University of Manitoba: Natural Systems Agriculture: Organic Crops Field Laboratory
University of Manitoba Faculty of Agricultural and Food Sciences Department of Plant Science

Grazed Green Manures:
Phase 2 - The Next Crop


Wheat following a grazed (right) and ungrazed (left) pea/oat green manure, July 2010. There was no significant difference in wheat yield.

Grazing green manure crops has been suggested as a possible approach to gaining some income from green manure crops while maintaining most of the N benefit to the following crop. Grazing livestock is known to excrete about 80% of the nutrients they ingest; however, little is known about the effects of grazing green manures on nutrient cycling, the agronomic performance of the following crops or the economics of such systems.

Study Objectives

The objectives of this study are:

  • to evaluate the potential of various green manure crops for grazing (Phase 1)
  • to evaluate the effect of grazing green manures on soil nutrient dynamics (Phases 1 and 2)
  • to evaluate the effect of grazing green manures on the yield of the following crop (Phase 2)

Experiment Description

Field trials were established in 2009 at Carman, Manitoba and Oxbow, Saskatchewan. Green manures tested in the Carman experiment were oat (non-legume control), pea/oat mix, black lentil (cv. Indianhead), hairy hetch, soybean, and cowpea. At Oxbow, the green manure crop was peas. Each plot was later split into grazed and ungrazed treatments. Read more about Phase 1 of the experiment in Grazed Green Manures.

In 2010, spring wheat was grown on all plots in both Carman and Oxbow to evaluate the effect of grazing on the nitrogen (N) uptake and yield of the following crop. Data collected from the Carman trial included crop establishment, weed ratings, lodging ratings, crop biomass and N content, and grain yield and N content. Soil samples were collected from selected treatments in spring and after wheat harvest. At Oxbow, wheat yield and N content were measured.

Results: Carman

Wheat performed very well at Carman in all treatments, with yields ranging from 44 to 54 bu/ac (see Figure 1 below). While wheat yield was somewhat lower following the oat green manure than the legume green manures, this difference was not statistically significant. Grazing vs. not grazing the green manure crop did not have a significant effect on wheat yield.

Figure 1. Grain yield of wheat at Carman in 2010 as influenced by previous green manure crop and grazing vs. not grazing in 2009.



Analysis on other parameters such as grain protein and total N uptake by the wheat crop will follow at a later date.

Results: Oxbow

Wheat yield at Oxbow was 34 bu/ac in the grazed treatment and 39 bu/ac in the ungrazed treatment. However, this difference was not statistically significant.

Conclusions and Recommendations

  • According to preliminary results, grazing a green manure crop rather than working it into the soil did not affect the performance of wheat in the following year.
  • This experiment is being repeated in 2010-2011.

Funding for this project has been provided by:

  • Agriculture and Agri-Food Canada through the Canadian Agricultural Adaptation Program (CAAP). In Manitoba, this program is delivered by the Manitoba Rural Adaptation Council.
  • The Canadian Wheat Board, through the Organic Sector Market Development Initiative.


Copyright and Liability

This page created January 2011.