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

Five 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.