Legume based pasture rejuvenation for greenhouse gas outcomes
Incorporating legumes into a grass based pasture system has multiple benefits. A grass/legume blend increases the dietary protein of foraging cattle over grass alone. Furthermore, symbiotic biological nitrogen fixation introduces additional nitrogen to the pasture system thereby potentially lessening the need for synthetic fertilizers. However, over time, pastures initially seeded with a blend of grasses and legumes will tend towards increasing grass dominance such that the presence and benefits of legumes diminishes. Reestablishing legumes on a mature pasture can restore these important functions. By improving ruminant diet and therefore feed conversion ratios as well as decreasing nitrogen fertilizer applications, pasture rejuvenation, through the introduction of legumes, is expected to lower the greenhouse gas cost of grazing livestock on a per output basis. However, disturbance of soils, which can be part of various rejuvenation techniques, can result in losses of soil carbon thereby offsetting potential at least some of the greenhouse gas benefits. Sod-seeding may be an effective strategy to establish legumes in a mature pasture thereby incurring benefits without heavily disrupting soils and incurring soil carbon loss. To test this, a multiyear experiment, including cattle, vegetation (specifically the incorporation of non-bloat legumes: cicer milkvetch and sainfoin), soils and microbiota, was established near Lanigan, SK to examine the impact of sod-seeded legume pasture rejuvenation on greenhouse gases.
Soils and Crops Workshop