THE EFFECTS OF TILLAGE SYSTEMS AND CROP SEQUENCES ON SOIL BULK-DENSITY AND PENETRATION RESISTANCE ON A CLAY SOIL IN SOUTHERN SASKATCHEWAN

Concern has been expressed that reduced tillage systems may lead to ex cess soil compaction, negatively impacting on crop growth. The objecti ves of this study were to determine the effects of tillage systems zer o (ZT), minimum (MT) and conventional tillage (CT) and crop rotations on soil bulk density and penetration resistance after 4 yr on an India n Head heavy clay soil, in southeastern Saskatchewan. Moisture content was similar among tillage systems, except for slight differences in t he lower soil depths with crop rotation. Penetration resistance and bu lk density of a heavy clay soil were increased in the surface 10 cm of the soil by ZT as compared to CT management. However, in the deeper s oil zones, tillage system did not consistently influence either bulk d ensity or penetration resistance. Inclusion of peas in the crop rotati on had a moderating effect on bulk density and penetration resistance, while inclusion of flax in a continuous rotation increased bulk densi ty and penetration resistance in the surface soil profile. At the 30- to 45-cm depth, ZT had a lower bulk density than CT or MT in the rotat ion which included fallow, possibly because the tillage operations ass ociated with the cultivated fallow led to compaction in the deeper soi l zone. Penetration resistance was great enough in the deeper soil zon e in all tillage systems to restrict rooting, but difference due to ti llage treatment or cropping rotation was not sufficient to markedly in fluence crop production.