Research On Nitrogen And Phosphorus Input/Output Of Farml And Soil In Hujiashan Small Watershed

As the country’s largest protection area of drinking water, the water source of South-North Water Transfer Project—Danjiangkou reservoir has a highly demanding for water quality, meanwhile, it’s the key to success of South-North Water Transfer Project to ensure clean water flows northward. However, this district across Hubei, Henan and Shanxi provinces, where 82.1% of the residents live in country, have 2.962 million poverties and among 40 counties there are 26 national poverty counties, so, there still has prominent contradiction between rural development and area of water source protection The data from Yangtze River Basin Water Conservation Monitoring Center show that: the area of soil and water loss in this district is 39515.4 square kilometers, which accounted 45% of the total area, and soil erosion in a year is 1.69 hundred million ton, erosion modulus reach 3572 ton each year each square kilometer. Accompany with soil and water erosion, nitrogen and phosphorus are carried, which can seriously affected water quality in reservoir. Therefore, it is critical to control non-point source pollution in Danjiangkou reservoir.Non-point source pollution is due to nutrient imbalance in space and time, then, the most reliable method to reduce non-point source pollution is control of sources of pollutants. Therefore, an important way to control the occurrence of non-point source pollution is strive to make nutrient reach profit and loss balance at each landscape unit. If nutrients reach profit and loss balance, then, there will not be excess nutrients, and will not be nutrients loss when rainfall and runoff occur, so, will not form non-point source pollution. This article selected a typical small watershed in Danjiangkou reservoir which named Hujiashan as study area, based on the surface soil balance of nutrient profit and loss, and got basic data by farmland investigation, then, did research on profit and loss of soil nitrogen and phosphorus in this watershed, and did analysis on crop planting structure and strength and spatial characteristics of nitrogen and phosphorus balance in this watershed, finally, did evaluation on loss risk and pollution potential. Thus concluded the following studies:1、It is same in each catchment in Hujiashan small watershed that fertilizer nitrogen and phosphorus input is the main input of surface soil nitrogen and phosphorus input. Secondly is the other nitrogen and phosphorus input and then is the organic fertilizer nitrogen and phosphorus input. Thus, if we want to achieve the balance of surface soil nitrogen and phosphorus in Hujiashan small watershed, we have to make strengthen management for field fertilizer.2、There is a same performance in each catchment that surface soil nitrogen and phosphorus are all profit. As the farmland soil loss risk of phosphorus in 2012 and nitrogen and phosphorus in 2013 are all highest in catchment nine, and the farmland soil loss risk of nitrogen in 2012 and nitrogen and phosphorus in 2013 are all lowest in catchment twelve, the farmland soil nutrient loss risk in catchment nine is highest and catchment twelve is lowest.3、There is apparent spatial variation in the balance of per unit area of farmland surface soil nitrogen and phosphorus in each catchment of Hujiashan small watershed.On the whole, the surplus amount of nitrogen in catchments that along middle west-sided river and that located in southeastern boundary of Hujiashan watershed is higher than the other. Besides,the surplus amount of nitrogen in catchments that along middle east-sided river are lowest And the surplus amount ofphosphorus in catchments that along Mid-west river is higher than that along east river.The surpluses of nitrogen and phosphorus are both planting driven and the use of fertilizer in farmland is the main reason.4、The total surplus amount of farmland surface soil nitrogen of Hujiashan small watershed in 2012 and 2013 are 88.4 and 88.8t per year respectively, and nitrogen surplus load are 167 and 168 kilogram per hectare per year, all close to 180 kilogram per hectare per year which characterized the value of loss risk. Meanwhile, they are both higher than 154 kilogram per hectare per year which characterized the value of national average. Besides, the total surplus amount of farmland surface soil phosphorus of ujiashan small watershed in 2012 and 2013 are 18 and 15 t per year respectively, and phosphorus surplus load are 34 kilogram per hectare per year in 2012 which higher than the value of loss risk that is 35 kilogram per hectare per year, while, 29 kilogram per hectare per year in 2013 which lower than the value of loss risk that is 35 kilogram per hectare per year, but are both higher than 26.1 kilogram per hectare per year which characterized the value of national average. Come to the conclusion that the pollution potential of farmland soil had formed.