Effect of the Planting Density on Stem and Leaf Morphological Characteristics and Yield of Relay-cropping Soybean

[Objective] The key technical point of the relay-planting model of wheat-corn-soybean growth was sounded.[Method] The effects of planting density on stem and leaf morphological characteristics and yield of relay-cropping soybean were studied.[Results] The results showed that the diameter and dry matter accumulation of stem were decreased with the increasing of planting density.The changes of plant height between two varieties were different,the plant height of Gongxuan No.1 was increased with the increasing of planting density and the plant height of Ledou No.1 was decreased with the increasing of planting density.The SLW was increased firstly;then decreased and finally increased during the whole growth period,and the SLW was decreased with the increasing of planting density.The variation of LAI appeared a parabola curve,and The LAI was increased with the increasing of planting density.Under relay-cropping system,the yield of Gongxuan No.1 was higher than that of Ledou No.1,the best planting density of Gongxuan No.1 was 0.165 million plants per hm2,in high planting density, its yield was decreased seriously.The suitable planting density of Ledou No.1 was 0.165-0.21 million plants per hm2.[Conclusion] The scientific basis for the relay-planting model of wheat-corn-soybean growth was provide.