Harvest management and N-fertilization effects on protein yield, protein content and nitrogen use efficiency of smooth bromegrass, crested wheatgrass and meadow bromegrass

Abstract

There is a lack of information on the interaction of harvest management, grass species and N-fertilizer interaction on forage quality and nitrogen use efficiency of dryland grasses. In a 3-yr field trial, harvest management (2 cut, hay management vs. a 3–4 cut simulated pasture management system) and nitrogen fertilizer (0, 40, 80, 120, 160 kg N ha−1) were examined for their effects on protein yield (PY), protein content (PC), nitrogen use efficiency (NUE), nitrogen recovery (NR) and soil test nitrate-nitrogen (STN) under crested wheatgrass (Agropyron cristatum [L.] Gaertn.; CWG), meadow bromegrass (Bromus biebersteinii Roem & Schult.; MBR) and smooth bromegrass (Bromus inermis L.; SBR) swards. Generally, grasses managed under a two-cut hay system had lower (P < 0.05) PC than grasses managed under a 3–4 cut simulated pasture system (and occasionally higher NR and NUE) but harvest management did not consistently affect PY. There were few consistent differences between grass species for PY, PC, NUE and NR with relative ranking and significance changing between site-years. Generally, MBR responded to N-fertilizer in a similar manner to previously studied dryland grasses such as CWG or SBR. N-fertilization increased PY and PC but did not consistently affect NUE, NR and STN. Key words: Protein yield, protein, nitrogen recovery, nitrogen use efficiency, hay, pasture