Effects of new-type fertilizers and irrigation regimes on carbon footprint of double-season rice system.

To elucidate the responses of yield and carbon footprint of double-season rice production systems to new-type fertilizers and irrigation regimes, we investigated the effects of three new-type fertilizers, viz, controlled-release urea (CRU), nitrapyrin-treated urea (CP), and effective microorganisms (EM) (conventional fertilizer as control), and two irrigation regimes, conventional flooding (W1) and shallow water irrigation (W2), on yield, greenhouse gas emissions and carbon footprint of early- and late-season rice by the FAO-CROPWAT 8.0 modeling in combination with field experiments (2020-2021). The results showed that compared to the conventional fertilizer (CK), three new-type fertilizers increased rice yield. The average yield increases for early and late rice under the three fertilizer treatments were 14.2% and 17.1% in 2020, and were 36.7% and 23.1% in 2021. There was no difference in rice yield between W1 and W2. Application of new-type fertilizers reduced greenhouse gas emission in the double-season rice system, and the mitigation effect varied between early and late rice seasons. Compared to CK, CH4 emissions, global warming potential (GWP), and greenhouse gas intensity (GHGI) under CRU treatment were decreased by 22.2%, 22.9%, and 39.3% in early rice season, that under CP treatment were decreased by 20.7%, 19.3%, and 33.5% in late rice seasons. N2O emission and GHGI under EM treatment were decreased by 14.7% and 6.2% in early rice seasons. Shallow water irrigation significantly reduced greenhouse gas emission. Compared to the W1 treatment, CH4 emission, N2O emission, GWP, and GHGI under the W2 treatment were decreased by 21.9%, 42.0%, 24.7%, and 25.9% in early rice season, by 23.4%, 33.6%, 24.0%, and 23.7% in late rice season, respectively. There was a significant interaction effect between new-type fertilizers and irrigation regimes on carbon footprint. Compared to the CK treatment under the W1 irrigation, the interaction of new-type fertilizers and W2 irrigation significantly decreased the average value of carbon footprint in early and late rice seasons by 35.9% and 22.0%, respectively. In conclusion, the application of new-type fertilizers significantly increased the yield of double-season rice, while optimizing irrigation regime reduced greenhouse gas emissions. The implementation of appropriate new-type fertilizers under the shallow water irrigation could increase yield and decrease greenhouse gas emissions and the carbon footprint, which would promote clean production and contribute to the sustainable development of double-season rice systems.