the O/FP location
83
JOURNAL OF OIL PALM RESEARCH 11(2)
and the lowest value in the O/A location. Themean mineralization potential at O-15 cm soildepth for C/S and C/P treatments (with residueinputs) was 0.80 1.18 (or 438 kg ha-” yr’) andthe mean for C/R and O/A (without residueinput) was 0.55 pg g-l dry soil dayI (or 301 kgha-’ yr’).
Taking the averages of all data, the Nmineralization rates under anaerobic conditionswere (about twice) those under aerobic condi-tions. Waring and Bremner (1964) found a ratioof 1.23:1 for anaerobic: aerobic N mineralizationin agricultural soils. Gale and Gilmour (1988)also found N mineralization proceeded morerapidly under anaerobic conditions which wasattributed to the lower metabolic effkiencies ofthe anaerobic microbial populations.
Relationships between Carbon and Nitro-gen Mineralization
TuUes 4 and 5 show the relationship be-tween carbon mineralization and nitrogen mi-neralization under aerobic and anaerobic con-ditions throughout the period studied. Signifi-cant linear relationships between N minerali-zation under both conditions and C mineraliza-tion were found at each sampling date. Gilmour
et al. (19851, Gale and Gilmour (1936) andMoorhead et cd. (1987) also found Pinear rePa-tionships between the net N and net C mine-ralized from organic substrates with PQW C/Nratios under aerobic conditions. Similar Pinearrelationships were also observed during the netN mineralization under aerobic and anaerobicconditions (Gale and Gilmour, 1988). Theserelationships suggest that C and N are beingmineralized from the same labile (light fraction)pools under the same rate determinants. Theinputs of pruned fronds over long period caf timein the O/.FP location increased the Bevel of soilorganic matter compared to the O/A location(Khalid Haron, 1997). Similarly, crop residueinputs in the C/P and C/S treatments resultedin an increase in soil organic matter (KhalidHaron, 1997) and, thus, mineralization of soilorganic N. The increase in soil organic matterand mineralization of organic N in the @/I? andC/S treatments, however, did not represent theamounts of crop residues inputs in these treat-ments. This was possibly due to the residueplacement or localization of organic carbonwhich accumulated above the ground. It willtake a longer period of time for the soil organicmatter to enter the mineral soil as observed inthe O/E’P location.
TABLE 4. REGRESSION EQUATIONS SHOWING THE RELATIONSHIPSBETWEEN CARBON MINERALIZATION (C) AND NITROGEN MINERALIZATION
(N) OBTAINED FROM AEROBIC LABORATORY INCUBATION OF SOILS(O-15 cm) FROM THE DIFFERENT TREATMENTS
Months aftertreatmentestablishe Equation
Coefficientb-1 Significance
2 N = 0.26 +21.18C 0.9714 N = 0.21 + 10.9oc 0.8096 N = 0.08 + 5.84C 0.9518 N = -0.04 + 9.73C 0.958
10 N = 0.04 +12.68C 0.96712 N = 0.39 + 3.26C 0.99414 N = 0.15 + 3.71C 0.97516 N = 0.05 + 6.32C 0.9941 8 N = -0.004 + 10.48C 0.989
0.0050.100.0050.0050.0050.0010.0010.0010.001
84
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
TABLE 5. REGRESSION EQUATIONS SHOWING THE RELATIONSHIPS BETWEENNITROGEN MINERALIZATION (N) OBTAINED FROM ANAEROBIC LABORATORY
INCUBATION OF SOILS (O-15 cm) AND CARBON MINERALIZATION (C) FROM THEDIFFERENT TREATMENTS
Months aftertreatmentestablished Equation
2 -
4 N = 0.13 + 28.13@
6 N = 0.25 -I- 18.33@
8 N = -0.45 -I- 39.23C
BO N = 0.09 + 18.426
12 N = 0.50 + 8.16C
14 N = 0.17 + 11.68C
16 N = 0.08 + 13.67C
18 N = -0.10 + 24.35@
As reported by Mengel (1996), mineraliza-tion of organic N requires microbial conversionof organic matter. Nitrogen mineralization con-sists of a sequence of enzymatic processes forwhich the living microbial ‘biomass provides theenzymes and the dead microbial biomass thesubstrate. Only a small percentage of the totalsoil organic N is easily mineralizable and con-tributes to the pool of mineral soil N. Predomi-nant sources of mineralization are amino-N andpolymers of amino sugars present in the soilmicrobial biomass. The nitrogen mineralizationpotential is represented by some of the microbialbiomass (living + dead) and labile N sources.
