Effects of poly-γ-glutamic acid on soil pore structure, maize grain filling, yield and water use efficiency under mulched drip irrigation

Poly-gamma-glutamic acid (gamma-PGA) is a biodegradable and non-toxic and harmless water retention agent, contributing significantly to in the sustainable development of agriculture. This study focused that investigated effect of gamma-PGA on soil pore structure, maize growth, grain filling characteristics, maize yield and water use efficiency under mulched drip irrigation, and the optimal application strategy of gamma-PGA. The effect of gamma-PGA application rates (0, 40, and 80 kg ha(-1)) on soil structure was investigated using soil column experiments. Field experiments analyzed the effects of these gamma-PGA rates (0, 20, 60 and 80 kg ha(-1)) on maize growth. The results showed that gamma-PGA changed the position and number of soil pores; with the increase of gamma-PGA application rate, the number of soil pores increased. The number of soil pores with an equivalent diameter smaller than 300 mu m increased by 9-14 times, and those with an equivalent diameter larger than 1000 mu m increased twelvefold. The soil water storage increased by 2 similar to 27 %. gamma-PGA prolonged active grain filling period by 1-3 days, increased the maximum grain filling rate (Vmax) by 3 similar to 15 %, the average grain filling rate (Va) by 7 similar to 27 %, and grain weight by 12 similar to 37 %. gamma-PGA treatments significantly increased maize plant height, stem diameter, leaf area index (LAI), ear width, grain number per row and 100-grain weight. Compared with P0, yield and water use efficiency for gamma-PGA treatment were increased by 4.9 similar to 21.8 % and 1.0 similar to 18.1 %. Based on the Gaussian optimization model and considering local actual conditions, we recommend that the optimal rate of gamma-PGA is 70 kg ha(-1) in the region. This study provided a theoretical basis for water-saving irrigation of maize under mulched drip irrigation.