Rice-fish coculture contributes to improve nutrient availability, carbon sequestration and maintain rice yield under minimal tillage/no-tillage condition in double-season rice farming of South China

• Minimal tillage/no-tillage improved rice yield than that of conventional tillage treatment. • Rice-fish coculture improved nutrient availability and C sequestration, and maintain rice yield under minimal tillage/no-tillage. • Combination of rice-fish coculture and minimal tillage/no-tillage can solve the problems of temporal constraints in coculture system, and soil compaction and weed harm in minimal tillage/no-tillage system. Rice-fish coculture (RFC) is widely recognized for increasing soil fertility and crop yield. However, the introduction of fish in double-season rice planting areas of South China to balance relationship between rice yield, soil function and ecosystem services, and to develop an optimal model between RFC and minimal tillage/no-tillage (NT) practices in a complementary form need to be further investigated. Hence, we conducted a two-year field experiment through a combination between RFC and several tillage types including CT (conventional tillage), NT (no-tillage), Minimal tillage (e.g. ECT+LNT. ECT refers CT used in early rice phase; LNT refers NT used in late rice phase following the ECT of early rice phase) to evaluate soil nutrients, rice yields, carbon (C) components and C-related enzymes activities. Our study found that RFC significantly increased contents of available phosphorus (P) by 9.52-11.42%, nitrate nitrogen (N) by 11.90-12.82%, and rice yield by 3.25-10.13%, while NT significantly increased contents of available P by 26.96-35.64%, ammonium N by 9.40-12.33%, and organic C by 10.26-15.08%. We also found that the interaction between RFC and NT significantly took effect on rice yield and C process. Also, available N and P contributed to improve rice yield, while available P, partial organic C, pH, dissolved organic C and bulk density drove C process. Moreover, LNT treatment significantly improved rice yield than that of CT treatment. These findings suggest that rice-fish coculture combining with minimal tillage/no-tillage is a promising eco-farming model to improve nutrient availability and carbon sequestration, and maintain rice yield.