Mineralization of C and N from ‘LightFraction’ Soil Organic Matter
The C mineralized from the light fractionwas significantly higher than from the soilunder the organic layer. At the 12th month, themineralization rate of the light fraction C fromthe C/S treatment ranged from 1.09-1.52 mgCO2 g1 dry soil day-l with a mean of 1.30 (f0.101S.E) mg COZ g’ dry soil day’ . The C/P treatmenthad values ranging from 0.91-1.12 mg CO2gldry soil day-l with a mean of 1.03 (f0.050 S.E)mg COZ g-l dry soil day-‘. A slight decrease inC mineralization rate of the light fraction C wasobserved at 18 months in which the mean valuesofthe C/S and C/P treatments were 1.03 (f0.093
CoefficientW___--
Significance___-
0.929 0.010.912 0.020.953 0.005
0.984 Cl.0010.992 0.001
0.993 0.0010.997 0.001
0.989 0.001
S.E) and 0.92 kk0.047 S.E) mg COZ g’ dry soilday’ respectively. This means that the miner-alization rate of C from light fraction C wasabout 20 times higher than C mineralizationfrom the mineral soil under the organic layer.
Similarly, the N mineralization rate of thelight fraction C was also significantly higherthan in the soil sampled under the organic layer.At 12 months measurements, the mineraliza-tion rate of N from the C/S treatment rangedfrom 3.49-4.76 pg N g-’ dry soil day-l with amean value of 4.10 (f0.293 S.E) pg N g-l dry soilday-’ and the mineralization rate of N from theC/P treatment ranged from 2.81-3.62 pg N g-ldry soil day1 with a mean of 3.29 (+O.P77 SE)pg N g-l dry soil day’. The N mineralizationrates at 18 months sampling were decreasedslightly in the C/S treatment, ranging from 1.90-4.15 pg N g-l dry soil day-l with a mean valueof 3.24 (+0.475 S.E) pg N g-’ dry soil day-“, andthe C/P treatment had values ranging from 2.83-4.00 pg N g-l dry soil day’ with a mean valueof 3.16 (f0.369 S.E) pg N g-l dry soil day-‘. Itwas observed that the N mineralization ratesof light fraction C accumulated on the top soilsurface in the mulched area were about 6-7times higher than in soil under the organiclayer.
Accumulation of the light fraction C in theC/S and C/P treatments will give greater dif-ferences between treatments. In contrast, the
85
JOURNAL OF OIL PALM RESEARCH 11(2)
accumulation of light fraction C in the Pmtreatment due to burning was not found to besignificant as burning had destroyed the organicmatter and the light fraction C left over fromburning was probably of a different or lowquality. Similarly, in the C/R treatment and atO/A location, no light fraction C was present onthe soil surface.
CQNCLUSION
Substantial amounts of above-ground oil palmresidues during felling of old stands whichcontributed about 577 kg N ha-l and 40 t Cha-l and the root materials produced about 65kg N ha-’ and 8 t C ha-’ were the main sourcesof C and N which affect the mineralization ofC and N in the soil.
IDuring the study period, the C mineraliza-tion rates varied between treatments over time.The overall pattern of C mineralization wassimilar for all the treatments except for thedifference in magnitude and they are related tothe inputs of dead organic matter and soilorganic matter from the previous crops. Thehigher C mineralization rates in the C/S andC/P treatments and O/FP location than in theP/B and C/R treatments and O/A location indi-cated large amounts of microbial biomass andhigher microbial activity due organic C inputsin the former treatments and location, Thecarbon fluxes due to crop residue inputs contri-buted about 7.7 t CO* ha-’ yr-’ or the equivalentof 2.1 t C ha-l yr-’ (to a depth of 15 cm) whichwas released by the soil. Significantly higherrates of C mineralization from the light fractionorganic matter which accumulated on the topsoil surface of the C/S and C/P treatments. Themineralization rate of C from the light fractionC was found to be about 20 times higher thanin the soil under the organic layer. The fluxesof COz in the C/P and C/S treatments andO/FP location were higher than in the P/B andC/R treatments and O/A location. The COZ fluxesmay largely reflect the microbial activity fromdifferent treatments.
The N mineralization rates during the studyperiod also varied between different treatments.Similarly, fresh input of residue materials causedhigher soil N mineralization rates. The N
mineralization rate of the light fraction accumulated on the top soil surface was found to bfabout 6-7 times higher than in the soil undethe organic layer. The mineralization of Ebetween aerobic and anaerobic incubations werisignificantly correlated. Similarly, significanlinear relationships between C and N mineralization found in this study indicated that thfmicrobial activity regulated both the decompasition and mineralization processes and whiclhad similar factor affecting the processes.
