Harvest Frequency and Native Warm-Season Grass Species Influence Nutritive Value

Abstract

Core Ideas• Harvest interval had the greatest effect on nutritive value of native warm-season grasses.• Species had a significant impact on nutritive value of native warm-season grasses.• Nitrogen did not significantly influence nutritive value of native warm-season grasses. AbstractFive native warm-season grass species were grown in east-central Mississippi on a coarse-loamy, siliceous, semiactive, thermic Glossic Fragiudult, to determine forage nutritive value in response to harvest frequency and N application. Established stands were harvested at 30-, 40-, 60-, and 120-day intervals, and were fertilized with N rates of 0, 50, 100, 150, and 200 lb N acre -1 using ammonium sulfate (33-0-0) for two consecutive years (2016 and 2017). Nutritive value [crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), fat, lignin, and total digestible nutrients (TDN)] along with mineral (Ca, K, P, and Mg) concentrations were assessed using near-infrared spectroscopy (NIRS). Harvest interval (P < 0.0001) and species (P < 0.0001) had the greatest effect on all nutritive value parameters tested. The most frequent harvest interval (30 d) generated the greatest nutritive value and mineral concentrations for most variables tested. In terms of species influence on nutritive value, upland switchgrass (Panicum virgatum L.), and indiangrass [Sorghastrum nutans (L.) Nash] were consistent in desirable nutritive value attributes (CP, TDN, and minerals), while the lowland switchgrass cultivar had greater lignin and ash concentrations. Native Warm-Season Grasses as a Forage CropP erennial warm-season (C 4 ) grasses play a dominant role in livestock production systems in the southeastern United States. These species are used in the form of living pasture, stockpiled forage, or harvested hay. Introduced forages, such as bermudagrass [Cynodon dactylon (L.) Pers.] and bahiagrass (Paspalum notatum Flüggé), are widely established for beef production (Ball et al., 2007;Barnes et al., 2013), and pastures are often managed with high stocking rates and large inputs of fertilizer, specifically N (Phillips and Coleman, 1995;Hoveland, 2000). These C 4 grass species are able to persist on marginal soils and respond favorably to good management practices (Robinson, 1996). Native warm-season grasses (NWSG) are species that historically dominated eastern prairies, savannas, and longleaf pine (Pinus palustris Mill.) understories before being overgrazed and eventually replaced with non-native, sod-forming species (Harper et al., 2007). Examples of NWSG include: indiangrass, switchgrass (upland and lowland ecotypes), big bluestem (Andropogon gerardi Vitman), little bluestem [Schizachyrium scoparium (Michx.) Nash] and eastern gamagrass [Tripsacum dactyloides (L.) L.]. These species have been identified as having the greatest potential as pasture in the central and eastern Crop Forage Turfgrass Manage. 5:190030.

Beef cattle feeding costs as impacted by hay yield and quality

“…Total digestible nutrient values are highly correlated with plant maturity and are impacted by harvest frequency (Burton et al., 1963; Gillet, 1970; Horrocks & Washko, ; Mislevy et al., 1977). Native grasses harvested at 30‐d frequencies resulted in greater mean TDN values compared to those harvested at 40‐, 60‐, and 120‐d frequencies, while N rate was not significant (Rushing, Lemus, Lyles, 2019). In bermudagrass, greater digestibility can be achieved with higher N rates, however this is often minimal or insignificant (Kering et al., 2011; Monson & Burton, 1982).…”

“…Pete eastern gamagrass was significantly lower in FM than all other cultivars for the 60‐ and 120‐d frequencies. The same cultivar fertilized with 224 kg N ha −1 yr −1 harvested at 30‐d intervals in east‐central Mississippi resulted in cumulative yields of 7,175 and 7,120 kg DM ha −1 in 2016 and 2017 (Rushing, Lemus, Lyles, 2019). In Maryland, unfertilized mean cumulative yields of PET were 5,349, 6,270, 2,871, and 8,299 kg DM ha −1 from 1997 to 2000 (Krizek et al., 2003).…”

“…Total digestible nutrient calculations include CP, however, increasing N rate, unlike CP, does not necessarily coincide with increased digestibility (Reynolds et al., 1969; Rushing, Lemus, Lyles, 2019). Total digestible nutrient values are highly correlated with plant maturity and are impacted by harvest frequency (Burton et al., 1963; Gillet, 1970; Horrocks & Washko, ; Mislevy et al., 1977).…”

“…Hay production in the Southeast, not unlike the animal side of beef cattle production, is often riddled with inefficiencies, particularly in the form of harvest frequency and fertilizer demands (Hoveland, 1986). In native and introduced forages, improved forage quality is often achieved through the combination of harvest frequency and higher levels of N (Cuomo et al., 1996; Holt & Conrad, 1986; Johnson et al., 2001; McIntosh et al., 2016; Monson & Burton, 1982; Pequeno et al., 2015; Rushing, Lemus, & Lyles, 2019). Monson and Burton (1982) evaluated eight bermudagrass ( Cynodon dactylon L.) cultivars in Tifton, GA, under four harvest frequencies (1–8‐wk intervals) and two N rates (336 and 672 kg N a −1 ).…”

“…Small and inconsistent differences were observed for nutritive value among cultivars and harvest frequencies. As a native grass, eastern gamagrass ( Tripsacum dactyloides L.) FM was not influenced by N application, but harvest frequency had the greatest impact on FM (Rushing, Lemus, White et al., 2019) and nutritive value in Mississippi (Rushing et al., 2019b).…”