Prairiegrass–Brassica Hybrid Swards for Autumn Dry Matter Production

Stockpiling herbage can redistribute nutrient availability and supplement quantity for livestock, depending on production objectives. Brassicas (Brassica spp.) and improved prairiegrass (Bromus catharticus Vahl.) cultivars are adapted to growing conditions occurring in the Appalachian region and provide nutritionally valuable herbage in autumn; however, highly digestible brassica herbage may require supplementation with a fibrous companion species for efficient rumen microbe function and nutrient use by grazers. A prairiegrass– brassica hybrid [B. rapa L. 3 B. rapa subsp. pekinensis (Lour.) Hanelt.] mixture and pure stands of each were established to determine productivity and nutritive value of stockpiled stands in autumn. Field plots were established in late June of 2003 and 2004, and clipping began 74 and 63 d after planting, respectively. Prairiegrass coestablished with brassica hybrid and could be harvested in the establishment year. Sown species and year interacted to influence stand composition, dry matter productivity, and nutritive value. Dry conditions occurred shortly after planting in 2003 and slowed brassica hybrid establishment and productivity. Total dry matter varied for monospecific andmixed stands of prairiegrass and brassica hybrid each year, as did distribution during the season. Nutritive value varied with years and met or exceeded values suggested for efficient rumen microbe function. Herbage growth continued for about 80 d after the first clip in early September for all sward types and demonstrated the compatibility of co-seeded prairiegrass and brassica hybrid as well as the suitability of the mixture to provide adequate herbage mass and nutritive value when stockpiled in autumn. HERBAGE GROWTH is slow in autumn and ceases during winter in much of the central Appalachian region of the eastern USA, creating a potential shortfall of herbage in forage-based livestock production systems. Stockpiling, or accumulating herbage for later use, can supplement quantity, redistribute availability, reduce the need for purchased feed, and help meet livestock nutrient requirements when gaps occur. Important considerations when designing stockpile components of forage–livestock systems include dry matter production and nutritive value needs. Careful management is required to achieve the desired herbage mass and nutritive value. Trade-offs between herbage yield and nutritive value determine when stockpiling should begin and accumulated herbage used (Matches and Burns, 1995). Plants that resist the destructive effects of weather (e.g., frost and wind) and retain herbage nutritive value in late autumn or early winter {e.g., tall fescue [Lolium arundinaceum Schreb. Darbyshire (formerly Festuca arundinacea Schreb.)} are ideal for late-season stockpiling. Much of what is known about autumn stockpiled herbage focuses on tall fescue with tough, resilient leaves and orchardgrass (Dactylis glomerata L.), which is common in pastures throughout the Appalachian region (Baker et al., 1988). Alternative species that could be used for autumn stockpile include grasses with strong late-season production (e.g., Bromus spp.). For example, ‘Matua’ prairiegrass (Bromus willdenowii Kunth.) grew vigorously during autumn in central Appalachia (Belesky and Stout, 1994), but persistence was compromised by susceptibility to diseases. A stockpiled mixture of smooth bromegrass (Bromus inermis L.) and red clover (Trifolium pratense L.) was comparable to a mixture of tall fescue and alfalfa (Medicago sativa L.) in terms of productivity, nutritive value, and livestock performance (Hitz and Russell, 1998). New prairiegrass (Bromus catharticus Vahl.) cultivars with disease resistance, upright growth habit (‘Dixon’) (Rumball and Miller, 2003a), or ability to tolerate cold weather (‘Lakota’) (Rumball and Miller, 2003b) are suited to growing conditions in many parts of the USA. The new prairiegrass cultivars could prove to be useful components of systems requiring high quality herbage in autumn (Belesky and Cassida, 2004; Belesky and Ruckle, 2005). Forage brassicas are fast-growing, cold-tolerant annuals that can provide herbage mass and quality needed to sustain livestock late in the year. Brassicas planted in midsummer are productive in autumn and retain high nutrient concentrations when stockpiled (Guillard et al., 1988; Cassida et al., 1995). The high soluble nutrient content of brassica species should be supplemented with a source of fiber for efficient rumen function and nutrient use (Cassida et al., 1994). One means of achieving this in pasture would be to establish brassica along with a companion grass. Information demonstrating the compatibility of grass–brassica mixtures sown at the same time is scarce. Our objective was to determine the seasonal pattern of herbage production and nutritive value of a prairiegrass–brassica hybrid mixture sown in midseason and stockpiled in autumn. MATERIALS AND METHODS Plots were established on an upland site of the Allegheny Plateau in southern West Virginia (378469 N, 818009 W; 870 m elevation above sea level). Soil was a Clymer series, channery loam (coarse-loamy, siliceous, active, mesic Typic Hapludult) on a hilltop site with ,5% slope. Two glyphosate [N(phosphono-methyl) glycine] applications (2.5 kg a.i. ha each) and tillage eliminated existing cooland warm-season USDA-ARS, Appalachian Farming Syst. Res. Cent., 1224 Airport Rd., Beaver, WV 25813-9423. Received 9 Feb. 2006. *Corresponding author ([email protected]). Published in Agron. J. 98:1227–1235 (2006).