Effects Of Different Nutrient Management On Nitrogen Leaching Loss From Purple Soil

The dynamic and amount of nitrogen leaching loss, impact factor of nitrogen leaching loss, as well as effect of different nutrient management on maize- mustard tuber yield and their absorption and utilization efficiency of nitrogen were studied using lysimeter experiment in the maize-mustard tuber rotation system.The main purpose was to provided for scientific application and optimization management of nitrogen,as well as to provided data for the calculation of the N leaching loss amount in the maize-mustard tuber rotation.The result showed that the nitrogen leaching loss dynamic and leaching loss amount differ in the growth of mustard tuber and maize.As far as the dynamic is concerned, the loss in the mustard tuber was greater in its prophase than in its anaphase, and the loss mainly occurs within the 40 days since its transplant, during which it amounts to 85.8% of its total loss. The loss of nitrogen in maize, however, is the reverse. The loss reaches its peak mostly after 60 days since its transplant. As to the amount of loss, it is remarkably higher in the season of maize than in that of mustard tuber-5.6 times higher. In this rotation period, the character of this dynamic movement is mainly influenced by the seasonal rainfall, while the quantity of loss was obviously proportional to the rainfall in the corresponded period. In the prophase of the mustard tuber propagative period (From November to February), the rainfall was more than that in its anaphase, so that the loss mainly was occured in its prophase. As to the maize, its transplant in March was followed by the rainy season and therefore the nitrogen leaching loss increased. The rainfall during the propagative period of maize amounts to about 80% of the total rainfall of the year, correspondingly, the nitrogen leaching loss in this period amounts to 86% of the total loss in the whole rotation period. That is, the loss mainly occurs in its propagative period. In the maize-mustard tuber rotation,the total nitrogen leaching amount was 3.7～23.8 kg·hm^-2 with all treatments, and the average was 10.8 kg·hm^-2,the average loss coefficient (the proportion of loss to the total application of nitrogen) was 3.0%, among which the average loss amount and coefficient in the maize propagative period were respectived 9.4 kg·hm^-2 and 5.5%, and those in the mustard tuber period were 1.43 kg·hm^-2 and 0.42%. Consequently, nitrogen leaching loss was not the main caused of nitrogen fertilizer.On the condition of different nutrient management, the nitrogen leaching amount differ remarkably. Compared to the conventional fertilization by the peasants, optimized fertilization could remarkably reduced the loss, so as to increased mustard tuber and maize absorbed Nitrogen, and increased the utilization of the fertilizer and production. The amount of loss in mustard tuber season has been reduced by 20.3%, and that in maize season reduced by 47.4%. The production of mustard tuber has increased by 23.6%, and the utilization of the nitrogen fertilizer has increased by 5%. Presently, the conventional fertilization mode was characterized by overproportion of nitrogen, so as to cause the disproportion of nitrogen, phosphorus and potassium. This disproportional used of N leads to great N leaching loss and high risk in the environment. Therefore, optimized fertilization based on the necessities and soil nutrient property is the best nutrient management mode in developing high-yield, high-efficiency crops and realizing a better environment.