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.

Core Ideas Within year, harvest frequency has the greatest effect on DM production of native warm‐season grasses. Nitrogen has little effect on native warm‐season grass DM yield. Eastern gamagrass can tolerate consecutive years of frequent defoliations and maintain yield. Five native warm‐season grass species and mixtures were grown in east‐central Mississippi on a coarse‐loamy, siliceous, semiactive, thermic Glossic Fragiudult, to determine their potential as forage grasses in response to harvest frequency and N application. Established stands were harvested at 30, 40, 60, and 120 d intervals, and were fertilized with N rates of 0, 56, 112, 168, and 224 kg N ha−1 for two consecutive years (2016 and 2017). Dry matter (DM) yield and agronomic nitrogen use efficiency (aNUE) were analyzed. Year, treated as a repeated measure, was the main source of variation affecting DM yields. Within year, harvest frequency had the greatest effect on cumulative yields in 2016, accounting for 44% of the variation observed. This effect was not observed in 2017. Frequent defoliations led to overall lower yields in 2017. Nitrogen was significant, but moderately, accounting for 2 and 4% of variation for 2016 and 2017, respectively. Species was also significant for both years. Agronomic N use efficiency varied between year, species, N rate, and harvest frequency. Eastern gamagrass [Tripsacum dactyloides (L.) L.] was the only species in which cumulative DM yield remained consistent across both years of the study, regardless of harvest frequency or N application. Results suggest that rest periods should be based on species present, and that less frequent harvests are required for sustained DM yields.

Beef cattle (Bos taurus) production systems in the southeastern United States are often riddled with inefficiencies, particularly when it comes to forage management, and the lack of high‐quality forages utilized during the warmer months of the year. A grazing trial was conducted in east‐central Mississippi on a fine sandy loam soil in which bermudagrass (Cynodon dactylon L.) was interseeded with ‘Bulldog 505’ alfalfa (Medicago sativa L.). The randomized complete block design consisted of three treatments: (a) unfertilized bermudagrass (BG), (b) fertilized bermudagrass (100 lb N acre–1 yr–1) (BGN), and (c) bermudagrass interseeded with alfalfa (BGA). Forage production, along with animal performance, and economic analysis were compared across all three treatments for three grazing seasons (2017–2019). The BGA system had greater cumulative forage mass (FM), crude protein (CP), and total digestible nutrients (TDN) compared with the BG treatment. The BGA treatment had the greatest average daily gain (ADG; 1.83 lb head–1 d–1) and GAIN (178 lb acre–1). Based on increased forage and animal performance, the BGA treatment had a net revenue of US$75.61 acre–1, compared with the BG ($15.49 acre–1) and BGN (–$26.50 acre–1) treatments. Our results indicate that interseeding alfalfa into bermudagrass pastures has the potential to increase farm profitability, especially with fluctuations in N prices.

A grazing trial was conducted in Mississippi during 2016 and 2017 to compare pasture, animal, and economic performance of three perennial, warm-season grass systems. Grass treatments included: (i) Argentine bahiagrass (Paspalum notatum Fluegge; BAH); (ii) KY Ecotype big bluestem (Andropogon gerardii Vitman; BBS); and (iii), KY Ecotype indiangrass [Sorghastrum nutans (L.) Nash], big bluestem and little bluestem [Schizachyrium scoparium (Michx.) Nash; MIX]. Paddocks were continuously stocked using weaned beef (Bos taurus) steers across three grazing intervals (I, II, and III) during late spring and summer. Pasture measurements included forage mass (FM) and nutritive value. Greatest FM was observed during grazing interval II in 2016 (931.70 kg ha -1 ). Nutritive values declined as the season progressed. The BAH had greater CP and TDN, and lower ADF and NDF concentrations than BBS and MIX in 2016. Differences were not as discernable in 2017. Greatest ADG were observed for BBS interval I in 2017 (1.34 kg d -1 ), MIX interval I 2017 (1.21 kg d -1 ), and BBS interval I 2016 (1.19 kg d -1 ). Beef yield per hectare (GAIN) was greatest for interval I across both years (464.78 kg ha-1). By species, GAIN was greatest for BBS in interval I (451.32 kg ha -1 ). For economic analysis, BBS had the lowest total annual pasture cost (US$142.65 ha -1 ), and had the greatest NET returns for 2016 ($268.96 ha -1 ) and 2017 ($249.98 ha -1 ). Implementing native warm-season grasses (NWSG) in stocker cattle systems for early-season grazing can be productive in Mississippi.

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