MARDI Res. J.20(1) 1992:93-104

Root activity patterns of twoCoffea robusta) grown underusing 32P tracer technique*lCorak aktiviti akar bagi dua spesies kopi (Coffea liberica dan Coffea robusta) dalampersekitaran tanah yang berlainan: satu kajian dengan teknik penyurih 32Pl

K. C. Thamt, B. Kadmin'1, P. Y. Yau3, W. M. Wan Othmana, K. Ambak5, C. C.Ting6 and Y.

AhmadT

Key words: Coffea liberica, Coffea robusta, root activity, 3T tracer technique, distribution of

root activity

Abstrak

Taburan aktiviti akar dua spesies kopi (C. liberica dan C. robusta) yang ditanam

di empat lokasi iaitu Serdang, Kluang, Pontian dan Parit Botak, meliputi enarn

siri tanah: Bungor, Munchong, Rengam, Parit Botak, tanah gambut cetek dan

tanah gambut sederhana dalam, dikaji dalam lapan ujikaji dengan menggunakan

teknik per"ryurih 12P.

Walaupun pokok kopi Liberica mempunyai hamparan akar penyerap

permukaan aktif yang lebih luas daripada kopi Robust4 taburan akar aktif di

dalam lingkungan silara adalah sama apabila diukur berhubungan dengan

hampiran silara. Dalam keduadua spesies, aktiviti akar di kawasan yang

berhampiran dengan pangkal pokok (dalam jejari 25-50 cm dari pangkal pokok)

ialah 3-4 kali ganda lebih tinggi daripada aktiviti di hu.lung silara (dripline).

Akar penyerap pe,mukaan bagi pokok kopi Liberica muda mempunyai

aktiviti akar yang tinggi di kawasan jejari 50 cm dari pangkal pokok. Aktiviti ini,

walau bagaimanapun menurun beransur-arsur dengan umur pokok, menghasilkan

hamparan akar penyerap permukaan aktif yang bertambah luas. Corak aktiviti

akar adalah sama bagi pokok yang ditanam di tanah gambut atau tanah

pedalaman.

Saiz lilitan batang kopi Liberica tiada kesan ketara terhadap tabruan akar

penyerap permukaan (10 cm dalam) aktif.

Di tanah siri Munchong, hampir kesemua akar penyerap aktif bagi Robusta

(957o) dan kopi Liberica (83Vo) terdapat dekat permukaan (5 cm) tanah. Kira-kira

l5Vo daripada aktiviti akar kopi Liberica tertabur di kedalaman 50 crn.

*A joint MARDI-PUSPATI technical cooperation project cr the use of nuclear technique in fenilizer studiesrBasic Research Division, MARDI Headquarters, P.O. Box 12301,5A174 Kuala llmpur, Malaysia2Nuclear Energy Unit, Bangi, 43000 Kajang, Malaysia3Division of Horticulrurc , MARDI Station, P.O. Box 525, 86007 Kluang, MalaysiaaDept. of Agruromy and Honiculture, Univenity of Agriculturc Malaysia, 43400 Serdang, Malaysia5Basic Research Division, MARDI Stariqr, P.O. Box 506, 80720 Pontian, Malaysia6Basic Research Divisiqr, MARDI Statiqr, Kuala Linggi, P.O. Box 16, 782O7 Melaka, MalaysiaTCommodily Development Brandr, Dept. of Agriculturc, P.O. Box 506, 80720 Pontian, Malaysia

Authors' full names: Tham Kah Cheng, Bajuri Kadmin, Yau Peng Yam, Wan Mohamad Wan Othman, Kamaruddin

Ambak, Ting Chaong Chaang and Yacob Ahmad

OMalaysian Agricultural Research and Development lnstilute 1992

coffee species (Coffea liberica anddifferent soil environments: a study

93

Root activity distribution of Liberica and Robusta coffee

Di tanah asid sulfat iaitu sii Parit Botah kesemua (96Vo) aku penyerap

aktif bagi kopi Liberica berkumpul berdekatan dengan permukaan tanah (5 cm

dalam). Di tanah gambut taburan akar penyerap aktif yang lebih dalam temyata.

