Poly‐γ‐glutamic acid application promoted nutrient uptake and productivity of soybean by improving soil properties

Abstract Poly‐γ‐glutamic acid (γ‐PGA) has great agricultural potential due to its water‐retention ability, but its effects at different application amounts on soybean [ Glycine max (L.) Merr.] productivity and soil properties remain unclear. In this study, γ‐PGA was applied at five amounts (0, 10, 20, 40, and 80 kg ha −1 , denoted as CK, T10, T20, T40, and T80, respectively) via drip irrigation to soybean plants to evaluate its impact on soil physical and hydraulic properties, nutrient availability, crop growth, and yield. The results showed that γ‐PGA application increased soil porosity, reduced bulk density, and improved soil temperature in the 0–25 cm layer. Soil hydraulic parameters, including field capacity and plant‐available water, also improved with γ‐PGA application. However, γ‐PGA application reduced soil nitrogen, phosphorus, and potassium levels at harvest. Nutrient uptake efficiency and soybean growth initially increased and then declined with higher γ‐PGA application amounts, with the highest yield observed under the T40 treatment. Overall, applying γ‐PGA at 40 kg ha −1 effectively enhanced soil properties and nutrient uptake, leading to improved soybean productivity.