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分析了北京市大兴区1980年以来耕地种植结构的变化规律,核算了不同种植制度下的投入产出效益,并研究其对土壤肥力的影响。结果表明:(1)大兴的耕地种植结构已经从粮食为主转变成瓜菜为主,而且受政策引导效果明显。(2)不同种植制度下耕地的投入差异悬殊,表现出两极分化的趋势。耕地投入的顺序为:蔬菜>西瓜-蔬菜>小麦-玉米>一茬大田作物(粮食或油料)。(3)若不计劳动力成本,不同种植制度的净收益排序同耕地投入排序是一致的。若计入劳动力成本,一茬大田由于省工,其净收益反而高于小麦-玉米轮作。(4)高投入的种植制度下土壤肥力水平相对较高,各项养分含量最高的是蔬菜地,而且不同种植制度下磷、钾含量的差异比氮含量的差异要显著。(5)不同种植制度下的土壤养分变化幅度差异显著。速效磷变化差异最明显,瓜菜种植的速效磷增幅远高于粮食作物。速效钾除了蔬菜地略有增加,其他都呈减少趋势,小麦-玉米轮作制度下的土壤有机质增幅最大。
The changing regularities of cultivated land structure in Daxing District, Beijing since 1980 were analyzed. Input-output benefits under different planting systems were calculated and their effects on soil fertility were studied. The results showed that: (1) The planting structure of cultivated land in Daxing has changed from grain-based to melon-based, and the effect of policy guidance has been obvious. (2) The difference of cultivated land inputs under different cropping systems shows great disparity and shows the trend of polarization. Cultivated land input order: vegetables> watermelon - vegetables> wheat - corn> Crops crop (grain or fuel). (3) If excluding labor costs, the net benefits of different cropping systems will be sorted in the same order as cultivated land inputs. If labor costs are included, the net income of a crop of Daejeon is higher than that of a wheat-corn crop because of labor-saving. (4) The soil fertility of high-input cultivation system was relatively high, and the highest contents of all nutrients were vegetable land, and the differences of phosphorus and potassium contents under different planting systems were more significant than those of nitrogen contents. (5) The difference of soil nutrient changes under different planting systems was significant. Available phosphorus changes the most obvious differences, vegetables planting quick-acting phosphorus increased much higher than food crops. Available potassium in addition to a slight increase in vegetables, the other showed a decreasing trend, wheat - corn rotation under the greatest increase in soil organic matter.