Optimized planting time and co‐growth duration reduce the yield difference between intercropped and sole soybean by enhancing soybean resilience toward size‐asymmetric competition

摘要

Selecting optimum planting time (PT) in maize–soybean relay intercropping system (MSRI) is important to obtain higher intercrop yields because planting time decides the co‐growth duration and competitive ability of intercrop species in MSRI. However, little is known on how planting time (co‐growth duration) changes the interspecific interaction resulting in a seed‐yield difference between intercropping and sole cropping system. Therefore, this field study was initiated to determine the effects of changing co‐growth duration on competitive interactions, growth, and yield of intercrop species under MSRI. The sole soybean and relay‐cropped soybean were planted on PT1 (15–20 May, 90?days of co‐growth duration in MSRI); PT2 (5–10 June, 70?days of co‐growth duration in MSRI); and PT3 (25–30 June, 50?days of co‐growth duration in MSRI) to generate different size‐asymmetric competition between component crops in MSRI. Results showed that sole soybean produced the mean highest (2.93?t/ha) seed yield under PT2, and the mean lowest (2.51?t/ha) seed yield under PT1. However, in MSRI, PT3 increased the soybean yield by 29.1% and 13.3% compared to PT1 and PT2, respectively. The PT3 also increased the maize yield by 7.4% and 2.9% than PT1 and PT2, respectively, and it reduced the yield differences of maize and soybean between relay intercropping and sole cropping systems. In MSRI, decreased co‐growth duration promoted the soybean plants to achieve the higher crop growth rate, and biomass accumulation, which ultimately improved the soybean resilience toward size‐asymmetric competition created by maize plants. Furthermore, as compared to PT1 and PT2, planting time PT3 significantly increased the competitive ratio (by 10.1% and 17.3%, respectively) of soybean plants. Overall, the PT3 achieved the average highest land equivalent ratio of 1.63, which is significantly higher than PT1 (by 12.3%) and PT2 (by 10.6%). In conclusion, this study implied that in MSRI, the determination of proper soybean planting time (co‐growth duration) is one of the most critical factors to reduce the competition between the intercrops and to obtain higher crop yields.