Influence of Harvest Frequency and Season on Bermudagrass Cultivar Yield and Forage Quality¹

Abstract

Abstract Digestibility of bermudagrass [ Cynodon dactylon (L.) Pers.] decreases with age and varies during the growing season, but cultivar responses are not well documented. Five cultivars of bermudagrass (‘Coastal’, ‘Callie’, ‘Tifton 68’, ‘S‐16’, and ‘S‐83’), representing a wide range in digestibility, were grown in replicated plots at College Station, TX on a fine, loamy, mixed, thermic Typic Udifluvent soil and harvested at 14‐, 28‐, 42‐, and 56‐day intervals for 2 yr to determine responses to harvest frequency and seasonal trends in digestibility. Forage was separated into leaf and stem tissue to determine leafiness the first year and also analyzed for dry matter digestibility both years using the in vitro fermentation technique (IVDDM). Coastal produced significantly more forage than the other cultivars, but was the lowest in IVDDM. Total annual forage yield increased 0.15 Mg ha 1 for each day of advancing age at harvest > 14 days of age, total yields being 58% higher when harvested every 56 days than when harvested every 14 days. Both IVDDM and leafiness declined with advancing age, 56‐day‐old forage having 89 g kg 1 less digestibility and 180 g kg −1 less leaf content than 14‐day‐old forage. Leafiness closely correlated to age of forage at harvest but not to IVDDM within specified ages. One cultivar (S‐83) tended to increase in yield more rapidly and to decrease in IVDDM less rapidly with advancing age than the other cultivars. The rate of decline (average of all cultivars) in forage IVDDM was 2 g kg 1 of dry matter for each day of advancing age between 14 and 56 days. Forage IVDDM declined from spring to early summer, independent of age at harvest and somewhat independent of leafiness. Young forage increased in IVDDM after midsummer. Results of this study suggest that cultivars of bermudagrass can be selected for higher forage digestibilities. However, cultivars with higher digestibility tend to follow the same pattern as Coastal, which is a decline in digestibility with increasing age and advancing season.