Effect of balanced fertilization on production of pineapple in Hainan

Hainan Island of China, due to its unique tropical and subtropical climate, is well suited to produce a number of agricultural products that cannot grow elsewhere or during the winter season in the country. The high value associated with this vegetable production usually leads to over-use of fertilizers by farmers. Thus, the objective of this study was to determine the optimal fertilizer rates for chili pepper, one of the most widely grown vegetables in winter, to guide fertilizer application for local technicians and vegetable growers. The experiment consists of six rates of N, P and K (i.e., 0,150, 300, 450, 600, and 750 kg N/ha; 0, 60, 120, 240, and 300 kg P₂O₅/ha; 0,150, 300, 450, 600, and 750 kg K₂O/ha). The experiment was conducted on a sandy soil typical of Hainan.

Results showed that chili pepper yield responded to N and K, but not P. Pepper yields leveled off at 300 kg N/ha and 300 kg K₂O/ha and then fell when the fertilizer rates continued to rise. This fertilizer combination could produce 63.7 t/ha of chili pepper and USD 8,030/ha of net income. Furthermore, it also achieved the highest agronomic efficiency for N (82 kg pepper/kg N) and K (32 kg pepper/kg K₂O). The crops lack of response to P is due to high soil P reserves that have accumulated in previous years. Further research needs to be conducted to determine how long the accumulated P reserves can support crop growth without either no P input or with maintenance levels of P application. For the time being, recommendations for chili pepper fertilization on Hainan Island can be adjusted to 300-60-300 kg N-P₂O₅-K₂O/ha based on this current study. Hainan-BFDP-08