Screening and comprehensive evaluation of shade tolerance of forage soybean varieties

Maize intercropped with soybean can significantly increase the protein yield of feed, and the selection of shade tolerant soybean varieties is particularly important. In this study, five treatments including soybean intercropped with maize, monocropping, shading at seedling stage, shading at branching stage, shading at flowering and podding stage were conducted. The biomass, morphology, and nitrogen content were investigated at filling stage among the treatments. The shade tolerance coefficient (STC) of each index was used to measure the shade tolerance of each tested variety. A few key indexes at key growth stages under shading were screened out by stepwise regression analysis to predict the shade tolerance of soybean varieties, which could be used to simplify the screening protocol. The results showed that there were significant differences of shade tolerance between soybean varieties under intercropping. Shade tolerance of shading at flowering and podding stages was positive correlation to shade tolerance