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Roots and rhizomes can play an important role in nutrient cycling, however, few studies have investigated how their decomposition pattern is affected by defoliation and time of the year. This 2-year study evaluated root-rhizome composition and decomposition of a warm-season rhizomatous perennial legume [rhizoma peanut (RP; Arachis glabrata Benth.)] under continuous stocking or when defoliated by clipping every 56 days. A 168-days incubation trial was performed to determine disappearance of biomass and N and changes in acid detergent fiber (ADF), acid detergent insoluble N (ADIN), and C:N ratio. Additionally, three 56-days incubations were performed each year to evaluate the disappearance coefficient ( B 0 ) and relative decay rate ( k ). There were no treatment differences in any response for the 168-days incubation. After 168 days, 21 and 60% of initial biomass and initial N remained, respectively. Relative decay rate for OM and N were 0.0088 and 0.0035 g g −1  day −1 , respectively. Carbon-to-N ratio decreased from 29 at day 0 to 17 at day 168. Concentration of ADIN increased from 6.9 to 19.3 g kg −1 , plateauing at day 79. The B 0 and k for remaining OM and N were greater in late than early season and could be explained by greater N concentration and lesser C:N ratio. Rapid decomposition, difference in C:N ratio from day 0 to 168, and the increase in ADIN concentration during incubation indicate large amounts of root-rhizome-soluble C at initiation of incubation. These data indicate that RP root-rhizome turnover is more responsive to season than defoliation frequency.

The objectives of this study were to determine the emission of nitrous oxide (N 2 O), methane (CH 4 ), and carbon dioxide (CO 2 ), as well as the isotopic composition of N 2 O from excreta of beef steers fed ‘AU Grazer’ sericea lespedeza hay [SL; Lespedeza cuneata (Dum. Cours.) G. Don]. Fifteen Brahman × Angus crossbred steers were fed one of three experimental diets: 0, 50, or 100% inclusion of SL into ‘Tifton 85’ bermudagrass hay ( Cynodon spp.). Gas sampling occurred on days 0, 1, 3, 5, 7, 14, 18, 25, and 32 after urine or feces application to static chambers for two experimental periods. Effect of the day after feces application ( P  < 0.001), while day × inclusion of SL interaction was observed in urine ( P  < 0.001) for all greenhouse gases (GHG) analyzed. Peaks of emission of all GHG in urine and feces occurred in the first days ( P  < 0.001), with days 3 and 5 being most depleted in 15 N-N 2 O in feces, and days 3, 5, and 7, in urine ( P  < 0.001). Feeding SL to beef steers was effective in mitigating the emission of GHG from the excreta, but further research is necessary to investigate the mechanisms behind the reductions.

Legumes are a potentially important N source in pasture systems, but quantifying the transfer of biologically fixed N from the legume to the grass component is difficult. A greenhouse H-pot system was developed to directly estimate belowground N transfer from biological N 2 fixation (BNF) using 15 N 2 . The system was tested with ‘Prine’ annual ryegrass ( Lolium multiflorum L.) and ‘Dixie’ crimson clover ( Trifolium incarnatum L.). Legume and grass root systems growing in either individual or H pots were exposed to 15 N 2 . Control H pots were separated by mesh to prevent contact between roots from each side of the pot. To reduce enriched gas volume demand and avoid cross-contamination in the greenhouse, the gas was supplied through underground tubes in the root zone. Ryegrass and clover exhibited an enrichment of 15 N 2 when their respective root systems were supplied with 15 N 2 . Additionally, ryegrass also showed enrichment when clover roots received the gas, provided there was direct contact between the root systems on both sides of the H pot; however, this enrichment did not occur when such contact was prevented. Plants cultivated in monoculture without the application of 15 N 2 did not present enrichment. The H-pot facilitates the evaluation of belowground transmission, an essential mechanism for N transfer. The technique of gradually supplying 15 N 2 directly to the root system may serve as a valuable labeling method for tracking nitrogen transfer. The absence of enrichment when plants were not directly supplied indicates negligible atmospheric enrichment. However, the enrichment observed in ryegrass when supplied with the gas suggests BNF through alternative pathways.

