Dynamic model and characteristics analysis of dry matter production after light recovery of different soybean varieties in relay strip intercropping systems

Maize-soybean relay strip intercropping is a widespread practice in soybean production areas in southwestern and southern China and has been the main mode of increasing total output of soybean in China. To provide theoretical basis for the selection and breeding of high yield soybean varieties for intercropping, this study used fourteen soybean varieties with different yield levels to analyze the characteristics of dry matter production after light recovery (after maize harvest) of different yield types of soybean varieties relay strip intercropped with maize. Results indicated that average grain yield of high yield soybean varieties was 1 408.17 kg·hm^-2, which was 37.45% and 57.25% higher than those of medium and low yield varieties, respectively. Dry matter accumulation of high yield soybean varieties was on an average of 32.99 g·plant^-1, which was 26.82% and 91.51% higher than those of medium and low yield varieties, respectively. Logistic equation was used to simulate the relationship between dry matter weight and days after light recovery for three types of soybean varieties (R²≥0.960). Paired t-test for independent samples showed no significant difference between the simulated and measured values. After light recovery, the rate of dry matter accumulation of three types of soybean varieties increased before declining. The order of maximum rate of dry matter accumulation and the mean rate of dry matter accumulation was high yield type > medium yield type > low yield type. The average time to maximum rate of dry matter accumulation after light recovery of the high yield soybean varieties was 41-42 days, while that of both medium and low types was 33-37 days. The duration, accumulation rate and accumulation amount of dry matter of gradual increase stage; the accumulation rate and amount of dry matter accumulation of both fast increase and slow increase stages of high yield soybean were significantly higher than those of other two yield types of soybean. The yield had a significantly positive correlation with the maximum dry matter accumulation rate, time reaching the maximum dry matter accumulation rate, mean dry matter accumulation rate, duration of gradual increase stage, dry matter weight of gradual increase stage, dry matter accumulation rate and weight of both fast and slow increase stages. Two years data indicated that leaf area index, light interception rate, population growth rate and leaf area duration of high yield soybean were 2.52 g·m^-2·d^-1, 0.81 g·m^-2·d^-1, 6.02 g·m^-2·d^-1 and 317.84 m²·d·m^-2, respectively, which were significantly higher than those of both medium and low yield types. Our results suggested that greater dry matter accumulation mainly occurred at gradual increase stage after light recovery for high yield soybean varieties, which was mainly attributed to the longer duration of the stage.