Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2001
Publication Date: N/A
Interpretive Summary: Forages adapted to cool climatic conditions dominate pastures in the Appalachian region, but mid- summer weather conditions often depress productivity. Forages capable of sustaining vigorous growth during warm and dry periods in summer might help buffer variation in available herbage and meet grazing livestock demands. In many instances extra land resources sare not available or the producer may not have the technology or specialized management skills needed to optimize production from warm- season forage resources. Creating a self-regulating mixture of forages that grow and persist in the same stand may be one means of achieving stability in production where wide fluctuations in growing conditions occur among and within years. We established a stand of cold-tolerant bermudagrass and seeded bluegrass and white clover into the sod to create a mixture of cool- and warm-season grass along with a legume to supply nitrogen and improve forage nutritive value. No specialized defoliation management was required for the mixture. We found that close or frequent clipping favored the presence of bermudagrass in the stand and that this treatment favored vigorous white clover growth. Maximum forage production occurred later in the growing season where bermudagrass presence was strong, suggesting that a producer could supplement summer forage availability by growing a cool- and warm-season grass mixture. Including bermudagrass in the stand also allows for a relatively greater number of grazers per unit of land area and should lead to improved production and land-use efficiency.
Technical Abstract: Cool-season forage species dominate pastures in the Appalachian region, but mid- summer weather conditions often depress productivity. Warm-season forages might help buffer variation in available herbage but land resources may limit the area dedicated to special use crops. A replicated field-plot experiment was established in a bermudagrass (Cynodon dactylon L.) stand over-sown with Kentucky bluegrass (Poa pratensis L.) and white clover (Trifolium repens L.) and was conducted for 4 consecutive years (1994-1997) to determine productivity, nutritive value and botanical dynamics of the mixture. Botanical composition changed as a function of the interaction of defoliation treatment with year and varied among years as a function of growing conditions. As much as 55% of the sward in mid and late season was bermudagrass in 1995. By 1997, the proportion of bermudagrass was similar to other grasses and rarely exceeded 20%. This is reflected in maximum instantaneous growth rate, which occurred later in the growing season of 1995 when bermudagrass was a dominant sward component, than in subsequent years when bermudagrass often comprised less than 10% of the sward. Rates in 1995 were greatest for canopies clipped at 6-wk intervals (70 kg ha-1 d- 1) or clipped when the canopy reached 20 cm, and least when clipped at 2-wk intervals (33 kg ha-1 d-1) and when the canopy reached 10 cm (45 kg ha-1 d- The trend was reversed by 1997 when sward composition shifted away from bermudagrass to cool-season grasses and white clover. Yields were greatest when cool-season species dominated the sward. Creating a self-regulating mixture of warm- and cool-season perennial forages may be one means of achieving some level of stability in the sward and might be useful where wide fluctuations in growing conditions occur among years.