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Granules composed of cocoa pod husk enriched with minerals and their effects on growth of coffee and cocoa seedlings

Diterima (Received): 19 September 2009.1) Pusat Penelitian Kopi dan Kakao Indonesia, Jl. PB. Sudirman No. 90, Jember, Indonesia.*) Alamat penulis (Corresponding Author) : [email protected].

Pelita Perkebunan 2009, 25(3), 199—215

Granules Composed of Cocoa Pod Husk Enrichedwith Minerals and Their Effects on Growth

of Coffee and Cocoa Seedlings

Granul Asal Kulit Buah Kakao yang Diperkaya dengan Mineral dan PengaruhnyaTerhadap Pertumbuhan Bibit Kopi dan Kakao

Pujiyanto1*)

Summary

Up to now, cocoa pod husk is commonly collected as heap nearby process-ing facilities or in the field and being considered as waste. To minimize the nega-tive impact of the husks and to obtain added value an effort to develop the huskinto granule fertilizer has been carried out. Fresh cocoa pod husk was hulled toobtain organic paste, then mixed with 5% zeolite and 5% rock phosphate powder(w/w). The mixture was kept for 2 weeks prior to granulation. The granules werecharacterized for their physical and chemical properties. Agronomic tests of thegranules were conducted on coffee and cocoa seedlings as indicator plants. Thetests were set according to completely randomized design and the treatments werearranged factorially. The evaluated treatments consisted of rates of granules andrates of inorganic fertilizer applications. The granules were applied at 7 levels: 0,5, 10, 15, 20, 25 and 30 g/seedling. The granule treatments were combined withapplication of inorganic compound fertilizer at rates of 0 and 2 g fertilizer/applica-tion of N-P-K compound fertilizer of 15-15-15. The inorganic fertilizers wereapplied four times during experiment. The results indicated that the granule hashigh water holding capacity; cations exchange capacity, and high content of or-ganic carbon and phosphorus. The growth of coffee and cocoa seedlings increaseddue to application of granules derived from cocoa pod husk. Responses of coffeeand cocoa seedlings to granule application conformed to quadratic equations. Theoptimum application rate of granules was 14.5 g/seedling for Robusta coffee seed-lings and 14.6 g/seedling for cocoa seedlings. Granule application may replacedrole of inorganic fertilizer to increase growth of cocoa and coffee seedling.

Key words: Cocoa pod husk, organic waste, seedling growth, zeolite, rock phosphate,minerals, Theobroma cacao L., Coffea canephora.

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Ringkasan

Kulit buah masih sering dipandang sebagai limbah yang dapat berdampaknegatif terhadap lingkungan. Penelitian ini merupakan upaya untuk memperolehnilai tambah dari limbah kulit buah kakao dan menekan dampak negatif pencemaranyang ditimbulkan. Kulit buah kakao diproses menjadi pupuk granul dengan campuranzeolit dan fosfat alam. Pembuatan pupuk granul dimulai dengan penghancurankulit buah kakao sampai terbentuk pasta yang selanjutnya dicampur dengan bubukzeolit dan fosfat alam. Hasil pendahuluan menunjukkan bahwa komposisi campuran90% pasta kulit buah kakao dengan 5% zeolit dan 5% fosfat alam (b/b) mampumembentuk pupuk granul yang mudah digranulasi dan secara visual tampak baik,sehingga komposisi tersebut yang dipakai dalam penelitian ini. Sebelum dilakukanpengujian agronomi, beberapa karakteristik fisik dan kimia granul ditentukan dilaboratorium. Pengujian agronomi dilakukan di rumah kaca dengan mempergunakankopi Robusta dan bibit kakao lindak sebagai tanaman indikator. Penelitianmenggunakan rancangan acak lengkap faktorial yang menguji tujuh taraf aplikasigranul kulit buah kakao, yaitu: 0, 5, 10, 15, 20, 25 dan 30 g/bibit dan dua tarafaplikasi pupuk anorganik, yaitu: 0 dan 2 g/bibit/aplikasi. Aplikasi granul dilakukanhanya satu kali sebelum tanam dengan cara mencampur merata dengan tanahsebanyak 3 kg/polibeg. Aplikasi pupuk anorganik dilakukan 4 kali, yaitu pada umurbibit kopi 2, 4, 6 dan 8 bulan, sedangkan pada bibit kakao aplikasinya dilakukanpada umur bibit 1, 2, 3 dan 4 bulan menggunakan pupuk majemuk N-P-K 15-15-15. Hasil penelitian menunjukkan bahwa granul memiliki retensi air, kapasitastukar kation, kadar karbon organik dan fosfor yang tinggi. Respons pertumbuhanbibit kopi maupun kakao terhadap pemberian pupuk granul kulit buah kakao bersifatkuadratik. Aplikasi pupuk granul kulit buah kakao sampai taraf tertentu mampumeningkatkan pertumbuhan bibit kakao maupun bibit kopi Robusta. Dosis opti-mum aplikasi granul adalah 14,5 g/bibit untuk kopi, sedangkan dosis optimumuntuk kakao adalah 14,6 g/bibit. Aplikasi granul kulit buah kakao mampumenggantikan peran pupuk buatan untuk meningkatkan pertumbuhan bibit kakaomaupun kopi.

