Synchronizing Nitrogen Application With Uptake Using Urease and Nitrification Inhibitors to Maximize Nitrogen Use in Forage Seed Stands in Northeastern Saskatchewan.

Managing nitrogen inputs in forage seed production systems continues to be a significant challenge for forage seed producers. In western Canada urea is commonly used to meet nitrogen requirements in perennial forage seed stands. The nitrogen use efficiency (NUE) of surface broadcast urea in established forage stands typically is low due to lack of incorporation. Lower NUE has both environmental and economic implications due to increased rates of ammonia volatilization and denitrification losses of nitrous oxide, and consequent yield reductions. Urease and nitrification inhibitors applied both alone and in combination have shown promise in reducing greenhouse gas emissions and producing increases in dry matter production. However, little data exists on the use of these inhibitors in forage seed production systems. The objective of this study was to evaluate the impact of using urease and nitrification inhibitors on seed yield in a Saskatchewan perennial forage seed production system.

A commercial urease inhibitor “Agrotain®” nitrification inhibitor “Alzon®” and a combination urease and nitrification inhibitor “Super U ®” were evaluated alongside urea in four established forage seed production sites in northeastern Saskatchewan. Timothy (Pheleum pretense L.) or hybrid bromegrass (Bromus spp. L.) received 92 kg N ha ^-1 as urea (with and without inhibitors) during the autumn of 2012 or spring of 2013. Plant biomass and seed yield will be monitored during the 2013 growing season to determine if the use of urease and nitrification inhibitors, either alone or in combination provide an economically sound and agronomically practical approach to nitrogen management in perennial forage seed stands.