Untuk mencapai penggrmaan baja secara lebih cekap, baja haruslah diletak

berhampiran dengan pangkal pokok di bawah silara.

Abstract

The root activity distribution of two coffee species viz. C. liberica and C. robusta

grown in foru locations viz. Serdang, Kluang, Pontian and Parit Botak covering

six soil series viz. Brmgor, Munchong, Rengam, Parit Botak, shallow and

moderately deep peat was studied in eight experiments using radioactive tP soil

injection tracer technique.

Although Liberica coffee trees have a wider spread of active surface feeder

roots than Robusta coffee, their respective active root disribution within the

crown area were similar when measured in relation to the spread of the tree

crown. In both species, the average activity close !o the trunk (25-50 cm radius

from trunk) was 3-4 times higher than those at the dripline.

The surface feeder roots of young Liberica coffee nees had high root

activiry within the 50 crn radius from the trunk, which declhed progressively

with age resulting in a wider spread of active feeder roots. In spite of the decline,

activity remained highest within the 50 cm radius irrespective of age. The resultswere similar on both the peat and inland soils.

Girth size of Liberica coffee had no significant effect on the active surface(10 cm depth) feeder root distribution.

On Munchong series, almost all the active feeder roots of Robusta (95%)

and Liberica (839o) coffee were distribtrted near the soil surface (5 cm). About

l1Vo of. the root activity of Liberica coffee were distribtrted at the 50 cm depth.

On the acid sulphate soil viz. Parit Botak series, almost ̂ lI O6qo) the active

feeder roots of Liberica coffee were confined to the soil surface (5 cm depth). Onpeat, a deeper disribution of the active feeder roots was observed.

To achieve greater fertilizer use efficiency, fertilizer should be applied

closer to the trunk below the canopy.

Introduction to harvest entire mature tre€s to measureOne of the major factors affecting crop yield nutrient uptrake from fertilizers applied. Asis the supply of adequate plant nurient. In such, crop yields are commonly used as atheory, an increase in nutrient supply is most criterion to estimate such responses.easily met by the addition of nutrient in tlre Unfortunately, yield is often a poor crit€rionform of fertilizers. However, fertilizers are to estimate fertilizer use efficiency due toexpensive and fertilizers not utilized by the the multiplicity of the factors affectingcrop may represent an environmental yields. Conventional yield trials of treepollutant Efficient fertjlizer use can be crops are often expensive to run as largeachieved by applying the most suitable form experimental plots are usually involved andof fertilizer and placing it in an area where it yield data have to be collected over severalcan be rapidly taken up at times when the seztsons. Thus, root activity studies areplant's ne€ds are most crucial. considered good preliminary approach in the

Unlike an annual crop, it is not practical case of tree crops as such studies provide

94

K. C. Tham, B. Kadmin, P. Y. Yau, W. M. Wan Othman, K. Ambak, C. C. Ting and Y. Alrnad

basic information as to when and wherefertilizen should be applied to ensuregFeater effrciency of fertilizer use. Isotopetechniques make determination of activeroot distribution comparatively easy. Theirapplication t0 tree crops has beendemonstrated for coffee (Saiz del Rio et al.196l; IAEA 1975), pepper (Sankar et al.1988), guava (Purohit and Mukherjee 1966),cocoa (Comwell 1957; IAEA 1975), mango(Bhajappa and Singh 1973), oil palm(Broeshart 1959) and rubber (Singh et al.1972).

In Malaysia, the study of root systems,parficularly of tree crops, has beensomewhat neglected as it involved elaborateand pinstaking evacuation of the roots. Inmany instances, the spread of the lateralbranches is often taken as a rough guide inestimating the lateral root spread. Hence,dripline fertilizer placement and spreadingfertilizer under the tree crown is oftenpractised. While the use of this criterionmay or may not adequately indicate thespread of the lateral roots, the overridingfactor in optimizing fertilizer use lies in theability of the root to take up the fertilizersapplied. The use of soil injection techniquewith racer vu. nP allows the most directand non-destructive method in delineatingthe root acrivity pattern.

