Research On High-yield Culture Mode Of Maize By Control Of Nonpoint-source Pollution Through Applying Fertilizer Accurately

Agricultural nonpoint-source pollution, extensively distributing, is the most important nonpoint-source pollution. The statistic data of 1990 showed 90% suspended substance, such as most nitrogen and most phosphorus, came from farmland run-off in the region of the Three Gorges where the pressure of dense and large population caused intensively exploitation of agricultural land resources, and application of more and more fertilizer or agrochemical became the main way to higher-yield. Therefore sustainable development of agriculture and society economy in a reign is determined by the control of nonpoint-source pollution.After the Three Gorges engineering is accomplished, the speed of water through cross section, 0.04 m/s, is only 1/6 times of natural average speed. The change of the water flow construction will let the river in the danger of excessive nourishment.Nitrogen or phosphorus in the region of the Three Gorges primarily came from the farmland. In order to prevent the excessive nourishment of water, we should first administer farmland, the origin of the problem. As far as maize planting, there is usually 53-67 ha planting area in Chongqing. On the basis of calculation of applying fertilizer application amount on the average level, 225 kg pure nitrogen per ha, equal to 489 kg urea roughly, 375 kg calcium phosphate per ha should be applied. In China, the quantity of fertilizer application is high, but the utilization, only 20-25% of fertilizer applied, is low (Zhu Zhaoliang), and much fertilizer in the river or in the lake is from soil erosion. Suppose there is 530,000 ha maize-planting area in Chongqing, then 240,000 tons urea and 200,000 tons calcium superphosphate should be applied. But the plant in this area could only absorb 180,000 tons urea and 150,000 tons calcium superphosphate. Subtract 20% of the fertilizer vaporized to the air or fixed by soil, there is 144,000 tons urea and 120,000 tons calcium superphosphate reaching Yangtze River directly through the groundwater or run-off annually.According to our initial research, all kinds of crops have their unique technology of fertilizer applying. If we apply fertilizer with low quantity in the key period, we can get high-yield. It means that we can get high-yield with fertilizer saving. For example, when we applied fertilizer to corn only in the seedling period, organism fertilizer while transplanting the seedlings, and fertilizer in the cave trumpet period, the yield could retain high and much fertilizer was saved. Therefore, we can control nonpoint-source pollution by preventing much fertilizer reaching Yangtze River.Three-factor orthogonal quadratic regression design was adopted, two replications, in the field experiment. Small test plot, six-row plot, covered 24 square meters, and the length of the plot was 4m, width between the plots was 1m, fifteen small areas insides the replication were arranged with the machine. There were aisles, 0.6m wide, between test plots of the two replications, and no aisles between small test plots in order to be observed more clearly. Excess five protecting-corn plots were planted surrounding experiment areas.Data collecting and calculation (including regression analysis) was done on the basis of three-factor orthogonal quadratic regression design, and the model was established, and then computer network was adopted to search the optimum result. The ideal planting model was acquired for the purpose of popularizing in larger area.If research on high-yield culture mode of maize by control of nonpoint-source pollution through applying fertilizer accurately is done and popularized in larger area, 51,000 tons urea and 66,000 tons calcium superphosphmte will be prevented entering into rivers in the region of the Three Gorges. Then, the problem of excessive nourishment of water can be avoided.