Effect of Conservation Tillage on the Physical and Mechanical Properties of Silty-Clay Loam Soil

Effect of different tillage methods on the physical and mechanical properties of silty-clay loam soil was evaluated in corn-wheat system during 2011 in Fars Province, Iran. Field trial was conducted in the split plot design with two factors (tillage methods and soil depth) and six replications for soil bulk density and penetration resistance. Main plots were tillage methods including conventional tillage, reduced tillage, and zero tillage. Soil depth of 0-10, 10-20, and 20-30 cm were considered as sub plots. A randomized complete block design with three treatments and six replications was used for the soil coefficients of friction, adhesion, and cohesion. Soil bulk density, soil penetration resistance, coefficients of soil internal and external friction, adhesion, and cohesion were measured. Results showed that tillage methods had significant effect on the soil bulk density so that the conventional and reduced tillage methods had the lowest soil bulk density, and zero tillage method had the highest. Soil bulk density was also affected by soil depth in such a way that bulk density increased when soil depth increased from 0 to 20 cm, and then decreased by increasing soil depth from 20 to 30 cm. The maximum soil penetration resistance was recorded from the zero tillage, and the conventional tillage had the minimum soil penetration resistance. Soil penetration resistance increased with increasing soil depth from 0 to 30 cm. Results also indicated that zero tillage significantly decreased the coefficient of soil internal friction; whereas, the coefficient of soil external friction was not affected by tillage methods.