oil palm nutrition management ijor - caliman
TRANSCRIPT
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Oil Palm MineralNutrition Management
J.P. CalimanDivision Head of SMARTRI PT SMART, Indonesia
ABSTRACT
Irrespective of soil and climate, fertilisation is essential in oil palm cultivation ifgrowth and production potential is to be achieved. It is also necessary for maintainingand improving soil fertility, which is very often a limiting factor on tropical soils.
Oil palm is usually very responsive to fertiliser application. However, significantdifferences in yield responses between distinct pedo-climatic areas, as well as differentialnutrient requirements between mature and immature stages are observed. Manuringgenerally represents the largest, single component of production cost, accounting todayfrequently for around 65% of expenditure for maintenance cost in South East Asia,while in the sixties accounted for 54% according to Piggott (1968) in Malaysia. Comparedto total production and management cost, fertiliser remains at the first rank (Baskett etal., 2002). Actually scientific methods for management of mineral nutrition that givehighly satisfactory results if correctly applied are available. Such managementapproaches are generally based on the response of the palms, aiming at determiningthe rate of fertiliser and the nutrient level in the leaf to achieve the best performance.The most performing plantation companies are also looking for a best balance betweenproduction level and economic factors. This can be achieved by taking into considerationeconomical parameters (like the price of palm products and the cost of applied fertilisers)and scenario about their trends, as the time lag between fertiliser applications and theoil palm response can be up to 3 years. Beside these two main factors for fertilisermanagement, environmental impact of agricultural practices are becoming a majorconcern for environmentalists and consumers, and it is assumed that this aspect willhave to be taken into account in oil palm manuring. Relatively few studies have beencarried out on the relation between mineral nutrition of the palms and water management,especially for irrigated palms. Some past results will be presented.
METHODOLOGY FOR MINERAL NUTRITIONMANAGEMENT : AN EMPIRICAL METHOD
Talking about fertiliser management forcrop cultivation, Gros (1979) emphasize thefact that there is no “master key” acceptablefor all types of ecological and economical
circumstances, but each situation has to beconsidered as a specific case. In other wordsa set of results obtained in one site may notbe appropriate in an other site. On theother hand, a general comprehensivemethodology can be defined to cover mostsituations.
e-mail : [email protected] or [email protected]
Note : Dr. Caliman could not attend the conference and present the lecture due to some last minute pressingengagement in Indonesia. However, the editors felt that the article will provide valuable information to the oilpalm farmers and others who are concerned with oil palm, hence the article is included in this proceedings.
Oil Palm for Farmers’ Prosperity and Edible Oil Security
Eds : Rethinam, P., Reddy, V.M., Mandal, P.K., Suresh, K. and Prasad, M.V.
SOPOPRAD, Pedavegi-534 450, A.P., India pp. 107 - 127
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For oil palm mineral nutritionmanagement, the methodology has beendescribed by Ochs (1985). It is an empiricalmethod based on a combination of fieldexperimentation and monitoring of the palmsmineral nutrition status through leaf diagnosis.
The first step is to define a land unit areadefined as an homogeneous agro-ecologicalzone, i.e. with similar climatic, soil and plantingmaterial characteristics. The size of such aunit may cover from a few hundred up to afew thousand hectares. On each unit area,the decision support system described inFig. 1 must be run:
! Yield (for mature area), vegetativegrowth and nutrient leaf contentsresponse curves to the rate of fertiliserscan be obtained based on the results offield fertiliser trials. Maximum economicalyield and optimum leaf nutrient contentcan then be calculated, taking intoaccount several economical parameters.
! For each homogeneous block of theestate, the fertiliser rates arerecommended depending on the resultof plant analysis (leaf sampling).
! Based on plantation performanceobjectives, agronomists can thenestablish the fertiliser recommendationprogramme adapted to each singleblock.
! Soil fertility monitoring (soil analysis) isnecessary to ensure the sustainability ofthe cropping system.
An extensive fertiliser trials networkcovering the various ecological situations isrequired to feed up decision support systemsto determine the best strategy to be adopted.
In a major number of situations, yieldresponse curves obtained in fertiliser trialsfollow the Mitscherlich model:
Y=a–bEXP(-cX) (1)Where : Y = yield or growth
X = rate of fertiliser Xa, b, c constants with followingmeaning :a : maximum potential of the palms,defined by all limiting factors exceptfertiliser X.b: maximum impact of fertiliser X.c: relative to the curvature of theresponse curve.b * c : slope at the origin = initialefficiency of fertiliser X.
