| Straw returning,nitrogen fertilizer application and water management have important effects on the growth and development,yield and quality formation of rice.There are many studies on the effects of nitrogen fertilizer and alternate wet and dry irrigation on rice quality under straw return,but most of them are based on wheat straw return.There are few reports on the effects of cultivation measures such as nitrogen application ratio and alternate wet and dry irrigation on rice yield,quality and its formation mechanism under rape straw return.Therefore,taking rice varieties Nanjing 9108 and Huaidao 5 as materials,this study studied the effects of different nitrogen application ratios and alternate wet and dry irrigation treatments during panicle differentiation on Rice Yield and quality under the condition of wheat and rape straw returning,in order to provide a theoretical basis and practical reference for high-yield and high-quality cultivation of rice.The main findings are as follows.1.At 270 kg hm-2 of nitrogen application,under the condition of straw returning,compared with the conventional nitrogen application ratio(base fertilizer:tiller fertilizer:panicle fertilizer=5:1:4),increasing the base fertilizer ratio(base fertilizer:tiller fertilizer:panicle fertilizer=7:1:2)increased the panicles per unit area,grains per panicle and seed setting rate of rice,and increased the yield.Under the same nitrogen application ratio,the seed setting rate of wheat straw returning was higher than that of rape straw returning,but the number of ears per unit area and the number of grains per ear were reduced,and there was no significant difference between the two yields.2.Under the condition of straw returning,increasing the proportion of base fertilizer improved the processing and cooking taste quality of rice.Compared with the conventional nitrogen application ratio,the chalkiness rate and chalkiness degree of rice were reduced,the appearance quality was better,the amylose and total starch content were lower,and the gel consistency,appearance,viscosity and balance degree were improved,which improved the cooking and eating quality of the two tested varieties of rice.Compared with the conventional nitrogen application ratio,increasing the base fertilizer ratio also increased the disintegration value,hot paste viscosity,peak viscosity and final viscosity of rice flour starch,decreased the digestion value and gelatinization temperature,and improved the quality of rice starch.Under the conventional nitrogen application ratio,the contents of protein,protein components,essential and nonessential amino acids of Nanjing 9108 and Huaidao 5 were higher than those of the treatment of increasing the base fertilizer ratio,and the nutritional quality was better.Under the same nitrogen application ratio,the brown rice rate,milled rice rate and head milled rice rate of rape straw returning treatment were higher than those of wheat straw returning treatment,with lower chalkiness rate and chalkiness,better processing appearance quality,and higher protein and amino acid content.Wheat straw returning reduced the amylose content and reduction value of rice,increased the gel consistency,peak viscosity,disintegration value and final viscosity,and the cooking and eating quality was better.In addition,the activities of APG pyrophosphorylase and starch branching enzyme in grains were higher under the treatment of increasing base fertilizer ratio and wheat straw returning than those under the treatment of conventional nitrogen application ratio and rape straw returning.Zeatin,zeatin nucleoside,auxin and abscisic acid in grains at the filling stage also showed the same rule.3.Under the condition of returning rape straw to the field,the number of primary and secondary spikelet differentiation and extant number of rice were increased by alternate wet and dry irrigation during panicle differentiation stage,and the yield was higher than that of routine irrigation treatment.According to the analysis of yield components,the number of panicles per pot was reduced,but the number of grains per panicle and seed setting rate were increased in the alternate wet and dry irrigation treatment.4.Under the condition of returning rape straw to the field,compared with the routine irrigation treatment,the alternate wet and dry irrigation at the panicle differentiation stage increased the head rice rate,reduced the chalkiness rate and chalkiness degree,and improved the appearance quality of rice processing.The alternate wet and dry irrigation treatment also reduced the reduction value,hot paste viscosity and final viscosity of rice starch,increased the disintegration value and peak viscosity,decreased the amylose content of rice,increased the branch to straight ratio,increased the gel consistency,and increased the taste value.The cooking and taste quality was better than that of routine irrigation treatment.However,the protein,essential and nonessential amino acids decreased,and the nutritional quality was poor.In addition,the activities of APG pyrophosphorylase,starch branching enzyme and starch debranching enzyme in grains and the contents of four endogenous hormones,zeatin,zeatin nucleoside,auxin and abscisic acid in grains were increased by alternate wet and dry irrigation of rice at the panicle differentiation stage. |
