The Economics of Including Annual Legumes in Crop Rotations in the Dark Brown Soil Zone of Saskatchewan
Edgar, Peter George
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An economic model was constructed to estimate profitability and relative productivity of grain-fallow and grain-legume crop rotations in one-year, six-year, 30-year and 100-year time frames in the Dark Brown soil zone of western Canada. Five three-year crop rotations were employed in the model, namely continuous wheat (WWW), wheat-wheat-fallow (WWF), wheat-wheat-legume green manure (WWGM), wheat-wheat-grain legume (WWL), and wheat-wheat-flex (WWFLEX), a variable legume grain /green manure rotation based on soil moisture levels. Individual production functions were developed for each rotation using agronomic research data from the Scott Agriculture Research Farm and the Agri-Food Canada Research Centre in Swift Current, Saskatchewan. By employing marginal physical product and total physical product equations combined with profit maximisation, a method was developed to show short-and long-term changes in relative productivity and profitability resulting from adoption of the individual rotations. The study found that legume-based rotations yield significant long-term economic and productivity gains over WWW and WWF cropping systems. However,a minimum of two cropping cycles (six years) was required to achieve these gains; there was little economic benefit to green manure rotations in the short-term.