TILLAGE PRACTICES ON A NORTHERN CLAY SOIL: EFFECTS OF SOD BREAKING METHODS ON CROP PRODUCTION AND SOIL PHYSICAL PROPERTIES

Abstract

Crop production in northern regions is mainly affected by a short growing season, and can also be further limited on heavy-textured soils by cool, wet spring conditions. Selected sod breaking practices were carried out resulting in maximum differences with respect to sod burial and soil physical properties. Soil physical properties measured included bulk density, air-filled porosity, aggregate size distribution, surface roughness and soil temperature. The main effects of the different tillage systems were: (1) differences in soil structure in terms of density and air-filled porosity, and (2) differences in the degree of residue incorporation. Moldboard plowing resulted in more favorable aeration porosity and soil temperature in spring than chisel plowing or discing. Rotovating prior to either moldboard plowing or chisel plowing had only a minor effect on soil physical conditions. In general the more effective the tillage was in incorporating crop residue and thatch, the higher was the subsequent soil temperature during the first 5 wk of the growing season. The differences in crop production followed the same trend as did differences in soil structure. This effect persisted through the third cropping season. Increasing levels of fertilizer N increased barley yields in all tillage treatments but did not offset the effect of physical differences caused by the tillage implements. Key words: Northern soils, tillage, soil temperature, soil structure, fertilizer nitrogen, barley