INTRODUCTION

Soil degradation in existing cocoa farmsoccured due to excessive soil exploitation andimproper application of soil degradation con-trol measures. The degradation took placethrough several processes, namely soil ero-sion, leaching by deep water percolation, ex-cessive organic matter degradation, and nu-trient out flow due to harvesting of cocoabeans. Indicators for soil degradation aredeminishing of soil-organic matter content,reduction of soil-effective depth due to losses

of the uppermost soil layer, and decreas-ing soil capacity to supply nutrients andwater.

Organic matter is the most activesoil component for many reaction pro-cesses in soil. Therefore, soil-organicmatter has vital role for many chemi-cal reactions in soil. For that reasonorganic matter is being used as soilfertility indicator. Research findingspointed out that organic matter appli-cation stimulated better physical,

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chemical and biological soil properties.The effect of organic matter on improve-ments of soil properties had been studiedextensively, namely: reduced soil compact-ness, increased soil porosity, stimulate ag-gregation and formation of stable aggre-gates (Pujiyanto et al., 2003), increasedcation exchange capacity (Obi, 1999), in-creased N content (Cobo et al., 2002a;Cobo et al., 2002b), increased availablesoil-P (Erich et al., 2002; Laboski et al.,2003; Salas et al., 2003), favored soil pHfor plant growth (Irianto et al., 1993) andfavored soil biological properties throughenergy supply for soil microbial activi-ties, especially for N fixer (Kahindi et al.,1997).

Deminishing of soil organic matteroccurred due to imbalanced of organicmatter supply rate and their decomposi-tion. Application of organic matter doesnot increase soil organic matter contentpermanently in the long run, because theapplied organic matter will be decomposedand the soil organic matter content willlead back to the initial equilibrium state.Pujiyanto et al. (2003) showed that or-ganic matter application at 5 and 10 tons/ha increased significantly soil organicmatter content in 3 and 6 months afterapplication. Nine months after its appli-cations, the organic matter content wentback to the initial level. All applied or-ganic matter had been decomposed andtransformed to CO2 and microbial biom-ass. It implies that organic matter appli-cation has to be conducted periodically tomaintain high level of soil organic mat-

ter content to support optimum growth andproduction of plants.

Though organic matter application willonly increase temporary soil organic mat-ter, research findings indicated an improve-ment of vegetative growth of cocoa andcoffee trees and yield increment due to or-ganic matter application. Based on longterm observation in the field, Baon &Soenaryo (1989) pointed out better soiland plant nutrients status of coffee andcocoa and yield increase of coffee farmdue to application of organic matter wastein form of filter press cake. It was alsonoted a trend of steady yield increase whenorganic matter application was repeatedin the following years.

Most coffee and cocoa farmers hadconvinced about the effect of organic matteron cocoa yield improvement, but implemen-tation of the technology in the field wasstill very limited due to scarcity of organicmatter. Meanwhile, cocoa pod husk is notyet being considered as ameliorant mate-rial for coffee and cocoa farm improve-ments. The cocoa pod is commonly col-lected as heap nearby processing facilitiesor in the field and being considered as waste.The pod husk is not quickly degraded andwill contribute to deminishing environmentquality due to formation of odor which con-taminate air. During pod husk decompo-sition, organic leachate will be producedwhich may contaminate well and river. Thisstudy is an effort to develop cocoa podhusk into granule fertilizer to minimize nega-tive impact of the pod husk and to obtainadded value of the waste.

