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3107. Dormaar, J.F. and C.W. Lindwall. 1989. Chemical differences in dark brown chernozemic Ap horizons under various conservation tillage systems.. Can. J. Soil Sci. 69:481-488.
Soil properties were investigated in two long-term studies: a 19 yr study of till vs. no-till in wheat fallow, and a 9 yr study of till vs. no-till with 3 rotations, including continuous cropping. No-till had the predominant influence on improving various soil physical and microbial properties. There was little difference in continuous cropping versus wheat-fallow, with tillage. The study compared soil from the entire plow depth, and concluded that 19 yr was long enough for the entire Ap horizon to benefit from no-till. No-till in both studies led to 40% of the dry aggregates being >0.84 mm. Dehydrogenase and phosphatase activities were twice as high under no-till as under cultivatiion. No-till also led to the largest monosaccharide accumulation in the soil.
10576. Janzen, H.H. and G.D. Radder. 1989. Nitrogen mineralization in a green manure amended soil as influenced by cropping history and subsequent crop.. Plant Soil 120:125-131.
In a greenhouse study, surface soil from long-term experimental spring wheat rotations was amended with 15N labelled legume green manure and subsequently cropped (canola and spring wheat) or incubated. N mineralization from both the indigenous soil N and from green manure was suppressed in cropped soil. Net N mineralization in the uncropped and cropped treatments averaged 73 and 43 mg/kg, respectively. This difference was attributed in part to enhanced biological immobilization in the rhizosphere. These data suggest that short-term N mineralization is favored by fallowing soil after green manure application whereas N retention in organic matter is favored by immediate cropping.