Study On Distribution And Migration Pattern Of N,P And Environmental Effects In Lactuca Sativa L. Planting Area In Dianchi Lake Basin

In the vegetable production, as the use of chemical fertilizer is increasing constantly, a large number of farmland nutrients aggravates a huge surplus of soil nitrogen and phosphorus, which inflow water bodies and resulted in environmental pollutions. The loss use of nitrogen fertilizers will not only cause water pollutions, but also impact the yield and quality of vegetables, which brought a lot of pressure on vegetable production. Because of these problems, differences of Nutrient Management research has significant importance in vegetable production.This paper selected lettuce vegetable areas of facilities vegetable soil in Dianchi Lake basin. Lettuce bengined planting widely and was not studied on Metastaic Characteristics of N,P. From August to september in 2008, through lettuce field experiment of high fertilization level and low fertilization level, the Indicators of lettuce yield and nitrate content, lettuce TN and TP, soil TN and TP, soil available phosphorus, soil available nitrogen and organic matter had been analyzed. The experiment set 9 fertilizer treatments. The behavior characteristics of lettuce absorption, lettuce yield, nitrate content, soil nitrogen and phosphorus transfer and ecological benefit law had been probed into combining with discussion of Differences of Nutrient. The results of our study are as follows:1. The yield of Lettuce was increased by 32.4%, when the rates of N and P were reduced to 46.4% of high fertilizer. N,P, applied in proper combinations, is an important factor for high yield of lettuce. The optimal nitrogen level for high Lettuce yield was 180-270 kg·ha-1, and the optimal phosphorus level was small and about 63 kg·ha-1, in order to coordination economic benefits and environmental benefits. On appropriate nitrogen application, the absorption rate of lettuce reached over 20%, while the highest value 28%. In maturing stage, the nitrogen absorption amount of lettuce was higher than that in growing stage. The phosphorus absorption rate of lettuce was low. On appropriate phosphorus application, the phosphorus absorption rate was only about 10%. 2. The content of nitrate increased with the increasing of nitrogen levels. Appropriate phosphorus levels could restrain nitrate accumulation in Lettuce. Proper N,P combinations could improve the quality of lettuce and increase yield. The nitrate content of edible parts of lettuce accorded with the standard of nitrate pollution in China. The control of nitrogen and phosphorus fertilizer is a important aspect of decreasing nitrate content. It is important that nitrate content was reduced by reasonable control of nitrogen and phosphorus fertilizers.3. Soil total nitrogen had no law in treatment level. The correlation analysis showed that the available nitrogen within 0-20cm soil layer was significantly positively related with the nitrogen application(P<0.05). In 0-40cm soil layer, the total phosphorus increased with phosphorus application amount. The trend of available phosphorus was consistent with the total phosphorus. The total phosphorus and available phosphorus in 0-40cm soil layer showed significant positive linear correlation with phosphorus application amount(P<0.05). Organic matter had little change in a short period. In the vertical gradients, the soil nutrients decreased with depth decrements.4. The correlation analysis showed that the total nitrogen accumulation was significantly positively linear related with the nitrogen application(P<0.05). This was an common phenomenon and had little relationship with crop. In the soil phosphorus accumulation was more significant than nitrogen and reached over 80%. In 0-20cm and 20-40cm soil layer, total phosphorus showed significant positive linear correlation with phosphorus application amount(P<0.05). The soil nitrogen accumulation decreased in appropriate nitrogen application and increased in excess nitrogen application. P-fertilizer showed a surplus of phosphorus accumulation.5. In appropriate nitrogen application, the yield of lettuce was increased by 32.4%,when the rates of N and P were reduced to 46.4% of high fertilizer. Farmers could save fertilizer of 1814.2yuan per hectare and the income increased by 13275yuan per hectare by applying appropriate fertilizers. In lettuce-growing areas of Dianchi Lake Basin, the appropriate nitrogen application would reduce nitrogen loss of 101.53t and phosphorus loss 60.86t. There would be direct environmental economic benefit 401.14yuan per hectare lettuce in appropriate nitrogen application and in lettuce-growing areas of Dianchi Lake Basin there was direct environmental economic benefit 842,000yuan per year.Based on the above result, the loss and accumulation of soil nitrogen and phosphorus was related to the amount of nitrogen and phosphorus. Involving farmers' economic benefits and environmental benefits, this paper proposed implementing differences of nutrient management about "control of nitrogen and little phosphorus".the optimal nitrogen level was 1/2 of current level and was 180-225 kg·ha-1. Phosphorus absorption of lettuce was little and farmers could apply a little and the application of phosphorus was about 63 kg·ha-1.