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MATERIALS AND METHODS

The experiment was conducted atIndonesian Coffee and Cocoa ResearchInstitute (ICCRI). Fresh cocoa pod huskwas ground manually into organic paste,then mixed thoroughly with 10% mine-rals (w/w) consisted of 50% Zeolite and50% rock phosphate powder. The zeolitepowder was 90% passing through 80 meshsieves with cation exchange capacity of94.1 me % which was originated fromSouth Malang mining site. Suwardi et al.(1995) showed that zeolite deposit fromthis area contained clinoptalite of 37% andMordenite of 34%. The rock phosphatewas originated from Egypt with 27% P2O5

content. Prior to granulation, the mixtureof cocoa pod husk paste and minerals wascomposted for 2 weeks followed by airdrying up to 10% water content for aboutone week. The granules were character-ized for their physical and chemical pro-perties viz. water holding capacity, con-tent of organic carbon, nitrogen, phospho-rus, potassium, and cation exchange ca-pacity (CEC).

Testing for agronomic effectivenessof the granules was carried out in greenhouse using coffee and cocoa seedlings asindicator plants. Media used to fill plas-tic bag is top soil of Inceptic hapludalfderived from Kaliwining ExperimentalGarden. The soil sample was air dried andsieved at 2 mm sieves. Laboratory analysesindicated that the soil media contained1.48% organic-C, N total of 0.24%, pHof 5.9, sand of 14%, silt of 57% and clayof 29%. The dominant minerals in sandfraction of the media are labradorite (29%)

and volcanic glasses (22%) and the domi-nant mineral in clay fraction is amorphousclay (Pujiyanto et al., 2004).

The tests were set according to com-pletely randomized design and the treat-ments were arranged factorially. The evalu-ated treatments consisted of rates of gra-nules and rates of inorganic fertilizerapplications. The granules were appliedat 7 levels: 0, 5, 10, 15, 20, 25 and 30g/seedling. The granule treatments werecombined with application of inorganiccompound fertilizer at rates of 0 and 2 gfertilizer/application of N-P-K compoundfertilizer of 15-15-15. Each treatment wasreplicated four times. The granules weremixed thoroughly with the soil media andit was applied before transplanting. Inor-ganic fertilizer was applied four timesduring nursery of cocoa and coffee seed-lings. Application scedule for cocoa seed-lings was at the age of 1, 2, 3, and 4 monthold, meanwhile for coffee seedlings at theage of 2, 4, 6 and 8 month old.

Seedlings of F1 cocoa hybrid andRobusta coffee were used as indicatorplants for agronomic test. All plantingmaterial for this experiment was originatedfrom coffee and cocoa seed garden ofICCRI. Cocoa seeds originated from openpollination of ICS 60 clone and coffeeseeds of BP 42 X BP 358 were used forthe agronomic tests. In each plastic bagwas planted one seedling. Maintenance ofthe seedlings was carried out accordingto handbook of coffee and cocoa culturalpractices of ICCRI. During the experiment,soil water content was maintained at fieldcapacity through daily watering. Obser-

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vation of cocoa seedling growth was con-ducted up to 5 month old, meanwhile forcoffee up to 10 month old. The selectedvariables for seedling growth were seed-ling height, stem diameter, leaf number,fresh weight of shoot and root, and dryweight of shoot and root.

RESULTS AND DISCUSSION

Characterization of the cocoa pod huskgranules indicated that the physical andchemical properties were appropriate toincrease soil capability to support plantgrowth. The granules contained 17.9% or-ganic matter (10.4% organic-C), nitrogenof 6.7%, phosphate (P2O5) of 5.06%, po-tassium (K2O) of 1.23%, cation exchangecapacity (CEC) of 49.2 me %, bulk den-sity of 0.46 g/cm3, and average weightof 0.15 g/granule. Visually, the granuleshave white gray color. High content oforganic matter in the granules is presum-ably suitable to alleviate soil fertility dueto the fact that most of coffee and cocoaareas in Indonesia have low organic mattercontent (less than 2% organic-C). Incre-ment of organic matter content in the soildue to application cocoa pod husk will in-creased soil capability to support plantgrowth and increased farm productivity.Function of soil organic matter are to sup-ply nutrients to plants, stimulate aggre-gation and stabilize the newly formed ag-gregates, increase soil-water retention,increase retention of nutrients through soilcharge increment, immobilize anthropo-genic substances and heavy metals, in-crease soil-buffering capacity, increase soil

temperature, supply energy for soil or-ganisms, and favor saprophytic organismand suppress parasitic organisms.

