SUBSOILING TO IMPROVE SNOWMELT INFILTRATION AND ALFALFA YIELDS WITHINTALL WHEATGRASS WINDBREAKS

An Orthic Brown silt-loam Chernozemic soil near Swift Current, Saskatc hewan, was subsoiled with a Paraplow to a depth of 350 mm prior to see ding alfalfa. Snowmelt infiltration through silty soils often improves following subsoiling, especially if the technique is coupled with pra ctices to augment the snowcover. The subsoiling treatment followed a s plit-plot design superimposed on a randomized-block experiment with th ree alfalfa varieties (Rangelander, Beaver, and Angus) grown in an ope n field and within a grass windbreak system. Double rows of tall wheat grass (Thinopyrum ponticum), averaging 1.2 m in height and spaced on 1 5.2-m centres, formed vegetative windbreaks designed to enhance snowco vers and moderate growing-season evapotranspiration. Snowcover water e quivalents, spring soil water contents, and forage production from all the alfalfa varieties were greater in the windbreak shelter than in t he open field. Hay-crop yields and soil water reserves were not signif icantly improved by subsoiling during any of the five production years following treatment either within or outside the wind shelter. Theref ore, Paraplow subsoiling to improve infiltration is not recommended fo r dryland alfalfa grown on Orthic Brown Chernozemic soils of silt-loam texture in southern Saskatchewan.