Effects of sowing water and the ratio of base N to top N in the straw-returning field on fluorescent characteristics of the flag leaf and yield in winter wheat
Crop straws are always burnt or discarded in China, which causes more and more environmental issues. Meanwhile, use of a large amount of nitrogen fertilizer has become a serious problem in agricultural field. This study was to investigate the effects of sowing water and the ratio of base N to top N on the fluorescent characteristic of the flag leaf and yield of wheat in the straw-returning field. The results showed that under the condition of maize straw-returning to field, sowing water, and increasing the ratio of base N to top significantly lowered Fo during the flowering and early grain filling stage of wheat(P0.01), increased Fm during the middle grain filling stage, and delayed the reduction of Fm during the late grain filling stage. Application of sowing water significantly delayed the reduction of Fv/Fo and Fv/Fm. Straw-returning to field could delay the reduction rate of Y(Ⅱ) during early grain filling stage, while sowing water could delay the decrease of Y(Ⅱ) during middle grain filling stage. Under the conditions of straw-returning to field and sowing water, increase the ratio of base N and top N increased Y(Ⅱ) during the grain filling stage. Sowing water decreased Y(NPQ)during the flowering and early grain filling stage,increased Y(NPQ) during the middle late filling stage, and significantly increased Y(NO)(P0.05) during the middle grain filling stage in the straw-returning field. Postponing N supply was in favor of reducing Y(NO) during all grain filling stage; therefore, increased light use efficiency and reduced light damage. Straw-returning to field and application of sowing water and nitrogen could increase the number of functional wheat heads and yield, particularly in the sowing water applied field. Straw-returning to the field was in favor of increasing the number of kernels per head on the main stem and the second tiller of wheat.