Effects Of ?-PGA On Soil Water And Nitrogen Move And Physiological Growth Index Of Lettuce

Agriculture is the foundation of China's national economy.Drought and low nitrogen use eff-iciency have become two important factors restricting the sustainable development of agricultural production in China,so it is an important issue improving water and nitrogen utilization efficiency in agricultural development in China.Poly-?-glutamic acid(y-PGA)as a green "environmental friendly" macromolecule material.It shows great potential in drought resistance,seedling conservation and improving water and nitrogen use efficiency of crops and the rational use of y-PGA also provides new ideas for solving the sustainable development of agriculture in China.In this paper,they were studied which different y-PGA application rates?different concentrations of nitrogen fertilizer solution?different y-PGA and nitrogen fertilizer applied layers influence soil infiltration characteristics and water and nitrogen transport,at the same time,the changes of physiological indexes,yield and water use efficiency of Rapeseed under water-nitrogen coupling of y-PGA were analyzed.The main results were as follows.(1)Under the condition of water infiltration,the higher the application of y-PGA,the smaller the cumulative infiltration,infiltration rate and wetting front migration.Compared with the control group,the cumulative infiltration,infiltration rate and wetting front of 0.4%?-PGA respectively decreased by 38.19%,48.08%and 46.1 5%.The higher the position of y-PGA applied,the smaller the cumulative infiltration,infiltration rate and wetting front migration,and compared with the application of y-PGA in 15-25 cm layer,the cumulative infiltration,infiltration rate and wetting front of y-PGA applied in 0-10 cm layer respectively decreased by 11.11%,4.35%and 20 83%.Infiltration of different concentration of nitrogen fertilizer solution had no significant effect on cumulative infiltration,infiltration rate and wetting front migration(P>0.05).(2)The simulation results of Philip formula and Kostiakov formula infiltration model parameters show that:compared with the control group,with the increase of y-PGA application,the infiltration rate in Philip infiltration formula decreased from 1.046 to 0.727,the empirical coefficient in Kostiakov formula decreases from 0.924 to 0.546,and the empirical index beta increases from 0.534 to 0.647.With the deviation of y-PGA application position,the infiltration rate in Philip infiltration formula decreased from 2.354 to 1.820,the empirical coefficient in Kostiakov formula decreases from 7.949 to 5.013,and the empirical index beta increases from 0.675 to 0.707.Infiltration of different concentration of nitrogen fertilizer solution has no significant effect on the absorption rate,empirical coefficient and empirical index.(3)The higher the application of y-PGA,the higher the soil profile moisture,nitrate nitrogen and ammonium nitrogen content,compared with the control group the average water content of y-PGA added with 0.1%,0.2%and 0.4%increased by 7.14%,17.80%and 28.57%,the average nitrate nitrogen content increased by 7.92%,25.47%and 34.19%,and the average ammonium nitrogen content increased by 13.20%,28.8847%and 43.02%,on the 4th day after infiltration.The effect of nitrogen fertilizer on soil profile moisture was not significant,but the greater the amount of nitrogen fertilizer applied,the greater the nitrate nitrogen and ammonium nitrogen in soil.The higher the position of y-PGA applied,the smaller the soil water content.Compared with the position of y-PGA applied 0-10 cm,the average soil water content of gamma-PGA applied 5-15 cm,10-20 cm and 15-25 cm increased by 6.78%,10.03%and 14.28%respectively.In addition,different y-PGA application positions had no significant effect on the average nitrate and ammonium nitrogen.(4)With the increase of y-PGA application,the soil water characteristic curve and solute penetration curve shifted to the right.The soil water characteristic curve was fitted by Van Genuchten model.The coefficient and shape coeff-icient related to air intake value were negatively correlated with the amount of y-PGA applied,while the retention water content and saturated water content of soil were positively correlated with the amount of y-PGA applied.Using the parameters of CXTIFIT back-flow dispersion equation,SSQ is not large,which shows that the convective dispersion equation can well describe the Cl-concentration.The hydrodynamic dispersion coefficient is negatively correlated with the y-PGA application,and the hydrodynamic dispersion coefficient is negatively correlated with the y-PGA application.(5)In pot experiment,the coupling of y-PGA,water and nitrogen changed the net photosynthetic rate,intercellular CO2 concentration,stomatal conductance and the distribution of soil water and nitrogen profile of rapeseed.The yield of 10#treatment group was the largest,but the water use efficiency was only 1.86 and the water use efficiency of 6#treatment group was the largest,and the yield was 48.19×103kg/hm2.Compared with 6#,the yield of 10#increased by 3.47%,but the eff-iciency of water utilization decreased by 34.27%,so it can be seen that the best growth combination of rapeseed was 6#treatment with y-PGA,water and nitrogen.