Environmental Influences on Fiber Component Concentrations of Warm-season Perennial Grasses 1

Evaluation and management of warm-season perennial grasses are complicated by seasonal fluctuations in forage quality. Field studies have indicated that a significant proportion of this seasonal variation is due to environmental conditions. Due to confounding effects under field conditions the variation cannot be directly attributed to specific environmental factors. In this study, Coastal and common bermudagrass [Cynodon dactylon (L.) Pers.], Pensacola bahiagrass (Paspalum notatum Flugge), and dallisgrass (Paspalum dilatatum Poir.) were grown in an artificial medium under 4 day/night temperatures (35/24, 32/31, 29/18, 26/15 C), 4 photon flux densities (1,050, 840, 630, 420 µE m⁻² sec⁻¹ PAR) and two soil moisture levels (high and low) in growth cabinets to evaluate the relative influence of each factor on fiber component concentrations. Grasses were harvested at 14 and 21 days and analyzed for neutral-detergent fiber (NDF), acid-detergent fiber (ADF), cellulose (CEL), hemicellulose (HEM), permanganate lignin (LIG), and silica (SIL) concentrations. multiple regression analysis was used to obtain reduced prediction equations for evaluating responses of all measured variables to temperature (T) and photon flux density (L) at each soil moisture level. Prediction equations for fiber component concentrations of each grass included T effects at both soil moisture levels but did not consistently include L effects. Coefficients of determination (R² values) for the prediction equations indicated that T and L effects on fiber component concentrations varied with the fiber component, grass, and soil moisture level. Concentration of NDF increased in the Cynodon species and decreased in the Paspalum species as T increased. In all grasses, predicted concentrations of ADF, CEL, LIG, and SIL increased with increasing T at both soil moisture levels, while HEM concentrations decreased. In all grasses L effects consistently influenced ADF, LIG, and SIL concentrations at both soil moisture levels and CEL concentrations at the low moisture level. Concentrations of ADF, CEL, and SIL decreased slightly, while LIG concentrations increased with increasing L. Although T effects consistently had greater influence in this study, both T and L and their interaction effects significantly influenced predicted fiber component concentrations. The data emphasize the importance of considering environmental influences when evaluating forage quality differences of warm-season perennial grasses.