Co-application of Molybdenum with Phosphorus Improves the Growth of Soybean Seedling Under Shade Stress

Soybean (Glycine max) is often planted in intercropping systems; thus, the shade stress is a serious concern in soybean cultivation. Both molybdenum (Mo) and phosphorus (P) can enhance photosynthesis under low-light conditions. In the present study, two soybean varieties (Nakasennari and Sachiyutaka) were cultivated under normal-light conditions or low-light conditions with the application of five different Mo and P treatments: NLCK (normal light; 0 mg Mo and P kg(-1)), LLCK (low light; 0 mg Mo and P kg(-1)), LLP100 (low light; 0 mg Mo and 100 mg P kg(-1)), LLMo0.2 (low light; 0.2 mg Mo and 0 mg P kg(-1)), and LLMo0.2P100 (low light; 0.2 mg Mo and 100 mg P kg(-1)). Under shade stress, the growth of the roots, leaf area, and root-to-shoot ratio of soybean were improved when Mo and/or P were applied. The photosynthetic pigment, carbon, and nitrogen contents of soybean were also affected positively by the application of Mo and P. Due to Mo and P applications enhanced photosynthetic capacity and the absorption of nutrients, the soybean biomass under LLMo0.2P100 was 33.3% higher than LLCK in Nakasennari. In Sachiyutaka, LLMo0.2P100 also had a 21.4% increase compared to LLCK. These results show that treatment with Mo and P, especially during their co-application, can alleviate the inhibitory effect of shade stress on soybean growth.