TILLAGE AND FALLOW FREQUENCY-EFFECTS ON SELECTED SOIL QUALITY ATTRIBUTES IN A COARSE-TEXTURED BROWN CHERNOZEM

An 11-yr study was conducted on a coarse-textured Brown Chernozemic so il in the semiarid prairie of southwestern Saskatchewan. Soil was samp led after 3, 7 and 11 yr, and the results were used to assess the infl uence of fallow frequency and tillage on selected soil quality attribu tes [e.g., total soil organic C and N, microbial biomass C (MB-C) and microbial biomass N (MB-N), C mineralization (C-min) and N mineralizat ion (N-min), and specific respiratory activity (SRA)] in the 0- to 7.5 -cm and 7.5- to 15-cm depths. Although it took 11 yr before we observe d significant treatment effects on total organic C or N, effects on C- min and N-min were observed in 7 yr in the 0- to 7.5-cm depth and by 1 1 yr, MB and SRA also showed significant treatment effects in this dep th, Generally, soil quality attributes were greater in no-tillage (NT) systems than in conventional mechanical tillage (CT) or minimum tilla ge (MT), and greater in continuous wheat (Triticum aestivum L.) (Cont W) than in fallow-wheat (F-W) systems. With time, the labile constitue nts tended to increase under the Cent W cropping, but to decrease when F-W was coupled with MT. After 11 yr there was a strong, direct assoc iation between the labile attributes (viz., C-min, N-min and MB-C) in the 0- to 7.5-cm depth and the mean annual straw produced (kg ha(-1)yr (-1)) in the four cropping systems tested. Of the soil quality attribu tes tested, C-min and N-min were the most sensitive indices to tillage and fallow frequency effects.