CEC value of the cocoa pod huskgranules is high (49.2 me/100 g). The highCEC value of the granules is due to con-tribution of organic matter and zeolite.Granules application will increase soilCEC. Increment of soil CEC will increasesoil capability to retain cations, reducenutrient losses due to leaching. In ge-neral, each percentage of humus contri-butes to CEC increment of 2 me(Sudarsono & Hasibuan, 1995). Follow-ing granule decomposition, several nutri-ents will be released to increase more avail-able nutrients for plants.

Bulk density of the granules is about1/3 of average soil bulk density contri-buted by organic matter in the granules.It implies that granule porosity is highwhich enable the granules to store muchmore water than bulk soil. The low bulkdensity has other advantages, viz. easy han-dling and capable to reduce soil bulk den-sity. Content of nutrient (N, P, K) in thegranules are considered much higher thanbulk soil. It implies that granules appli-cation will improve nutrient status in thesoil.

Figure 1 showed water retention ca-pacity of the granules at field capacitywhich hold water of 69%, while bulk soilonly 38%. Amount of retained water cor-relate with available pores within the gran-ules. The higher available pores, the morewater could be retained. In term of plantgrowing, the more available water is fa-vorable to accelerate growth.

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Agronomic test on coffee seedling

Granules derived from cocoa pod huskgave positive effect on several growth vari-ables of coffee seedling up to the optimumapplication rate. Single effect of granulessignificantly increased height of seedlings,fresh weight and dry weight of seedlings.Relationship between rates of granule ap-plications and height of coffee seedling wasquadratic both for combined treatment withinorganic fertilizer, and for treatment withno inorganic fertilizer (Figure 2). The twoequations indicated that slight applicationof cocoa pod granules improved the soilmedia for coffee-seedling growth. The qua-dratic equation also indicated that therewas an optimum level of granule appli-

cation. Application at higher rates than theoptimum level induced negative effect. Thebeneficial effect of organic matter appli-cation on plant growth have been demon-trated by several researchers. Haron (2003)pointed out better soil status and oil palmresponse due to combined application oforganic and inorganic fertilizers, whileLorion (2004) indicated that yield of po-tato from organic fertilizer system werecomparable with synthetic inorganic fer-tilizers.

Result of variants analysis on vari-ables of coffee seedling growth indicatedno interaction between granule applicationand inorganic fertilizer applications on vari-ables of height, fresh weight and dry

Figure 1. Water retention of cocoa pod husk granules at field capacity.

Gambar 1. Retensi air oleh granul kulit buah kakao pada kapasitas lapang.

Soil agregatesAgregat tanah

Wat

er r

eten

tion

, %

Ret

ensi

air

, %

Cocoa pod granulesGranul kulit buah kakao

0

10

20

30

40

50

60

70

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weight. The granules increased height ofcoffee seedling at relatively low rates,about 5 to 10 g/seedling. At granules ap-plication about 10 g/seedling, the heightof coffee seedling reached their maximum.The positive effect of granules was dueto improvement of the soil media relatedto their chemical and physical character-istics; especially improvement of availablewater and nutrients derived from decom-position of organic matter of the granules.At application rates higher than 10 g/seed-ling, the effect of granule application wasnegative.

In line with their effect on variableof seedling height, single effect of gra-nules derived from cocoa pod husk showedpositive effect on total seedling-freshweight. There is no interaction betweengranules and inorganic fertilizer.

Relationship between rates of gran-ule applications and total fresh-weight ofcoffee seedling was quadratic for combinedtreatment with inorganic fertilizer, and fortreatment with no inorganic fertilizer(Figure 3A). The two equations indicatedthat slight application of cocoa pod gran-ules improved the soil media for coffee-seedling growth. Application at higherrates than the optimum level induced nega-tive effect on seedling growth. At gran-ule application level higher than 10 g/seed-ling, there was a trend of decreasing re-sponse.

The effect of granules derived fromcocoa pod husk on total dry weight ofcoffee seedlings had a similar trend withthe variables of seedling height and totalfresh weight. Relationship between totaldry weight of coffee seedling at 10 month

Figure 2. Relationship between height of coffee seedlings at 10 month old and application rates of cocoapod husk granules.

Gambar 2. Hubungan antara tinggi bibit kopi umur 10 bulan dengan dosis aplikasi granul kulit buahkakao.