The objective of this study is oinvestigate the active root distribution of twocoffee species (viz. Coffea liberica and C.robusta\ grown under differentenvironments using 3? radioactive tracertechnique.

Materials and methodsThe basic concept and methodology ofdelineating active root distribution pattern oftrees have been previously described (IAEA1975). The concept is based on theassumptions that:o for maximum efficiency of utilization,

fertilizcn should be applied in areas ofhighest root activity,

o the isotope content of the sampled leafreflects the root activity in the area in

which the isotope was applied,o leaves of a defined leaf type (e.g.

morphological position) will pnovide thesame results, and

o the delineated root activity pattern with agiven isoope would be the same forother nutrients.

The method involves soil in!:ction withlabelled 32P solution at specific distance(lateral) from the tree at different depths andsubsequent isotope assay in the leaf sample.Treatments were tested in a completelyrandomized design. All lateral placement xdepth treatments were ananged in a facorialcombination. Single trees were used asexperimental units in all the experiments.

The root activity pattems of coffee reesgrown in four locations viz. Serdang,Kluang, Pontian and Parit Botak, coveringsix soil viz. Bungor, Munchong, Rengam,Parit Botak, shallow and moderately deeppeat (Appendix,l) were studied.Experimental details are summarized inTable l.

The trees in each experiment wereselected from existing plots which weregrown from seeds as monocrop (except forexperiment 8 which was intercropped withcoconut). The trees were detopped at 3 yearsof age and regulady pruned !o remove watershoots. Depending on the si!e, each treereceived 0.8-1.0 kg of either l5 N:7 PrOr:18

\O:2 MgO or 12 N:12 P,Q:17 I!O:2MgO fertilizer mixture per annum in fourequal split applications. The fertilizers werebroadcasted under the crown. The trees werecarefully selected to ensure uniformity interms of biomass, girtl size, crown size andplant vigour. Each tree received a knownamount of. eP (2-3 mCi), depending on theexperiment (Table /), distributed in eightequal aliquots containing 5 mL of I 000ppm P KIIPO. carrier solution. The eightaliquots were applied around the Eee at afixed radius at equidistant from each otherand at a given depth. The injection pointswere made l-3 days in advance using anauger and plugged. The 32P labelled solution

95

Root aaivity distribution of Liberica and Robusta coffee

was dispensed into the hole through a glasstube using an auto-pipette. The glass tubewas then flushed with 20 mL of water. Theholes were then covered with soil takenfrom the same area. All experiments weretimed to coincide with the rainy season.

Twenty l0 cm length recently maturedshoos (plus leaves) were sampled over theentire upper exposed canopy from each treeat various intervals (Table 1) after soilinjection with 3?. The samples were driedin a forced draught oven at 60 "C for 24 hand then crushed. Five gram sub-sampleswere then taken for ashing at 550 "C. Theash was dissolved in 20 mL of 2 M HCIbefore being filtered. Ten millilitres of theextract was then pipetted ino plasticscintillation vial for Cerenkov countingusing a liquid scintillation counter.

In all experiments, the combined resultsof harvest I and II were presented sincenone had shown any significant interactionbetween harvests and treatments.

ResultsLateral root spreadSpecies effect The active root distributionof surface lateral roots (10 cm depth) ofLiberica and Robusta coffee grown on twosoils viz. Rengam series and Munchongseries soil is presented in Figure I.

The interactions between species andplacement were significant (p = 0.05) onboth soils. Generally, both Liberica andRobusta species had the highestconcentration of active roots located close tothe trunk within the 50 cm radius anddeclined thereafter. The decline was lessmarked in Liberica coffee, indicating awider spread of its lateral roots. The effectswere similar on both soils.

