Switchgrass (Panicum virgatum L.) is a warm‐season native grass, used for livestock feed, bioenergy, soil and wildlife conservation, and prairie restoration in a large portion of the USA. The objective of this research was to quantify the relative importance of latitude and longitude for adaptation and agronomic performance of a diverse group of switchgrass populations. Six populations, chosen to represent remnant prairie populations on two north–south transects, were evaluated for agronomic traits at 12 locations ranging from 36 to 47°N latitude and 88 to 101°W longitude. Although the population × location interactions accounted for only 10 to 31% of the variance among population means, many significant changes in ranking and adaptive responses were observed. Ground cover was greater for northern‐origin populations evaluated in hardiness zones 3 and 4 and for southern‐origin populations evaluated in hardiness zones 5 and 6. There were no adaptive responses related to longitude (ecoregion). Switchgrass populations for use in biomass production, conservation, or restoration should not be moved more than one hardiness zone north or south from their origin, but some can be moved east or west of their original ecoregion, if results from field tests support broad longitudinal adaptation.

ble. Kust and Smith (1961) reported that 'Vernal' alfalfa ideally would be harvested three times (at about 42-d Producers in the lower Midwest often plant grazing-type alfalfa intervals) before 1 September in Wisconsin as a compro-(Medicago sativa L.) cultivars assuming they can withstand frequent hay harvests. However, little research has examined the long-term mise among forage yield, quality, and stand persistence. effects of frequent hay harvests on grazing-type compared with hay-However, harvesting four or more times during the type alfalfa. Our objective was to determine how cultivar-type and growing season or after 1 September reduced yields the harvest frequency change long-term alfalfa yields, quality, and stand following year by 30 to 78%. Subsequent studies by persistence. 'Alfagraze' (grazing-type), 'Pioneer 5373' (modern, Matches et al. (1970), Brink and Marten (1989), Brown multipest resistant hay-type), and 'Cody' (older hay-type) alfalfa were et al. (1990), and Sheaffer et al. (2000) have shown that seeded on 1 Apr. 1994, near Mt. Vernon, MO. Cultivars were main alfalfa should be harvested every 30 to 35 d during the plots, and four, five, or six harvests before 15 September (42, 34, and growing season to maximize forage yield, quality, and 28 d between harvests, respectively) were subplots in a randomized stand persistence. complete block in a split-plot arrangement. Cumulatively, over 5 yr, Research from Georgia suggests that harvesting al-Pioneer 5373 produced 6% (2.8 Mg ha Ϫ1 ) more forage than Alfagraze and 10% (5.0 Mg ha Ϫ1 ) more than Cody. Alfalfa harvested four times falfa frequently during the growing season may be less yielded 7% (0.8 Mg ha Ϫ1 ) more per year than when harvested five detrimental for grazing-type cultivars than for traditimes, and 28% (3.1 Mg ha Ϫ1 ) more than when harvested six times.tional hay-types Bouton, 1991, 1992).Alfagraze and the hay-types yielded equally when harvested six times. Brummer and Bouton (1991) found that Alfagraze, a Alfagraze usually had equal or lower detergent fiber, and equal or cultivar selected under continuous grazing pressure, was greater crude protein (CP) concentrations than other cultivars. Harmorphologically different than modern hay-types, being vesting more frequently improved forage quality but had little impact more decumbent and having many, thin stems compared on plant density. We concluded that a grazing-type, like Alfagraze, with modern hay-types. They suggested that these mordoes not show a yield or persistence advantage over a modern hayphological traits made grazing-type alfalfa cultivars toltype under frequent hay harvest regimes in the lower Midwest. Howerant of frequent harvests. Subsequent research with ever, the grazing-type used in this study often had superior forage quality.

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Tall fescue (Festuca arundinacea Schreb.) infected with an endophyte that does not produce ergot‐like alkaloids (nontoxic endophyte) has not been evaluated for herbage mass, nutritive value, and ergovaline concentration when stockpiled during winter. Our objective was to quantify these responses for tall fescue infected with a native endophyte (K31 E+), a nontoxic endophyte (HiMag NTE), and with no endophyte (HiMag E−). Responses were measured on a fine, mixed, active, mesic Oxyaquic Fragiudalfs soil monthly from mid‐December through mid‐March in 1999‐2000 (Year 1) and 2000‐2001 (Year 2) in southern Missouri. Herbage mass for K31 E+ averaged 2370 kg ha−1, which was ≈20% greater than HiMag E− or HiMag NTE. Herbage mass did not change from mid‐December through mid‐March for any entry. The nutritive value of all entries was equal on comparable dates with acid detergent fiber (ADF) ranging from 285 to 338 g kg−1 during the winter. Nutritive value was highest in mid‐December of each year and then declined slowly after that. Neither HiMag E− nor HiMag NTE contained ergovaline, but K31 E+ had substantial concentrations of ergovaline in both years. The ergovaline concentration of K31 E+ was 454 μg kg−1 in December of Year 1 and 175 μg kg−1 in December of Year 2, but declined by ≈85% by March each year. The stable herbage mass, slowly declining nutritive value, and absence of ergovaline in HiMag E− and HiMag NTE suggest that livestock producers could eliminate toxicosis problems by stockpiling these forages for winter grazing.

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country.