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Figure 3. Relationship between total fresh (A) and dry (B) weight of coffee seedlings at 10 month oldand application rates of cocoa pod husk granules.

Gambar 3. Hubungan antara bobot basah (A) dan bobot kering (B) bibit kopi umur 10 bulan dengan dosisaplikasi granul kulit buah kakao.

A

B

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old and application rates of granules con-formed to quadratic equations of both forcombined treatment with inorganic fertil-izer application, and for treatment whichhas no combination with inorganic fertil-izer application (Figure 3B). The quadraticgrowth response to granule applicationsindicated that applications more than theoptimum rate, growth response deminisedsteadily.

Total dry weight of coffee seedlingis a resultant of all growth variables.Therefore, total dry weight could be usedas main indicator for seedling growth.Based on the above two equations, the cal-culated optimum rates of granules for cocoaseedling is 14.5 g/seedling for combinedtreatment with inorganic fertilizer appli-cation. Single application of granules withno inorganic fertilizer application had thesame effect with application of both gra-nules and inorganic fertilizer on coffeegrowth. It implies that inorganic fertilizercan be completely replaced by cocoa podhusk granules. The effect of granules de-rived from cocoa pod husk on growth ofcoffee seedling was similar with the ef-fect of coffee pulp which has quadraticresponse. The optimum application rateof coffee pulp is 120 g/seedling, whichis much higher than that of cocoa pod husk(Pujiyanto, 2007). Effect of inorganic com-pound fertilizer represented in Figure 4pointed out that no significant effect onheight, while for fresh weight and dryweight were significant. Application ofinorganic fertilizer accelerated seedlinggrowth of 18%.

Agronomic test on cocoa seedling

Agronomic test indicated that singleeffect of granule and inorganic fertilizerapplication increased significantly height,fresh weight and dry weight of cocoa seed-ling, meanwhile the effect on leaf num-ber and stem diameter were not signifi-cant. There was a significant positive qua-dratic relationship between rates of granuleapplications and seedling height of cocoa(Figure 5). The equations both for com-bined treatment of granules with inorganicfertilizer and for non-combined with in-organic fertilizer was quadratic.

Observation on variable of seedlingfresh weight indicated a similar trend withvariable of seedling height. Relationshipbetween total seedling fresh weight andapplication rates of granules was quadraticboth for treatment which has combinationwith inorganic fertilizer application, andfor treatment which has no combinationwith inorganic fertilizer. The two equa-tions implied that granules application withno inorganic fertilizer is sufficient to fulf ilthe need of cocoa seedling to grow nor-mally (Figure 6A).

Relationship between total dry weightof cocoa seedling and application rates ofcocoa pod husk granules was quadratic bothfor treatment which has combination withinorganic fertilizer application, and fortreatment which has no combination withinorganic fertilizer (Figure 6B).

The quadratic responses implied thatseedling growth was boosted by granuleapplication up to the optimum rate. At ap-

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Figure 4. Relationship between growth variables of coffee seedlings at 10 month old and application ofinorganic compound fertilizer of N-P-K 15-15-15.

Gambar 4. Hubungan antara variabel pertumbuhan bibit kopi umur 10 bulan dengan dosis aplikasi pupukanorganik majemuk N-P-K 15-15-15.

Figure 5. Relationship between height of cocoa seedlings at 5 month old and application rates of cocoapod husk granules.

Gambar 5. Hubungan antara tinggi bibit kakao umur 5 bulan dengan dosis aplikasi granul kulit buah kakao.

plication rates of granules more than theoptimum, response of cocoa seedling wasnegative, which implied that seedlinggrowth deminised. Total dry weight is aresultant of all variables of cocoa-seed-ling growth, therefore this variable canbe used as main indicator for seedlinggrowth. Based on the above equation, the

calculated optimum application rates ofgranules for cocoa seedling is 14.6 g/seed-ling for treatment which has combinationwith inorganic fertilizer application, whilefor treatment which has no combinationwith inorganic fertilizer application, therate is 11.2 g/seedling.

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Figure 6. Relationship between total fresh (A) and dry (B) weight of cocoa seedlings at 5 month old andapplication rates of cocoa pod husk granules.

Gambar 6. Hubungan antara bobot basah (A) dan bobot kering (B) bibit kakao umur 5 bulan dengan dosisaplikasi granul kulit buah kakao.

