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

The influence of tillage and cropping system on soil organic matter, structure and infiltration was studied in a rolling, glaciolacustrine landscape in Saskatchewan with slopes ranging from 6 to 30%. A field that had been continuously cropped using zero tillage (ZTCC) for 11 yr was compared with conventional tillage in a crop–summerfallow rotation (CTCF) on an adjacent field. Soils in each field were sampled according to their position in the landscape. Soil organic C, aggregrate size and aggregate stability were significantly 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 between 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, infiltration rates correlated with initial moisture, aggregate stability and bulk density but on the ZTCC plot consistent correlations were only found between infiltration and bulk density. When measured infiltration rates were compared with expected storm intensities, the differences in infiltration rates between treatments and their distribution in the landscape resulted in substantially more runoff from the CTCF plot than the ZTCC. Key words: Zero tillage, cropping frequency, infiltration rate, aggregation, organic carbon, landscape