Assessing the Impact of Grazing Annual Forage Cover Crops in an Integrated Crop-Livestock System

Background

Cover crops are known not only for their nutritious feed value for cattle but also their ability to improve certain aspects of soil health. This suggests that there are opportunities for synergies between livestock and crop producers to provide both animal feed and soil improvements. These synergies have yet to be quantified under Canadian conditions.

Objectives

To quantify the benefits associated with integrated crop-livestock systems; specifically to assess the impact of grazing a forage cover crop within an annual cropping rotation.

What you did

Researchers accessed the value of integrated livestock and crop systems. This trial took place at four different sites in SK and MB (two research farms and two producer operations). This project looked at the soil health, productivity, ecosystem services, and economics of adding cover crops into an annual cropping system.

They used 3 treatments:

• control (annual crop rotation of legume, cereal, oilseed, cereal)
• simple mixture (oats & barley)
• complex mixture (oats, barley, millet, peas, hairy vetch, forage radish, hybrid brassica, phacelia)

The trial ran for 4 years, rotating between the mixtures and a cereal. Cattle grazed the standing forage mixtures in late July through August (at three sites) or in the fall on regrowth after a summer silage cut (one site).

What you learned

When growing conditions were favorable, researchers found that the complex mixture (8 species) produced higher dry matter biomass than the simple (2 species) mixture. However, under very dry conditions, biomass production of both mixtures was low, resulting in low forage availability. Weed pressure was very high, as weed control options are limited for diverse crop mixtures. In regards to forage nutrition, fiber content (ADF and NDF) were similar between the simple and complex mixtures, and crude protein, calcium, copper, and iron were higher in the complex mixture compared to the simple mixture.

Soil characteristics changed with the cropping treatment, but not with the inclusion of grazing. The mixtures significantly increased the biological properties of the soil (molecular microbial biomass, bacterial and fungal abundance, and enzyme activity) compared to the annual crop rotation at the Swift Current site, but similar effects were observed with and without grazing. Grazing also had no significant effect on the soil chemical properties, but the complex mixture had higher ammonium, potassium, and lower pH than the simple mixture. The complex mixture had higher soil water infiltration and slightly greater aggregation compared to the simple mix and the annual crop rotation. These soil factors were not correlated with the production of the following crop, as the annual crop rotation had the highest forage barley biomass in 2020 compared to the mixtures, and in 2022 there was no significant difference between hard red spring wheat production, yield or quality based on any of the previous cropping treatments (annual crop, mixtures or grazing).

Researchers also performed economic analyses to better understand the willingness of producers and ranchers to undertake integrated crop-livestock arrangements. The economics of these arrangements is more complicated than it first appears, and even in situations where both parties would financially benefit from a partnership, a lack of trust or familiarity with potential partners may prevent the partnership from occurring in the first place.

What it means

While there are many suggested benefits to integrated crop-livestock systems, this research project didn’t capture specific agronomic evidence to support the inclusion of animals on annual cropping land. This may have been due to the dry growing conditions and the general reduction in productivity that was experienced during the research trial. Weed competition was particularly high in the diverse mixtures and presented a significant concern. However, there was evidence that diverse annual crop mixtures may significantly alter the biological, chemical, and physical properties of the soil compared to annual cropping systems. These differences, however, did not notably impact the productivity of an annual cash crop grown the year following the mixtures. As with all agriculture, crop success is still largely dependent on environmental conditions, and integrated crop-livestock systems did not appear to provide an advantage over traditional crop rotation systems under difficult growing conditions. Adoption of integrated crop-livestock practices that rely on partnership with other producers will require trust and existing relationships. In general, more evidence is needed on the Canadian prairies to support the claims of the overarching benefits of integrated crop-livestock systems.