Study On Sustainable Nutrient Management In Wheat-Maize Double Cropping System

Wheat-maize double cropping system is the main cropping system in Huabei region, which has greatly potential productivity. Studying on the sustainable nutrient management in this cropping system can provide some scientific basis for reasonable fertilization, improving soil fertility and sustainable high yield in this region. Sustainability is an abstract conception and it can be evaluated by material index. In most of the research, farm productivity and soil fertility were always used to evaluate whether the soil is sustainable. Soil fertility greatly depends on management method of production besides some natural factors. The impacts of long-term method of fertilization for the changes of soil fertility and crop yield and the current nutrient management in wheat and maize production in piedmont plain of Hebei were studied systematically according to the results of 25-year long-term located experiment and the investigation of farm household. The main results were summarized as follows:1. Analysing the yield changes of long-term located experiment within twenty-five years could draw the conclusion: Single N can raise wheat yield obviously in the earlier years, but it can't raise wheat yield significantly in the long term. The yield of NP and NPK trements is higher than CK, and the impact increase gradually. But the difference between the two treatments of NP and NPK is very little. It illustrated that application of potassium can't increase yield significantly on the base of application of N and P fertilizer in the region where straw returned to soil. Combination of N, P fertilizer and organic manure can increase wheat yield significantly, and the fluctuation of yield decrease obviously. The longer the experiment time is, the more evident the trend is. It illustrated that the aftereffect is very long; the application of organic manure can diminish the disadvantage effect for wheat yield.Maize yield is less insensitive to fertilizer than wheat especially in the first twenty years of the experiments, and the difference among all chemical fertilizer treatments is inconspicuous. The difference increase gradually after 1999, and the declined trend of maize yield is NPK, NP, N, CK. Combination of chemical fertilizer and organic manure can increase the maize yield. The differences of yield among all the applying fertilizer treatments increase gradually after 1992. It illustrated that the contribution of fertilizer for maize yield increase gradually with the experiment time prolonging.2. Analysing the changes of surface layer soil nutrient of long-term locatedexperiment within the twenty-five years could draw the conclusion: the changes of soil organic matter, available nitrogen, available phosphorus and available potassium are stable under the treatments of single application of chemical fertilizer; Combination of chemical fertilizer and organic manure can increase the content of soil organic matter, available nitrogen and available phosphorus significantly, and it is more evident with the experiment time prolonging. Combination of chemical fertilizer and organic manure is not effective for soil available potassium, because returning straw to field offered lots of potassium, and the effect of organic manure is not evident in short term experiment. This study did not test the total potassium, so the contribution of organic manure for total potassium is waiting for further researchment.3. One-meter depth soil of long-term located experiment was divided into five layers. Analyzing the soil nutrient content could draw the conclusion: The content of soil organic matter, available nitrogen, available phosphorus and available potassium in 0~20cm layer are higher than other soil layers' in all treatments, and the content of soil nutrient declining along with the depth increasing. It illustrated that application of fertilizer can increase soil nutrient significantly, and the effect is less for the under layers. In all applied fertilizer treatments, the content of soil organic matter, total nitrogen, total phosphorus, available nitrogen, available phosphorus and available potassium in 0~20cm layer are extremely higher than CK, and it does not have obvious regulation in other layers.4. The total input nutrient of wheat and maize was about 398.6-513.7kg/hm2. and the average input was 464.1kg/hm2; Farm household attach importance to wheat when they applied fertilizer and the nutrient about 61%~72.4% of total into wheat. Most of the farmers apply higher rate of fertilizer but harvest less compared with the output from the recommended fertilizer of experiment; Most of the farm household could not choose the rate and time of fertilizer reasonablly on the base of their soil nutrient conditions and crop growth conditions. The single nitrogen fertilizer was the main type of nitrogen fertilizers, and the compound-fertilizer was the main phosphate fertilizer and the application potassium fertilizer was little. The main application method of fertilizer was spread and the main basis of choosing farm material was convenience and purchase nearby.5. Among the multitude factors which affect the action of farm household, the degree of farmer education is the inside factor. It can not pledge the soil sustainability essentially unless the farmer education were improved; State policy has the oriented function for the action of farm household, but the effect of relative benefit of farm production increase gradually for Chinese farm household which are being logos gradually and even determine the action of farm household. The field area and income degree have important effect for the action of farm household in the conditions of little difference in nature and society; prolonging the using years of soil can enhance the investment desire of farm household in the conditions of not changing other factors.