Rice - Wheat / Oil Tankers For Nitrogen Leaching And Utilization Of The System

Nowadays, the human society has been puzzled by two intractable problems, which are the progressively demand-increased grain and the deteriorated environment that is caused by the efforts of promoting grain-production. Nitrogen is one of the primal elements of biomass. Nitrogen fertilizer has been undoubtedly playing an important role in the development of agriculture. However, it is impossible to infinitely increase for the crop output of unit area and the biological utilized rate of nitrogen with continuously increasing the nitrogen fertilizer application. It was reported, the utilized rate of nitrogen was lower, which average was in the range from 30% to 42% for wheat and rice, while the rate of loss was higher, which was in the range of 30%-70% for paddy field, and 20%-50% for dry-crop field. Those nitrogen either enter into atmosphere causing "the greenhouse effect"; or leach into water leading to the eutrophication of water body. In recent years, with the rapid increase of nitrogen fertilizer and the quality-declined of environment, the transformation and transference of nitrogen in the farmland ecosystem, and the problem of environment have gradually been the research hotspot. The study of such transformation occurred in wet-soil, dry-soil and paddy-soil, has already been excessive, whereas the study of it in purple soil paddy-upland field rotation system was relatively insufficient. In the investigation, the characteristics of nitrogen leaching loss in three types of purple soil were studied using lysmeter. The results of research were as follow:(1) The dynamics of nitrogen leaching loss are similar in the rape and wheat growing seasons, taking the shape of wave-like changes. There exist 4 peaks of leaching loss in the whole growth period in the dry crop. The peaks of leaching loss occurred on the 10th day, the 40th days, the 90th days and about the 110th days after the rape transplanting or the wheat seeding, among them the largest in intensity is the 10th day and about the 110th day. The first two peaks of nitrogen leaching lose have something to do with the usage of base fertilizer and topdress; and the latter two have something to do with the temperature rising, rape nitrogen ore strengthening and the rainfall increasing. So to reduce base fertilizer amount of application is a very important measure to reduce the leaching loss of nitrogen in the early rape growth period.(2) The leaching losses of nitrogen during paddy growing season are obviously different from those in the dry season. There is relatively small fluctuation in the leaching losses of nitrogen in the whole growth period of paddy. The obvious leaching loss peak has appeared only in 25 days after transplanting. The variation of NH₄⁺-N components is small without N fertilizer. And the contents of NH/-N in the waters of seepag to which the N fertilizer is applied are high on the 1 Oth and 25th day after the paddy transplanting. They have something to do with the base fertilizer and topdressed (the 20th day) respectively.The leaching loss peak of NO₃^--N has appeared on the 5th day after the paddy transplanting in the all treatments, and it explains the N₃^--N of leaching loss mainly coming from soil N remained in dry season. So in the paddy-upland rotation system, we should try our best to reduce the remaining nitrogen in the soil after the drought is done. In the paddy-rape rotation, the moving of NH/-N and NCV-N in the three soils operates in accordance with the similar laws. In the paddy-wheat rotation, the moving of nitrogen is similar to that of nitrogen in the paddy-rape rotation during paddy growing season.(3 ) During rape growing season, the total amount of the leaching losses of nitrogen changes in the range of 1.81-5.43kg/hm2 and 3.35kg/hm2 on average. The leaching loss of nitrogen is increasing with rising of nitrogen consumption. The leaching losses are 3.59% of applying fertilizer, among them the fertilizer nitrogen accounts for 1.56%. In the different rape growing stage, the leaching loss of nitrogen is most heavy in the earlier stage (0⁵0days after transplanting), is second in the later stage, and is minimum in the middle period (50-100 days after transplanting), the proportion is about 3:2:1. During rape growing season, the net rate of leaching loss of nitrogen is 0.82%-2.56%, and it is 1.60% on average. It is the effective way to reduce crop base fertilizer and topdressing consumption in the seedling stage for reduction in leaching loss of nitrogen in the dry season.In the neutral purple soil, the amount, rate and dynamics of nitrogen leaching loss in the growth period of wheat (1.84-4.58kg/hm2 and 3.46kg/hm2 on average) are unanimous basically with those of rape.(4) The leaching loss of nitrogen in the paddy growing season is 3 times high of dry season crop usually. In the system of paddy-rape rotation, the total amount of leaching loss of nitrogen is 11.50-16.27kg/hm2 and 13.88kg/hm2 on average in paddy growing season, and 3.35kg/hm2 on average in the dry season. The amount of leaching loss is 16.27% of applying N fertilizer. But the net rate of nitrogen leaching loss is very low, the change is in 1.06%-3.63%. The nitrogen of leaching loss comes from the soil mainly, taking up 90%. There is less nitrogen coming from the fertilizer, only accounts for 10%. So the amount of nitrogen of leaching loss in the paddy season depends on remaining inorganic nitrogen in the soil of dry crop. In the system of paddy-upland rotation, it is an effective measure to reduce the leaching loss of nitrogen by reducing nitrogen remained in the soil of dry season in the paddy season. On the neutral soil, the amount of leaching loss of paddy-wheat rotation is (13.2kg/hm2) less than that of paddy-rape rotation (14.4kg/hm2).(5) The nitrogen consumption, rainfall, temperature, and soil nature have influenced the migration and leaching loss of nitrogen in the soil, and the amount of nitrogen leaching loss is increasing with the rising of nitrogen consumption. As the rising of the rainfall and temperature, the...