MINERAL NUTRITION MANAGEMENTDURING THE IMMATURE PERIOD
Although the immature period, startingfrom planting time until the first harvestinground, is a key phase for the futureperformance of the palms, little appears in theliterature about the importance of optimumyoung palm development during the immatureperiod. The few publications highlight theimpact of fertilisation on the performance ofpalms in terms of production (Ng, 1970; Ng,1972; Hartley (1988) acknowledged thatinadequate fertilisation during the immatureperiod might irrevocably affects the potentialof the palms.
The lack of economic returns in the veryshort term during this period of immaturity maytempt some companies to reduce upkeepcosts in young plantings. Yet the considerablesusceptibility of young palms to any shortfallsin upkeep is an acknowledged fact. Forexample, if a fertilisation round is cancelled,rapid yellowing occurs and growth is retarded.Such susceptibility is counterbalanced by therobustness of the palm, which will surviveeven in highly unfavorable conditions and willend up ensuring a certain degree ofproduction in many cases.
Recently, the importance of an optimumfertiliser management during the immaturestage has been stressed by Caliman et al.(2002). Based on several trials in South East
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Mineral Nutrition in Oil Palm
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Asia and in Africa, as well as observations atcommercial plantation scale, these authorshave established very close relationshipsbetween the precocity of young palms or theyield levels recorded during the first 2 to 3years of harvesting, and their vegetativedevelopment during immaturity. In mostecological situations only adequate fertilisermanagement can ensure the optimumvegetative development of young palms.
In South East Asia, nitrogen is the mostcommon fertiliser application required duringthe young age together with phosphate, andto a less extend potassium and magnesium.However, a high site specificity is observedbased on the characteristics of each soil, andthe need for an optimum nutrient balance.
In one experiment in Sumatra(Indonesia), the time to maturity as well asthe yield performance during the first year ofharvesting are linearly related to the palmvegetative growth during the immature period(Fig. 2, 3). The nitrogen nutrition of the palmsappears to be the main factor controlling theirvegetative growth (Fig. 4).
In a second experiment, a positivevegetative growth response is observed tophosphorus, nitrogen and to a less extentpotassium fertilisation, while magnesiumapplications did not present any impact (Fig.5 a, b, c, d). This vegetative growth
Nitrogen 2.85-2.90 %Phosphorus 0.175-0.180 %Potassium 1.35-1.40 %Magnesium < 0.28 %
Table 1 : Optimum nutrient leaf level at 24months old (Frond 9)
improvement with N, P and K fertilisers is aconsequence of a significant increases of N,P and K nutrition of the palms (Fig. 6 a, b, c).These results confirm the optimum nutrientleaf contents for this type of planting materialat that age (Table 1). The yield levels recordedduring the first two years of harvesting areclosely related to the vegetative developmentof these palms at the end of the immatureperiod (Fig. 7 a and b). The yield levelsobserved during the third harvesting year
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Mineral Nutrition in Oil Palm
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(from month 49 to month 60 after planting)are less-dependant to the vegetativedevelopment of the palms during immaturestage, although the relation is still highlysignificant (Fig. 7c).
Similar results can be obtained atcommercial scale. Fig. 8a shows the strongimpact of the nitrogen nutrition on thevegetative growth (Length of frond 17) ofyoung palms. Subsequently, the yieldsrecorded are very closely related to thevegetative development achieved at the endof the immature period (Fig. 8b).
One important point to notice is that inthese two charts, each dot represents anaverage value for a thirty hectares block. Inaddition every block has received the sameamount of fertiliser since planting time.Therefore the scattering of the dots indicatesthe necessity of site specificity managementof fertiliser recommendations. There istherefore a need for an appropriate method
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of monitoring the mineral status of the palms.Leaf sampling is usually implemented yearly,starting at the mature period or just before it,i.e. at 24 months old. An earlier leaf sampling,at 12 months old, would certainly help tooptimize the mineral nutrition management inthe latest stages of the immature period, butwill not ensure a full satisfactory results duringthe first 12-14 months, where any nutrientdeficiency would have significant impact onthe growth of the palms.
