Effect of minimum tillage and crop sequence on physical properties of irrigated soil in southern Alberta

Abstract

Adoption of conservation tillage practices has been much slower on irrigated land than on dryland in southern Alberta. This study investigates the effect of conventional tillage (CT) and minimum tillage (MT) on soil physical properties for two crop sequences on an irrigated Dark Brown Chernozemic clay loam from 1994 to 1998. For soft wheat and annual legumes, CT consisted of chisel plowing and double discing in the fall and light duty cultivation and harrow packing in spring. The MT treatment consisted of only light cultivation and harrow packing in spring. For sugar beets, CT consisted of moldboard plowing, double discing, light cultivation, harrow packing and ridging in fall and de-ridging in spring, while MT consisted of chisel plowing, harrow packing and ridging in the fall and de-ridging in the spring. Crop sequence 1 was spring wheat ( Triticum aestivum L.)–sugar beet ( Beta vulgaris L.)–spring wheat–annual legume, while sequence 2 was spring wheat–spring wheat–annual legume–sugar beet. Soil physical properties measured included bulk density (BD) and cone index (CI) after 1 and 5 years of treatment and soil aggregation and residue cover after 4 years of treatment. There were no significant differences between MT and CT for BD and CI. Use of MT resulted in a larger geometric mean diameter (GMD) of aggregates (6.52 mm) and a lower erodible fraction (EF) of 23.4% compared to a GMD of 3.81 mm and an EF of 31.5% (EF) for CT. Use of MT also resulted in better residue cover than CT, reducing susceptibility to wind erosion. Crop sequence is crucial to the successful implementation of MT systems. Since the two crop sequences tested resulted in similar soil physical conditions after 5 years, each could be successfully used with MT for irrigated cropping in southern Alberta.