Temperate grasslands can be highly productive. However, those that are productive are generally heavily dependent on high inputs of nitrogen (N) fertilizer. Including legumes such as white clover (Trifolium repens L.) in the sward can reduce reliance on N fertilizer. Recent investigations have evaluated the potential of multispecies swards, which are defined as agronomically improved grasslands that include multiple plant functional groups, e.g., grasses, legumes, and forage forbs. Several of the benefits and challenges of multispecies swards are summarized in this review. To date, the most prominent forb species included in multispecies swards are chicory (Cichorum intybus L.) and ribgrass/ribwort plantain (Plantago lanceolata L.). Multispecies swards grown under reduced N fertilizer input conditions can produce as much biomass as monocultures receiving large quantities of N fertilizer. The nutritive value of multispecies swards may potentially be greater than grass-only swards, especially since forbs may contribute additional micro and macro minerals to livestock diet. While challenges associated with multispecies swards may include weed management and facilitating persistence of the forb species in particular, the overall evidence suggests that well-managed multispecies swards can enhance the productivity as well as environmental sustainability of grazing systems.

Stable isotopes are useful for estimating livestock diet selection. The objective was to compare δ 13 C and δ 15 N to estimate diet proportion of C 3 –C 4 forages when steers ( Bos spp.) were fed quantities of rhizoma peanut ( Arachis glabrata ; RP; C 3 ) and bahiagrass ( Paspalum notatum ; C 4 ).Treatments were proportions of RP with bahiagrass hay: 100% bahiagrass (0%RP); 25% RP + 75% bahiagrass (25%RP); 50% RP + 50% bahiagrass (50%RP); 75% RP + 25% bahiagrass (75%RP); and 100% RP (100% RP). Feces, plasma, red blood cell (RBC), and hair were collected at 8-days intervals, for 32 days. Two-pool mixing model was utilized to back-calculate the proportion of RP based on the sample and forage δ 13 C or δ 15 N. Feces showed changes using δ 13 C by 8 days, and adj. R 2 between predicted and observed RP proportion was 0.81 by 8 days. Plasma, hair, and RBC required beyond 32-days to reach equilibrium, therefore were not useful predictors of diet composition during the study. Diets were best represented using fecal δ 13 C at both 8-days and 32-days. By 32-days, fecal δ 15 N showed promise (R 2  = 0.71) for predicting diet composition in C 3 –C 4 diets. Further studies are warranted to further corroborate fecal δ 15 N as a predictor of diet composition in cattle.

Black oat (Avena strigosa Schreb.) might be an attractive forage species in the northeastern United States, since it is generally more heat tolerant and disease resistant than other cool‐season grasses. Black oat is currently recommended for fall and winter production in USDA Plant Hardiness ones 8b–10a, which is beyond the northeastern United States (Zones 2a–6a). The objective was to evaluate 10 black oat breeding lines (referred to as “UF1” through “UF10”) for forage accumulation, crude protein (CP), neutral detergent fiber (aNDF), acid detergent fiber (ADF), and in vitro digestible organic matter (IVDOM) concentrations. The experiment was carried out in April–July 2022 in Pennsylvania Furnace, PA. Triticale (× Triticosecale Wittmack cv. TriCal 342) and Legend 567 oat (Avena sativa L.) were included as controls, as well as Haden oat and Gunner triticale, as regionally recommended cultivars. The forage accumulation within the black oat germplasm ranged from 364 to 864 lb dry matter (DM) acre−1, observed in UF7 and UF9, respectively, during the first harvest. During the second harvest, forage accumulation within black oat ranged from 1048 to 1408 lb DM acre−1, from UF8 and UF1, respectively. Crude protein concentrations ranged from 16% to 23% across all black oats, with no differences found within the germplasm. The IVDOM concentrations averaged 78% across all treatments during the first harvest and decreased to 66% during the second harvest. Overall, this study showed that black oat merits further evaluation as forage species in the northeastern United States, but further studies are required to address management of the species. Core Ideas Black oat is heat tolerant and therefore might be an alternative forage species for the northeastern United States. Further evaluation is required to establish production potential and nutritive value of black oat in the northeastern United States region. Best management practices for black oat are lacking and warranted, especially for future cultivar release.

