Close mixed-planting with paddy rice reduced the flooding stress for upland soybean

ABSTRACT Close mixed-planting is a new concept of mixed cropping that allows greater complementary effects under various stress conditions; in this system, oxygen and/or water transfer occurs through the tightly entangled root system of the two species. We aimed to assess whether rice can alleviate flood stress in soybeans via close mixed-planting. A three-year field experiment and one water culture experiment were conducted to compare the crop performance between single and close mixed-planting under short-term flood (or anoxia) stresses. The survival rates, photosynthetic rates, and biomass production were higher in the mixed soybean than in the single soybean plants. Moreover, as the modified land equivalent ratio under flood stress was always >1, rice exhibited greater complementary effect on soybean against short-term flood stress in an upland field converted from paddy. Thus, rice planted as the partner crop of soybean can alleviate short-term anaerobic stress to enhance soybean growth. Graphical Abstract