Therefore, although vegetative growth isthe result of all agricultural practices includingmanuring but also upkeep and landmanagement (drainage, …), it seems that anindicator based on the measurement of oneof the growth parameters could be of first helpfor an early detection of under-performingareas and then-after possible localadjustments of the fertiliser regime of thepalms, if nutrient deficiency is confirmed. Theadvantage of such an indicator is that it isstraight forward as the results are readilyavailable, relatively cheap and easy toimplement at high frequency (every 6 months)and therefore makes possible early correctiveactions.
As most of vegetative parameters likefrond length, girth circumference, petiolecross-section, frond area or relative frondarea, are closely correlated each other, anyof them could be chosen as an appropriateindicator, the easiest to implement beingprobably the length of the frond, measuredfrom the top extremity to the limit of leaflet.
Scoring of the indicator could be doneby comparison to an optimal growth curve,established before hand for each ecologicalsituation and each planting material based ontrials results, or by comparison between areaswithin the same estate. Subsequently, generalinvestigation about under-performing areas,including specific leaf sampling will allow totake rapidly any necessary corrective action.
CHOICE OF FERTILISER TYPE FORIMMATURE PALMS
Generally speaking straight fertilisersgive very good results as far as they are usedwith appropriate care. For example nitrogenvolatilization from urea can be reasonablylimited when the fertiliser is applied during thewet season, and slightly mixed with the topsoilin the circle. Ammonium sulfate isrecommended in location where sulfur is alimiting factor and if no other form of fertilisercontaining sulfur is applied to the palms inenough amounts.
Limited access to manpower is usuallythe reason why many companies preferapplying compound fertilisers rather thanstraights despite the higher cost of theprevious one. This results in a reduction ofthe number of application rounds, so thatscarce manpower can focus on other taskslike harvesting of mature areas. Finally thetotal cost of compound applications (cost offertiliser + cost of application) is often highercompared to straight fertilisers, even througha slight reduction of the rate of compound issometime suggested.
On specific situation like very sandy soils(texture with 90% of sand), high quality coatedfertilisers give very good results in terms ofefficiency per unit of nutrient applied,especially in the very short term (Fig. 9a, b).However, an appropriate fertiliser regimeusing straight fertilisers can also give as goodresults on the development of the palms. Itremains to compare the “energy” required forboth type of fertilisers, but for the time being,these quality-coated fertilisers present sucha high price that they are very scarcely usedin oil palm plantation.
MICRO-NUTRIENT REQUIREMENT:SPECIFIC SITUATION
There are a number of situations wheremicronutrient fertilisers have to be applied tothe palms. The most frequent is on peat soils
Mineral Nutrition in Oil Palm
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where copper, zinc, boron and sometimes ironmust be supplied. It is not the objective of thispaper to review all these situations.Nevertheless, as an example, it is interestingto present some results obtained on very
sandy soils, where a copper deficiency canoften be observed.
Copper deficiency is not very oftenmentioned in the literature unless on peat soil(Ng and Tan, 1974; Gurmit, 1982). One casehas been observed in Brazil on tertiarysedimentary soil (Pacheco et al., 1986). InSumatra, on very sandy soils (80 to 95% ofsands), copper deficiency symptoms appearon young palms shortly after field planting.Beside the typical yellowing foliar symptoms,the growth of the palms is highly affected.Field fertiliser trials show that regular coppersulphate applications since planting time canprevent the occurrence of this deficiency. Anapplication of 10g of CuSO4 in the plantinghole, followed by application of 12.5g every 3months, give very good results in terms ofpalms growth (Table 2).
Leaf analysis results show that theoptimum Cu content for fronds 3 and 9 isaround 5ppm.
MINERAL NUTRITION MANAGEMENTDURING THE MATURE PERIOD
During the mature period, the key finalindicator for the planter is the yield of thepalms. Indeed, although yield is not anoptimum scientific indicator as it is the resultof the whole set of agricultural practices, itrepresents the income that planter will put inhis budget.
As mentioned before, one of the pillarsof the methodology consist in establishingyield and leaf nutrient content response curves
Planting Hole Surface application Frond 9 length Cu leaf content(g/palm) (g/palm/year) (cm) Frond 3 Frond 9
(ppm) (ppm)
Cu0 0 0 182 2.3 2.3Cu1 10 30 208 4.5 4.2Cu2 10 60 232 5.0 4.8Cu3 10 90 233 5.7 5.0
Table 2 : Copper application, leaf analysis and growth
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to the rate of fertiliser applied in field trials.Economical parameters, targeted yield level,and soil fertility trends are also taken intoconsideration.