From the mineralization study conductecover 18 months, it was found that the inputof crop residues in the C/P and C/S treatmentcan significantly increase the availability oN to the young palm in which about 421 kg2ha-l y-r-l (to a depth of 30 cm) were mineralize1from the mineral soil and made available to thlpalm. In contrast, the plots without crop residue,inputs or planting the young palm in the olcinterrow or O/A location only received 312 klN ha-’ yrp from N mineralization which wa,probably from decomposed roots. Thus, thlfluxes of 109 kg N ha-’ yr-’ was transferred tithe soil as a consequence of leaving crop residue,above the ground during clearing and replanting of the plantation. However the mineralization potential or the ‘N mineralization indelifrom anaerobic incubation was almost doubllthat of the above figures indicating there is eve]more N potentially available than was releaserby the aerobic incubation. In addition, tremendous amounts of N were in the labile pools othe light fraction organic matter near the soisurface which mineralized above-ground antbecame available for young palm which can bltaken up by feeder roots underneath the organifresidues.
The C and N mineralization rates obtainerduring the study period in the plots whiclreceived residues inputs did not reflect thlamounts of crop residue inputs. This was probably due to the localization or residue placemenabove-ground at the soil surface. A budget 01N requirement for the growth of young palm\can be made from the results of the presenmineralization study.
ACKNOWLEDGEMENTS
The authors would like to thank the Director
MINERALIZATION OF SOIL ORGANIC CARBON AND NITROGEN IN RELATION TO RESIDUE MANAGEMENTFOLLOWING REPLANTING OF AN OIL PALM PLANTATION
General of PORIM for permission to publish thispaper. The authors also wish to gratefullyacknowledge the funding from PORIM for thisstudy.
REFERENCES
‘ALEXANDER, M (1977). Introduction to SoilMicrobiology. John Wiley & Sons, New York.467~~.
ANDERSON, J P E (1982). Soil respiration.Agronomy 9, Part 2 (41). In Chemical andBiological Methods. 2 ed. Am. Sot. Agronomy.Madison Wise. p. 831-871.
ANDERSON, J M; PROCTOR, J andVALLACK,H W (1983). Ecological studies in four contrast-ing lowland rain forest in Gunung Mulu Na-tional Park, Sarawak. III. Decomposition pro-cesses and nutrient losses from leaf litter.Journal of Ecology, 71:503-527.
ANDERSON, J M and SPENSER, T (1991).Carbon, nutrient and water balances of tropicalrainforest ecosystems subject to disturbance.Mm Digest, 7, UNESCO, Paris, 95pp.
ANDERSON, J M and INGRAM, J S (1993).Tropical Soil Bio 1 ogy and Fertility, A Handbookof Methods. Second edition. CommonwealthAgricultural Bureau, Oxon, 221~~.
BANDARA, W M P T (1991). The effects ofmulching practices on soil properties and pro-cesses in an agroforestry system, Sri Lanka. M.Phil. thesis. University of Exeter. 244~~.
BREMNER, J M (1968). The nitrogen consti-tuent of soil organic matter and their role in soilfertility, In Organic Matter and Soil Fertility.423~~.
BUOL, S W (1973). Soil genesis, morphology,and classification. In Sanchez, P A (ed.) Areview ofsoils research in tropical Latin America.North Carolina Agr. Exp. Sta. Tech. Bull. 219:l-38.
BUYANOVSKY, G A; WAGNER, G H and
GANTZER, C J (1986). Soil respiration m awinter wheat ecosystem. Soil Sci. Sot. Am, J.,50:338-345.
CORLEY, R H V; HARDON, J J and WOOD,B J (1976). Developments in crop science I, InOil Palm Research, Elsevier, Amsterdam, 532PP.
GALE, P M and GILMOUR, J T (1986). Carbonand nitrogen mineralization kinetics for poultrylitter. J. Environ. Qual., X:423-426. ’
GALE, P M and GILMOUR, J T (1988). Netmineralization of carbon and nitrogen underaerobic and anaerobic conditions. Soil Sci. Sot.Am. J., 52:1006-1010.
GILMOUR, J T; CLARK, M D and SIGUA, GC (1985). Estimating net nitrogen mineraliza-tion from carbon dioxide evolution. Soil Sci. Sot.Am. J., 49:B398-1402.
HARRIS, P J (1988). Microbial transformationsof nitrogen. In Alan, W fed.) Russell’s SoilConditons and Plant Growth. 11th ed. LongmanScientific & Technical. p.608-651.
HARTLEY, C W S (1988). The Oil Palm. Thirdedition. Longman Group UK Limited. 761pp.
