Foliar Application of γ-Polyglutamic Acid Enhances Growth, Yield, and Rhizosphere Microbiota of Summer Maize Under Varied Water Regimes

Amidst escalating global water scarcity and the urgent need for sustainable agricultural practices, the exploration of efficient and eco-friendly agricultural aids has become paramount. This field experiment investigated the effects of foliar γ-polyglutamic acid (γ-PGA) application on summer maize under two irrigation levels (0 m3·ha−1 and 900 m3·ha−1 at the bell-mouth stage) and three γ-PGA spraying treatments. The results demonstrated that both irrigation and γ-PGA spraying significantly influenced maize yield and various growth parameters, with notable interaction effects. Compared to the control, single and double applications of γ-PGA increased summer maize yield by 33.3% and 37.0%, respectively, while enhancing dry matter accumulation and nutrient uptake. Foliar γ-PGA application also altered the rhizosphere microbial community composition, increasing the abundances of Proteobacteria and Actinobacteria, as well as beneficial bacteria such as Arthrobacter, Sphingomonas, Streptomyces, and Altererythrobacter. Additionally, it significantly increased the population of Dung Saprotroph fungi, which are beneficial for crop growth. These findings suggest that foliar γ-PGA application can promote summer maize growth and holds significant potential for agricultural applications.