Effect of swath grazing an annual polycrop mixture of brassica, legume, and grass species versus barley monocrop on forage yield and quality, soil organic matter, cattle grazing capacity, and crop system economics in east-central Saskatchewan

Abstract

The objective was to determine the suitability of polycrop mixtures compared to barley for swath grazing. The trial was conducted over two years at the Livestock and Forage Centre of Excellence Termuende Research Ranch near Lanigan, Saskatchewan. A 13.2 ha site was divided into two fields (with three replicate paddocks each) that were seeded in 2017 and 2018 to one of two treatments (systems): annual polycrop mixture of grass, legume, and Brassica species, or barley monoculture. Each grazing season, dry pregnant Angus cows were randomly allocated to a paddock. The objective was to evaluate the system effect on forage quality and yield, soil organic carbon and nitrogen, cow performance, and system economics. Forage, cattle and economic data were analyzed using PROC MIXED while soil data was analyzed as an ANOVA using PROC GLIMMIX of SAS. Compared to the barley, gains were observed in total organic carbon and nitrogen mass (0-20 cm depth) in the polycrop in upslope positions (P<0.05), despite higher above-ground biomass yield of the barley (P<0.05). Higher levels of sulfur and nitrates (P<0.05) in the polycrop biomass compared to the barley were observed. In year one, forage dry matter intake and utilization were lower, cost of crop production and cost cow-1 day-1 were higher, and no differences were observed in body condition or weight of cattle in the polycrop compared to barley. With proper management, there is potential for the use of annual polycrop mixtures for grazing in western Canada, with opportunity for gains in soil organic matter.