HENSON, I E (1993). Carbon assimilation,water use and energy balance of an oil palmplantation assessed using micrometeorologicaltechniques. In Jalani Sukaimi et al. (eds.) Proc.of PORIM International Palm Oil Congress‘Update and Vision’ -Agriculture Module, PalmOil Research Institute of Malaysia, Bangi.p.137-158.
JENKINSON, D S (1981). The fate of plant andanimal residues in soil. In Greenland, D J andHayes, M H B (eds.) The Chemistry of SoilProcesses. Wiley, New York. 495pp.
KEENEY, D R and BREMNER, J M (1966).Comparison and evaluation of laboratorymethods of obtaining an index of soil nitrogenavailability. Agron. J., 58:498-503.
KEENEY, D R and BREMNER, J M (1967).
87
JOURNAL OF OIL PALM RESEARCH 11(2)
Determination and isotope-ratio analysis ofdifferent forms of nitrogen in soil. VI. Minera-lizable nitrogen. Soil Sci. Sot. Am. Proc., 31:34-39.
KEENEY, D R (1982). Nitrogen - availabilityIndices. In Page, A L et al. (eds.) Methods ofSoilAnalysis. Part 2.2nd. ed. Agron. Monogr. 9. ASAand SSSA, Madison, WI. p.711-733.
KHALID HARQN (1997). Nutrient cycling in anoil palm (EZaeis guineensis Jacq.) plantation:residues decomposition and implications formanagement. Ph.D thesis, University of Exeter,U.K. 298pp.
MENGEL, K (1996). Turnover of organic nitro-gen in soils and its availability to crops. Plantand Soil, P86:83-93.
MOORHEAD, K K, GRAETZ, D A and REDDY,K R (1987). Decomposition of fresh andanaerobically digested plant biomass in soil. CB.Environ. Qual., 16125-28.
MYERS, R J K, PALM, C A; CUEVAS, E;GUNATILLEKE, I U N and BROSSARD, M(1994). The synchronisation of nutrient mine-ralisation and plant nutrient demand. InWoomer, P L and Swiff, M J (eds.) The BiologicalManagement of Tropical SoiZ Fertility. Chi-Chester. John Wiley-Sayce. p* 81-116.
OGAWA, H (1978). Litter production and carboncycling in Pasoh forest. Malaysian Nature Jour-nal, 30:367-373.
RAISON, R J; CONNELL, M J and KHANNA,P K (1987). Methodology for studying fluxes ofsoil mineral-N in situ. Soil Biology and Bio-chemistry, 19:521-530.
REINERS, W A (1968). Carbon dioxide evolu-tion from the floor of three Minnesota forests.Ecology, 49:471-483.
RYAN, J A; SIMS, J L and PEASLEE, D E(1971). Laboratory methods for estimating plantavailable nitrogen in soil. Agron. J., 63:48-X.
SANCHEZ, P A (1976). Properties and Manage-ment of Soils in the Tropics. John Wiley andSons, New York, p. 162-183.
SCHOLES, M C and SANCHEZ, P A (1989).Nitrogen mineralization and leaching as affected by crop-management practices. In NeilC (ed.) Trop Soil Technical Report, 1986-1987North Carolina State University, Raleighp. 122-126.
SCHWARTZKOPF, S (1978). An open chambetechnique for the measurement of carbon dioxide evolution from soils. Ecology, 59:1062-106t
SINGH, J S and GUPTA, S R (1977). Plandecomposition and soil respiration in terrestriEecosystems. Bot. Rev., 43:449-528.
SINGH, R S; RAGHUBANSHI, A S and SING1J S (1991). Nitrogen-mineralization in dry tropcal savanna: effects of burning and grazing. SoBioZ. & Biochem., 23:269-273.
SMITH, J L; PAPENDICK, R I; BEZDICEED F and LYNCH, J M (1992): Soil organic rnatttdynamics and crop residue management. 1
il
3:n
Blaine, M F, Jr. (ed.) Soil Microbial Ecology.Marcel Dekker, Inc, U.S.A. 646~~.
SMITH, J A (1966). An evaluation of nitrogensoil test methodes for Ontario soils. Can. J. SoiESci., 46:185-194.
WARING, S A and BREMNER, J M (1964).Ammonium production in soiP under water-logged conditions as an index of nitrogen avail-ability. Nature, 201:951-952.
![The Global Stoichiometry of Litter Nitrogen Mineralization ... · Stefano Manzoni, 1. Robert B. ]ackson, 2. John A. Trofymow, 3. Amilcare Porporato. 1* Plant residue decomposition](https://static.documents.pub/doc/80x56/5c65fb7609d3f20f218b94bd/the-global-stoichiometry-of-litter-nitrogen-mineralization-stefano-manzoni.jpg)