Study on the Influences of Plant Densities on Yield,Yield Traits and Canopy Photosynthesis Characteristics of Summer Maize

In this study,by using three widely-cultivated summer corn varieties( Zhengdan 958,Xianyu 335 and Zhongdan 909),the leaf area index( LAI),leaf area duration( LAD),yield and yield traits responses to planting density were studied under five density levels. The results indicated that: in the range of 69 × 104plants / ha,the spike lengths,number of grains per spike,100-kernel weight and per spike kernel weight decreased while the LAI and LAD increased and positively correlated with the increase in plant density. The increased plant density also promoted the population photosynthetic intensity. As to yield,Xianyu 335 had the highest average yield,next was Zhongdan 909 and the lowest was Zhengdan 958. The Zhengdan 958 and Xianyu 335 varieties presented linear while the Zhongdan 909 a parabolic relationship with plant density. The yield of Zhengdan 958 was highly correlated with LAI and LAD,and the amount of yield increase was greater than the other two varieties for same density increment, and showed less spike traits reduction,so it has good density tolerance. The slopes of the linear correlation of Xianyu 335 and Zhongdan 909 with plant density were smaller than that of Zhengdan 958. The amount of yield increase was less for same density increment for Xianyu 335,thus it suits for lower plant density. While for Zhengdan 909,it had an optimum density of around 8. 56 × 104plants / ha. So adopting a reasonable intensified planting density in accordance with variety traits can improve crop yield and gives full play to the characteristics of corn varieties.