Corn (Zea mays) is a globally important crop to produce grain and silage for livestock systems. However, corn generally requires high levels of nitrogen (N) fertilizer. Introducing sunn hemp (Crotalaria juncea L.; SH), an annual legume, is a potential option for reducing N inputs. This study aimed to evaluate initial insights of herbage accumulation (HA), nitrogen biological fixation, and nitrogen use efficiency (NUE) using SH intercropped with corn in two locations, Marianna, FL, and Marshfield, WI. Treatments were SH monoculture, corn without N‐fertilizer (Corn − N), N‐fertilized corn (Corn + N), corn and SH planted on the same day (Corn + SH0), and corn and SH planted 4 weeks later (Corn + SH4). Corn + N had greater HA at both sites. The treatment SH fixed 87 kg N ha−1 and had a greater %N derived from the atmosphere (%Ndfa) in Marianna (71.4%). N yield was greater for Corn + N in both sites, and no difference was found between the intercropped treatments. Corn + SH0 in Marianna and Corn + SH4 in Marshfield resulted in great NUE (72% and 69%, respectively). The data indicate that intercropping corn and SH can enhance NUE. However, intercropping corn and SH reduces the overall HA, which requires further evaluation to promote producer adoption of these systems. Plain Language Summary Corn is an important crop used for grain and silage production in livestock systems. However, corn crops require high nitrogen fertilizer to support plant development. A strategy to decrease nitrogen in crops is to use legume species. Sunn hemp (SH) can be an example since it may biologically fix nitrogen from the atmosphere for the soil. Our goal was to mix SH and corn in the field to produce forage for silage and to verify if SH could reduce nitrogen fertilizer. We consider different ways to mix SH and corn: corn and SH planted on the same day and corn and SH planted 4 weeks later. We compared corn without N‐fertilizer and corn with N‐fertilizer in two locations (Marianna, FL, and Marshfield, WI). Our results showed that using nitrogen on the corn crop increased the forage production in both sites. SH fixed 87 kg N ha−1 in Marianna. Mixing SH and corn on the same day improved the nitrogen efficiency in both sites. However, mixing corn and SH reduces the forage production.

Stable isotopes are an important tool to assess livestock diet in binary mixtures of C3-C4 forages. However, the use of stable isotopes to trace livestock diet using tropical arboreal legumes has been limited. The objective of this study was to evaluate the use of 13C stable isotopes to identify the proportions of grass (C4) and legume in sheep diet, when consuming various inclusion levels. We evaluated models correlating faecal δ13C to diet δ13C and inferred which model can better predict the different proportions of grass or legume consumed by sheep. Thirty male lambs (17 ± 1.3 kg) were used, and the experiment was set up in a randomised complete block design with body weight being the criteria for blocking. Treatments included various inclusion levels of Sabiá (Mimosa caesalpiniifolia Benth) in signalgrass (Urochloa decumbens Stapf) hay (100:0, 75:25, 50:50, 25:75 e 0:100%). Total faecal production and in vivo digestibility were calculated, as well as δ13C of diet and faecal samples. Sabia diet (100%) showed the greatest overall intake, and the lowest faecal production was observed when forages were fed alone, both for signalgrass or sabia hays, with 234 and 245 g dry matter animal−1 d−1. The models used within this study estimated with high accuracy the grass-legume proportions within the diets of sheep (R2=0.97). Our results indicate that using additional coefficients (digestibility, discrimination) did not increase the accuracy of the models, since using only isotopes from faeces was sufficient to predict the contribution of C3 or C4 species in the diet.HighlightsStable isotopes are an efficient tool to trace back dietary sources in binary mixtures of C3-C4 forages.Faecal samples are accurate to use to trace back dietary changes using stable isotopes.Addition of digestibility and isotope discrimination coefficients did not improve prediction models.

