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A Landscape-Scale Study of Soil Quality in Three Prairie Farming Systems

Boehm, M. M., Anderson, D. W.
Soil Science Society of America journal 1997 v.61 no.4 pp. 1147-1159
prairie soils, soil, farming systems, fallow, soil heterogeneity, soil properties, physicochemical properties, soil biology, landscapes, frequency, Saskatchewan
The relationship between farming practices and the quality or function of agricultural soils is difficult to characterize because of the complexity of soils and spatial variability within the landscape. This study in Saskatchewan, Canada, tested the hypothesis that soil quality differed among farming systems that varied in fallow intensity (crop-fallow [fallow every second year], extended rotation [fallow every 3–5 yr], and continuous cropping [no fallow]) and that differences could be assessed using soil properties as indicators of soil quality. In 20 fields with coarse to fine loamy, glaciolacustrine soils (Typic Haploborolls), major landform elements were sampled. As years of continuous cropping and related fertilizer inputs increased, increases in organic C (by weight [C] 22%, by volume [C] 3%), aggregate size (24%) and stability (45%), microbial biomass (50%), resin-sorbed N (503%) and P (227%), and nitrification potential (≈25%), decreases in bulk density (8%) and infiltration time (19%), and greater solum thickness (26%) were measured. We postulate that the changes in soil properties indicate an improvement in soil quality under the continuous cropping system and that the observed changes were caused by more frequent additions of crop residues (organic C), especially near the soil surface, which resulted in lower bulk density, more microbial biomass, and greater soil aggregation. It seems that the annual inputs of crop residues in conjunction with nutrients, such as N and P, resulted in the formation of an active and labile soil organic matter, increased availability of soil N and P, and a comparatively large pool of microbial C.