中文摘要：

对陇中黄土高原至少50年传统耕作历史的农耕地和退耕20年的草地土壤理化性状进行了比较研究。结果表明，1）不同土地利用方式对土壤有机碳、全氮、速效磷、pH值和容重有显著影响。0～10cm土层土壤有机碳含量草地显著高于农田，全氮含量差异不显著，20～100cm土层有机碳和全氮农田高于草地（P〈0．05）；土壤全磷含量农田虽高于草地但无显著差异。土壤C／N除0～10cm土层外，农田高于草地。在整个土壤剖面上，草地土壤pH值显著高于农田（P〈0．05）；除10-20cm和底层土壤外，草地土壤容重也高于农田。2）草地土壤有机碳和全氮随土壤深度增加而降低，而农田土壤在0～30cm土层随土壤深度的增加而增加，在30cm土层以下与草地有相同趋势。草地土壤全磷含量各土层间没有显著差异，农田土壤全磷含量与土壤有机碳和全氮含量变化趋势一致；草地和农田土壤速效磷含量都呈减少趋势。土壤pH值随土壤深度的增加而增加。3）各样地土壤有机碳、全氮、全磷、速效磷与土壤容重和土壤pH值之间呈极显著负相关，土壤容重与土壤pH值呈极显著正相关，土壤有机碳、全氮、全磷和速效磷之间也呈极显著正相关关系。

英文摘要：

In this study we analyzed soil physical and chemical properties in croplands which were cultivated under traditional tillage for at least 50 years and grasslands which had been restored from cropping for 20 years in the Loess Plateau in Gansu Longzhong. 1） Different land uses resulted in significant differences in soil organic carbon （SOC）, total nitrogen, total phosphorous, available phosphorous, soil bulk density and soil pH. In surface soil （0-10 cm）, SOC contents were significantly higher in grasslands than those in croplands, while total nitrogen was not significantly different. In the soil layers from 20 to 100 cm, SOC and total nitrogen contents were significantly （P〈0.05） higher in croplands than those in grasslands. The soil total phosphorous was higher in croplands than that in grasslands but not significantly so. In the soil profile down to 100 cm, the C/N ratios in croplands were much higher than those in grasslands, except for the 0-10 cm layer. The soil pH in grasslands was significantly （P〈0.05） higher than that in croplands in each layer. The soil bulk densities in the grasslands were higher than in croplands, except for t decreased with soil depth in grasslands, but this was only the upper 30 cm soil layers, SOC increased with depth. T he 10-20 cm layer. 2） The SOC and total nitrogen found in the soil layers below 30 cm in croplands; In otal phosphorous did not show significant differences in different soil layers in grasslands while in croplands, the changes of total phosphorous showed the same trends as those of SOC and total nitrogen. The available phosphorous contents decreased with soil depth in both grasslands and croplands while the soil pH was the reverse. 3） In both grasslands and croplands, soil organic carbon, total nitrogen, total phosphorous and available phosphorous showed significant negative correlations with soil BD and soil pH. There were significant positive correlation between soil BD and soil pH. Significant positive correlations were also found betw