Influencing Factors And Estimation Of Nitrogen And Phosphorus From Farmlands In China

Eutrophication of water body is a global issue in controlling water pollution,has becoming one of the world’s most concerned environmental problems.There are many factors that affecting water eutrophication and the sources of nutrient is very complex.In order to solve this problem,many countries invest a lot of manpower and financial resources to control the source of nutrients（mainly of nitrogen and phosphorus）.Initially,developed countries were focus on point source pollution,such as urban wastewater.But,the effect was not significant,the phenomenon of eutrophication did not significantly reduced.A lot of research results show that water eutrophication is closely related to nitrogen and phosphorus loss in farmland.Therefore,controlling nitrogen and phosphorus loss from farmland has becoming more and more concerned.Agricultural non-point pollution is formed mainly by 4 processes of rainfall runoff,soil erosion,surface solution stripping and soil solution leakage.Based on the characteristics of widespread,fuzzy,latent,hidden,the non-point source pollution is difficult to control.Facing the great pressure of population,agricultural land resources has close to the intensive utilization since the beginning of the 21st century in china.Fertilizer has become an important way to improve the level of land productivity.The methods of guaranteeing the agricultural product output and controlling agricultural non-point source pollution is related to sustainable development of agriculture and regional social economic.In this paper,we extracted the influencing factors of nitrogen and phosphorus loss of mainland China by statistical analysis.After that,we analyzed TN and TP loss of farmland quantitatively with the method of linear regression and stepwise regression.The Results show that:TP runoff negatively correlate with soil TP and clay content,but positively correlate with P application rate and rainfall.According to China Statistical Yearbook and China Meteorological Yearbook in 2012,TP runoff of the paddy field and upland field was estimated for each province.The simulation showed that TP runoff in 2011 ranged from 0.59 to 3.02 kg·hm^-2 in the paddy field and 0.05 to 0.48 kg·hm^-2 in the upland field.The gross amounts of TP runoff losing in the paddy field was 0.05 Tg;The gross amounts of TP runoff losing in the upland field ranged was 0.02 Tg.Our results arrived at a conclusion that the average losing of TP runoff was 0.06 Tg and the rate of TP runoff losing was 0.41%from national farmland in 2011.TN runoff negatively correlated with soil TN and clay content,but positively correlated with N application rate and rainfall.According to the stepwise regression model of total nitrogen runoff in farmland,we arrived at a conclusion that TN runoff ranged from 3.16 to 16.43 kg·hm^-2 in paddy field and 8.53 to 91.68 kg·hm^-2 in upland field.The gross amount of TN runoff losing was 0.26 Tg in paddy field and 2.11 Tg in upland field.The average losing of TN runoff was 2.37 Tg and the rate of TN runoff losing was 7.95%from national farmland in 2011.TN leaching negatively correlated with soil clay,but positively correlated with soil TN,N application and rainfall.According to China Statistical Yearbook and China Meteorological Yearbook in 2012,we estimated TN leaching ranged from 3.60 to 7.44 kg·hm^-2 in paddy field and 2.43 to 82.44 kg·hm^-2 in upland field.The gross amount of TN leaching loss was 0.16 Tg in paddy field and 1.64 Tg in upland field.The average loss of TN leaching was 1.80 Tg and the rate of TN leaching was 6.04%from national farmland in 2011.