Abstract
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 NH4+/NO3− 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.
Highlights
Farms usually apply excessive nitrogen (N) fertilizers, especially in a vegetable production system, resulting in severe N leaching loss
Biochar amendment promoted the growth of water spinach
The accumulative dry biomass yields of spinach amended with biochar was from 1357 to 1678 kg ha−1, which was 13.3–40.1% more than that of chemical fertilizer treatment (NPK, 1197 kg ha−1)
Summary
Farms usually apply excessive nitrogen (N) fertilizers, especially in a vegetable production system, resulting in severe N leaching loss. Usually alkaline, and exhibit large specific surface area[10] Owing to these inherent physicochemical properties, biochar affects many soil properties including soil pH, organic matter, water holding capacity and microbial composition and diversity[11,12]. NPKM with nutrient ions by electrostatic, complexation, or capillary forces[15,16] These properties of biochars can reduce the leaching of nutrients from soil and subsequent accessibility of nutrients to crops[17]. Biochar addition to soil showed inconsistent results on crop growth, soil properties and nutrient N leaching[10,23,24,25,26] because biochar properties vary widely, depending on the biomass source, pyrolysis temperature (350–900 °C) and application rate (4–90 t ha−1)[8,20,27,28]
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