Poor Growth of Alfalfa (Medicago sativa) on Some Alberta Soils¹

Alfalfa grows poorly on certain soils in central Alberta where it had previously grown well. All affected (“poor”) soils studied to date have light textured surface horizons. Plants are generally short, spindly, yellowish‐green, and poorly nodulated with patches of vigorous growth often scattered throughout the fields. Macro‐ and micro‐nutrients applied in the field have produced unsatisfactory responses. A number of greenhouse experiments have been conducted using soils collected from areas of good and poor alfalfa growth and from an area that has never grown this crop. Steaming increased yields for two “poor” soils, and “Vaparn” increased yields and nodulation to a much greater extent than did fertilizer for one of these. Aqueous extracts from some “poor” soils, depressed growth and nodulation appreciably. Liming and nutrient solution increased yields for all soils, but failed to promote nodulation or produce healthy plants in soil sampled from areas of very poor growth. These treatments eliminate nutrient deficiency or toxicity as the primary causes for the poor growth. It would appear that these “poor” soils contain an agent toxic to alfalfa that is probably of biological origin. Barley was not affected by the toxic agent.