Effects of Soil Bulk Density and Moisture Content on the Physico-Mechanical Properties of Paddy Soil in Plough Layer

For paddy-upland rotation areas in the middle and lower reaches of the Yangtze River, the paddy soil has undesired physico-mechanical properties of tillage during the dry season. The purpose of this study is to determine the effects of soil bulk density and moisture content on the physico-mechanical properties of paddy soil in the plough layer. The bulk density and moisture content were selected as experimental factors, and the cohesion, tangential adhesion, plasticity index, and soil swelling rate were chosen as experimental indices from physico-mechanical properties of paddy soil in the plough layer. The experimental factors were quantitatively analyzed to explore the change characteristics of the physico-mechanical properties of paddy soil in the plough layer. Conclusions were obtained that show that when the bulk density increased in the range of 1 to 1.6 g·cm⁻³, the cohesion, tangential adhesion, plasticity index, and swelling rate of paddy soil increased in different degrees. Between 15% and 35% moisture content, the cohesion increased first and then decreased with the increase of moisture content, while the peak cohesion value occurred at the moisture content of 20%. Moisture content was positively correlated with tangential adhesion and negatively correlated with soil swelling rate. This study provides a reference for the regulation of paddy soil tillability in the middle and lower reaches of the Yangtze River Basin.