Poly‐γ‐glutamic acid improved biological nitrogen fixation, water‐nitrogen productivity, and nitrate residue in cotton/soybean intercropping

Abstract

BackgroundPoly‐γ‐glutamic acid (γ‐PGA) can promote crop growth and improve soil properties efficiently. However, the optimal application rate of γ‐PGA in legume/non‐legume intercropping systems is still unclear. A potted experiment was conducted to investigate the effects of five γ‐PGA rates (0%, 0.1%, 0.2%, 0.3%, and 0.4%, represented by CK, P1, P2, P3, and P4, respectively) on biological nitrogen (N) fixation (BNF), water‐N productivity, and nitrate distribution in a cotton/soybean intercropping system.ResultsThe results showed that the growth indicators (plant height, stem diameter, leaf area index, root dry weight, root length) of cotton and soybean increased first and then decreased with increasing γ‐PGA rates, and all growth indicators of cotton and soybean showed peaks in P3 and P2 treatments. The stable 15N isotope method indicated that γ‐PGA promoted the BNF capacity of soybean and soil. In particular, the percentage of N derived from the atmosphere (Ndfa) in soybean reached 61.94% in the P2 treatment. Poly‐γ‐glutamic acid improved the water‐N productivity, and the total N partial factor productivity (NPFP) and water productivity (WP) in P3 treatment increased by 23.80% and 43.86% compared with the CK treatment. The γ‐PGA mitigation of potential nitrate residue also decreased first and then increased with increasing γ‐PGA rates.ConclusionMultivariate regression analysis showed that 0.22% of the optimal γ‐PGA application rate could obtain a higher yield and water‐N productivity in cotton/soybean intercropping system simultaneously. © 2023 Society of Chemical Industry.

Poly‐γ‐glutamic acid enhanced the yield and photosynthesis of soybeans by adjusting soil aggregates and water distribution

“…The results of our previous investigation demonstrated that the γ-PGA application of 0.22% in potted conditions can improve WUE. 51 In addition, the optimal γ-PGA application level for improving WUE and cotton yield obtained in cotton fields was 80 kg ha −1 . 16 Nevertheless, the impact of γ-PGA on soil improvement is intricately linked to variations in soil texture, climatic conditions, and application method.…”

“…19 Poly-γ-glutamic acid also promotes crop root growth, leading to increased root deposition in the soil. 51 Roots and their associated fungi, such as ectomycorrhizal species, intricately intertwine to create a network that effectively binds fine soil particles together, resulting in the formation of robust aggregates. 52 In this study, the soil water content in the 0-60 cm soil layer was increased significantly by the application of γ-PGA.…”