Rice-fish coculture contributes to improve nutrients availability, carbon sequestration and maintain rice yield under minimal tillage condition in double-season rice farming of South China

Rice-fish coculture (RFC) is widely recognized for increasing soil fertility and crop yield. However, the introduction of fish in double-season rice areas of South China to balance relationship between soil function and ecosystem services, and to develop an optimal model between RFC and no-tillage (NT) practices in a complementary form need to be further investigated. Hence, we conducted a two-years field experiments through a combination between RFC and tillage types (CT, conventional tillage; NT, no-tillage, minimal tillage (e.g., ECT, CT in early rice phase; LNT, NT of late rice phase developed on ECT of early rice phase)) to evaluate soil quality, rice yields, carbon (C) components and C-related enzymes activities. Our studies found that RFC significantly increased available phosphorus (P) by 9.52-11.42%, nitrate nitrogen by 11.90-12.82%, and rice yield by 3.25-10.13%, while NT significantly increased available P by 26.96-35.64%, ammonium nitrogen by 9.40-12.33%, and organic C by 10.26-15.08%. We also found that the interaction between RFC and NT significantly influenced rice yield and C process, and C process had a positive impact on rice yield. Also, available N and P contribute to improve rice yield, while available P, partial organic C, pH, dissolve organic C and bulk density could drive C process. Moreover, LNT treatment significantly improved rice yield than that of NT and CT treatment, which may be related to suitable ploughing transfers nutrients from top to subsoil. These findings suggest that RFC contribute to improve nutrient availability and carbon sequestration, and maintain rice yield under minimal tillage.