The study evaluated forage and livestock performance in different grazing systems over two years. Treatments were three contrasting grazing systems: (I) N-fertilized bahiagrass ( Paspalum notatum Flüggé) in the summer overseeded during the winter by N-fertilized ryegrass ( Lolium multiflorum ) and oat ( Avena sativa L.) (Grass + N); (II) unfertilized bahiagrass during the summer overseeded with ryegrass + oat and a blend of clovers ( Trifolium spp.) in the winter (Grass + Clover); (III) unfertilized bahiagrass and rhizoma peanut (RP; Arachis glabrata Benth.) mixture during summer, overseeded during winter by ryegrass + oat + clovers mixture (Grass + Clover + RP). Average daily gain (ADG), gain per area (GPA), and stocking rate (SR) in the winter did not differ across treatments and averaged 0.87 kg/d ( P = 0.940), 303 kg/ha, and 2.72 AU/ha. In the summer, Grass + Clover + RP had greater ADG than Grass + N (0.34 vs. 0.17 kg/d, respectively). During the summer, the GPA of Grass + Clover + RP was superior to Grass + N (257 vs. 129 kg/ha, respectively), with no difference in SR among treatments at 3.19 AU/ha. Over the entire year, ADG and GPA tended to be greater for Grass + Clover + RP. Annual SR differed between treatments, where Grass + N was greater (3.37 AU/ha) than the other treatments, which averaged 2.76 AU/ha. Integration of legumes into pasture systems in the summer and winter contributes to developing a sustainable grazing system, reducing N fertilizer use by 85% while tending to increase livestock productivity even though SR was decreased by 18%.

Core Ideas Grass–legume forage systems outperformed grass monocultures. Arachis glabrata had greater potential for N2 fixation than other peanut species. Grass enhanced its nutritive value and obtained N from legumes when grown in mixtures. Bermudagrass hybrids (Cynodon spp.), such as Tifton 85, are among the most widely used forages for hay production in the southeastern United States, although large N fertilizer inputs are often required for sustained productivity. Grass–legume mixtures can reduce the need for N fertilization. The objective was to assess peanut species (Arachis spp.) as alternatives to N fertilizer. One annual species (Arachis hypogaea L. cv. TUFRunner ‘727’) and two perennials, pintoi peanut (A. pintoi Krap & W.C. Greg cv. ‘Amarillo’) and rhizoma peanut (RP; A. glabrata Benth., cv. ‘Florigraze’ and germplasm Ecoturf) were evaluated in Tifton 85 swards. Planting occurred in 2014 and mixtures were evaluated through 2016. Responses included herbage accumulation (HA), peanut proportion in HA, nutritive value, biological nitrogen fixation (BNF), %N derived from atmosphere (%Ndfa), and %N of grass N that was transferred from peanut. Ecoturf–grass mixtures had the greatest HA (900 kg DM ha−1 harvest−1), while TUFRunner 727–grass mixtures had the least (690 kg DM ha−1 harvest−1). Mixing peanuts with Tifton 85 increased in vitro digestible organic matter (IVDOM) concentration of the grass from 588 g kg−1 in monocultures to 620 g kg−1 in mixtures, but did not increase grass crude protein (CP) concentration. Contribution of Amarillo peanut was minimal throughout the study, TUFRunner 727 contributed significantly in the year of planting only, but RP contribution increased each year. Although peanut species were unable to replace the amount of N typically applied to bermudagrass hay fields, there is evidence RP in particular could contribute to mixture productivity and nutritive value.