SUMMER FALLOW SUBSTITUTES FOR WESTERN MANITOBA

Abstract

Two experiments, each consisting of six 3-yr crop rotations were conducted in Manitoba from 1965 to 1970, one on Assiniboine clay loam soil and the other on Miniota sandy loam soil. Each crop rotation included 2 yr of wheat (Triticum aestivum L.), after summer fallow, biennial yellow sweet clover (Melilotus officinalis (L.) Lam.), potatoes (Solanum tuberosum L.), corn, (Zea mays L.), oat hay (Avena sativa L.) or flax (Linum usitatissimum L.). On the clay loam soil, yields of wheat were not significantly higher after summer fallow than after sweet clover, and on the sandy loam soil no higher than after sweet clover, potatoes, corn or oat hay. On both soils, protein content of the wheat grain was highest after summer fallow and sweet clover, which can be related to the higher nitrate content of the soils. Summer-fallowing did not increase fall moisture and nutrient reserves significantly above the levels reached after some of the summer fallow substitutes and did not control weeds any better than potatoes or oats. Potatoes, sweet clover and oat hay on clay loam soil, and potatoes, corn and oat hay on the sandy loam soil yielded well and thus were profitable summer fallow substitutes. Consequently, summer-fallowing as a cultural practice should be minimized in western Manitoba and probably in all of the Black soil zone of the Canadian prairies.