Between 30Vo to 40Vo and 30Vo of thetotal root activity of Liberica coffee wereobserved atthe25 cm and 50 cm radiusrespectively, while 10-127o was observed atthe 150 cm radius which is near the dripline(Figure 1). Only 54Vo of the total activitywas located at the 200 cm radius. ForRobusta coffee. the concentration of active

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Robusta,(dripline,

K. C. Tham, B. Kadmin, P. Y

Munchong series

Yau, W. M. Wan Othman, K. Ambak, C. C. Ting and Y. Ahmad

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Age efTect Generally, younger Libericacoffee trees grcwn on peat had higherconcentmtions of active roots located closerto the trunk than older tre€s as indicated bythe sharp decline in the root activity beyondthe radius of 50-lm cm. The decline wasprogressively less pronounced with age,

fe.67,\\ \\ 'Kuu"

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Liberica -A(dripline, 150 cm)\o- \

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7o distribution of activiry = DPM values of Eeatrnentx lfi)

Total DPM values of all treatments

Figure L Raot activity and percertage distribution of surface ( l0 cm depth) lateral roots of Libericaand Robusta coffee on thc Murclung ard Rengatn series

1501005025

roots found near ille trunk was higher,accounting for 3745Vo of the toral activityat the 25 cm radius and 38437o at the 50cm radius while only l0-127o was located atthe 100 cm radius which is located near thedripline, l77o at the 150 cm and l-57o atthe 200 cm radius.

3.7%\;

97

Root aeivitv distribution of Liberica and Robusta coffee

Root activity in disintegration/min (DPM)

I I 000.

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RooL activity in disintegration/min (DI'M)

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indicating a wider spread of the activesurface roots of older trees (Figure 2).Similar trends were observed on the inlandsoils (Flgure 3) although the experimentswere conducted on three different soil series(viz. Bungor, Rengam and Munchongseries). It is, however, noteworthy that the

98

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25 50

lareral ttP

placement (crn frorn trunk)

Figure 2. Root activity and percentage

distribution of surface (10 cm depth) Iateral roots

of 5 and 8-year-old Liberba coffee grown onpeat soil

4.sEo6.17o0.3Vo

three soil series have several similarities interms of their physical (viz. texture and bulkdensity) and chemical (viz. pH and CEC)properties.

On both the peat and inland soils, theroot activity of 5-year-old Liberica coffeetrees increased marginally from 32-34Vo at

,4V"t50

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(dripline 115 cm)

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F igure 3 . Root activity and. percentage distribution of surface ( I0 cm depth) lateral roots of 5 , 8 and13-year-old Liberica coffee grown on tlvee inland. soils

K. C. Tham, B. Kadmin, P. Y. Yau, W. M. Wan Othman, K. Ambak, C. C. Ting and Y. Ahmad

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99

Root activity distribution of Liberica end Robuste coffee

Root activity in disintegraticninin @PM)

40mPrir Bouk sies(Libcrio) 8 Ocx

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Figure 5. Rnt activity ard percentage distribution of lateral ard vertical rots of Liberica and Robustacofee grown on 3 diferent soils.

r00

37.9%

LSDo.os = 150C.V. = lT79o

K. C. Tham, B. Kadmin, P. Y. Yau, W. M. Wan Othman, K. Ambak, C. C. Ting and Y. Ahmad

the 25 cm radius to 45-50Vo at the 50 cmradius. Thereafter, the activity declinedmarkedly to ll-l4Vo at the 100 cm radiusbefore [apering off at4-7Vo and0-24o atthe150 cm and 200 cm radius respectively. Forthe older 8-year-old Eees, the activityshowed a more gradual decline from amaximum of 30-34Vo at the 25 cm radius toabou 25Vo at the 100 cm and 247o at the200 cm radius. Except for a lower activity(137o) at the 100 cm radius, the active rootdistribution of the l3-yearold trees wassimilar to that of the 8-year-old rees.

