砂姜黑土界限含水率及适耕性研究

Atterberg Limits and Tillability of Different Types of Lime Concretion Black Soil

对砂姜黑土区不同类型耕地土壤进行了实地调查采样,以区域内分布的其他类型土壤作为对照,研究了河南省砂姜黑土区不同类型土壤的界限含水率,探讨了界限含水率与土壤其他物理性质之间的关系。结果表明,对照土壤塑性指数低于15.00,相比之下不同类型砂姜黑土的塑性指数总体较高,普通砂姜黑土超过3/4的样点塑性指数大于15.00,可塑性较强。普通砂姜黑土和残余黑土层土壤平均缩限含水率最低,胀缩性最强,而漂白砂姜黑土缩限高于对照土壤。虽然土壤可塑性和胀缩性均与黏粒含量呈正相关,但是这些性质受土壤活性或黏土矿物类型的影响却不相同。不同黏土矿物对土壤塑性的贡献为高岭石>伊利石>蒙脱石,而对胀缩性的贡献正好相反,为蒙脱石>伊利石>高岭石。土壤的吸湿水含水率与土壤界限含水率的相关性优于黏粒含量。以土壤最大吸湿水含水率与土壤不同界限含水率的关系构建一元线性回归模型,模型的残差标准差小于2%,可以用来较准确地预测土壤界限含水率。总体来说,砂姜黑土塑性指数较高,虽然有较大的适合耕作的含水率范围,但同时萎蔫系数比较高,因而含有较大部分的无效水分。因此,砂姜黑土最适合耕作并且有利于播种后种子发芽及幼苗生长的含水率为接近且不大于塑限时的含水率。

Poor tillability and structural property are characteristics for lime concretion black soil. The determination of Atterberg limits is of great significance for preventing the degradation of cultivated land,improving cultivation quality,and reducing consumption of tillage energy. Different types of lime concretion black soil in the main allocation region of Henan province with other soil types in the same region as control were investigated and sampled. The Atterberg limits of different soil types were tested and their correlations with other soil physical properties were investigated. The results showed that the plasticity indexes of all samples of the control were not higher than 15. 00,while the overall plasticity indexes of lime concretion black soil were higher. The plasticity indexes of over 3/4 of the common lime concretion black soil were higher than 15. 00,which meant a strong plasticity. The topsoil of the common lime concretionblack soil and the residual black layer showed the lowest average shrinkage limit,with the strongest shrinkage capacity. The bleached lime concretion black soil showed higher shrinkage limit than the control. The correlation of soil activity and Atterberg limits showed that,although the plasticity and shrinkability had positive relationship with clay content,the activity which reflected the dominant clay mineral type of this fraction had different influences on these properties. The order in which plasticity increased with the clay mineral type was kaolinite,illite and smectite respectively,while it was reverse for shrinkability. The hygroscopic water content showed a better correlation with Atterberg limits than clay content.Linear regression models between maximum hygroscopic water content and Atterberg limits were constructed and the residual standard deviations of the models were less than 2%. So the Atterberg limits can be predicted accurately with maximum hygroscopic water content. Highly plastic and expansive soils have wider moisture range between plastic limit and shrinkage limit,and tillage is suitable between these limits.But concerning their low soil moisture availability,the demand of seed germination and cultivation,the optimal moisture condition for plowing is at the moisture content close but not higher than the plastic limit.