旱地土壤氮素、有机质状况及与作物吸氮量的关系

在具有典型半干旱气候特征的陕西永寿选取6种不同肥力水平的田块，分层采集0～100cm土样，测定各土层可矿化氮、全氮及有机质含量，研究其与作物吸氮量之间的关系，结果表明，各土层可矿化氮、全氮及有机质之间存在着良好的相关性，可矿化氮与作物吸氮量之间的相关程度高于与全氮、有机质间的相关性，可矿化氮加上土壤起始矿质氮后，相关系数更高，0～45cm土层的可矿化氮、全氮、有机质与作物吸氮量的相关性高于45cm以下的土层，且以30～45cm土层的为最好；以土壤全氮或有机质作为评价土壤供氮能力的指标，效果不如可矿化氮。

The relationship between soil N, organic matter and N uptaken by crops on dryland

Six arable soils with different fertility in Yongshou county, Shaanx Province with typical semiarid-climate characters were chosen. Soils were sampled at different depth within 0-100 cm before sowing. The content of mineralizable nitrogen (MAN), total nitrogen (TN) and organic matter (OM) at different depth of soils were analysed to study the relationships between these three indices and crop uptake of nitrogen (CUN). The results showed that there were good correlations among MAN, TN and OM in different soil layers. The correlation between MAN and CUN was higher than that between MAN and TN, as well as MAN and OM. The correlation coefficient between the sum of MAN plus initial mineral nitrogen in soils and CUN was higher than that between MAN and CUN. MAN, TN and OM had higher correlation to CUN at the depth of 0-45 cm than that at the depth below 45 cm, and the correlation was the highest at the depth of 30-45 cm. As an index to evaluate soil nitrogen availability, MAN was better than TN or OM (or modified value).