Impacts of partial substitution of chemical nitrogen fertilizer with different organic fertilizers on double cropping rice growth and yield

ObjectiveThe impacts of substitution of chemical nitrogen(N)fertilizer with different organic fertilizers on rice growth,N accumulation and yield of double cropping rice were studied to provide theoretical basis and technical support for improving soil fertility of double cropping rice fields.MethodIn 2016-2017,early rice variety Zhongzao 39 and late rice variety H You 518 were used as materials. Under the condition where nitrogen application rate was 150 kg/ha and the ratio of basic fertilizer:tiller fertilizer:granule fertilize was 5:3:2,four organic fertilizer+chemical N fertilizer treatments were set:T1:Astragalus sinicus(early rice)/rice straw(late rice)+chemical fertilizer;T2:biological activated carbon+chemical fertilizer;T3:barnyard manure+chemical fertilizer;T4:rapeseed cake+chemical fertilizer,and 100% chemical N fertilizer treatment was as control(CK). Effects of various treatments on growth,N accumulation and yield components of double cropping rice were studied.ResultCompared with CK,the average yield of early rice in organic fertilizer treatments was increased greatly. In T1-T4,the yields of early rice in 2016 and 2017 increased by 4.86%-7.74% and 0.12%-3.50% compared with CK,and yields of late rice in 2016 and 2017 increased by 1.27%-8.10% and 2.01%- 6.27%. The improvement of yield of early and late rice treated by organic fertilizer mainly induced by the increasing of seed setting rate. Compared with CK,leaf area in the middle and late stage of rice under T1,T3 and T4 decreased,leaf area index and leaf relative chlorophyll content(SPAD value)were high. At mature stage,the dry matter accumulation in organic fertilizer treatments as a whole was higher than that of CK. N accumulation was low in early stage but was high in late stage under T1,T3 and T4,with T3 treatment showed the most significant increasing in plant N accumulation.Con-clusionTwo-year location experiment shows that under the same nitrogen application level,partial substitution of chemi-cal N fertilizer application with organic fertilizer application can promote growth and development of rice and nitrogen ac-cumulation in late stage to a certain extent,and then increase the yield. The soil-returning effects of A. sinicus in early rice and effects of barnyard manure and rapeseed cake in late rice are obvious,which are suitable for application in double cropping rice area with three-crop a year system.