Nitrogen And Phosphorus Runoff Characteristics Of Organic Fertilizer Returning And Riparian Buffer Ecological Interception Technology

In recent years,our government has issued a series of policies to encourage and guide farmers to apply organic fertilizer and promote the green development of agriculture.With the implementation of the national action plan of replacing chemical fertilizer with organic fertilizer,it is expected that the use and scope of organic fertilizer will increase greatly.Large amount of fertilizer application is easy to cause farmland runoff pollution.To explore the impact of farmland runoff on surface water,we must clarify the characteristics of farmland nitrogen and phosphorus runoff.However,the existing research on the characteristics of farmland nitrogen and phosphorus runoff is mostly based on the application of chemical fertilizer,and the research related to organic fertilizer is not deep enough.Mathematical model is the most commonly used method to study the runoff characteristics of farmland pollutants.By collecting the rainfall runoff data,the prediction model is established for relevant simulation research.Surface water is the direct victim of nitrogen and phosphorus runoff pollution in farmland.It is difficult to develop cost-effective runoff pollution control technology in the field of water pollution control.In the process of migration,the pollutants from farmland runoff far away from the river bank are difficult to flow into the surface water with precipitation,infiltration and plant absorption.However,the farmland runoff near the river directly flows into the river,which has a serious impact on the surface water,Therefore,riparian buffer ecological interception technology is the most effective measure to alleviate water pollution caused by fertilizer nutrient loss.Riparian vegetation buffer zone is considered to be an economic and effective ecological interception technology for agricultural runoff pollution.There are some cases of riparian vegetation buffer zone application in China,but the construction,management and maintenance of the buffer zone have not formed a standard and lack of guidance.In this paper,the nitrogen and phosphorus runoff model of organic fertilizer returning was constructed to simulate the nitrogen and phosphorus loss intensity of organic fertilizer under typical scenarios in China,and to explore the nitrogen and phosphorus runoff characteristics of organic fertilizer returning.Taking the water quality standard required by water function zoning as the control point,the optimal width of riparian buffer zone is set according to local conditions,and suggestions are given for vegetation planting and agricultural management of buffer zone.The ecological interception pollution control technology of surface water near farmland is proposed,which provides an effective technical means for the quantitative control and management of agricultural non-point source pollution.The results show that:(1)By analyzing the runoff characteristics of nitrogen and phosphorus,it was found that the loss intensity of particulate nitrogen PN and particulate phosphorus PP in organic fertilizer increased with the increase of ground slope,and the slope was less than 5°There was no significant difference in the loss intensity of PN and PP between the two groups;The loss intensity of PN and PP decreased with the increase of vegetation coverage.When the vegetation coverage was more than 80%,the fertilization intensity had little effect on the runoff loss intensity;The runoff loss intensity of organic fertilizer PN and PP increased nonlinearly with the increase of rainfall intensity.The greater the rainfall intensity was,the greater the change was,and the influence of rainfall intensity on the loss of PP was greater than that of PN.(2)The concentrations of dissolved nitrogen(DN)and dissolved phosphorus(DP)in organic fertilizer runoff increased with the increase of rainfall intensity and fertilization intensity.Based on the water environment safety,the application level of organic fertilizer is 120 kg N/hm~2,and the application level of phosphorus is more than70 kg P/hm~2,which will lead to the excessive concentration of DP in runoff.In daily agricultural activities,if heavy rainfall occurs in a short time after fertilization,the near farmland water body may be polluted.(3)When the width of fertilization zone is 100 m,the optimum width of buffer zone for Type V,Type IV and Type III water in Northwest China and Northeast China are 0～5 m,5～10 m and 5～10 m,respectively;The corresponding buffer widths in North China are 5～10 m,5～10 m and 10～15 m,respectively;The width of buffer zone in Southwest China and the middle and lower reaches of Yangtze River are 5～10 m,10～15m and 15～20 m respectively.In South China,the most suitable buffer zone width is10～15 m,15～20 m and 20～30 m,respectively.(4)Suggestions for vegetation planting and agricultural management in riparian buffer zone:Returning farmland to river and lake in buffer zone;The buffer zone is divided into three functional zones,which are shrub grass complex zone,natural tree zone and herb vegetation zone;Vegetation selection follows the principle of local riparian plants.As a buffer zone for agricultural land use,conservation tillage such as stubble mulching and ridge tillage should be adopted;The application level of organic fertilizer should be lower than 120 kg N/hm~2 and 70 kg P/hm~2;The disturbance to the land in the buffer zone should be minimized.