Research In Nitrogen And Phosphorus Leaching In Three Gorges Reservoir Region

Nitrogen and phosphorus are important elements which causes agriculturalnon-point source pollution. Leaching is the important way of agricultural non-pointsource pollute. Purple soil is the main soil types for the Three Gorges Reservoir area,the soil characteristics and weathering characteristics determines the prevalence of soilleaching process, so study the purple soil in the three nitrogen and phosphorus leachingloss is very necessary. Soil nitrogen and phosphorus leaching loss varies from farmlandcrop types, vegetation coverage, fertilizer varieties and amount of fertilization soil totalnitrogen and phosphorus content and other factors, the resulting soil nitrogen andphosphorus leaching loss risk is also different. Research aiming at soil nitrogen andphosphorus leaching of the Three Gorges Reservoir region is still relatively small.This paper selects4kinds of typical land use patterns: forest fruit, dry land, paddyfield and the hydro-fluctuation belt, at a small watershed in Three Gorges Reservoirarea, studied soil nitrogen phosphorus leaching loss characteristics; the indoor soilcolumn experiment under different land use patterns in situ, selected ammoniumbicarbonate, urea and phosphate fertilizer,3kinds of commonly used fertilizers,research soil phosphorus forms various nitrogen leaching loss characteristics ofdifferent fertilizer application; further analysis of nitrogen and phosphorus leaching lossin purple soils and main influence factors of the risk of loss combining rainfall, physicaland chemical properties of soil, fertilization. The research obtained the followingconclusions:For soil nitrogen leaching of different land use patterns in situ study, we found,TDN leaching loss ranged from0.48~72.58kg/hm~2, ammonia nitrogen accounted for5.7%~26.5%of TDN leaching loss, nitrate nitrogen accounted for71.6%~86.7%,nitrate nitrogen is the main form of TDN loss. No fertilization nitrate nitrogen leachingamount was significantly lower than the fertilization soil nitrogen leaching loss ofnitrogen leaching amount, while no significant difference. Under the condition of dryland soil nitrification is stronger, make the ammonia nitrogen transfer into nitrogen,making nitrate leaching amount of the hydro-fluctuation belt, dry land and orchard, ismuch higher than the paddy field.TDP leaching loss ranged from0.01~3.23kg/hm~2, MRP accounted for64.3%~95.8%, MRP is the main component of TDP leaching loss. After fertilized soil MRP, TDP leaching loss is two times than that with no fertilization. Phosphorus leaching frompaddy field is at a low level all the year round.Through the purple soil leaching simulation of different fertilizers study,we found,different amount of ammonium bicarbonate treatment, soil column leaching loss ofTDN between43.49~251.2kg/hm~2, nitrate accounted for60.8%~83.2%of TDN.Different application rate of urea treatment, soil column leaching loss of TDN between52.82~216.4kg/hm~2, nitrate content accounted for59.7%~73.4%of TDN. Nitrogenleaching amount from soil and nitrogen fertilizer amount were positively related. To thesame amount of fertilizer, nitrogen leaching amount of urea is higher than the treatmentof ammonium bicarbonate. Under different P fertilizer treatment, soil column leachingloss of TDP between3.67~8.44kg/hm~2, MRP accounted for89.6%~96.3%of TDP.Phosphorus loss quantity and fertilizer application amount was positively related.From soil nitrogen and phosphorus leaching riskof the different land use types insitu analysis results show that, the soil nitrogen leaching losses, in order: dry land> fruitforest> water-level-fluctuating zone> paddy. Soil phosphorus leaching losses, in order:fruit forest> dry land> water-level-fluctuating zone> paddy field. Nitrate nitrogencontent in5~20cm soil is the main influence factors of soil TDN loss, and soil totalphosphorus and phosphate content in0~5cm soil are the main influencing factors of soilphosphorus leaching loss. Soil nitrogen and phosphorus leaching losses of paddy fieldare small, which is environment friendly land use pattern.Fertilizer effect soil nitrogen and phosphorus leachate content of purple soilstrongly. Nitrogen leaching risk of nitrogen fertilizer on purple soil by the equation:Y=30.17+0.41X-0.0003X~2(ammonium bicarbonate), Y=74.39+0.564X-0.0005X~2(urea)representation. P leaching risk of P fertilizer on purple soil by the equation: Y=4.24+0.00569X.The research is aiming at providing basic data for the estimation of nitrogen andphosphorus leaching loss of purple soil in the Three Gorges Reservoir area, andproviding a scientific basis to reduce nitrogen and phosphorus leaching loss.