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Associative nitrogen (N2)‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive >30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15N2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15N of soil, chicory, and sorghum, δ15N~+7.0). Isotopically labeled 15N2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15N2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil. Associative nitrogen (N2)‐fixation by bacteria in the root‐zone of perennial bioenergy grasses have the potential to replace or supplement nitrogen fertilizer and support sustainable production of feedstock biomass. A 3 year field 15N natural abundance and a greenhouse enriched 15N feeding experiment were conducted to assess the possibility of bacterial supply of atmospheric nitrogen to feedstock grasses. It was shown that temperate bioenergy grasses switchgrass, miscanthus, and energycane can attain ~30%–50% of nitrogen from atmospheric N2 via bacterial diazotrophs.

Weed control during the establishment year of switchgrass (Panicum virgatum L.) is critical for a successful stand. Laboratory and field studies were conducted for 2 yr to evaluate the effectiveness of seed safeners for protecting switchgrass seed from the preemergent herbicide metolachlor. Initial evaluations of six seed safeners determined that fluxofenim was the only successful protectant tested for switchgrass seedling germination. Safener rates 0, 25, 50, and 100% of the recommended rate (40 mg a.i. 100 g per seed), method of application (coating vs. controlled hydration), ecotype (lowland vs. upland), dry matter yield, and number of crowns per row were analyzed in replicated field trials conducted in Starkville, MS, Ames, IA, Blacksburg, VA, and Brookings, SD, in a randomized complete block design. Two establishment years were planted in single‐row (6.1 m) plots spaced 50.8 cm apart. Subsequent biomass yield was harvested at the end of each growing season. Exceptional stands were achieved with all rates of safener in both years due to the reduction or elimination of annual grassy weeds and no crop injury was experienced at any test location. The controlled hydration (combination of 25, 50, or 100% fluxofenim) method resulted in significantly greater yields and crown counts than the coating technique at most locations for both years.

Cover crop grazing can be used as a strategy to meet nutritional requirements for livestock while simultaneously enhancing soil ecosystem services without sacrificing subsequent crop yield. Field research was conducted in east‐central Mississippi from 2019 to 2021 on a sandy loam soil to assess the impacts that grazing, tillage, and cover crop species had on corn (Zea mays L.) grain yield and soil characteristics. The main plot was grazed (G) and un‐grazed (UG) cover crops, tillage (conventional and no‐till [NT]) was the subplot, and cover crop species the sub‐subplots. Cover crops were grazed using beef (Bos taurus) heifers at a stocking density of approximately 3300 kg ha−1 each growing season as forage mass (FM) allowed. No differences were observed in FM among cover crop treatments; however, FM, crude protein (CP), and total digestible nutrients (TDN) were affected by tillage and grazing. Corn grain yield was unaffected by grazing or tillage but was impacted by cover crop treatment. Cereal rye (Secale cereale L.; 11.99 Mg ha−1), crimson clover (Trifolium incarnatum L.; 11.67 Mg ha−1), and cereal rye + radish (Raphanus sativus L.; 12.07 Mg ha−1) had greater grain yield compared to the un‐planted control (10.99 Mg ha−1). The combination of G × no‐till (NT) resulted in greater penetration resistance (71.07 J); however, G plots contributed to greater organic matter(OM) concentrations. Overall, our data suggest that complimenting G and NT practices does not impact subsequent corn grain yield and could add value to cover cropping systems. Core Ideas Grazing cover crops and no‐till do not affect corn grain yield. Grazing cover crops increases organic matter concentration. Cover crop species affects corn grain yield.

Reducing dependence onstored feed, particularly dry hay, is a major factor in beef cattle production systems in the southeastern United States. Increasing the nutritive value of the hay that is fed, however, can ultimately reduce total feed costs and boost profitability. A field trial was conducted in east‐central Mississippi evaluating several warm‐season perennial grass hay crops under varying N and harvest regimes in order to assess their ability to meet beef cow nutritional demands and to estimate total feed costs. Cultivars included ‘Argentine’ (ARG) and ‘Pensacola’ (PEN) bahiagrass (Paspalum notatum Flueggé), ‘Common’ (COM) and ‘Cheyenne II’ (CHE) bermudagrass (Cynodon dactylon L.), and ‘Pete’ (PET) eastern gamagrass (Tripsacum dactyloides L.). Plots were assigned to an annual N treatment (0, 112, 224, 336, or 448 kg N ha−1 yr−1) and a harvest frequency (30, 40, 60, and 120 d). Argentine produced the greatest amount of forage mass (FM) at the 448 kg N ha−1 yr−1 rate (14,422 kg DM ha−1). Increasing N rates resulted in greater mean crude protein (CP) values, whereas harvest frequency had a greater impact on total digestible nutrients (TDN). Total feed costs were calculated based on field trial data and were combined with either soybean [Glycine max (L.) Merr.] hulls (SH) or corn (Zea mays L.) gluten (CG) to match nutritional demand. The most economical feed costs were those where hay was fertilized (>224 kg N ha−1 yr−1) and harvested three or more times a year and was combined with CG. Core Ideas Increasing N rate and harvest frequency increases forage mass and crude protein. Several warm‐season perennial hay crops cannot meet energy requirements of lactating beef cows. Total feeding costs can be reduced by producing hay with greater nutritive value.