As an example, in North Sumatra(Indonesia) on sedimentary soils, two fertilisertrials have been set up to study the mineralnutrition of mature palms (7 years old at thebeginning of the trial) relative to four majornutrients N, P, K and Mg. Positive responsesof the yield have been observed for urea, MOPand kieserite applications, with an antagonismbetween K and Mg (Caliman et al., 2001).
Fig. 10 presents the yield responsecurves (based on the Mitscherlich model (2))fitted to the average results recorded duringthe 10 to 12 years old period, for each fertiliser(Urea, MOP and Kieserite). In order to“reduce” the impact of the antagonismbetween K and Mg nutrition in this specificstudy, low rates of kieserite have not beenpart of the analysis for the response curve toMOP application. Likewise, low rates of MOPhave not been part of the analysis for theresponse curve to kieserite application.
YIELDm = am – bm EXP(-cm FERm) (2)with : YIELDm = yield response to fertiliser m
FERm = rate of fertiliser m.
am, bm, cm = constants described earlier, respective to fertiliser m.
! The a values show that N and K arelimiting factors for the yield of the palmswhen kieserite is no more limiting.
! The b values shows that MOPapplications have the strongest impactin terms of yield improvement (42.7 kgFresh Fruit Bunches/palm/year). Thelowest one is obtained with ureaapplication (23.2 kg FFB/palm/year).
! The a and b*c values show the very highefficiency of small rates of kieseriteapplications (at low fertiliser regime, anadditional unit of kieserite applied resultsin an increase of 59.4 units of FFB/palm/year).
Mineral Nutrition in Oil Palm
Fertiliser am bm cm bm* cm
Urea 186.7 23.2 0.37 8.5MOP 187.3 42.7 0.56 23.8Kieserite 179.6 39.4 1.51 59.4
(From Caliman et al. (2001)
Table 3 :Parameters of Mitscherlich yieldresponse curves to fertiliser
Urea Potash Kieserite
(KCl)
Pfer
(US$/t) 122.3 143.8 91.2
R= Pfer
/Ppro
5.3 6.3 4.0
OFR (kg/palm) 1.3 2.4 1.8
Mopt
(%) 2.50 0.97 0.19
- Cost of production= 150 USD/tonne CPO- Oil Extraction Rate: OER = 23%
- Income= 250 USD/tonne CPO (± 300 USD/tonneCPO CIF Rotterdam)
(From Caliman et al. (2001)
Table 4 : Optimum economical FertiliserRate (OFR) and nutrient leafcontent Mopt
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This Mitscherlich model reflects the pointthat the level of yield increase declines whenthe fertiliser rate increases. It is clear thatbeyond a certain dosage, any additionalfertiliser application cannot be paid back bythe small corresponding increase of yield.
This point is called the optimum fertiliserrate (OFR), which gives the maximumeconomical yield. This optimum fertiliser ratedepends on the generated income (related toCPO price Pyield), and on the cost of fertilisersPfer. These two parameters can be presentedthrough a financial ratio R = Pfer / Pyieldgiving the number of units of FFB required topay back a unit of fertiliser applied.
The OFR can be calculated from theeconomical efficiency curve specific to thefertiliser
m : dYIELDm/dFERm = bm*cm EXP(-cmFERm) (3)
This curve shows the economicalefficiency of the fertiliser applied, in otherwords the expected increase of yieldsubsequent to an addition of one unit offertiliser. The maximum profit is obtained foran efficiency equal to R:
dYIELDm/dFERm = bm*cm EXP(-cm OFR)= Rm (4)
then : OFRm = -1/cm LN( Rm/ bm*cm) (5)
Subsequently the nutrient leaf contentresponse curve gives the corresponding valueof the optimum potassium leaf content Kopt.FOLm = aFm – bFm EXP(-cFm FERm) (6)with : FOLm foliar content with application offertiliser rate FERm. Mopt = aFm – bFmEXP(-cFm OFRm) (7) with : Mopt optimumleaf content of nutrient m, relative to optimumfertiliser rate OFRm.
Fig. 11 and 12 show the economicalefficiency curve, and the determination of OFR
and Kopt relative to the potassium fertiliserin the previous example in North Sumatra.Table 4 presents OFR and Mopt related tothe three fertilisers from the North Sumatraexample.
