RESIDUAL EFFECTS OF ALFALFA AND BROMEGRASS CROPPING ON YIELDS OF WHEAT GROWN FOR 15 SUBSEQUENT YEARS

Twelve crops of Triticum aestivum were grown over a 15-yr period after forage hay swards or a fallow-wheat rotation (control) on a fine-textured soil in N Alberta. Nitrogen fertilizer was not applied to the forage crops nor to the wheat. Yields of wheat following alfalfa Medicago sativa ranged from 66-114% greater than those following control for the first 8 crops. Yield differences started to decline thereafter, although the wheat yield after alfalfa was significantly higher than that after the control for the 10th crop in the 13th year after the sward breaking. Yields of wheat after an alfalfa and bromegrass Bromus inermis mixture were only slightly less than those after alfalfa alone, but those after bromegrass alone were much less than those following alfalfa. -from Author