Influence of tillage and cropping system on soil organic matter, structureand infiltration in a rolling landscape

The influence of tillage and cropping system on soil organic matter, struct ure and infiltration was studied in a rolling, glaciolacustrine landscape i n Saskatchewan with slopes ranging from 6 to 30%. A field that had been con tinuously cropped using zero tillage (ZTCC) for 11 yr was compared with con ventional tillage in a crop-summerfallow rotation (CTCF) on an adjacent fie ld. Soils in each field were sampled according to their position in the lan dscape. Soil organic C, aggregrate size and aggregate stability were signif icantly greater on the ZTCC plot than the CTCF. Infiltration rates averaged 74 and 52 mm h(-1) on the ZTCC and CTCF plots, respectively. Differences b etween treatments were most pronounced at the shoulder positions. Increased soil strength was measured on the CTCF plot at depths corresponding to the action of tillage implements (0.05 m and 0.15 m). On the CTCF plot, infilt ration rates correlated with initial moisture, aggregate stability and bulk density but on the ZTCC plot consistent correlations were only found betwe en infiltration and bulk density. When measured infiltration rates were com pared with expected storm intensities, the differences in infiltration rate s between treatments and their distribution in the landscape resulted in su bstantially more runoff from the CTCF plot than the ZTCC.