It has to be emphasized that the valueof OFR is specific to the trial conditions, wherethe same rate of fertiliser has been appliedevery consecutive year. In commercial fieldsituation, the optimum rate may differdepending on the historical fertiliser regimeof the palms. On the other hand, the optimumnutrient leaf content values have been shownmore independent of the history of the palms.
These two parameters (OFR and Mopt)as defined previously are the basis keys tobuild up a fertiliser recommendationprogramme. Indeed it is therefore possible todetermine the rate of fertiliser to be applied ineach estate block based on the palm nutritionlevel (8a) (8b):
FERmi = OFRm – COR mi (8a)
with : FERmi is the rate of fertiliser m to beapplied on commercial block i.
CORmi is the corrective rate of fertiliserm relative to commercial block i.
then : CORmi = OFRm – FERmi (8b)
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and : CORmi = -[1/cTFm LN((aTFm -FOLmi )/ bTFm)] -[1/cm LN( Rm/ bm*cm)](9)
with : FOL mi is the nutrient m foliar contentobserved on commercial block i.
Fig. 13 shows the variations of thepotash corrective rate for a wide range ofpotassium nutrition levels. Expected yieldincrease can be forecasted from these curves.It is also possible to quantify the impact onyield and the cost of any over-fertilisation.
basic biological balances between nutrients.Most of them are well known by oil palmagronomists as the consequence is oftenvisible through antagonisms or synergies innutrients absorption. For example the trendfor a decrease of the nitrogen optimum leaflevel with the age of the palm, the frequentantagonism between potassium andmagnesium absorption, the synergy betweenpotassium and copper, calcium and chlorine,etc…
One interesting case is the synergybetween the nitrogen and phosphorus nutritionobserved in Sumatra (Tampubolon et al.,1990) and other situations (Foster, 1993). Theconsequence is that phosphorus impactshould be analyzed considering the relativevalue to an optimum determined based on thelevel of nitrogen. In a trial about phosphatefertilisers in Sumatra, a close relationship isobserved between the yield level and thisrelative P value (Fig. 14a). Similar result isobtained on young palms in commercialblocks in Kalimantan (Fig. 14b).
IMPORTANCE OF ECONOMICALPARAMETERS
During the last decade, CPO price hasfluctuated between US$ 255 and 700/tonne.These variations are part of cycles with
Mineral Nutrition in Oil Palm
As a conclusion, the standard fertiliserrecommendations for the palm can then bebased on the following four components:
- the current nutrition palm status revealedthrough the leaf content value FOLm,
- the optimum nutrient level Mopttargeted,
- the optimum fertiliser rate OFR,- the corrective fertiliser rate COR which
is related to the intensity of the responsecurve observed in the fertiliser trial,
BASIC BIOLOGICAL BALANCE BETWEENNUTRIENTS
Mineral nutrition studies andmanagement have to take into consideration
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frequency and amplitude related to changesin the production and consumption levels, andstock balance (Oil World, 1999). Theseparameters depend on natural events (climatevariations), but also on changes in agriculturalpolicies in major importer countries.
To some extent such kind of variationsmay have to be considered by plantationcompanies, in order to adjust their productioncost to the commodity price and possiblescenario about their short and mid-termevolution. Several authors have shown thatthe optimum fertiliser rate largely depends onCPO (Gunn, 1962; Piggott, 1968; Ng, 1972,Lo and Goh, 1973; Ochs and Ollagnier, 1977;Ochs, 1985; IRHO-CIRAD, 1992; Caliman etal., 2001). It is therefore understandable thatoil palm fertiliser regime has to be adaptednot only to ecological situations as it is usuallyaccepted and implemented, but also toeconomical parameters in order to maximizeprofit.
