Effects of biochar on aggregate characteristics of upland red soil in subtropical China

Soil aggregation is one of the key properties affecting the productivity of soils and the environmental side effects of agricultural soils. In this study, we aimed to identify whether biochar could be used to improve aggregate stability. A 2-year field experiment was conducted to investigate the effect of biochar application ( 0, 2.5, 5, 10, 20, 30 and 40 t ha(-1)) on aggregate characteristics of upland red soil under a rapeseed-sweet potato rotation in subtropical China. Percentage of aggregate destruction ( PAD(0.25)), mean weight diameter (MWD), geometric mean diameter (GMD) and fractal characteristics of soil aggregates were measured using both wet and dry sieving methods. Results showed that applying biochar significantly decreased the percentage of aggregate destruction and soil fractal dimension and increased the MWD and GMD. The optimal amelioration was observed when biochar was applied at a rate of 40 t ha(-1). The decline of the fractal dimension of dry aggregates was 2-9 times as much as that of water-stable aggregates in the 0-15 soil layer and 1-4 times in the 15-30 cm soil layer. These results suggested that biochar could improve the resistance of aggregates to stresses and provide scientific strategies for the agricultural production.