References
- Acharya, C. L. 2002. Integrated input management for sustainable crop production in rainfed agro-ecosystem. Journal of the Indian Society of Soil Science 50 (4): 398–413.
- Ali, M. 1999. Evaluation of green manure technology in tropical lowland rice systems. Field Crops Research 61 (1): 61–78. doi:10.1016/S0378-4290(98)00149-X
- Ayoola, O. T., and O. N. Adeniyan. 2006. Influence of poultry manure and NPK fertilizer on yield and yield components of crops under different cropping systems in southwest Nigeria. African Journal of Biotechnology 5 (15): 1386–92.
- Brady, N. C., and R. R. Weil. 2006. Nature and properties of soils, 13th ed. London: Prentice-Hall.
- FAOSTAT. 2011. Food and agriculture organization statistical year book 2010–11. Rome, Italy: FAO.
- Halavatau, S. M., J. N. O’Sullivan, C. J. Asher, and F. P. C. Blamey. 1998. Better nutrition for the improvement of sweet potato and taro yields in the South Pacific. Tropical Agriculture 75: 6–12.
- Hartemink, A. E. 2003. Integrated nutrient management research with sweet potato in Papua New Guinea. Outlook on Agriculture 32 (3): 173–82. doi:10.5367/000000003101294442
- Hartemink, A. E., and J. N. O’Sullivan. 2001. Leaf litter decomposition of Piper aduncum, Glyricidia sepium, and Imperata cylindrical in the humid lowlands of Papua New Guinea. Plant and Soil 230: 115–24. doi:10.1023/A:1004868502539
- Hill, W. A. 1984. Effect of nitrogen nutrition on quality of three important root/tuber crops. In Nitrogen in crop production, ed. R. D. Hauck, 627–41. Madison, WI: ASA-CSSA-SSSA.
- Humphries, E. C. 1956. Mineral components and ash analysis. In Modern methods of plant analysis, vol. 1, eds., K. Paech and M. V. Tracey, 468–502. Berlin/Heidelberg, Germany: Springer.
- Jackson, M. L. 1973. Soil chemical analysis. New Delhi, India: Prentice Hall of India.
- Janssen, B. H. 1993. Integrated nutrient management: The use of organic and mineral fertilizers. In The role of plant nutrients for sustainable food crop production in sub-Saharan Africa, ed. H. van Reuler and W. H. Prins, 89–105. Leidschendam, the Netherlands: Dutch Association of Fertilizer Producers.
- Kamara, A. Y., and M. T. Lahai. 1997. Differential response of sweet potato (Ipomoea batatas) to green manuring with elephant grass (Pennisetum purpureum) and spear grass (Imperata cylindrica) on a ferralitic soil in Sierra Leone. Tropenlandwirt 98: 229–35.
- Martí, H. R., and H. A. Mills. 2002. Nitrogen and potassium nutrition affect yield, dry weight partitioning, and nutrient-use efficiency of sweet potato. Communications in Soil Science and Plant Analysis 33: 287–301. doi:10.1081/CSS-120002394
- Moorthy, S. N., and G. Padmaja. 2002. A rapid titrimetric method for the determination of starch content of cassava tubers. Journal of Root Crops 28 (1): 30–37.
- O’Keefe, D. M., and D. M. Sylvia. 1993. Seasonal dynamics of the association between sweet potato and vesicular-arbuscular mycorrhizal fungi. Mycorrhiza 3 (3): 115–22. doi:10.1007/BF00208919
- Ojeniyi, S. O. 2000. Effect of goat manure on soil nutrients and okra yield in a rain forest area of Nigeria. Applied Tropical Agriculture 5: 20–23.
- Ossom, E. M., and R. L. Rhykerd. 2008. Effects of lime on soil and tuber chemical properties and yield of sweet potato [Ipomoea batatas (L.) Lam.] in Swaziland. American-Eurasian Journal of Agronomy 1 (1): 1–5.
- Singh, S., R. N. Singh, J. Prasad, and B. Kumar. 2002. Effect of green manuring, FYM, and biofertilizer in relation to fertilizer nitrogen on yield and major nutrient uptake by upland rice. Journal of the Indian Society of Soil Science 50 (3): 313–14.
- Subba Rao, N. S. 1999. Soil microbiology. Fourth edition of soil microorganisms and plant growth. New Delhi, India: Oxford & IBH Publishing Co. Pvt. Ltd.
- Subramanian, K. S., and K. Kumaraswamy. 1989. Effect of continuous cropping and fertilization on chemical properties of soil. Journal of the Indian Society of Soil Science 37 (1): 171–73.
- Svotwa, E., R. Baipai, and J. Jiyane. 2007. Organic farming in the small holder farming sector of Zimbabwe. Electronic Journal of Environmental, Agricultural and Food Chemistry 6 (2): 1820–27.
- Thakuria, K., B. Borgohain, and K. K. Sarma. 1991. Effect of organic and inorganic sources of nitrogen with and without phosphate on fibre yield of white jute (Corchorus capsularis). Indian Journal of Agricultural Sciences 61 (1): 49–50.
- Vele, P. I., B. Pax, and J. A. Colin. 2000. Effects of lime and gypsum on growth of sweet potato in two strongly acid soils. Australian Journal of Agricultural Research 51 (8): 1031–37. doi:10.1071/AR00043