Equation (5) previously defined showsthat the OFR (Optimum Fertiliser Rate) isdirectly depending on the ratio R between thecost of fertiliser and the price of CPO.Consequently the optimum nutrient leafcontent Mopt also vary with R, as it dependsdirectly on the OFR value (7). In the example
Situation a Situation b
CPO (US$/t) 300 550R= Pfer/Ppro 6.3 1.8OFR (kg/palm) 2.4 4.65Mopt (%) 0.97 1.09
- Cost of KCl: Pfer = 143.8 US$ / tonne
- Cost of production= 150 USD/tonne CPO
- Oil Extraction Rate: OER = 23%
- Situation a: Income= 250 USD/tonne CPO (± 300USD/tonne CPO CIF Rotterdam)
- Situation b: Income= 500 USD/tonne CPO (± 550USD/tonne CPO CIF Rotterdam)
(From Caliman et al. (2001)
Table 5 : Optimum Economical FertiliserRate (OFR) of MOP, and optimumK leaf content (Kopt) based ontwo economical situations
of North Sumatra Fig. 11 and 12 show thelevel of OFR and Kopt when the CPO pricechanges from US$ 300 /tonne (situation a) toUS$ 550 /tonne (situation b), the cost of MOPremaining unchanged. Table 5 summarizesthese situations and parameters.
Significant differences are observedbetween the two values of OFR relative toMOP, with 2.4 kg/palm and 4.65 kg/palm forsituation a and b respectively. Fig. 15a and15b show the variations of OFR and Kopt withboth CPO and MOP prices, while Fig. 16shows OFR and Kopt variations with CPOprice only, MOP price remaining unchanged .Similar analysis could be done about the otherfertilisers being part of the standard fertilisationregime.
These results confirm that the mineralnutrition management of oil palm plantationsand the fertiliser recommendations should notfollow a static procedure, but should beadapted to the economic environment, as faras possible scenario for commodity prices canbe clearly forecast, and keeping in mind the
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time-lag between any change in the fertiliserregime and the reaction of the palms whichcan reach up to 3 years.
ADJUSTMENTS OF THE STANDARDFERTILISER RECOMMENDATION RATE
There may be mainly two reasons callingfor an adjustment of the calculated fertiliserrecommendation rate:
- companies facing a temporary cash-flowproblem.
- expected yield significantly higher orlower than usual.
Companies facing a temporary cash flowproblem may have no other choice thanreducing production cost including fertiliserexpenditure. Fertiliser rationing should be thelast stage, priority for savings being targetedfirst:
- in cheaper substitutes for expensivefertilisers, for example through amaximization of the valorization offactory wastes (Empty Fruit Bunches,Effluent, …).
- in a maximization of the efficiency of anyamount of fertiliser applied.
Should fertiliser rationing be finallynecessary, the implementation of such apolicy should be very selective in the type offertiliser to be reduced, and the palmsconcerned. The objective is to limit as far aspossible negative impact on the futureperformances of the palms.
In the example from North Sumatrapresented before, the yield response curvesgive an opportunity to assess, to some extent,the impact of rationing (10a). Althoughrationing policies are not expected to last fora long period, such analysis provides sometool for decision-making.
Mineral Nutrition in Oil Palm
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dPROm = PROm opt -PROm rat (10a)
with : dPROm is the yield impact related tothe rationing rate rat of fertiliser m.PROm opt is the optimum economical yieldrelated to the yield response curve to thefertiliser m.
PROm rat is the expected yield related to apermanent rationing of fertiliser m.
then : dPROm = bm [ EXP(-cm OFRm(1 – rat)) -EXP(-cm OFRm )] (10b)
As no effect of phosphate fertiliserapplications has been recorded since thebeginning of the trials, phosphate must be theprioritized fertiliser in terms of rationing, oncommercial blocks where P leaf contents areof the same order or higher than the oneobserved in the trials. About urea, MOP andkieserite, Fig. 17 show the expected yielddecline relative to continuous rationing. Whenthe past fertiliser regime is high(corresponding to high CPO prices = US$ 550CIF/tonne), rationing below 60% of initialfertiliser rates should focus on kieserite as theexpected yield decline will be more limitedthan rationing urea or MOP (Fig. 17a). Thislast one (MOP) will have the highest negativeimpact. When the past fertiliser regime ismoderate (corresponding to low CPO prices= US$ 300 CIF/tonne), rationing below 80%should follow a different sequence: urea, thenkieserite and finally MOP (Fig. 17b).
The difference of behavior between ureaand kieserite is due to the difference of theshape of the yield response curve of the twofertilisers: as already mentioned earlier in thispaper, low fertilisation regime for kieseritehave high impact on palm yield. Of course ithas to keep in mind that a minimum balancemust be kept between nutrients. Therefore“prioritized fertiliser” in terms of rationing doesnot systematically means than 100% of thisfertiliser has to be cut before rationing asecond one.
