Effects Of Cross Ridge Covered With Plastic Film On Net Nitrogen Mineralization Of Yellow Brown Soil In Danjiangkou Reservoir Area, China

As one of the main ways of soil inorganic nitrogen accumulation,soil net nitrogen mineralization has an important influence on agricultural non-point source pollution caused by soil inorganic nitrogen loss and leaching.Soil net nitrogen mineralization was affected by soil water content,soil temperature and soil nitrogen content.As a kind of plastic film mulching ridge-furrow cultivation can adjust soil water and heat conditions and nitrogen content,which can affect soil net nitrogen mineralization.Effects of plastic film mulching ridge-furrow cultivation on soil net nitrogen mineralization can reveal soil nitrogen cycling mechanism and provide a theoretical basis for the agricultural non-point source pollution prevention and control measures.The yellow brown soil of sloping farmland in the Wulongchi small watershed of Danjiangkou River was studied.A field plot experiment was conducted to explore the effects of cross ridge covered with plastic film on soil net nitrogen mineralization by adjust soil water and heat condition and nitrogen content in Wulongchi small watershed during maize growing period.The quantitative relationship between soil nitrogen mineralization and soil water content,soil temperature and soil nitrogen content was established.The major conclusions include:(1)Changes of soil water content and temperature can be regulated by cross ridge covered with plastic film during the growth period of maize.Soil water content under cross ridge covered with plastic film were significantly greater than those of non-mulched treatment at heading stage and mature stage.Among them,the growth rate was the highest in the jointing stage and heading stage,with an average increase of 47.24% and 34.16%,and an increase in the maturity period was small,with an average increase of about 7.43%.The soil temperature under cross ridge covered with plastic film was significantly greater than those of non-mulched treatment at the seedling and jointing stage.However,in the late stage of jointing stage,heading stage and maturity stage,the effect of cross ridge covered with plastic film was not obvious.(2)Changes of nitrogen content in soil could be changed by cross ridge covered with plastic film during the growth period of maize.The soil total nitrogen contents under cross ridge covered with plastic film were significantly lower than those of non-mulched treatment at the mid-term stage of seedling.The soil total nitrogen contents under cross ridge covered with plastic film were significantly greater than those of non-mulched treatment at the later stage of seedling jointing stage,heading stage and maturity stage.Among them,the growth rate was the highest in late seedling stage,the average increase was 26.94%,the growth rate was the lowest in heading stage,and the average increase was about 17.22%.(3)During the growth period of maize,the cross ridge covered with plastic film can adjust the soil water and heat conditions and nitrogen content,and then affect the soil net nitrogen mineralization.The amounts of net nitrogen mineralization under cross ridge covered with plastic film were significantly lower than that those of non-mulched treatment at the middle of seedling stage and jointing stage.Among them,the maximum decline in the middle of seedling period,an average reduction of 27.81%,the lowest decline in the early jointing stage,an average reduction of 22.36%.The amounts of net nitrogen mineralization under cross ridge covered with plastic film were significantly higher than that in the ridge and those of non-mulched treatment at the jointing stage,heading stage and maturity stage.Among them,the highest growth rate in the late jointing stage,the average increase of 550.29%,the lowest growth rate in the mature period,an average increase of 114.32%.(4)There were incidence relationship and linear relationship between soil nitrogen mineralization and soil water and heat conditions,soil nitrogen content during the growth period of maize.There were the higher correlation between the soil net nitrogen mineralization contents under cross ridge covered with plastic film and the soil moisture,temperature and total nitrogen contents at the seedling stage,jointing stage,heading stage and maturity stage(0.6<Grey correlation degree≤0.8).Linear function relationship between the soil net nitrogen mineralization contents under cross ridge covered with plastic film with soil temperature at the seedling stage(F=7.205,P=0.023).Linear function relationship between the soil net nitrogen mineralization contents under cross ridge covered with plastic film with soil moisture and temperature at the jointing stage(F=36.861,P=0.001).Linear function relationship between the soil net nitrogen mineralization contents under cross ridge covered with plastic film with soil moisture at the maturity stage(F=42.438,P=0.007).