The Effects of Constructing Fertile Cultivated Layer in Black Soil on Soil Physical Properties.

Black soil is one important arable soil in China with high soil productivity, but undergoing soil physical properties deterioration and soil fertility decline due to the present of plough layer and the decrease of soil organic carbon resulting from mechanical compaction and unreasonable tillage since black soil was cultivated. The technology of constructing fertile cultivated layer in black soil was proposed, was defined as organic material was incorporated into 0-35 cm soil layer by plowing, which constructs a fertile and thick plow layer with the aims of supplying enough water and nutrient for plant growing. The effect of different practices of constructing fertile cultivated layer including subsoil (ST), organic manure incorporation (ST+M) and straw incorporation (ST+S), on soil physical properties in order to reveal the mechanism enhancing soil water pool and soil nutrient pool by constructing fertile cultivated layer based on a field experiment. Comparison with CK treatment, soil bulk density in ST, ST+M and ST+S treatments was decreased by 6.2%-11.2% for 0-20 cm soil layer, 10.7%-13.7% for 20-35 cm soil layer, soil porosity in ST, ST+M and ST+S treatments was increased by 7.8%-10.35% for 0-20 cm soil layer and 13.56%-18.72% for 20-35 cm soil layer, indicating that destroyed plough layer and organic material incorporation could effective improve soil structure in 20- 35 cm soil layer. Field water capacity and saturation water capacity under ST, ST+M and ST+S treatments were both increased by 5.9%-14.7% and 5.4%-17.6%，respectively, due to the improvement in the distribution and structure of soil porosity. Subsoil, the incorporation of organic manure and straw increased saturation conductivity rate (increased by 9.45%-15.49% compared with CK), and infiltration rate. Therefore, constructing fertile cultivated layer could improve soil structure, increase water infiltration. The effect of organic manure incorporation was better than straw incorporation in subsoil.