Adams, F. (1984). Crop responses to lime in the southern United States. In Soil Acidity and Liming, (Ed Adams, F.). 2nd ed. Madison: American Society of Agronomy.
Adejuwan, J. O. and Ekanade, O. (1988). A comparison of soil properties under different land use types in a part of the Nigerian cocoa belt. Catena 15:319–331.
Agoume, V. and Birang, A. M. (2009). Impact of land-use systems on some physical and chemical soil properties of an oxisol in the humid forest zone of Southern Cameroon. Tropicultura 27:15–20.
Baligar, V. C. and Fageria, N. (2005). Soil aluminum effects on growth and nutrition of cacao. Soil Science & Plant Nutrition 51:709–713.
Bartlett, R. J. and Riego, D. C. (1972). Effect of chelation on the toxicity of aluminium. Plant & Soil 37:419–423.
Burger, M. and Jackson, L. E. (2003). Microbial immobilization of ammonium and nitrate in relation to ammonification and nitrification rates in organic and conventional cropping systems. Soil Biology & Biochemistry 35:29–36.
Chong, C. F. and Shepherd, R. (1986). Promising prang beser clones. In Cocoa and Coconuts: Progress and Outlook, 3–20 (Eds Pushparajah, E. and Soon, C. P.). Kuala Lumpur: Incorporated Society of Planters.
Daniel, R., Konam, J. K., Saul-Maora, J. Y., Kamuso, A., Namaliu, Y., Vano, J. T., Wenani, R., N'nelau, P., Palinrungi, R. and Guest, D. I. (2011). Knowledge through participation: The triumphs and challenges of transferring Integrated Pest and Disease Management (IPDM) technology to cocoa farmers in Papua New Guinea. Food Security 3:65–79.
de Geus, J. G. (1973). Fertilizer Guide for the Tropics and Subtropics. Zurich: Centre d'Etude de l'Azonte.
Fahmy, F. N. (1977). Soil and leaf analyses in relation to the nutrition of tree crops in Papua New Guinea. In Proceedings of the Conference on Classification and Management of Tropical Soils. Kuala Lumpur: Malaysian Society of Soil Science.
Hardy, F. (1958). Cacao soils. In Proceedings of the Soil and Crop Science Society of Florida, vol. 18, 75–87.
Hartemink, A. E. (2005). Nutrient stocks, nutrient cycling and soil changes in cocoa ecosystems: A review. Advances in Agronomy 86:227–252.
Hue, N. V. (2011). Alleviating soil acidity with crop residues. Soil Science 176:543–549.
Kurvitis, A. and Kirkby, E. A. (1980). The uptake of nutrients by sunflower plants (Helianthus annum) growing in a continuous flowing culture system, supplied with nitrate or ammonium as nitrogen source. Zeitschrift für Pflanzenernährung und Bodenkunde 143:140–149.
Marschner, H. (1995). Mineral Nutrition of Higher Plants, London: Academic Press.
McMahon, P., Bin Purung, H., Lambert, S., Mulia, S., Nurlaila, Susilo, A. W., Sulistyowati, E., Sukamto, S., Israel, M., Saftar, A., Amir, A., Purwantara, A., Iswanto, A., Guest, D. and Keane, P. (2015). Testing local cocoa selections in three provinces in Sulawesi: (i) Productivity and resistance to cocoa pod borer and Phytophthora pod rot (black pod). Crop Protection 70:28–39.
Murray, D. B. (1967). Leaf analysis applied to cocoa. Cocoa Growers' Bulletin 9:25–31.
Nelson, P. N., Webb, M. J., Berthelsen, S., Curry, G., Yinil, D. and Fidelis, C. (2011). Nutritional status of cocoa in Papua New Guinea. Canberra, Australian Centre for International Agricultural Research.
Noordiana, N., Syed Omar, S. R., Shamshuddin, J. and Nik Aziz, N. M. (2007). Effect of organic-based and foliar fertilisers on cocoa (Theobroma cacao L.) grown on an oxisol in Malaysia. Malaysian Journal of Soil Science 11:29– 43.
Panlibuton, H. and Lusby, F. (2006). Indonesia cocoa bean value chain case study. microREPORT#65. USAID.
Rengel, Z. and Robinson, D. L. (1989). Competitive Al3+ inhibition of net Mg2+ uptake by intact Lolium multiflorum roots: I. Kinetics. Plant Physiology 91:1407–1413.
Ruf, F. and Yoddang, (2001). Cocoa farmers from boom to bust. In Agriculture in Crisis: People, Commodities and Natural Resources in Indonesia, 1996–2000 (Eds Gerard, F. and Ruf, F.). Richmond: Curzon Press.
Ruf, F. and Yoddang, (2004). Tropical deforestation to forest cover dynamics and forest development. In The Sulawesi Case: Deforestation, Pre-Cocoa and Cocoa Migrations, 277--229 (Ed D. Babin). Paris: UNESCO.
Shamshuddin, J., Muhrizal, S., Fauziah, I. and Husni, M. H. A. (2004). Effects of adding organic materials to an acid sulfate soil on the growth of cocoa (Theobroma cacao L.) seedlings. Science of the Total Environment 323:33–45.
Steiner, C., Teixeira, W. G., Lehmann, J., Nehls, T., De Macedo, J. L. V., Blum, W. E. H. and Zech, W. (2007). Long term effects of manure, charcoal and mineral fertilization on crop production and fertility on a highly weathered central amazonian upland soil. Plant & Soil 291:275–290.
Suthipradit, S., Edwards, D. G. and Asher, C. J. (1990). Effects of aluminium on tap-root elongation of soybean (Glycine max), cowpea (Vigna unguiculata) and green gram (Vigna radiata) grown in the presence of organic acids. Plant & Soil 124:233.
Tiessen, H., Cuevas, E. and Chacon, P. (1994). The role of soil organic matter in sustaining soil fertility. Nature 371:783–785.
Toxopeus, H. (1985). Botany, types and populations. In Cocoa. 4th ed., 11–37 (Eds , G. A. R. Wood, and Lass, R. A.). London; New York: Longman.
Van Lauwe, B., Aihou, K., Aman, S., Iwuafor, E. N. O., Tossah, B. K., Diels, J., Sanginga, N., Lyasse, O., Merckx, R. and Deckers, J. (2001). Maize yield as affected by organic inputs and urea in the West African moist savanna. Agronomy Journal 93:1191–119.
Wessel, M. (1985). Shade and nutrition of cocoa. In Cocoa, 4th ed., 166–194 (Eds Wood, G. A. R. and Lass, R. A.). Essex: Longman Scientific and Technical.
Woomer, P. L., Martin, A., Albrecht, A., Resck, D. V. S. and Scharpenseel, H. W. (1994). The importance and management of soil organic matter in the tropics. In The Biological Management of Tropical Soil Fertility, 47–80 (Eds Woomer, P. L. and Swift, M. J.). Chichester, UK: Wiley-Sayce Publications.