Nonstructural Carbohydrate in the Spring Herbage of Temperate Grasses1

Abstract

Nonstructural carbohydrates are sources of readily available energy that enhance rumen microbial activity and forage utilization. Experiments were conducted in Pennsylvania and West Virginia to determine the effect of maturity on total nonstructural carbohydrate (TNC) concentrations in spring herbage of eight grass species and determine TNC concentrations in herbage at immature and mature growth stages on a given day. The grasses were fertilized early each spring and summer with 0, 60, 120, or 240 kg N/ha.Determinations for TNC were made using the Smith takadiastase technique. Mean TNC concentration in the spring herbage of ‘Masshardy’ orchardgrass (Dactylis glomerata L.), ‘Climax’ timothy (Phleum pratense L.), and ‘Sac’ smooth bromegrass (Bromus inermis Leyss.) decreased seven or more percentage units with maturation from vegetative to full bloom stage, but decreased less than four percentage units in ‘Fawn’ tall fescue (Festuca arundinacea Schreb.), ‘Kenblue’ Kentucky bluegrass (Poa pratensis L.), and redtop (Agrostis alba L.). Mean TNC concentration was 50% higher in ‘Pennfine’ perennial ryegrass (Lolinm perenne L.) than in Kenblue Kentucky bluegrass or redtop. Concentration of TNC was inversely related to maximum air and soil temperatures and was affected much more by harvest date than by maturation of the herbage. Concentration of TNC was usually lower in N‐fertilized herbage than in unfertilized controls at early growth stages, but N had little effect on TNC concentration of herbage at full bloom.Maximum yields of TNC were obtained at the stem elongation stage with ryegrass, at flower‐head emergence with Pennmead orchardgrass and ‘Ky. 31’ tall rescue, and at full bloom with other grasses. N fertilization increased TNC yield of orchardgrass, tall rescue, and reed canarygrass; decreased TNC yield of smooth bromegrass and redtop; and had little effect on TNC yield of ryegrass and timothy.