γ‐PGA Enhances Wheat Productivity Through Coordinated Improvements in Root‐Zone Water Availability, Salinity Alleviation and Nitrogen Retention

ABSTRACT Despite growing interest in γ‐PGA as a soil amendment for salt‐affected soils, its integrated effects on root‐zone water and salt conditions, nitrogen retention and crop productivity remain insufficiently understood. A soil box experiment was conducted to evaluate the effects of four γ‐PGA application rates, designated as CK (0), T1 (0.05%), T2 (0.10%) and T3 (0.15%), on grain yield and resource use efficiency. γ‐PGA significantly increased soil water availability while reducing salt accumulation within the root zone throughout the wheat‐growing season. These effects became particularly evident during the reproductive stages, when the soil water content increased by up to 24% and the soil salt stock decreased by up to 37% relative to CK. γ‐PGA enhanced mineral N retention and increased soil enzyme activities, indicating improved nutrient conservation under saline conditions. The T2 treatment achieved the greatest agronomic benefits, increasing grain yield by 55% compared with CK. Mantel tests and random forest modelling consistently identified soil water availability, root‐zone salinity alleviation and mineral N retention as the major factors associated with yield improvement. Collectively, γ‐PGA enhanced wheat productivity through improved root‐zone water availability, reduced salt accumulation and enhanced nitrogen retention, underscoring its potential for sustainable agriculture in salt‐affected soils.