Study On Nitrogen Transformation Response In Vadose Zone Of Irrigation Area Based On Structural Equation

With the increase of nitrogen fertilizer application and the unreasonable and unscientific application,the negative effects of nitrogen at the same time promote crop growth;the long-term excessive nitrogen input will not only lead to a series of soil environmental pollution,but also benefit the efficient use of nitrogen in farmland and the reasonable control of fertilizer.In order to improve the utilization rate of nitrogen fertilizer,reducing nitrate pollution has important theoretical and practical significance.Based on the statistical characteristics and correlation analysis of laboratory data,SPSS statistical analysis and Amos simulation software were applied to analyze the effects of soil minerals,soil environment conditions,nitrogen transformation microorganisms and nitrogen substrate concentration on soil nitrogen transformation.The ion changes of soil mineral ions and environmental conditions in the soil water flow path of the aeration zone were simulated and the biogeochemical effects of the ions were discussed.The following conclusions are drawn:(1)The ammonium nitrogen transformation model in summer and winter had obvious difference,the soil environmental conditions and microorganism had different response to nitrogen transformation,the correlation of soil environmental conditions was prominent,the correlation coefficient of summer was-0.96,winter was-0.44;The relationship between soil environmental conditions and the potential variables of nitrogen transformation microorganisms was stronger in summer and winter.The change of soil environmental conditions not only had strong correlation with ammonium nitrogen,but also could further affect soil nitrogen transformation through soil microbial action process.The direct effects of pH,temperature and organic matter on soil environmental conditions are reflected in the whole model through potential variables,the effect of ammonium nitrogen test on soil environmental conditions is the organic matter and pH;The path coefficient of soil environmental conditions was-0.87,-0.24 in summer and winter respectively,and the path coefficient of soil environmental conditions was greater than summer(0.98,0.79)in winter.The correlation coefficient of latent variable microorganism and nitrogen substrate was higher than summer(0.61,0.50).(2)In the nitrate-N transformation model,the correlation between soil environmental conditions and nitrogen substrate is stronger in summer,the correlation coefficient of summer is-0.96,winter is-0.42,summer soil environmental conditions play an important role in the whole model.The correlation between soil nitrogen transformation microorganism and nitrogen substrate was stronger in winter than in summer,the correlation coefficient was 0.68 and 0.58 respectively.The difference of the effect of pH on soil environmental conditions is not obvious,the difference between the two seasons is mainly temperature,organic matter and water influence,the temperature of summer and the response coefficient of organic matter to the soil environmental conditions are-0.61 and-0.92,respectively.(3)In the reverse simulation of soil water flow path,the precipitation of aragonite,calcite and dolomite in the water flow path is simulated and calculated,which makes the content of yang and magnesium decrease,and the dissolution of salt makes the content of sodium chloride and chloride ion increase;The precipitation of aragonite or calcite and the overflow of CO2 reduce the content of HCO3-.The precipitation effect of ionized calcium,magnesium and anion SO42-in the flow path is weakened,but the dissolution of rock salt will be enhanced.