模拟机械压实黑土持水特征与孔隙分布

Water Retention Characteristics and Pore Size Distribution of Black Soil under Simulated Mechanical Compaction

以东北典型黑土区耕种作物和耕作措施均一致的农田土壤为研究对象,用MT865履带式拖拉机对其进行不同次数的压实处理,绘制碾压剖面不同深度土层范围内水分特征曲线,分析模拟压实对农田黑土总孔隙度、持水能力及不同径级孔隙分配的影响规律。结果表明：随着压实次数的增加,土壤的总孔隙度降低,饱和持水能力相应减弱;但不同土层土壤的非饱和持水能力,并没有随着压实程度的变化表现出显著的规律;与未压实处理相比,不同次数的压实,可通过增加较小径级孔隙的体积比例保持其非饱和持水能力,并以少次压实（3次）的效果较为明显。农田黑土耕作区的土壤孔隙,主要由中孔隙和微孔隙（孔径〈30μm）组成,体积百分比均超过30%;其次为大孔隙（孔径〉100μm）,体积百分比为2.42%-7.89%;二者受模拟机械压实的影响较大。次大孔隙（孔径介于30-100μm）所占比例不足1%,受模拟机械压实的影响较小。

An experiment was conducted to study the effects of mechanical compaction on water retention characteristics , porosity and pore size distribution of black soil of Northeast China .MT865 caterpillar tractor was used as external load to roll through farmland soils by growing same crop , conducting same tillage measures and carrying out same working machine . Total soil porosity decreased with the increasing of the tractor pass times , the retention capacity of the water saturation was weaken .The unsaturated water holding capacity did not show a significant trend with changing compaction treatments .The pores volume of smaller diameter could increase when few （ three passes ） compaction treatments was executed and resulted to a higher unsaturated water holding capacity comparing to non-compaction treatment .The tilling area of black soil is mainly consisted of pores with diameter smaller than 30μm and those with their diameter larger than 100μm with volume percent of more than 30%and 2.42%-7.89%, respectively .This type of soil pores could be affected more intensively by the mechanical compaction than those pores with diameter between 30-100μm, which is composed of less than 1%of total porosity , and there was no significant change by soil compaction .