Nutrition aspects and fertilizer recommendations on CACAO (Theobroma cacao) Contents: 1. General features.... 2 2. Main factors affecting cacao production....... 3 3. Plant nutrition.... 4 4. Fertilizer recommendations.. 4 5. References... 5
1. General features Cacao (Theobroma sp.) is a perennial tree that belong to the family of Malvaceae. It is cultivated for its fruits, known as cacao pods containing the seeds that once fermented and dried are used to make chocolate: the fruits grow on both the trunk and the branches in flower cushions. It is a neotropical, small, evergreen tree native to South America, growing between 20 latitude north and south of the Equator and introduced in Asia and Africa in 1670 and 1822 respectively. Nowadays it continues to be cultivated in South America, but also in the Central America, Africa and Asia (fig. 1). Figure 1 Production of cacao beans (FAO, 2011) The main groups of cultivated cacao are three: Criollo, Trinitario and Forastero. It is sown directly in nursery under shade and then planted out in the field after 7-8 months. Maturation phase is achieved when the stem bearing the newly formed leaves begins to form phloem. The first useful flowering occurs at 18-24 months after planting. Flowering is continuous, but favourable pollination period occur about 2 months after the beginning of rainy seasons. After anthesis the growth and maturation process of the cacao fruit takes approximately 150 days: young fruits grow slowly during the first 40 days after pollination and are prone to wilting; subsequent growth is more rapid up to 75 days and full maturity is reached 150 days after fertilization while ripening follows immediately taking about 20-30 days to complete (its characteristics is that the colour of the husk changes externally). Altogether, the maturation process of the fruit from the pollination to fully mature fruit, takes 160-210 days. Plant density is generally 950-1330 trees/ha. Expected yield is 1 t/ha of dry beans (7 % humidity) with 1.4 t/ha of husks. 2
2. Main factors affecting cacao production The natural habitat of the cacao tree is in the lower storey of the evergreen rainforest and climatic factors, particularly temperature and rainfall, are important in encouraging optimum growth. Cacao needs a soil containing coarse particles and with a reasonable quantity of nutrients, to a depth of 1.5 m to allow the development of a good root system. Cacao can grow in soils with a ph in the range of 5.0-7.5. It can therefore grows in both acid and alkaline soil, but excessive acidity (ph 4.0 and below) or alkalinity (ph 8.0 and above) must be avoided. Cacao is tolerant of acid soils, provided the nutrient content is high enough. The soil should also have a high content of organic matter: 3.5% in the top 15 cm of soil. Soils for cacao must have certain anionic and cationic balances. Exchangeable bases in the soil should amount to at least 35% of the total cation exchange capacity (CEC), otherwise nutritional problems are likely. Cacao plants respond well to relatively high temperatures, with a maximum annual average of 30-32ºC and a minimum average of 18-21ºC. Variations in the yield of cacao trees from year to year are affected more by rainfall than by any other climatic factor. Trees are very sensitive to a soil water deficiency. Rainfall should be plentiful and well distributed through the year. An annual rainfall level of between 1,500 mm and 2,000 mm is generally preferred. Dry spells, where rainfall is less than 100 mm per month, should not exceed three months. A hot and humid atmosphere is essential for the optimum development of cacao trees. Cacao is a shade tolerant species, in which appropriate shading leads to relatively high photosynthetic rates, growth and seed yield. However, heavy shade reduces seed yield and increases incidence of diseases; in fact, cacao yields and light interception are tightly related when nutrient availability is not limiting: fertilization of shade cacao commonly produces only modest yield increments. Fertilization of sunlight- exposed plantations generally results in significant yield responses because of greater photosynthetic activity. In the world three shade management systems are spread: rustic cacao management, widespread in the humid portion of West Africa and local in Latin America, is characterized by the planting of cacao under thinned primary or older secondary forest. Planted shade systems vary widely, from traditional polycultural systems to commercial shade where other crops are interspersed among planted shade trees and the cacao, to monocultural, specialized shade, where the shade is dominated by one or a few tree species. Zero- shade cacao cultivation, without shade, is common in Malaysia and becoming more widespread in parts of Colombia and Peru. 3
3. Plant nutrition Average nutrient removal in a crop of 1 t/ha dry cacao beans (7 % humidity) with 1.4 t/ha husks is: N P 2 O 5 K 2 O MgO CaO Beans 19-23 7-10 9-13 2-5 0.5-1.5 Husks 11-17 3-5 52-93 4-9 4-10 Total 31-40 11-14 61-103 9-12 5-11 The N:P 2 O 5 :K 2 O ratio is 1:0.4:0.5 in the beans and 1:0.3:5 in the husk, indicating that while there is a greater proportion of absorbed N and P in the beans, husk is richer in K and also in Ca. Magnesium is about equally divided between the beans and the husk. 4. Fertilizer recommendations Ilsa suggests the use of the fertilizer PROGRESS MICRO 6.5.13, a pelletized organo- mineral NPK fertilizer. It only contains organic Nitrogen deriving from Agrogel and it is allowed in organic agriculture. It well reflects the ratio N:P 2 O 5 :K 2 O of the total nutrient removal equivalent to 1:0.3:2.5. PROGRESS MICRO can be applied at doses of 700-800 kg/ha, corresponding to 40-45 g of N, 30-35 g of P 2 O 5 and 80-95 g of K 2 O per tree, split in three applications every 120 days. It is recommended the application around each tree, either in band 0.6-1.0 m around stem or in 80 cm- wide strips between rows and between trees as most feeder roots (80%) are in the top 0-20 cm of soil and develop where the fertilizer is applied. It is recommended to distribute pod husks evenly in the orchard to reduce nutrients removal. 4
5. References IFA, 1992, IFA World Fertilizer Use Manual. International Fertilizer Industry Association, Paris. TANDON H.L.S., MURALIDHARUDU Y., 2010, Nutrient uptake, removal and recycling by crops. Fertiliser Development and Consultation Organisation, New Delhi (India). NIEMENAK N., CILAS C., ROHSIUS C., BLEIHOLDER H., MEIER U., LIEBEREI R., 2010, Phenological growth stages of cacao plants (Theobroma sp.): codification and description according to the BBCH scale. Annals of Applied Biology 156 (2010) 13-24. RICE R. A. and GREENBERG R., 2000, Cacao cultivation and the conservation of biological diversity. Ambio Vol. 29, N. 3, May 2000. URIBE A., MÉNDEZ H., MANTILLA J., 2001. Effect of balanced fertilization on Cocoa yield. Better Crops International, Vol. 15, N. 2, November 2001. DE ALMEDIA A.- A. F. and VALLE R. R., 2007. Ecophysiology of the cacao tree. Brazilian Journal of Plant Physiology, 19(4):425-448, 2007. FAO STAT, www.faostat.fao.org. INTERNATIONAL COCA ORGANIZATION (ICCO), http://www.icco.org/ 5