Effects of nitrogen fertilizer management on rice yield and quality under rice shrimp rotation system
[Objective]The aim of this study was to explore the effects of nitrogen fertilizer management on rice yield and quality under rice shrimp rotation mode.[Method]Using Yexiangyou Mingyuesimiao and Nongxiang 42 as experimental materials,different nitrogen application mounts and ratios at different stages were designed.[Result]With a 15%or 30%reduction based on the conventional nitrogen application amount(195 kg/hm2),the yield of Yexiangyou Mingyuesimiao did not significantly decrease,while the yield of Nongxiang 42 significantly increased.When the ratio of basal fertilizer:tillering fertilizer:panicle fertilizer was 4∶4∶2,the number of grains per panicle,seed setting rate and 1 000-grain weight of Yexiangyoumingyuesimiao were the highest,and the yield was the highest.When the ratio of basal fertilizer:tillering fertilizer:panicle fertilizer was 5∶3∶2,the effective panicle number per unit area,grain number per panicle,seed setting rate and 1 000-grain weight of Nongxiang 42 were the largest,and the yield was the highest.With the decrease of nitrogen application rate,the milled rice rate of Yexiangyou Mingyuesimiao and amylose content was significantly increased,while the protein content was significantly reduced.The peak viscosity and breakdown viscosity showed a trend of first increasing and then decreasing,reaching their maximums with the nitrogen application amount of 165.8 kg/hm2.When the ratio of basal fertilizer:tillering fertilizer:panicle fertilizer was 4∶4∶2 for Yexiangyou Mingyuesimiao and 5∶3∶2 for Nongxiang 42,the milled rice rate,head milled rice rate,gel consistency,peak viscosity and breakdown viscosity were the highest,while chalky grain rate,chalkiness degree,and amylose content were the lowest.[Conclusion]Under the rice-shrimp rotation system,reducing nitrogen application rate by 15%-30%and applying nitrogen at a ratio of 4∶4∶2 or 5∶3∶2 is beneficial to rice nitrogen efficiency,high quality and high yield.