The Study Of Source Reduction And Recycle On Rice Runoff Nutrient

At present, the important of ecological reconstruction in Taihu Lake is control blue algae, and it is promote the industrial and agricultural mode of production in Taihu Lake change to ecological and clean. Generally control eutrophication of water body from two ways, the first is control the cause of eutrophication of water body and the second is water self-purification. One of the most reasons of leading to the algae blooming in Taihu Lake is agricultural runoff, so one of the key measures of control eutrophication of water body in Taihu Lake is control nitrogen and phosphorus content in rice water runoff, under water self-purification, the key is aquatic plants absorbing and recycling. The research was completed in Institute of Agricultural Sciences of the Taihu Lake District,Suzhou from 2007 to 2009. Researching the utilizing rates of nitrogen and phosphorus content in rice and the variation characteristics of the nitrogen and phosphorus content in rice water runoff through different cropping systems on rice,different rice varieties and different fertilization strategies as well as researching the effects of returning field of water hyacinth which is made different fertilizers. Not only does it provides the evidence for fertilization management for runoff of low nutrition rice ecosystem in Taihu Lake but also make it possible to use water hyacinth to reabsorb nitrogen and phosphorus in runoff water and fertilizer return to field, all this have important significance to coordination and optimization for rice ecosystem and production relations in Taihu Lake. The main achievements are as following:1.Through eco-economic evaluation for multiple cropping patterns of rice-vegetable for Taihu Lake rice ecosystem, we found different previous vegetables have different effects for nutrient accumulation,fertilizer use efficiency and yield of rice. When conventional and decrement fertilization in rice fields, compared with the previous crop type of wheat, the output of rice while planting potato in previous season has been significantly increased. Besides, planting vegetables in wheat seasons contributes to fertilizing the soil fertility. And compared with wheat, the contents of organic matter, total phosphorus and available potassium are significantly higher after planting potato. At the same time, it turns out that the economic yield, output value and benefit of cropping pattern of rice—vegetable are much higher than cropping pattern of rice—wheat.2. The effect of two different kinds of rice varieties under the same conditions of nitrogen and phosphorus, Hybrid Rice Changyou 1 plant height , leaf area, biomass, spike number and economic yield are superior to Conventional Japonica Rice Wuyunjing 7,Japonica Hybrid Rice Changyou 1 with 40% spike fertilizer and nitrogen fertilization treatment of which helps to improve the biomass and economic yield of rice population. Both nitrogen agronomic efficiency and nitrogen and phosphorus use efficiency of Japonica Hybrid Rice Changyou 1 are higher than Conventional Japonica Rice Wuyunjing 7 and 40% spike fertilizer higher than 20%, the result shows that the ability of fertilizer absorption of Changyou 1 is much greater than Wuyunjing 7. After fertilization, contents of ammonium nitrogen and total nitrogen in soil surface water increased rapidly while contents of nitrate nitrogen and total phosphorus did not change significantly. And the order of ammonium nitrogen concentration in soil surface water after fertilization is: Wuyunjing 7 with 20% spike fertilizer is higher than Changyou 1 which is higher than Wuyunjing 7 with 40% spike fertilizer which is higher than Changyou 1 with 40% spike fertilizer. In a word, it is necessary to reduce the use amount of spike nitrogen to reduce the risk of nitrogen loss. 3. The effect of organic fertilizer treatment of different forms of water hyacinth. The output of rice of organic fertilizer treatment of different forms of water hyacinth is lower than chemical fertilizer, but it is much higher than no fertilizer,and the order of increase rate is: filth, swamp, air dry matter, biogas slurry and worm cast. Among them, the plant height of filth and swamp is taller and the single area of leaf is lager. At the same time, the single stem weight of them is heavier while the spike number is much more than others.