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

Abstract

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.

Burn and mechanical residue removal methods on production‐life of Kentucky bluegrass

“…The factor that most positively affected seed yield was N content of STB (STB %N) measured in the fall (Table 5; Figure 4b). This research, like previous studies, showed the importance of the fall period for determining seed production the following year (Holman, Hunt, Johnson‐Maynard, et al., 2007). Nonstanding biomass remaining in the field during late summer and fall have long been associated with decreased yields (Lamb & Murray, 1999).…”

“…Nonthermal residue management, therefore, generally results in premature stand decline as compared with field burning. In addition, postharvest residue is low in forage nutritive value, economic value, and demand (Holman, Hunt, & Thill, 2007; Holman, Hunt, Johnson‐Maynard, et al., 2007; Holman et al., 2011), all of which are disincentives to manage postharvest residue other than through field burning.…”

“…It has long been known that accumulation of postharvest residues reduces Kentucky bluegrass (Poa pratensis L.) seed Washington and Oregon (Chastain et al, 1997;Evans, 1980;Holman, Hunt, Johnson-Maynard, et al, 2007;Lamb & Murray, 1999;Youngberg, 1980). Generally, these mechanical methods provide seed yields comparable with burning during the first 1-2 yr of seed production, yet with certain methods and cultivars, comparable yields were achieved through the third (Lamb & Murray, 1999) and fifth (Chastain et al, 1997) seed harvest.…”

Effect of Harvest Processes on the Nutritive Value of Kentucky Bluegrass Residue from Seed Harvest

“…The experiment was conducted on a grower-cooperator farm in an established Kentucky bluegrass stand that was previously burned every fall prior to initiation of the study. Data were collected from the rake + bale (non-burn) treatment of a larger residue management study randomized in complete block design with four replications (10). Plots were 16.5 m wide by 122 m long.…”

“…The baled residue can be sold as hay that can help offset some of the increased production costs (6,15). Forage nutrient content and economic value of Kentucky bluegrass residue were reported (10,11). Yet, the effect of harvest processing (swathing, combining seed, and baling) and changes in forage nutrient content after combining seed are unknown.…”