Spring Growth and Use of Cool-Season Graminoids in the Nebraska Sandhills

Abstract

Upland sites in the Nebraska Sandhills are dominated by warm-season grasses, although cool-season graminoids often produce from 10% to 40% of the herbage. The grazing season on uplands traditionally begins when warm-season grasses have initiated rapid growth, which coincides with declining nutrient density of cool-season plants. Earlier initiation of grazing would improve the efficiency of use of cool-season plants. A study was conducted in 2001 and 2002 to characterize the growth of cool-season species on upland range and to determine the use and herbage production in response to spring grazing date and stocking rate. Grazing dates were 10 April, 1 May, and 22 May, combined with stocking rates of 3, 6, and 9 AUD (animal unit days) ha-1. Needleandthread (Stipa comata Trin. Rupr.) and sedges (Carex spp.) accounted for an average of 48% of the spring herbage yield. Amount of total current-year herbage ranged from 114 to 472 kg ha-1 over the grazing dates. Overall, paddock use of needleandthread and sedges averaged 11% and 4%, respectively. Use on 10 April averaged 61% of that observed on 1 and 22 May, likely because of short plant height (5 cm). Residual (prior-year) herbage probably was a substantial component of animal diets on 10 April. Increasing stocking rate resulted in greater herbage use (% weight removed) and percentage of plants grazed (P < 0.1). Total herbage yield in mid-June (1 130 kg ha-1) and mid-August (1 350 kg ha-1) was greatest when paddocks were grazed in April, and it declined by approximately 20% when grazed in May (P < 0.1). Overall, upland grazing strategies that include a grazing period in early May will result in greater utilization of cool-season species, but summer yield will be reduced. However, utilization of cool-season species in the spring would be advantageous, because they are being consumed at a time when their nutritive value and palatability are greater.