有机质、全氮和可矿化氮在反映土壤供氮能力方面的意义

用 2 5个表层土壤样品和 6个土壤 3 6个不同层次的土壤样品研究了可矿化氮与有机质、全氮的关系。可矿化氮由通气培养法测定。研究结果表明 ,不论表层土壤或不同层次剖面土壤中的可矿化氮都与有机质、全氮高度正相关。但是由于可矿化氮与有机质、全氮有自相关存在 ,他们之间的相关有一定的不真实性。而且 ,土壤的可矿化氮并不与全氮或有机质成正比 ,可矿化氮与有机质或全氮的比值因土壤而不同 ,差别很大。特别重要的是 ,可矿化氮对有机质或全氮的比率几乎在一条直线上 ,它们之间的相关性明显高于可矿化氮与有机质或全氮的关系。这些结果显示 ,矿化氮的数量取决于有机质和全氮中的可矿化部分 ,而不是其总量。土壤剖面中累积的硝态氮数量低时 ,作物的吸氮量与可矿化氮的关系远较与有机质或全氮的关系密切 ,更证明了测定可矿化氮有其特定意义 ,有机质、全氮的测定并不能代替可矿化氮的测定。

SIGNIFICANCE OF SOIL ORGANIC MATTER, TOTAL N AND MINERALI ZABLE NITROGEN IN REFLECTING SOIL N SUPPLYING CAPACITY

Summary Twenty five surface soil samples taken from different sites and 36 soil samples from 6 soils, each consisting of 6 layers, were used to study the relations of the mineralizable N to the organic matter and total N.The mineralizable N was estimated by an aerobic incubation.The results showed that the mineralized N was very well correlated with the organic matter and total N for all the soils. However, the ratios of mineralized N to the organic matter or to the total N were remarkably different, and the mineralized N was more correlated with the ratios.These results strongly demonstrated that the amounts of the mineralized N were dependant on both the contents and the potentially mineralizable proportions of the total N and organic matter, and that the contents of the total N or organic matter were unable to provide the information on the proportion made available to plants.Field experiments were conducted using 15 soils containing low accumulated nitrate N in soil profile, and the results revealed that the mineralizable N had good correlation with either wheat yield or N uptake. However, the organic matter or total N was not so as the mineralizable N, though the total N had a high correlation coefficient with wheat yield in case without P addition. The result further confirmed that determination of mineralizable N had its significance, and could not be replaced by determination of organic matter or total N.