A

B

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Compared to the previous finding onthe use of coffee pulp which indicated thatthe optimum application rates for cocoaseedling was 150 g/seedling (Pujiyanto,2007), the optimum application rates ofcocoa pod husk is much lower. It was notclear the cause of the phenomenon of qua-dratic response with low application rate.It was assumed that the deminishing growthresponses at application rates higher thanthe optimum is due to negative effect ofleachate produced by cocoa pod husk fol-lowing decomposition. Visual observationnearby heap of cocoa pod husks indicatedproduction of brown-liquid leachate flowout from the heap. The grass vegetationsurrounding the heap which were in di-rect contact with the leachate indicatedbrowning symptom on their leaves and thegrowth was hampered. Therefore, furtherresearch is necessary to confirm the phe-nomenon of negative responses of cocoaand coffee seedling at high application ratesof cocoa pod husk granules.

From the equation in Figure 6B, thecalculated maximum value of cocoa seed-ling dry weight is 42.5 g/seedling for gran-ule treatment with no inorganic fetilizerand for combined treatment of granule andinorganic fertilizer is 43.7 g/seedling. Itimplies that at optimum granule rate fortreatment without inorganic fertilizer hadthe same effect with application of bothgranules and inorganic fertilizer on co-coa seedling growth. It indicated that in-organic fertilizer can be completely re-placed by cocoa pod husk granules.

Growth acceleration of the seedlingwas a resultant of improvement effect on

soil-media; not only on their chemical prop-erties but also on their physical and bio-logical properties as well. Soil analysispointed out the improvement of severalnutrient content (Table 1). Nutrients de-rived from the granules will be taken upby the seedlings to boost growth. The gran-ules had much higher CEC than bulk soil.The high CEC value in the granules wasderived from both organic matter and zeo-lite. It is imply that granule appcicationsmay increase CEC of the media. HigherCEC values of the soil-media indicatedhigher capability to retain and to supplynutrients. Therefore, much more nutrientsespecially cations, can be retained and willavoid losses by leaching. The retained nu-trients gradually can be absorbed by plantroots through exchange processes. Zeo-lite application at rate of 2 g/kg soil me-dia was enough to increase the exchangesites in the soil in order to absorb the ap-plied nitrogen and prevent its leaching(Sepaskhah & Yousefi, 2007), while Omaret al., (2001) and He et al., (2002) provedthat zeolite application substantially re-duced leaching of ammonium and potas-sium in acid tropical soil, therefore it couldbe used as an effective soil amendment.

Following decomposition of the or-ganic matter in the granules, nutrients andorganic acids will be released to soil so-lution. The nutrients will be available forplant, while the organic acids may favorbetter condition for seedling growth. Re-search findings showed that organic ac-ids capabled to increase solubility of Cuand Zn (Wu et al., 2002), reduced alu-minum toxicity (Hu et al., 1985).

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Zeolite in the granules may improveavailablity of P derived from rock phos-phate, leading to better uptake by plant.The reaction involved in the processes was:(P-rock phosphate) + (NH4-zeolite) = (Ca-zeolite) + (H2PO4

-). The zeolite takes upCa2

+ from rock phosphate, thereby releas-ing both phosphate and ammonium ions.The released phosphate will readily avail-able for plant. The processes occuredgradually leading to controlled releasedof phosphate. As phosphate was taken upby plant or by soil fixation, the chemicalreaction releases more phosphate and am-monium in the attempt to reestablish equi-librium. Pickering & Menzies (2002)demontrated greatly enhanced plant up-take of P from RP when applied in com-bination with NH4-zeolite, though the Puptake was lower than that from the solubleP source. The zeolite/RP interaction wasmuch more effective with the reactive RPthan the non-reactive material. Root pro-

liferation was also greatly increased.Therole of zeolite as a controlling agent inreleasing nutrients has been demonstratedby Caballero et al., (2008) which pointedout the increasing nitrogen and potassiumuptake due to zeolite addition in the soilmedia. Similar study have been conductedby Milosevic & Milosevic (2009) who in-dicated that zeolite application in combi-nation with organic and inorganic fertil-izers significantly increased available ni-trogen, phosphorus and potassium in soiland promote apple biomass.

