Livestock Use as a Non-Thermal Residue Management Practice in Kentucky Bluegrass Seed Production Systems

Kentucky bluegrass (Poa pratensis L.) postharvest residue has historically been burned to maintain stand productivity and profitability. Recent regulations were imposed that prohibit or restrict field burning since it negatively impacts air quality. Stand life is reduced from approximately 8 yr in a burn system to 3 yr in current nonburn systems, resulting in increased production costs and potential for soil erosion. Postharvest grazing might remove as much residue as burning, and maintain stand life longer than the current nonthermal practice of raking, baling, and mowing postharvest residue. This study determined treatment affect on seed production, cattle (Bos taurus) stocking density required to remove as much residue as burning, supplement requirements for cattle grazing Kentucky bluegrass residue, and value of Kentucky bluegrass residue utilized by cattle in bale + graze (BG) and graze-only (G) residue management treatments. Graze treatments yielded comparable to burning. The stocking density required to remove 80% of the residue in 30 d by G ranged from 17 to 23 animal units (AU) ha^-1 and BG ranged from 9 to 14 AU ha^-1. Nutritive value of Kentucky bluegrass residue ranged from 35 to 52 g kg^-1 crude protein (CP), 390 to 438 g kg^-1 acid detergent fiber (ADF), 716 to 763 g kg^-1 neutral detergent fiber (NDF), and 388 to 473 g kg^-1 48h in vitro true digestibility (IVTD). Daily requirement needed to be provided by supplement was less when fall plant regrowth was increased, and in G since dry matter (DM) intake tended to be greater in G than BG. The calculated value of baled Kentucky bluegrass residue on a DM basis averaged $33.27 Mg^-1. The calculated value of grazed Kentucky bluegrass residue on a DM basis ranged from $38 to $74 ha^-1 in BG, and $133 to $240 ha^-1 in G. Overall, BG required fewer cattle than G, but G was the most profitable grazing treatment.