Nitrogen And Phosphorus Runoff In The Typocal Vegetable Fields In Tai Lake Basin

Agricultural non-point source pollution is one of major factors in resulting in eutrophication of surface waters in Tai basin, and nitrogen (N) and phosphorus (P) losses from land is one of major sources of it. With the planting industry structure adjustment, vegetable planting area is gradually expanded. N and P nutrition loss of the impact on the environment is more and more clear. The reason is that one is high vegetable multiple crop index, and the other is high fertilizing amount. It is important to distinguish of N and P runoff loss from vegetable fields, process, flux and chemical forms, and study the influence of vegetable yield, accumulation of N, P and K nutrition and utilization ratio of fertilizer on different fertilization treatments is critical to grasp the characteristics and laws of erosion and pollution about the vegetable plot nutrient runoff, to find out fertilization mode that was a high crop yield, optimal product and friendly environment, and to reduce environmental pollution of agricultural production process. Meanwhile, it will offer scientific evidence to prevent and control agricultural non-point pollution in Tai lake basin.In the present study,1.5km of vegetable field nearly Tai lake by field monitoring in situ located at Taihu village, Xueyan town, Changzhou city was selected to monitor and calculate the situation the loss of N and P with surface runoff after rainfall events all one year from2008to2009. The test of greens and eggplant designed six processing respectively and repeated three times, which were the blank control experiment (No fertilizer), conventional fertilization, optimized fertilization, single organic fertilization, increasing N fertilization and increasing P fertilization by randomized block design. Major results were summarized as bellow.1. Different fertilizer levels had a great effect on vegetable yield (a=0.01) Compared with blank, other fertilization modes were significantly increased the greens and eggplant vegetable yield of economic separately, which increased the rate of yield respectively100.2%to166.9%and135.7%to265.6%. The effect of organic fertilization was less than optimum fertilization, but optimum fertilization increased the yield of vegetable based on the conventional treatment, increased by25%. It can make vegetable keep a stable high yield for long-term vegetable crop land by chemical fertilizer matched with organic fertilizer.2. Different fertilizer levels were significantly increased nitrogen, phosphorus and potassium cumulate capacities and fertilizer utilization in the greens and eggplant. The N cumulate capacity was96.42to267.27kg· hm-2. The P cumulate capacity was19.03to117.15kg· hm2. The potassium cumulate capacity was117.69to209.47kg· hm2. Organic matched with chemical fertilizer could promote the plants nitrogen accumulation. Utilization ratio of N fertilizer was22.35%to36.23%, P fertilizer was9.34%to14.76%and potassium was14.88%to26.22%. The utilization ratio of single organic fertilization was lowest, but optimum fertilization could enhance utilization ratio of nitrogen fertilizer by23%, which showed that organic matched with chemical fertilizer made keep a high rate.3. Different fertilizer treatment on the surface runoff N and P concentration influenced significantly. Fertilization and early crop growth were important time period to control surface runoff loss. Planting the next crop, ploughing and farming activities influenced P loss.4. The mean annual discharge of nitrogen and phosphorus was different greatly, total nitrogen (TN) was45.76kg· hm-2to60.45kg· hm-2, optimization of vegetable runoff discharged nitrogen, whose14.5%are caused by fertilizer throughout the year, and conventional treatment of runoff discharged17.9%of the nitrogen fertilizer throughout the year. And total phosphorus (TP) was2.67kg· hm-2to3.95kg· hm-2, optimization of vegetable runoff discharged phosphorus, whose18.1%are caused by fertilizer throughout the year, and conventional treatment of runoff discharged25.2%of the phosphorus fertilizer throughout the year. Comparing with the conventional fertilization, optimum fertilization could reduce the discharge of nitrogen and phosphorus. The discharge amount of TN and TP reduced2.48kg· hm-2and0.31kg· hm-2. Nevertheless, increasing nitrogen fertilization and phosphorus fertilization increased the amount of TN loss respectively by4.69kg· hm-2and2.23kg· hm-2, while increased the amount of TP loss respectively by0.11kg·hm-2and0.38kg·hm-2. It was obviously that application of organic fertilizer could better inhibit nitrogen and phosphorus loss with surface runoff than chemical fertilizer. TN and TP loss were significant linear related with runoff, which TP loss was better than TN loss (correlation coefficient r=0.96>0.86). It should strengthen field management and monitoring of P in the period of flood season to reduce P loss. TN and TP loss of time the changing trends were similar to runoff change. Vegetable fields were chief of nitrate nitrogen, phosphorus loss, mainly in the form of particle state, including phosphorus loss of form soluble phosphorus loss is bigger, eggplant and rainfall may concerned.