In all cases, irrespective of age or soils,the root activity around the dripline waswell below the area closer to the trunk.

Girth size effect The analysis of varianceshowed no significant interaction betweengirth size and placement. This indicated thatgirth size did not have any significant effecton lateral root spread in any of the threesoils although on one site (shallow peat) thedifference in girth size was as high as 62Vo(Figure 4).

Root depth and spreadThe interaction between depth x lateral rootspread was highly signihcant (p = 0.01), ontwo soils (viz. Munchong series and peat)while on the Parit Botak series, only thedepth effect was significant (p = 0.0t,Figure 5).

The significant interaction is essentiallythe result of a sharp decline in root activityof the surface lateral roots with distancefrom the trunk and a markedly less orabsence of active sub'surface roots. OnMunchong series, 837o of the total rootactivity of Liberica coffee were located atthe 5 cm depth, 887o of which within the100 cm radius. Almost all the remainingactive roots (l1%o) were disributed at the50 cm depth while activity at the 100 cmdepth was negligible (2Vo).\\e trends weresimilar with Robusta coffee which hasalmost 95Vo of the active roots located at the5 cm depth and confined mainly to the 100cm radius.

On peat, almost all the active roots werelocated at the 5 cm (617o) and 30 cm(35Vo)depth, most of which within the 150 cmradius. Activity at the 50 cm deptlt was lesst}rin 5Vo of the otal activity.

In contrast, Liberica coffee grown onacid sulphate soil (Parit Botak series) hadvirtually zll (96Vo) the active roots confinedto the surface (5 cm depth).

DiscussionFertilizer placement poses unique problemsin tree crops. Besides wide plant spacing,several other factors viz. variety and plantage (Rogers 1953), soil type (Rogers andBooth 1960), moisture (Beukes l9&4) andplant nutrients (Gardner et al. 1952) caninfluence root distribution and consequentlyfertilizer placement. Purohit (1980), in hisreview on fertilizer placement in fruit trees,concluded that the spread of the crownserves only as a rough guide while thespread of the root system does notnecessarily coincide with maximum feedingarea.

From the present study, it can besummarized that both the coffee species viz.C . liberica and C. robwta grown under twodifferent inland soils (viz. Munchong andRengam soil series) and peat at differentlocations (viz. Serdang, Kluang and Pontian)have similar distribution of active surfacefeeder roots when measured in relation tothe spread of the tree crown (Figure 1). Thesimilarity is characterized by the highconcentration of active feeder roots nearer tothe trunk and low activity at the dripline(Figure 1). In both species, the activity atthe 25-50 cm radius from the trunk was 3-4times higher than those at the dripline.Similar trends were previously reported bySaiz del Rio et al. (1961) and Huxley et al.(1974) on Arabica coffee.

The effect of tree age on surface lateralroot distribution of Liberica coffee showedsimilar trends in both the peat and inlandsoils although the lauer were tested underdifferent soils and environmental conditions(Figure 2 andFigure 3). Generally, younger

10r

Root activity distriburion of Liberica and Robusta coffee

Liberica coffee trees had higher activity ofthe surface feeder roots located at the 25-50cm distance from the trunk. The activity,however, declined progressively witl ageresulting in a wider spread of the surfacefeeder roos. But in all cases, irrespective ofage, activity was 24 folds higher at the 25-50 cm radius than at the dripline. It is,however, interesting to note that inexperiments I and 6 (Figure 2 and Figure-3), a distinrively lower activity in the areaclose to the trunk (25 cm radius) wasobserved, all of which were associated withyounger S-yearold trees.

In all the three experiments (1, 6 and 7),girth size did not have any significant effecton the distribution of surface feeder roots(Figure 4).

