Effect of Shading on Nodule Growth at Seedling Stage in Relay Strip Intercropping System.

Relay strip intercropping (RSI) increases soybean nodule number and nitrogen fixation activity at the reproductive stage more than monocropping (M), but the effect of changes in the environment, especially light, on nodules during the coexistence duration and vegetative stage, is unclear. To determine the impact of shading on nodule development at the seedling stage, nodule traits, distribution, and physiological function were compared between M and RSI in a potting experiment in a field environment. Compared with M, nodule number and weight decreased significantly (an average of 81.77% and 93.16%, respectively); thus, the exponential relationship between them changed because of the smaller nodule in RSI. Nodules were clustered on the tap roots, but there was no effect on the distribution of nodule weight on the tap or lateral root. The nodule density of the tap root notably decreased by an average of 56.00%, whereas that of the lateral root showed no difference. Dry weight-specific nodulation (DW-specific), and the ratio of nodule weight to root or whole plant weight decreased (61.33%, 85.46%, and 88.50%, respectively). Nodule leghemoglobin and sucrose content decreased in RSI by 94.29% and 95.17% at the plant level, and nodule nitrogenase activity was suppressed, especially at the plant level. The nodule growth and nitrogen fixation ability of ND showed the strongest adaptability to shading among the varieties. [ABSTRACT FROM AUTHOR]