Nitrogen Loss Characteristics Of Vegetable Land Under Different Fertilizers And Its Source Control

Nitrogen is one of the main elements causing eutrophication in water.Point source pollution is gradually controlled,and eutrophication of water is further restrained with the intensification of environmental pollution treatment in China.However,agricultural non-point source pollution is still the main cause of eutrophication in rivers,lakes and other water bodies due to its wide and complex sources,uncertain discharge and difficult treatment,which seriously threatens the water environment security in China.The research of agricultural non-point source pollution caused by nitrogen loss is mostly controlled by process blocking or end treatment technology,but there are relatively few studies on reducing nitrogen loss from the source.In this study,the nitrogen loss characteristics of different fertilizers in vegetable lands were taken as the starting point,and four kinds of fertilizers including chemical fertilizer,chicken manure,pig manure and cow manure were selected for leaching test after application,in order to reveal the nitrogen loss amount,loss pattern and dynamic characteristics of different fertilizers.Based on the characteristics of fertilizer loss,the experiment of fertilizer reduction was carried out on the premise of ensuring the yield and quality of vegetables to minimize the application of fertilizers and explore the maximum amount of fertilizer reduction in vegetable land.On the basis of fertilizer reduction,different control modes of fertilizer reduction and synergism were established,and the best source control mode was sought to provide reference for rational application of fertilizer and control of nitrogen loss in vegetable lands.The main results were as follows:(1)The leaching experiment showed that the order of total nitrogen loss from high to low was chemical fertilizer(33.82 kg N/ha)>cow manure(32.08 kg N/ha)>pig manure(31.23 kg N/ha)>chicken manure(30.96 kg N/ha),and no fertilizer of blank control group total nitrogen loss was 14.03 kg N/ha,chemical fertilizer application leads to the highest amount of nitrogen loss,this indicates that the application of a large amount of fertilizer will cause serious nitrogen loss and make the water environment worse.(2)Nitrate nitrogen was the main form of nitrogen loss,the nitrate nitrogen accounted for 77.48%?94.32% of the total nitrogen in all the fertilization groups.In the early stage of fertilization,the amount of nitrogen loss was higher than that of organic fertilizer applied,and in the middle and late stage of fertilization,the amount of nitrogen loss was higher than that of chemical fertilizer(3)The fertilizer reduction experiment revealed that the total nitrogen loss decreased by 5.46 kg N/ha,12.18 kg N/ha,17.59 kg N/ha,20.03 kg N/ha and 22.37 kg N/ha when the fertilizer application decreased by 20%,40%,60%,80% and 100% from the current average application of 250 kg N/ha,reduced application of fertilizer can significantly reduce nitrogen loss.(4)With the decrease of chemical fertilizer application amount,the nitrate nitrogen content of Chinese cabbage showed a trend of decreasing gradually,plant height,fresh weight and vitamin C all showed a trend of increasing first and then decreasing,so the appropriate reduction of chemical fertilizer application can improve the yield and quality of Chinese cabbage to a certain extent.The yield of Chinese cabbage was the highest when the amount of fertilizer applied was 60%,and the content of vitamin C was the highest when the amount of fertilizer applied was 40%.Considered the amount of nitrogen loss,yield and quality of Chinese cabbage,reduced the amount of chemical fertilizer by 40% can reduce the loss of 12.18 kg N/ha,which had better economic and environmental benefits.(5)The optimization of the application model can reduce the loss of nitrogen,improve the apparent utilization rate of fertilizer,and improve the yield and quality of Chinese cabbage.The order of nitrogen loss control effects of different reduction modes was chemical fertilizer with fulvic acid fertilizer > chemical fertilizer with dicyandiamide> chemical fertilizer with foliar fertilizer > chemical fertilizer with organic fertilizer> single application of organic fertilize> single application of chemical fertilizer.Compared with the single application of chemical fertilizer,the nitrogen loss of fertilizer mixed with fulvic acid fertilizer decreased by 5.56 kg N/ha,which had best control effect on nitrogen loss.Combined with the comprehensive analysis of economic,environmental and social benefits,the application mode of chemical fertilizer with fulvic acid fertilizer had the best effect on nitrogen loss control.