On Munchong series, almost all theactive roots of Liberica and Robusta coffeewere confined to the soil surface (Figure 5).However, Liberica coffee appeared to have asomewhat deeper rooting habit than Robustacoffee as shown by the higher activity(l1%o) at the 50 cm depth. In both species,however, root activity was negligible at the100 cm depth. In contrast, Arabica coffeegrown on well-drained Kikuyu red loam inKenya has been shown to have deep activeroots (IAEA 1975). However on theMunchong soil, the decline in root activitywith depth may possibly be associated withthe lower fertility and bulk density of thesoil (Apperd'x 1). On the Parit Botak serieswhere the root activity of Liberica coffeewas confined to the 5 cm depth, theextremely low soil pH (3.a) and high levelsof exchangeable aluminium (6-7 meq/100 g)at the 15-30 cm depth may have restrictedthe root growth.

In contrast" Liberica coffee grown onpeat had deeper distribution of active rootswhere activity at the 5 cm and 30 cm depthsaccounted for 6l%o and35Vo respectively ofthe total activity. Very low root activity waslocated at the 50 cm depth which isprobably associated with the fluctuating highwatertable.

It is noteworthy that although the area

r02

below the canopy received regularapplications of fertilizers, root activity washigher in the area closer to the trunk.However, the presence of plant debriscommonly observed around the trunk mayhave influenced the moisture and nutrientstatus of the soil and consequently the rootactivity in the area.

From this study, it can be concludedthat C. liberica and C. robusta commonlygrown in Peninsular Malaysia have higheractivities located near the surface and closerto the trunk than the dripline. In view ofthis, current fertilizer management involvinginterrow application (Leong 1986) andbroadcast application below the canopy(Abd. Rahman Azmil et al. 1989) should beamended. This study recommends thatfertilizer application would be most effectivewhen 0re fertilizer is placed closer to thetmnk below the canopy.

AcknowledgementsThe authors would like to express theirsincere thanks o the Direcor General ofMARDI, DOA, PUSPATI and ViceChancellor of University of AgricultureMalaysia for their permissions to publishthis paper.

The auttrors wish to thank Dr AhmadZamzam and Dr Aminuddin Yusoff ofMARDI, and Dr Ahmad Sobri of PUSPAT]for support, and Dr Lee Chong Soon for thestatistical analysis.

They are indebted to Mr Ahmad Mardiand Mr Khairuddin AM Rahim for the 3?

assay and Mr Hussein Salihan, Mr KhairulAnuar, Mr Mohd Nor Yusuf and MrSuhaimi Hj. Aman for their technicalassistance.

ReferencesAbd. Rahman Azmil, I.. Yau, P. Y. and Shukor, N.

(1989). Syor senren[ara pembajaan kopiLiberica di tanah Siri Rengam. Ielnal.Pelbagai Tananan, MARDI S: 37-9

Beukes, D. J. (1984). Apple root distribution asaffected by irrigation at different soil waterlevels on two soil type,s.,f. Ancr. Soc. Hort.Sc. 109(5):72T8

K. C. Tham, B. Kadmin, P. Y. Yau, W. M. Wan Othman, K. Ambak, C. C. Ting and Y. Ahmad

Bhajappa, K. M. and Singh, R. N. (1973). Studieson the root activity and feeding zones ofmango (Mangifera indica L.) using r?.

Indian Soc. Nucl. Tech. Agric Biol. Newsl.2: 112

Broeshart, H. (1959). The application ofradioisotopic techniquas to fertilizerplacement studies in oil palm cultivation.Neth. J. Agric. Sc.7: 95-1@

Cornwell, P. B. (1957). A preliminary investigationinto the uptake and translocation of r2P incocoa (Theobroma cacao L.). Trop. Agric.Trin. 34: ll7

Gardner, V. R., Bradford, F. C. and Hooker, H. D.(1952). The fundamentals of fruit productionp. 68-81. New York: McGralew Hill BookCo.

Huxley, P. A., Patel, R. 2., Kabaara, A. M. andMitchell, H. W. (1974). Tracer studies withr2P in the distribution of functional roots ofArabian coffee in Kenyu Ann. Appl. Biol.77:1 59-1 80

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Accepted for publication on I0 October I99l

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