An agroclimatic risk assessment of Southern Manitoba and Southeastern Saskatchewan

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Ash, Guy H. B.,
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A quantitative spatial assessment of Southern Manitoba's and Southeastern Saskatchewan's agroclimatic resource base was undertaken to investigate agricultural risk and/or potentials. The research objectives were threefold in nature: l) to choose the appropriate climatic and agroclimatic events relevant to agriculture production on the Eastern Prairies, 2) to establish a climatic data base that would permit the highest spatial density to sufficiently analyze the agroclimatic resources and potentials of the regions, and to apply this knowledge in agricultural planning - sustainability, 3) to statistically analyze the data base in order to describe the agroclimatic risks and/or potentials as they apply to the various agroecological regions within the two provinces. This was accomplished through the establishment of a mean, 10%, and 25% statistical risk assessment. A number of thermal and moisture conditions were investigated using specially developed computer programs. The analysis of soil moisture conditions within each of the two provinces involved a soil moisture model, which simulated a number of physical processes: l) snowmelt and snowpack storage, 2) infiltration, and 3) evapotranspiration and phenological stage. These modelled processes were incorporated into a computer program and used to develop a number of agroclimatic parameters, e.g. available moisture status, which subsequently were used to mimic plant growth and development of a wheat, corn, and alfalfa crop on a daily and annual basis. The input for all thermal and moisture conditions was supplied by past records of daily data from climatological and synoptic stations within the study area. The derived thermal and moisture conditions focused on three essential agroclimatic parameters: l) the occurrence of spring and fall frosts and the subsequent lengths of the frost-free periods, 2) the accumulation of heat above a base threshold during a growing season, 3) the analysis of moisture conditions in the soil - plant - atmosphere continuum of a wheat, corn, and alfalfa crop. The probability analysis (mean, 10%, 25%) carried out on each of the agroclimatic parameters indicated that some general conclusions can be surmised about the suitability and production potential of the Eastern Prairies for agriculture. When considering moisture and precipitation limitations, the broad region in central Saskatchewan (i.e. Humboldt, Nokomis, Lumsden, and Cardrose) experienced the highest rates of plant moisture stress and the lowest levels of available soil moisture and growing season precipitation. The production potential of any crop is therefore limited within this region. On the other hand, the Red River Valley demonstrates some of the best soil moisture conditions and precipitation rates in the Eastern Prairies. This is coupled with some of the best soil type/texture conditions, highest accumulations of heat, and longest frost-free periods. This consequently indicates that the Red River Valley region is highly flexible for crop production. Severe thermal limitations are encountered within four general areas of the two provinces, i.e. Pelly -Prairie River, Wasagaming, Hodgson, and Sprague. Overall, both provinces are generally thermally suited for cereal and forage production but the production of grain corn is limited to specific regions of Southern Manitoba.