Dynamic changes and correlations of P and N concentrations in crop leaves under relay intercropping system of maize and soybean

A field experiment was conducted to investigate the dynamic changes of leaf N concentration and P concentration of maize and soybean at different growth stages, and analyze their relations in the typical maize/soybean relay strip intercropping system and the soybean monoculture. The soybean (Glycine max L. Merr.) cultivars, Gongxuan1 and Guixia3, and the maize (Zea mays L.) cultivars, Denghai 605, Chuandan 418 and Yayu13, were selected in this study. The N concentrations of leaves of two soybean cultivars at the V3 stage are lowest, while the concentrations are highest compared with those of other stages. The leaf N and P concentrations of the soybean intercropping with Yayu13 are 5.81% and 38.56% higher than those of the soybean monoculture. At the same time, the N∶P ratio of the relay intercropped soybean leaves is lower than that of the monoculture. After the R1 stage, these characteristics are not appeared. For maize, the change trend of leaf P concentration is a low-high-low mode through the growth stage, and the leaf N concentration is lowest at the R6 stage. In addition, the N∶P ratios of maize and soybean leaves in Renshou are higher than those in Yaan. The correlation between the N and P concentration of leaves of maize and soybean is significant (r0.46, P0.05), especially the P concentration and the N∶P ratio (P0.01).