Nitrogen fixation and isotope composition of native and tame forage plants

Abstract

A plant mixture of alfalfa, purple prairie clover and 7 natives grass species: western wheatgrass, northern wheatgrass, awned wheatgrass, Canada wildrye, green needle grass, little bluestem and blue grama was established at the south farm (SPARC) in Saskatchewan in 2006. Legumes were included in forage stands to sustain pasture production. The fixation of atmospheric derived nitrogen for forage plants was estimated by the method natural abundance of 15N. This method showed that The N2 fixation activity of both alfalfa and purple prairie clover was very important in 2008. They fixed about 90 % of their nitrogen needs. Alfalfa was the good candidate to sustain the production of high quality of forage because it increased the yield of native grass stand by 33 % and increased herbage stand protein by 45 % but this method is failed to detect fixed N in grasses.