Effects of Returning Double-Season Rice Straw to the Field and Reducing N-fertilizer on Yield and Quality of Rice

Abstract

Objective To study the effects of returning straw to the field and reducing nitrogen fertilizer application on rice yield and quality in double-cropping rice cropping areas，to provide a certain theoretical basis and technical support for high-yield，high-efficiency fertilization and comprehensive utilization of straw resources，and to guide local farmers to use theresults in practical production. Method Two years of experiments were conducted in Jiangxi from 2018 to 2019，and 6 treatments were set，namely JN100，JN50，JN30，JN10，JN0 and CK.The tested early rice variety was Tanliangyou 39，and the nitrogen fertilizer application rates per mu （pure N） were 0，6，8.4，10.8，and 12 kg，respectively.The nitrogen application rate of 10.8 kg without straw returning to the field was used as the control； the late rice variety was Yongyou 538.The amounts of nitrogen fertilizer applied per mu were 0，9，14.4，16.2，18 kg，respectively，and 16.2 kg of N fertilizer applied with straws not returned to the field was used as a control.The ratio of nitrogen fertilizer application was basic fertilizer∶tiller fertilizer∶ear fertilizer 5∶2∶3.Phosphorus and potassium fertilizers were 6 kg（P2O5）and 6 kg（K2O）per mu for early rice，and 9 kg（P2O5）and 9 kg（K2O）for late rice.），all phosphate fertilizers were used as basal fertilizer，potash basal fertilizer and panicle fertilizer were respectively applied in the ratio of 6∶4，basal fertilizer was applied deeply，straw was returned to the field，and the preparing method was tillage.Other agronomic management measures were consistent with local field production. Result With the increase of nitrogen application rate，the number of ears of the early rice and the late rice increased，the 1 000-grain weight of the early rice decreased slightly，but the change in the 1 000-grain weight of late rice was not obvious，with JN30 being the highest； compared with the control CK，returning straw to the field and decreasing Nitrogen by 10% had no significant effect on the composition of rice yield.Under the condition of returning straw to the field，reducing the application of nitrogen fertilizer by 10% had little effect on the yield of the early rice；the late rice was more sensitive to the replacement of part of nitrogen fertilizer by returning straw to the field than the early rice.With the increase of nitrogen application rate，the milled rice rate and head rice rate of the early rice increased first and then decreased，while that of the late rice increased.The chalky grain rate，chalky size，chalkiness，amylose content，gel consistency，hot pulp viscosity，disintegration value，final viscosity and other indicators of the early rice and the late rice showed an overall downward trend with the increase of nitrogen application rate.Under the treatment of returning straw to the field，the changes in rice quality of the early rice and the late rice tended to be the same，both showed that the whole rice rate，the chalky rice rate and the chalkiness reduced，while the amylose content，gel consistency，peak viscosity，and hot pulp viscosity，disintegration value，and final viscosity increased slightly. Conclusion Returning straw to the field and reducing the application of nitrogen fertilizer can comprehensively improve the processing quality，appearance quality and cooking quality of rice.Considering the yield and quality indicators，returning straw to the field can effectively replace 10%-30% of pure nitrogen.