Soil quality - Effect of tillage and fallow frequency. Soil organic matter quality as influenced by tillage and fallow frequency in a silt loam in southwestern Saskatchewan

Characterization of organic matter is valuable for identifying the overall quality of soils. Management will influence soil quality. The rate at which quality attributes change may depend upon soil texture and environmental conditions. We assessed the effects of tillage (no-tillage (NT) vs conventional mechanical tillage (CT)) and fallow frequency (continuous wheat (Triticum aestivum L.) (Cont W) vs fallow-wheat (F-W)) on selected soil quality attributes for a silt loam in semiarid southwestern Saskatchewan. Measurements were made in the 0-7.5 and 7.5-15 cm depths after 4, 8 and 12 y of study. After 4 and 8 y, only C mineralization (C-min) and N mineralization (N-min) showed significant treatment effects, but after 12 y specific respiratory activity (SRA) was also significant (P < 0.05). Total organic C and N and microbial biomass (MB) were not affected significantly by treatments (P < 0.05) even after 12 y. Cropping more frequently resulted in higher C-min, N-min and SRA, likely associated with higher crop residue production (e.g., correlation of C-min and N-min with mean annual straw production was 0.95, significant at P = 0.05). Tillage did not influence straw production nor any of the soil quality attributes assessed. The labile attributes were more sensitive than total organic C and N to fallow frequency, but they were generally less sensitive to method of tillage management. (C) 1998 Elsevier Science Ltd. All rights reserved.