Effects of nitrogen fertilizer application in rape season and nitrogen fertilizer management in rice season on photosynthetic productvity and yield of hybrid japonica rice under rape-rice rotation mode

Objective  To explore the effects of nitrogen fertilizer application in rape season and nitrogen fertilizer management in rice season on hybrid japonica rice photosynthetic productivity and yield, and provide a theoretical and practical basis for suitable nitrogen fertilizer operation mode of rice under paddy-upland rotation.

Method  The hybrid japonica rice ‘F you 498’ was used as experimental material to investigate the effects of two nitrogen fertilizer application amounts (conventional nitrogen fertilizer application of 180 kg·hm⁻², reduced nitrogen fertilizer application of 150 kg·hm⁻²) in rape season and three nitrogen fertilizer management methods based on 150 kg·hm⁻² nitrogen fertilizer in rice season on photosynthetic characteristics, material accumulation and transport and yield of hybrid rice. The concrete nitrogen fertilizer management methods were M1 (the mass ratio of base fertilizer, tiller fertilizer and panicle fertilizer was 2∶2∶6), M2 (the mass ratio of base fertilizer, tiller fertilizer and panicle fertilizer was 3∶3∶4) and M3 (the mass ratio of base fertilizer, tiller fertilizer and panicle fertilizer was 4∶4∶2).

Result  Compared to conventional nitrogen fertilizer application, reduced nitrogen fertilizer application affected photosynthetic characteristics of rice at full heading stage, but the effect was not significant. M1, M2 and M3 treatments increased photosynthetic productivity of rice at full heading stage and 15 days after full heading. The photosynthetic rate increased most in reduced nitrogen fertilizer application and M3 treatment. Reduced nitrogen fertilizer application increased rice stem-sheath dry mattar mass at full heading stage and maturity stage, conversion rate and yield. M1, M2 and M3 increased rice stem-sheath dry mattar mass at full heading stage and yield. The highest increase of dry matter accumulation was in reduced nitrogen fertilizer application and M3 treatment.

Conclusion  Reduced nitrogen fertilizer application in rape season and M3 management method in rice season can improve rice yield by enhancing photosynthetic performance at late growth stage, increasing leaf area index, and promoting dry matter accumulation and transportation. It is the best treatment in this study.