In order toclarify the water-saving and fertilizer-conserving effects of a new environmental sustained-release water-retaining agent

γ-polyglutamic acid (γ-PGA)

four kinds of γ-PGA gradients (0

0.1%

0.2% and 0.4%) were applied at the same nitrogen application rate (2 g/kg)

and no γ-PGA was taken as control.The effects of γ-PGA application rate on soil nitrogen transport characteristics were studied by one-dimensional soil column infiltration experiment in laboratory. The results showed that: (1) Under the condition of constant head infiltration

the cumulative infiltration amount

infiltration rate and the distance of wetting front migration all decreased with the increasing of γ-PGA application amount.Compared with the control group

the cumulative infiltration amount

infiltration rate

and distance of wet front migration in the experimental group with 0.4% γ - PGA application decreased by 27.64%

73.45% and 31.58%

respectively. (2) According to Philip formula simulation results

the permeability S decreased with the increasing of γ-PGA application

showing a negative correlation; in the results of Kostiakov formula simulation

empirical coefficient K decreased with the increasing of γ-PGA application

showing a negative correlation

and empirical index a increased with the increasing of γ-PGA application

showing a positive correlation.(3) With the increasing of γ-PGA application

the water content of surface soil (0-15 cm) increased gradually

while that of the deep soil (below 15cm) was the opposite.At the same time

the greater the γ-PGA application amount

the greater the content of nitrate nitrogen and ammonium nitrogen in each soil layer in the same period. On the fourth day after stopping the water supply

the average nitrate nitrogen content of the experimental group added with 0.1%

0.2% and 0.4% γ-PGA

respectively

increased by 29.55%

42.49% and 59.50% compared with thecontrol group

and the average ammonium nitrogen content increased by 43.97%

123.40% and 156.74%.In conclusion

applying γ-PGA to soil could effectively slow down water infiltration

gather more water in shallow soil layer

reduce fertilizer leaching rate

increase water and fertilizer utilization

reduce frequency and cost of irrigation

and achieve the purpose of improving soil structure and increasing crop yield.