Coconut shell derived biochar to enhance water spinach (Ipomoea aquatica Forsk) growth and decrease nitrogen loss under tropical conditions

Farms usually apply excessive nitrogen (N) fertilizers, especially in a vegetable production system, resulting in severe N leaching loss. Although there have been some reports on the impact of biochar on the N leaching in farmlands, most of them focused on field crops in temperate or subtropical religions. Limited information about N leaching in the tropical vegetable system is available regarding the quantitative data and effective countermeasures. A field experiment was conducted to quantify N leaching in a tropical leafy production system ( Ipomoea aquatica Forsk) and to evaluate the effects of coconut shell biochar on N loss and crop growth. The results showed that compared to conventional fertilization with the 240 kg N ha −1 application rate (NPK), biomass yield of water spinach increased by 40.1% under the high biochar application rate of 48 t ha −1 (HBC), which was significantly higher than that of NPK treatment. Moreover, The HBC treatment decreased N leaching by 34.0%, which can be attributed to enhanced crop uptake which increased by 40.3% as compared to NPK treatment. The NH 4 + /NO 3 − ratio in leachates was between 0.01 and 0.05. It was concluded that coconut shell derived biochar improved the biomass yields of water spinach and reduced the leaching N loss, which provides a promising amendment in tropical regions.