| Kentucky bluegrass (Poa pratensis, L.) is an important turf and forage grass, with seed production reliant on burning post-harvest residue to maintain productivity. However, air quality concerns have resulted in restrictions that limit or prohibit field burning. Thus, economically and environmentally sustainable reduced-thermal and non-thermal production systems must be developed to sustain seed production. These studies determined the effect of post-harvest grazing on Kentucky bluegrass seed production and the forage quality of bluegrass. A post-harvest grazing study and a forage evaluation study were conducted in 2003 and 2004. Grazing treatments included full-load graze (FLG) and grazing after baling (BG). Stocking density, supplement requirements, and residue forage value were determined. BG and FLG treatments needed to remove an average of 2,320 and 6,030 kg ha-1, respectively, or approximately 70% of the total residue to maintain seed productivity. The stocking density required to remove residue in 30 d was 11.3 and 19.8 animal units ha-1 in BG and FLG, respectively. Residue averaged 4.0% crude protein (CP), 41.3% acid detergent fiber (ADF), 74.7% neutral detergent fiber (NDF), and 44.6% in vitro dry matter digestibility (IVTD). Supplement requirements were dependent on forage quality, animal requirements, and dry matter intake. Baled residue was worth {dollar}33.27 t-1 on a dry matter basis. Four cultivars (Ascot, Kenblue, Limousine, and Touchdown) at three growth stages (boot, anthesis, and seed ripe), and anatomical composition (percent head, leaf, and stem) were evaluated for forage yield and quality. Forage quality measurements included CP, ADF, NDF, lignin, and IVTD. Tall cultivars produced more biomass than short cultivars at anthesis and seed ripe. Forage quality did not differ among cultivars, despite differences in anatomical composition and chemical composition among anatomical components. On average, CP decreased 0.39% d-1 and IVTD decreased 0.48% d-1 from boot to anthesis. Total digestible dry matter and CP yield were greatest at anthesis and seed ripe. Harvesting at anthesis rather than seed ripe reduces the amount of supplementation required. These studies indicated that integrating livestock and forage production into Kentucky bluegrass seed production systems can help sustain seed production in the absence of burning. |
