THE EFFECTS OF TILLAGE SYSTEMS AND CROP ROTATIONS ON SOIL-WATER CONSERVATION, SEEDLING ESTABLISHMENT AND CROP YIELD

The long-term productivity of soils in Western Canada can be maintained, even enhanced, providing changes in production practices occur to reverse the current trends of soil degradation. A study was initiated in 1986 to investigate the interactions of tillage systems and crop rotations on soil water conservation, seedling establishment and crop yields. The three tillage systems used were zero (ZT), minimum (one preseeding tillage operation) (MT) and conventional tillage (fall and spring preseeding tillage operations) (CT). Three 4-yr crop rotations were superimposed on the three tillage systems: fallow-spring wheat-spring wheat-winter wheat, spring wheat-spring wheat-flax-winter wheat and spring wheat-flax-winter wheat-field pea. The amount of water conserved during the fallow period was not significantly affected by tillage systems. Under stubble cropping, ZT and MT increased soil water in the 0- to 60-cm soil layer by 9% and in the 0- to 120-cm soil layer by 6% over CT. When spring soil moisture under stubble in the 0- to 120-cm soil layer was expressed as a percentage of a saturated soil profile, ZT and MT averaged 87% and CT, 82%. Seedling populations in spring wheat and field pea were not affected by tillage systems while flax seedling populations were 8% less under ZT and MT than CT. The rate of plant establishment for spring wheat was not affected by tillage systems. Yields of spring wheat, flax and field pea under ZT and MT were increased by 21, 23 and 9% over CT, respectively. Crop production practices that minimize soil degradation by maximizing the benefits of surface residues and standing stubble can successfully be adopted.