These conclusions do not take intoaccount any possible persistent effect of pastfertiliser applications (especially in ourexample with MOP and Kieserite), nor the factthat such rationing measures will probably betemporary. Nonetheless it gives an idea of themaximum impact that can be expected.
When production forecasts showsignificantly higher yield (for example followingtwo years of very low production) or lower yieldthan normal (for example the campaignfollowing a severe drought), it can beadvisable to adjust the fertiliser regime in orderto take into account variations in nutrientsremoval by the crop. Based on data presented
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by Ng L and Thamboo (1967), the impact of avariation of 5 tonnes of fresh fruit bunches ispresented table 6.
resistance: without water deficit, potassiumwas no more required for stomatal openingmechanisms.
Phosphorus optimum level was inaccordance with the Nitrogen-Phosphorusbalance mentioned just above in this paper.
Consequently, Prioux (1989) was usedto apply part of the fertilisers required by thepalms through the irrigation water (fertigation),and part during the rainy season withoutirrigation, in order to have an homogeneousdistribution of nutrient supply to the palmsthroughout the year. One kilogramme ofMuriate of postash was applied every yearthrough the irrigation scheme (at a rate of 7g/palm per hour of irrigation, with aconcentration of 0.05g/liter), plus an additional1 to 2 kg per palm per year during the rainyseason.
OIL PALM MINERAL NUTRITIONMANAGEMENT: PROSPECTS
A tentative evaluation of therequirements in terms of Research for afurther improvement of the mineral nutritionmanagement of oil palm would result in a longlist of interesting topics.
Obviously, a move toward precisionagriculture, based on the development ofappropriate GIS system, probably usingremote sensing technology will result in anincrease of the efficiency of the appliedfertiliser, through fine-tuning of applications inboth space and time scale (Nguyen et al.,1993; Fairhurst et al., 2000; Wanasuria etal.,1996).
In this paper we would like to mentionthree key subjects that we believe should bedeveloped in the future:
- The environmental impact of fertilisermanagement.
- The bio-disponibility of nutrients in thesoil, and the relation with the palms.
N P K Mg
Nutrient removal by 93.5 11.0 92.7 19.3
25 t FFB (kg/ha)
Fertiliser equivalent Urea TSP MOP Kieserite
for 5 t FFB (kg/palm) 0.280 0.080 0.250 0.160
Table 6 : Nutrients removal by oil palmcrop. (Ng and Thamboo (1967))
This table gives an idea of the level ofadjustment in fertiliser rates that could berecommended. However, such policy is mainlyapplied when high yield is expected, butscarcely when low production is forecasted.
OIL PALM MINERAL NUTRITION ANDIRRIGATION
Very little literature can be found aboutmineral nutrition management on irrigatedpalms, since irrigation is still not a commonpractice on oil palm cultivation. Theexperiment carried on in Ivory Coast by Priouxet al. (1992) was focussing on Potassium andPhosphorus nutrition. The K3-P3 trial (3 ratesof muriate of potash and 3 rates of single superphosphate) confirmed that the potassium levelin the leaf was relatively low in the irrigationtrial. The K critical level was estimated at 0.85% (actually currently close to 0.90% at currentpalm oil price) compared to a usual level of0.95 % without irrigation in that relatively dryarea (average water deficit = 448 mm/yearduring the period of the trial). This seems toconfirm the finding of Ollagnier et al. (1987)showing a link between the critical level forpotassium and the water supply to the palms:situations without water deficit showedsignificantly lower potassium critical levelcompared to situations with average waterdeficit. The explanation provided by Ollagnierwas based on the dual role of potassium, i.e.nutrient and element favouring drought
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- The characterization of the plantingmaterial.
THE ENVIRONMENTAL IMPACT OFFERTILISER MANAGEMENT
The impact of agricultural practices onthe environment has become a major issuefor environmentalist groups (NGO) andconsumers. Oil palm cultivation anddevelopment is included in activities targetedby NGOs. The challenge for the stakeholdersis to develop sustainable production systemsin its wide P
3 definition: Planet (environment),
People (social), Profit (economical).
For mineral nutrition management, thechallenge will consist in providing enoughnutrients to the palms in order to achieve itspotential, without any risk to the environment(surface and ground water pollution) andmaintaining natural resources (no mining ofthe soil or natural deposit).
