Effect of balanced fertilization on vegetables

Vegetable production provides Hainan’s farmers with a very lucrative business which has gained considerable momentum in recent years due to its ability to supply summer vegetables to northern regions during the winter season. This motivates farmers to manage for high yields. However, without concrete research, or science-based technology and related guidance in fertilizer management, farmers often produce suboptimal yield and quality and are exposed to greater costs and environmental risks. The objective of this study was to identify soil nutrient limiting factors and develop best fertilizer management practices for vegetables---chili pepper, wax gourd, and eggplant.

Soil testing indicated that N, P, K, and magnesium (Mg) were currently limiting vegetable production. These soil test results were further verified through field trials. Crop responses to different nutrients were highly diverse depending on the type of vegetables. Chili pepper was highly responsive to added K and N, with respective yield increases of 12.5 t/ha (59%) and 11 t/ha (48%). Chili responses to added P and Mg were smaller at 3.8 t/ha (13%) and 5.7 t/ha (20%), respectively. In wax gourd, N was most limiting as its application increased yield by 24.6 t/ha (35%), followed by K and Mg with yield increases ranging between 20% to 23%. Fertilizer P resulted in an average yield increase of 6.5%.

The balanced optimum (OPT) treatment increased eggplant yield by 23.1 t/ha (62%), 23 t/ha (62%), and 25.8 t/ha (75%) compared to treatments omitting N, P, and K, respectively. Addition of Mg reduced eggplant yield and zinc (Zn) application reduced wax gourd yields. The OPT treatments yielded the highest fertilizer use efficiencies in all three vegetables. Fertilizer rates verified in this study can be used throughout the surrounding area. Thus, 300-150-225 kg N-P₂O₅^-K₂O/ha plus 90 kg MgO/ha is recommended for chili pepper, 450-225-375 kg/ha plus 90 kg MgO/ha is recommended for wax gourd, and 400-220-525 kg/ha is recommended for eggplant. Hainan-BFDP-06