Core Ideas Southeastern wildrye produces adequate amounts of quality forage as a cool‐season native grass.Nitrogen and annual clover inclusion to southeastern wildrye stands improves nutritive values.Nitrogen and annual clover inclusion to southeastern wildrye stands improves dry matter yield. Southeastern wildrye [Elymus glabriflorus (Vasey ex L.H. Dewey) Scrib & C.R. Ball] has been identified as a potential native, cool‐season, perennial forage crop for the southeastern United States. This study was conducted to determine how annual clovers or N applications influenced dry matter (DM) yield and nutritive values in southeastern wildrye stands. Field trials were established in 2014 at Newton and Starkville, MS, and were conducted for two growing seasons (2015 and 2016). Plots received one of five N treatments (0, 56, 112, 168, and 224 kg N ha−1) or five annual legumes in a randomized complete block design. Plots were sampled to monitor DM and nutritive value (crude protein [CP], acid detergent fiber [ADF], neutral detergent fiber [NDF], and relative forage quality [RFQ]). All treatments maintained adequate nutritive values for growing beef cattle throughout the course of the study. Nutritive value declined as the season progressed at each location. Clover treatments had greater mean CP (146–222 g kg−1 DM) values compared to N treatments (141–191 g kg−1 DM), especially in earlier harvests. Greater RFQ values were also observed for clover treatments (115–132) compared to N treatments (113–118) across all harvests. Mean cumulative DM yield, however, was somewhat greater for N‐treated plots, compared to clover plots. This was more clearly observed in late season harvests, as clover composition diminished with increasing temperatures. Nutritive value and DM production of southeastern wildrye with N or annual clover inclusion produces quality feedstuffs worthy of further investigation.

Core Ideas Southeastern wildrye can be successfully established using imazapic as a pre‐ and post‐emergence herbicide. Lower rates of imazapic are successful at controlling winter annual weeds, such as henbit and little barley, during establishment of southeastern wildrye. Southeastern wildrye end of season dry matter yields decrease with increasing rates of imazapic. Southeastern wildrye [Elymus glabriflorus (Vasey ex L.H. Dewey) Scrib & C.R. Ball] is a native, cool‐season, perennial grass that shows promise as a forage crop for the southeastern United States. Little is known about the proper methods of establishment for this species, particularly its ability to tolerate pre‐ and post‐emergence applications of imazapic. Replicated field trials were established in Newton and Starkville, MS, in the fall of 2014 and 2015. Pre‐ and post‐emergence treatments included an untreated control, and application rates of 0.035, 0.07, 0.105, and 0.14 kg ai ha−1, which were applied to conventionally seeded plots. Seedling counts and height data were collected at bi‐weekly intervals, along with visual ratings for weed control. End of season dry matter (DM) yields were also recorded for both establishment years. As expected, higher rates (0.105 and 0.14 kg a.i. ha−1) of imazapic caused significant damage to emerging seedlings in both pre‐ and post‐emergence applications. These rates resulted in greater weed control, but ultimately, in reduced DM yields. Lower pre‐emergence application rates (0.035–0.07 kg a.i. ha−1) resulted in acceptable weed control, and minimal seedling damage. Results from these field trials demonstrates the ability to successfully establish southeastern wildrye with the use of imazapic, thus providing beneficial information for the development of this species as a forage crop for the Southeast.

As of date, information regarding seed physiology and germination requirements of southeastern wildrye (Elymus glabriflorus (Vasey ex L.H. Dewey) Scribn. & C.R. Ball [Poaceae]) is limited. Five seed accessions were collected across a variety of habitats at different latitudes and were placed under a range of temperature and light regimes to determine optimal conditions for germination. Temperature treatments for germination included alternating day/night regimes from 10 to 25 °C in 5° increments. Light testing consisted of 4 treatments: constant light, constant dark, short day (8 h), and long day (16 h). Results from the temperature experiment indicated no correlation between latitude and temperature for optimal germination. The collection from the southernmost site, Laurel, Mississippi, and the northernmost site, Upton, Kentucky, had an optimal germination temperature of 20 °C. The short-day (8-h) treatment had the greatest initial germination (41% for 2010 and 61% for 2013). These results indicate that temperature requirements for germination of E. glabriflorus seed range from 15 to 20 °C and that shortening day length (< 16 h) is optimum.

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.

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. Maximum average annual yield potential of herbaceous feedstocks (switchgrass, Miscanthus, sorghum, energycane, and Conservation Reserve Program mixtures) across the continental United States. Yield potential shown on this map is that of the highest of all species evaluated at a given location in the United States. This map was generated using the PRISM‐ELM model and is based in part on data from Feedstock Partnership Field Trials.

Southeastern wildrye (Elymus glabriflorus (Vasey ex L.H. Dewey) Scribn. & C.R. Ball [Poaceae]) is a native, cool-season, perennial grass that is commonly found along right-of-ways, woodland boundaries, and old fields across the Southeast, Midwest, and East Coast US. Recent interest in this species for forage plantings has generated the need to learn more about its propagation from seed, including appropriate sowing depth. We conducted greenhouse trials in 2011 and 2012; southeastern wildrye was sown in plastic trays at 5 depths (surface, 0.64, 1.27, 1.90, and 2.54 cm). Seedling counts completed 21 d after sowing showed 0.64 cm and 1.27 cm sowing depths produced a significantly greater number of seedlings compared with other treatments. Unlike some common warm-season grass species, southeastern wildrye was only slightly sensitive to deep sowing. Our finding that optimal sowing depth for southeastern wildrye is relatively shallow will simplify establishment of large plantings for this species since most conventional grass planting equipment is set to plant at similar shallow depths.