Residual effect of granule applicationon selected soil characteristics showed anindication of increment content of organicmatter, nitrogen, phosphorus, potassium andlower pH value. Decreasing soil pH wasan effect of greater cations absorbtion byroots. During cation absorbtion, hydro-gen was released by plant roots to replacedthe absorbed cations leading to the decreas-ing soil pH value. Residual effect of gran-

C (%) 1.98 2.23 2.20 2.19N (%) 0.21 0.24 0.23 0.23C/N 9.50 9.58 9.57 9.57P2O5 Bray-1 (ppm) 62 143 1.83 2.52K (me %) 1.97 2.21 112 151pH H2O 6.65 5.77 6.49 5.30

Table 1. Residual effect of granule and inorganic fertilizer application on several soil characteristics

Tabel 1. Efek residu aplikasi granul dan pupuk anorganik pada beberapa macam karakteristik tanah

No Tanpa

AppliedDiberi

NoTanpa

AppliedDiberi

GranulesGranul

Inorganic fertilizerPupuk anorganik

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ules on phosphate content in soil was 2.3times than that of no granule treatment.It was assumed that the remaining phos-phate in soil was mainly derived from rockphosphate which present in the granules.Solubility and agronomic effectiveness ofthe rock phosphate depend on their size(Lim et al., 2003). Data in Table 1 indi-cated that during 5 months in nursery, onlypart of the nutrient from the granules wasabsorbed by seedling to promote growth.Former research findings also indicatedthat organic matter application stimulatedbetter soil characteristics for plant growth,namely: increased CEC and nitrogen con-tent (Sudarsono, 1991), increase availablesoil-P (Irianto et al., 1993), exchangablesoil-K, exchangable Ca, Mg, K and Na(Situmorang, 1999), soil-pH (Irianto et al.,1993), and reduced exchangable alumi-num and iron leading to reduction of tox-icity (Situmorang, 1999), decreased per-manently fixed phosphorus by soil clay

(Zhang & MacKenzie, 1997) and increasedcontent of BAP and IBA hormones in thesoil (Pujiyanto et al., 2003).

The improvement on physical pro-perties of the media occured especially onthe increased of water retention. The gran-ules have much higher water retention com-pared to bulk soil. Granule application in-creased total water retention of the me-dia. Organic matter derived from cocoapod husk had a significant contribution onphysical improvement on mineral soil.Pujiyanto et al. (2003) indicated that or-ganic matter application significantly in-creased size of soil aggregates and per-centage of stable soil aggregates of co-coa farm. Organic matter acted as bind-ing agents among soil component (sand,silt and clay fractions) to form aggregatesand among soil agregates to form largerand more stable aggregates. The appliedorganic matter may increase meso andmacro pores, leading to improvement of

Figure 7. Relationship among growth variables of cocoa seedling and application of inorganic N-P-Kfertilizer.

Gambar 7. Hubungan antara variabel pertumbuhan bibit kakao dengan aplikasi pupuk anorganik N-P-K.

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soil porosity, aeration, permeability andrate of water infiltration. Organic frac-tions played the most important role forsoil aggregate stabilization (Oades, 1993;Situmorang, 1999). Organic matter frac-tions also played an important role forbiologycal soil improvement. The organicmatter fraction acted as energy sourcesfor soil organism. Activity of the soil or-ganisms induced aggregate formation andstabilization.

Figure 7 pointed out the relationshipamong growth variables of cocoa seedlingand application rates of inorganic N-P-Kfertilizer. Application of compound N-P-K fertilizer at 2 g/seedling/application whichwas applied four times during nurserysignificantly increased height, total freshweight and total dry weight of cocoa seed-ling.

The residual inorganic fertilizer wasdetected on the potassium and phospho-rus content and soil pH. There was no re-sidual effect of fertilizer on soil organicmatter and nitrogen content. The data in-dicated that all nitrogen derived fromcompound fertilizer has been absorbed bycocoa seedling or lossed from soil sys-tem in form of gas due to volatilizationor denitrification.

CONCLUSIONS

1. Granules composition of 90% cocoa podhusk and 10% minerals (Zeolite : Rockphosphate = 1:1) may be used as natu-ral soil ameliorant to increased soil ca-pability to support growth of cocoa andcoffee.

2. The optimum application rate of gran-ules was 14.5 g/seedling for Robustacoffee seedlings and 14.6 g/seedling forcocoa.

3. Granule application may replace roleof inorganic fertilizer to increase growthof coffee and cocoa seedlings.

REFERENCES

Baon, J.B. & Soenaryo (1989). Penggunaanbelotong sebagai sumber bahanorganik untuk kopi dan kakao. II.Pengaruhnya terhadap daya hasil kopi.Pelita Perkebunan, 5, 52–57.

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