Integrating legume cover crops or green manures into annual crop rotations has the potential to offer substantial benefits to Canadian prairie cropping systems including N, weed control, and improved soil structure. The price of N fertilizer is increasing and alternative N sources such as green manures may now be more practical for farmers to consider. In Manitoba, green manure systems can consistently enrich soils with at least 100 kg N/ha. However, the challenge of making green manures economically attractive is still an impediment.

Grazing the green manures may be one way around this economic impediment. Research has shown that green manures produce at least as much available N to the subsequent grain crops when they are grazed compared with the standard green manure practice (tilled and no plant material harvested). The green manures tested included pea/oat mixtures, hairy vetch, sweet clover, lentil, soybeans, oats alone, and a mixture (“cocktail”) of various plant species. Based on a green manure production of 5000 kg/ha, animal live weight gain is estimated at 175 kg/ha (Thiessen Martens and Entz, 2011). This translates into $315-481 ha-1 of income from the green manure year.

Project started: Fall 2011
Project Summary – Dr. Entz
Researcher: Dr. Martin Entz, U of Manitoba