The nutrient balance approach shouldallow agronomists in making short, mediumand long-term assessment of the land quality,as well as forecasting undesirableenvironmental effect such as surface andground water pollution or soil nutrient mining.Nutrient budget should be systematicallyestablished along with fertiliserrecommendation program.
In addition, an environmental riskresponse curve should systematically be builtup, along with the yield response curveobtained in the fertiliser trials. For exampleFig. 18 a, b, c show a tentative calculation ofthe environmental risk related to the fertilisertrial in Sumatra mentioned early in this paper.The estimation is based on the nutrientimmobilization, removal and recyclingproposed by Ng and Thamboo (1967). Herethe environmental risk is the differencebetween the palm requirements and theamount of nutrient applied, and presented in
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absolute value. The unit is in kilogram ofnutrient per hectare. ZR represents the rateof fertiliser with a theoretical zero risk ontothe environment. A lower fertiliser applicationregime will lead to a mining of the soil nutrientfertility, while higher fertiliser application rateswill result in possible ground water pollutionand a mining of natural deposit for potash,phosphate and kieserite for example.
The main challenge for researchers willbe to develop agricultural practices where theOFR and ZR will be confounded, in order tomaximize productivity while minimizing theenvironmental risk.
All these studies should results in thedefinition of specific indicators and thecorresponding scoring system useable byplanters and agronomists to evaluate theenvironmental impact of their practices.
A second source of worries, related tosome extent to the mineral nutritionmanagement, is about the valorization offactory wastes in oil palm plantation. For eachtonne of CPO produced, the oil palm industryhas also to deal with around one tonne ofempty fruit bunches (EFB) and three tonnesof palm oil mill effluent (POME). The highorganic nutrient value of these productsmakes it possible a valorization through asubstitution for mineral fertilisers. Severalstudies have confirmed the positive impact ofEFB field application on the palms nutrition.(Loong et al., 1987; Lim and Chen, 1989;Hornus and Nguimjeu, 1992). More recentstudies have revealed the kinetics of nutrientsrelease from EFB after field application (Fig.19a, b), and the positive impact on the soilchemical (Fig. 20) and physical characteristics(Fig. 21) (Caliman and et al., 2001b; Cirad,2001).
The situation is different for POME. Inmany cases, the recommended rate for landapplication, which can be as high as 750 m
3/
ha results in a very low nutrient efficiency,
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down to five or even seven times lower thanthe use of mineral fertilisers. In addition, wherethe flatbed application system is used, theenvironmental risk seems not negligible. Forexample the very high potassium content mayrepresent a risk of ground water pollution, aswell as for the soil physical stability. Moreresearch should be done in that field.
MINERAL NUTRITION MANAGEMENT:TOWARDS A FUNCTIONAL APPROACH
The trend towards sustainability seek forAgronomists to be more explanatory, in orderto improve and optimize agricultural practices.About fertiliser management, this could beachieved through a better knowledge of thebioavailability of the nutrients in the soil andthe palms. Then functioning models could bedeveloped and integrated in the modelscurrently developed related to carbonassimilation.
These studies should include:
! At the soil level: an evaluation of thebalance between nutrients, theiravailability for the palms.
! At the palm level: an evaluation of the
palm requirement for each nutrient ateach stage of vegetative andreproductive development.
! An evaluation of the palm reserves andthe kinetic of their mobilization.
Finally comprehensive studies aboutnutrient cycling in the oil palm agro-systemas a whole must be launched.
MINERAL NUTRITION MANAGEMENT:TOWARDS A CHARACTERIZATION OFTHE PLANTING MATERIAL
There are an increasing number ofstudies showing significant differences inmineral nutrition status of different plantingmaterial (Gnayoro, 1992; Caliman et al., 1994;Jacquemard et al., 2002). They do not yetallow specific fertiliser management, asrespective optimum leaf content levels andneeds for specific fertiliser rates have not beenproven yet.
As the planting material proposed bybreeders and seed suppliers will mostprobably be more and more homogeneouswithin categories, up to a suppose uniformclonal material, we assume that significantdifferences for nutrient requirements betweencategories will lead agronomists to proposeadjusted fertiliser regimes based on plantingmaterial.
For the future, the objective should befor seed suppliers to provide the planter withmaximum technical information about theirseed characteristics, including specificrequirements in terms of mineral nutrition.
In addition, such studies could leadbreeders to identify highly efficient plantingmaterial for nutrient assimilation, andincorporate these properties in future breedingprogrames.
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