Tillage and fallow frequency effects on selected soil quality attributes in a coarse-textured Brown Chernozem

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Abstract
An 11-yr study was conducted on a coarse-textured Brown Chernozemic soil in the semiarid prairie of southwestern Saskatchewan. Soil was sampled after 3, 7 and 11 yr, and the results were used to assess the influence of fallow frequency and tillage on selected soil quality attributes [e.g., total soil organic C and N, microbial biomass C (MB-C) and microbial biomass N (MB-N), C mineralization (Cmin) and N mineralization (Nmin), 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 observed significant treatment effects on total organic C or N, effects on Cmin and Nmin were observed in 7 yr in the 0- to 7.5-cm depth and by 11 yr, MB and SRA also showed significant treatment effects in this depth. Generally, soil quality attributes were greater in no-tillage (NT) systems than in conventional mechanical tillage (CT) or minimum tillage (MT), and greater in continuous wheat (Triticum aestivum L.) (Cont W) than in fallow-wheat (F-W) systems. With time, the labile constituents tended to increase under the Cont W cropping, but to decrease when F-W was coupled with MT. After 11 yr there was a strong, direct association between the labile attributes (viz., Cmin, Nmin and MB-C) in the 0- to 7.5-cm depth and the mean annual straw produced (kg ha−1yr−1) in the four cropping systems tested. Of the soil quality attributes tested, Cmin and Nmin were the most sensitive indices to tillage and fallow frequency effects. Key words: Mineralizable C, mineralizable N, microbial biomass, specific respiratory activity, crop residues

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