The purpose of the project was to improve understanding of the value of diversified cropping for three regions of the Canadian Prairies with different climatic conditions. These included the Parkland region where canola dominates cropping systems, southern Manitoba where warmer season crops such as corn and soybean can be grown, and the semi-arid prairies where pulse crops such as lentil are widely grown. The research motivating problem was how intensive cropping of a crop can eventually lead to reduced yields and productivity due to increased disease or allelopathic effects of previous crop residues.

Relevance to Farmers and Need for Future Research: The study of crop sequencing in Manitoba determined the sequencing of crops had a significant effect on crop yield, the main one being that planting the same crop for more for two years, or more, will depress yield. There were yield benefits to rotating crops and using a more diverse crop rotation. The studies of canola-based systems in the Parkland and pulse-based systems in the semiarid Prairies showed a long-term benefit to more diverse cropping systems. In most crop production situations, a diversity in cropping was profitable. Short-term benefits might be gained from fewer break-years between crops where there are known root diseases, but this will impose higher future costs and lower returns because of increased disease pressures.

Growers need to consider their cropping choices in a long-term framework to maintain productivity and profitability over time. A first step would be to follow industry recommendations on frequency of growing a specific crop. A minimum of two years between canola crops to lessen clubroot yield depression and slow its spread, and for pulse crops six years between pulse crops when Aphanomyces euteiches is severe enough for observable plant damage. The choice between growing canola or a pulse crop will reflect the grower’s perceptions of their productive capacity and of information communicated through relative prices. In the Parkland region, hard red spring wheat and barley are two options, but there are other minor crops that could also fit in well in some areas, such as oats, flax, grain corn and soybean in Manitoba. Field peas would be an option in a canola-based system. In the semiarid Prairie region, durum wheat and hard red spring wheat are most common, but there are opportunities for barley, oats, flax, chickpeas, and canola in a pulse-based rotation.