Cover crop effects on infiltration, soil temperature, and soil moisture distribution in the Canadian Prairies

Excess root zone soil moisture resulting from annual precipitation in excess of crop water requirements negatively affects crop yields. A field study was conducted in the 2005 and 2006 seasons on sandy loam soils to investigate the influence of berseem clover (Trifolium alexandrium L.) cover crop in oats (Avena saliva L.) on soil temperature, infiltration, and soil moisture redistribution within the growing season and during the fall to spring seasons. A 4-year crop rotation experiment to investigate farming with fewer chemicals was used to grow oats in a no-till cultivation system with and without the cover crop. The total and unfrozen water contents were measured in the field using neutron moisture meter and time domain reflectometry, respectively, at 0.2-m intervals from the surface to 1.8-m deep, plus a 0.1-m measurement depth. The cover crop significantly reduced soil moisture during the growing season resulting in significantly lower biomass yields (6146 kg ha(-1) combined biomass for oats and berseem clover, vs. 7327 kg ha(-1) for oats alone). By mid August 2005, the cover crop treatment had 34.6% lower water content (0.17 vs. 0.26 m(3) m(-3)) within the 0.0- to 0.7-m root zone depth compared to the non-cover crop. During the fall, the soil profile in the cover crop treatment was 3 degrees C warmer, thus delaying soil freezing and leading to a shallower depth of the frozen soil layer (0.4 vs. 0.6 m) in March 2006. During the spring, the cover crop treatment warmed and thawed earlier enabling more snow melt infiltration and deep percolation. Areas experiencing excess soil moisture could use annual cover crops as a means for reducing excess soil moisture during the summer growing season and avoiding accumulation of soil moisture during the fall, winter and spring seasons.