Effects Of Straw Returning Combined With Fertilizer Application On Soil Nitrogen And Phosphorus Loss

Huaihe River Basin is a major grain production area in China.Its transitional climatic characteristics provide a basis for multiple planting patterns.In this area,the main planting pattern is crop rotation of wheat and corn.The application of a large quantity of chemical fertilizer during corn season results in high concentration of nitrogen and phosphorus in surface runoff of field during concentrated rainfall periods in summer and winter.The loss of nitrogen and phosphorus not only aggravates the pollution to surface water,but also lowered the utilization ratio of fertilizer.To address above problem,based on the characteristics of absorption and utilization of fertilizer different crops during grow and with common local common crops i.e.corn,soybean,sweet potato and wheat as objects,Five planting patterns:sole cropping of corn;sole cropping of soybeans;sole cropping of sweet potatoes;intercropping of soybeans and sweet potato;intercropping of soybeans and corn,a research was conducted to figure out which planting pattern helps best control the loss of nitrogen and phosphorus by analyzing 5 planting patterns with different combination of fertilizers Conventional compound fertilizer,Slow-release fertilizer and straw organic fertilizer +non-turnover of straw,based on straw turnover.With maximum production and minimum loss of nitrogen and phosphorus as the objective,the traditional planting pattern which is suitable for plantation in Huaihe River Basin and effective control of loss of nitrogen and phosphorus was screened out.The research results are as follows:(1)Compared with sole cropping of corn,intercropping of soybean and corn resulted in higher content of total nitrogen,total phosphorus,total potassium and organic matter in the soil,thus effectively maintaining soil fertility and improving activity of urease and alkaline phosphatase in soil;intercropping of corn and soybeans resulted in minimum runoff under different simulated rainfalls.Therefore,it will effectively retain surface runoff during abundant rainfall period in summer and fall.Compared with sole cropping of corn,the total nitrogen loss in runoff could be reduced by 51.93%.Compared with sole cropping of corn,the intercropping of corn and soybeans improved the absorption of soil nutrient by crops and increased production of corn,without significantly reducing the production of soybeans.(2)Compared with non-turnover of straw,total straw turnover and 50% straw turnover resulted in increased content of nitrogen,phosphorus,potassium and organic matter in soil.In addition to effective retention and supplementation of soil nutrient,straw turnover also increased the quantity and species of soil nematodes(in particular,the quantity of nematodes which live on bacterium and hunting-omnivorous nematodes).Where,the nematode channel index,Wasilewska index and nematode maturity index were the highest with 50% straw turnover,reaching 0.80,2.85 and 2.18 respectively,effectively improving the health and anti-interference capacity of soil;there was a significant positive correlation between change of total nematodes and the content of total nitrogen,organic matter and rapid available phosphorus;where,there was significant correlation between the quantity of hunting-omnivorous nematodes and the content of organic matter and between Wasilewska index and the content of organic matter.Compared with total straw turnover,the physical and chemical property of soil with 50% straw turnover was not significantly changed.Therefore,50% straw turnover is more favorable for increasing soil nutrient and maintenance of soil ecological system.(3)Compared with application of conventional compound fertilizer,straw organic fertilizer + non-turnover of straw increased the content of nitrogen,phosphorus,organic matter and other nutrient in soil,improved the activity of urease and alkaline phosphatase in soil,increased the absorption of nitrogen and phosphorus by plants,increased the biomass of plants and improved production.However,compared with straw organic fertilizer +non-turnover of straw,straw turnover increased surface runoff and risks of loss of nitrogen and phosphorus as a result thereof.Compared with application of conventional compound fertilizer,slow-release fertilizer effectively maintained the soil fertility and increased absorption of nutrient by plants,above-ground biomass of plants and corn production.Compared with application of conventional compound fertilizer,intercropping of soybeans and corn improved content of soil nutrient.Furthermore,among the different combinations of fertilizer,intercropping of soybeans and corn not only maintained high nutrient content and effectively,lowered the risks of loss of nitrogen and phosphorus in soil,increased the above-ground biomass and improve the activity of urease and alkaline phosphatase in soil.Therefore,the yield of maize could be increased by 27.05% by increasing maize double ear rate.To sum up,among the different planting patterns and combination of fertilizer,intercropping of corn and soybeans will effectively retain and supplement nitrogen and phosphorus in soil,reduce the runoff and the loss of nitrogen and phosphorus,improve absorption of nutrient by crops and improve crop production;the combination with 50% straw turnover will effectively maintain the health of soil.Therefore,this planting pattern can serve as a key technique in optimization of planting pattern and prevention and control of loss of nitrogen and phosphorus in Huaihe River Basin.