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，ｔ＿（０．０１）＝４．０３２）。在实践中，对不能直接用同位素标记或用同位素标记有很大困难的某些营养元素，可利用示踪技 样品的全氮、重氮由河北省农科院理化所测定，谨此致谢。术Ａ值来估计它们供给植物营养的能力。我们应用Ａ值法测定紫云英肥效的有效性，得出每１００ｋｇ鲜紫云英相当０．３９ｋｇ尿素的氮量，而尿素对当季作物的效果是紫云英的２．６２倍。２．３ 有机—无机肥混合施用氨素的去向大量试验证明，施用氮素化肥虽能供给作物养分，但对保持土壤肥力的作用有限。而施用有机肥料，除向作物提供养分外，还能改良土壤理化生物性状，培育地力。在有机—无机肥混合施用情况下，其氮素的去向如图１。从图１看出，有机、无机肥混施，尿素的单季利用率都低于单施尿素的处理，但残留率提高，损失率下降。单施无机肥比单施有机肥的氮的利用率高出１倍，但氮的损失也大，残留在土壤中的氮较少。有机、无机肥料混合施用，虽然肥料氮的利用率没有明显提高，也不会消耗较多的土壤氮，但却显著提高了水稻产量。表３表明，不论何种处理，水稻植株吸收的总氮量有７０—７５％是由土壤供给的，由肥料供给的氮只占２５—３０％。同时还可看出，如果不施氮肥，则水稻吸收的氮全部由土壤提供。施氮?
, T_ (0.01) = 4.032). In practice, trace elements can not be directly labeled with isotopes or have great difficulties with some of the nutrients available tracer samples of total nitrogen, diazotization determined by the Physical and Chemical Laboratory of Hebei Academy of Agricultural Sciences, would like to express my gratitude. A value to estimate their ability to supply plant nutrients. We use the A value method to determine the effectiveness of Astragalus fertilizer efficiency, obtained per 100kg of fresh astragalus quite 0.39kg urea nitrogen, while the effect of urea on the crop is 2.62 times Astragalus. 2.3 fate of organic-inorganic fertilizer application of ammonia A large number of experiments show that although the application of nitrogen fertilizer can supply crop nutrients, but to maintain soil fertility is limited. The use of organic fertilizers, in addition to providing nutrients to crops, but also to improve soil physical and chemical properties, cultivate fertility. In the case of organic-inorganic fertilizer mixed application, its nitrogen to the direction of Figure 1. As can be seen from Figure 1, the organic and inorganic fertilizer mixed application, the single-season urea utilization rate is lower than the single urea treatment, but the residual rate increased, the loss rate decreased. Single application of inorganic fertilizer than single application of organic nitrogen fertilizer utilization rate doubled, but the loss of nitrogen is also large, leaving less nitrogen in the soil. Organic and inorganic fertilizers mixed application, although fertilizer nitrogen utilization did not significantly improve, it will not consume more soil nitrogen, but significantly increased the yield of rice. Table 3 shows that regardless of the treatment, 70-75% of the total nitrogen absorbed by rice plants is supplied by the soil, and the nitrogen supplied by the fertilizer accounts for only 25-30%. At the same time, it can also be seen that if nitrogen is not applied, all the nitrogen absorbed by the rice is provided by the soil. Nitrogen application?