Relay intercropped soybean promotes nodules development and nitrogen fixation by root exudates deposition

Area of Science:

• Agronomy
• Plant Science
• Soil Science

Background:

• Legumes attract rhizobia via root exudates (flavonoids).
• Soybean nodule development is influenced by root exudates and intercropping.

Purpose of the Study:

• Investigate the relationship between crop root exudates and soybean nodule development under intercropping.
• Quantify effects of planting mode and soybean genotypes on root exudates, rhizobia, nodule development, and nitrogen fixation.

Main Methods:

• Field and pot experiments over two years.
• Compared relay intercropping with monocropping.
• Evaluated soybean genotypes NTS1007 (NTS), Nandou-12 (ND), and Guixia-3 (GX).

Main Results:

• Maize-soybean intercropping increased soybean root exudates (daidzein, genistein) and altered rhizobia community structure.
• Nodule number decreased in intercropped soybeans, but nodule size, dry weight, and root dry weight increased in genotype ND.
• Intercropping enhanced nodule nitrogenase activity and nifH gene expression, particularly in ND and GX.
• Maize root exudates increased nodule diameter and nitrogen fixation, up-regulating GmEXPB2.

Conclusions:

• Maize-soybean relay intercropping enhances soybean nodulation signaling and nitrogen fixation.
• Maize root exudates improve nodule size and function, but effects vary with soybean genotype and nodulation capacity.