Study On The Influencing Factors Of Vadose Zone Nitrogen Transformation In Irrigation Area Soil

Soil nitrogen cycle is an important part of biogeochemical cycles, it not only affects the sustainable development of soil productivity, but also affects global environmental change, the current soil nitrogen pollution has become a common phenomenon in soil contaminated farmland. Soil properties and microbial produced different degrees of impact to soil nitrogen cycle, the important ecological processes involved, including adsorption, nitrification, denitrification and mineralization, etc., so irrigated soil nitrogen transformation vadose zone the influencing factors have important theoretical and practical value.The papers ordered irrigation soil as research the media, soil temperature, pH, redox potential and impact of changes in the number of microorganisms to investigate the effect of biogeochemical conditions on vadose zone soil nitrogen transformation before and after irrigation, and soil organic matter, ammonium, nitrate, total nitrogen transforming relationship with each other, the conclusions were followings:(l)The main change was rapid change layer moisture content of the soil after the irrigation, the growth rate of soil moisture in summer irrigation was less than winter irrigation, the impact on soil moisture in summer irrigation water did not exceed four days, but in winter the impact of irrigation on soil moisture and temperature would last one month; After the irrigation in summer soil pH significantly increased, after irrigation soil pH significantly reduced in winter, soil redox potential significantly increased after irrigation in winter.(2) In summer, before40cm, soil bacterium rose with moisture content increasing、soil temperature and pH decline; in winter, with water content and temperature increasing, soil bacterium decreased. In summer above100cm soil nitrogen-fixing bacterium reduced with pH rising; in winter under150cm soil nitrogen-fixing bacterium increased with temperature dropping. In summer, soil ammonifiers increased with soil temperature decline, above100cm it rose with the water content increasing; in winter ammonifiers increased with soil temperature、Eh decrease. In summer above100cm nitrite bacterium increased with soil pH rising; in winter from40cm to200cm soil nitrite bacterium decreased with soil temperature rising; In summer from40cm to100cm nitrate bacterium decreased with pH increasing; in winter before100cm nitrate bacterium rose with moisture and Eh rising. In summer under300cm denitrifying bacterium decreased with water content, temperature and pH rising; in winter above100cm denitrifying bacterium reduced with water content and Eh increasing.(3) In summer organic matter content decreased with the total number of bacteria increasing, above100cm the soil organic matter content increased with ammoniated bacterium, nitrifying bacterium decrease, under70cm organic matter content reduced with denitrifying bacterium increasing; in winter under200cm organic matter content decreased with ammonifiers increasing, atlOcm the organic matter and bacterium were significantly negatively correlated, at300cm it has a significant positive correlation with denitrifying bacteria. In summer above200cm TN increased with nitrogen fixing bacterium and nitrate bacterium increasing, and it reduced with denitrifying bacteria increasing; in winter TN decreased with bacterium rising, under100cm TN decrease with nitrite bacterium increasing. In summer above100cm ammonium nitrogen increased with ammonifying bacterium rising, and reduced with nitrogen-fixing bacterium and nitrite bacterium increasing, in winter above100cm ammonium nitrogen increased with bacterium and ammonifiers rising. In summer above150cm nitrate nitrogen increased with nitrifying bacterium and nitrogen-fixing bacterium increasing, and reduced with denitrifying bacterium rising, under300cm nitrate nitrogen rose with bacterium and nitrogen-fixing bacterium increasing, and decreased with ammonifying bacterium and nitrifying bacterium increasing; in winter above200cm nitrate nitrogen increased with denitrifying bacterium reducing.