Effects of biochar amendment on rapeseed and sweet potato yields and water stable aggregate in upland red soil

A field experiment was conducted to study the effect of biochar amendment (0, 2.5, 5, 10, 20, 30 and 40 t.ha(-1)) on rapeseed and sweet potato yields, aggregate particle size distribution, aggregate stability, soil organic carbon, total N content and C:N ratio in soil water stable aggregate under a rapeseed-sweet potato rotation system in upland red soil in Jiangxi Province of southern, China. The results were as follows: compared with control treatment (CK), when the amount of biochar was 40 t.ha(-1), rapeseed and sweet potato yields were increased by 36.02% and 53.77% respectively; the soil water stable aggregate (>0.25 mm) in the 0-15 cm soil layer had a remarkable increase than other treatments, especially the macroaggregate with particle size larger than >2 mm. In the rapeseed harvest season, the mean weight diameter of soil water stable aggregate was enhanced by 28.02% compared to CK with the application rate of biochar being 40 t.ha(-1). A significant increment in soil organic carbon, total N and C:N ratio was observed in the >2 mm, 2-0.5 mm, 0.5-0.25 mm and <0.25 mm aggregate fractions with respect to the maximum treatment. These results suggest that biochar's incorporation into upland red soil will increase crop productivity and improve soil structure. (C) 2014 Elsevier B.V. All rights reserved.