Environmental Effect Of Fertilizer Employing On Dry Farmland In Shanghai Suburbs

Soil nutrient, salinity study is increasingly a hotspot in agriculture and environment domain of all countries because employing too much fertilizer series environment problems caused by. Employing too much fertilizer increases dry farmland soil nitrogen and phosphorus losses, leads to soil and vegetable nitrate accumulation and brings soil of protected agriculture greenhouse secondary salted and crop growth obstacle. The farming of Shanghai suburbs, no matter what fertilizer dosage on dry farmland, index of multiple cropping, or level of yield and output value, is high active. Agriculture non-point pollution is becoming worse and worse. So the deeply study of soil nutrient and salinity transferring and leaching mechanism, discussing effect of fertilization to dry farmland ecosystem has great theoretic and practical significance.The dissertation is finished with the support of Shanghai science and technology promote agriculture project: "ration study of dry farmland fertilizer nitrogen and phosphorus losses process in Shanghai suburbs". "Environmental Evolution of Water & Land Resources and Its Control in Changjiang Delta" ( National Nature Science Key Foundation of China, No. 49831070). Biogeochemical Cycling of Pollutants in Complex Environments of Tidal Flats in the Yangtze Estuary (National Nature Science Key Foundation of China, No. 40173030). Foundation for the Excellent Youth Teacher by the Ministry of Education).Study of this dissertation is based on a great deal of basic data collected from field sampling. From 2002 to 2004, we sampled soil and vegetable from dry farmland and 1 year greenhouse watermelon soil, leakage and spot runoff experiments at vegetable soil open in the air in Shanghai suburbs. We get total above 20000 data after analyzing nitrogen, phosphorus of soil, vegetable, runoff and leakage water. The main conclusions can be summed up as followed:(1) In the past about 20 years' succession cultivation from 1980s, nitrogen and phosphorus nutrient of dry farmland soil in Shanghai suburbs increased greatly with fertilization increase. Especially, it is obvious that nitric nitrogen and Olsen-P accumulation in soil. Greenhouse melon and vegetable soil had acidification trend. Soil nutrient level of different cultivation model in turn (from high to low) is: greenhouse vegetable, melon and fruit soil> open vegetable soil >traditional vegetable soil>rice and wheat dry farmland. Nitrate content in vegetable of greenhouse cultivation is significantly higher than that of soil open in air. It depends onfertilization level. Employing too much fertilizer causes waste and increases dry farmland N, P potential losses possibility.(2) Soil of Shanghai suburbs greenhouse has partially salted trend. The form of soil secondary salted protected cultivation in suburbs of Shanghai has close relationship with improper fertilization or employing too much fertilizer. According to soil salt degree classification level, proportion of non salt where grows melon or vegetable in suburbs of Shanghai city is 88.52%, gently salt 10.37%, middle salt 0.74%, severely salt 0.37%. Anion component of soil salt salinity in Shanghai suburbs establishment cultivation were mainly NO₃^-1 , Cl^-1, SO₄^2-, which are from fertilizer auxiliary or transformation, except soil original deposition.(3) Soil salinity has relationship with different cultivation mode and cultivation age. Rotate cultivation helped to reduce soil salinity content. In same region, protected soil salinity with different crop age increases and accumulates with protected utilization age increase. This related to fertilizer remained in soil with years increased. There is no great difference among salinity content of all layers with 1 year protected cultivation. Total salinity content in soil section and salinity accumulation velocity from down to up increased with cultivation age extended. Salinity accumulates from down to up quickly with planting age. Total soil salinity quantity and all ion components content in 0-20 cm depth soil are higher...