Establishment, Forage Production and Drought Resistance of Native Perennial Legumes of the Canadian Prairies

Abstract

Forage production of perennial legume-grass mixtures and their effect on soil fertility are expected to be greatly influenced by growth environment, but many questions remain for native legume variability and performance in mixtures in semi-arid environments for forage production. Field research on four native legume species (Astragalus flexuosus, Dalea purpurea, Hedysarum boreale and Vicia americana) evaluated their establishment and early vs. late season forage production in monoculture, and in mixtures with Bromus riparius, in the Brown and Dark Brown soil zones of the Canadian Prairies near Swift Current and Saskatoon, SK. The experimental design was a Randomized Complete Block Design with four replicates with treatments being species mixtures/monocultures and harvest dates (July and August). The native legume-grass mixtures performed differently at the sites, with better overall establishment at Saskatoon but greater percentages of legumes present in mixtures at Swift Current. The mixtures had similar forage quality as monoculture B. riparius, with legumes contributing 10% or less of the forage dry matter yield at both sites. Soil nitrogen was not greater in legume-grass mixtures compared to monocultures B. riparius. Based on this study, native legumes would need to make up a larger proportion of forage dry matter yield to change the nutritional value and soil nutrient levels of mixture plots. In a seeding rate evaluation, the four legume species were planted in monoculture at three seeding rates (300, 200 and 100 PLS m-1) and tested for forage dry matter yield near Swift Current, SK one year after seeding. While increasing seeding rates up to 300 PLS m-1 in the Brown soil zone corresponded to increasing seedling density and foliar cover, dry matter yield was not affected by seeding rate and there was no correlation between dry matter yield and native legume seed size (R2=0.0895). In a greenhouse drought study, four watering regimes (100, 75, 50, 25% field water holding capacity) were applied to seedling monoculture legume and legume-grass mixtures with B. riparius. A. flexuosus was the only native legume that showed differences in above and belowground biomass by watering treatment, with greater aboveground biomass at the moderate watering levels (50% and 75%), and greater belowground biomass at the 50% watering level. Of the four legume species, A. flexuosus showed the greatest establishment and produced the greatest dry matter yield in monoculture at Saskatoon (2934 kg ha-1, 3107 kg ha-1) and Swift Current (3938 kg ha-1, 3920 kg ha-1) in July 2018 and August 2018, respectively.