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Aeschynomene (Aeschynomene americana L.) is a warm‐season annual legume forage used in tropical and subtropical regions; however, there is limited information on agronomic and environmental benefits of aeschynomene when overseeded into bahiagrass (Paspalum notatum Flüggé) swards. The objective of this study was to evaluate the effects of overseeding aeschynomene or applying N fertilizer to existing bahiagrass on forage characteristics, atmospheric N fixation, and N2O‐N emissions. The study was conducted in Ona, FL, from April 2019 to March 2021. Treatments were the split‐plot arrangement of bahiagrass‐aeschynomene or bahiagrass monoculture (main plot) and N fertilization level (0 or 60 kg N ha−1; subplot), distributed in a randomized complete block design with four replicates. Nitrogen fixation was estimated in plots receiving no N fertilization. The static chamber technique was used to estimate N2O‐N emissions. Overseeding aeschynomene did not increase forage accumulation (mean = 1300 kg dry matter [DM] ha−1 harvest−1) or N2O emissions (mean = 15 g N2O‐N ha−1 per day), but increased forage crude protein (CP) concentration (from 98 to 108 g kg−1) when compared to bahiagrass monoculture. Nitrogen fertilization increased forage accumulation (from 1200 to 1400 kg DM ha−1 per harvest) but it did not affect aeschynomene N fixation (84% N derived from atmospheric fixation [Ndfa]). Nitrous oxide emissions had significant temporal variability across all treatments; however, there were no differences in accumulated N2O‐N emissions among treatments (mean = 2.4 kg N2O‐N ha−1 per year). Overseeding aeschynomene is an effective management practice to increase forage CP concentration in pastures without increasing N2O‐N emissions. Core Ideas: Overseeding aeschynomene into bahiagrass increased sward bahiagrass‐aeschynomene forage nutritive value.Nitrogen fertilization increased 18% forage accumulation of bahiagrass.Forage accumulation was the main factor affecting legume atmospheric N fixation.Overseeding aeschynomene into bahiagrass pastures had no impact on soil N2O‐N emissions. [ABSTRACT FROM AUTHOR]

Plant litter is an important nutrient pool in grasslands. Most estimates of N return from litter are based on incubation of attached plant material (live or senescent) instead of dead, detached material on the soil surface. Our objective was to quantify mass, chemical composition, and N disappearance from soil‐surface litter for year‐round forage systems based on N‐fertilized grasses (GN) (290 kg N ha–1 yr–1) or legume–grass mixtures (LG) (30 kg N ha–1 yr–1) when grazed or harvested for hay. Litter mass and composition were measured in winter and summer over 2 yr, and litter was incubated for 180 d to quantify N disappearance. Summer litter mass was greater for GN than LG under grazing (2,840 vs. 1,730 kg ha–1) and hay management (2,780 vs. 1,240 kg ha–1). Cool‐season litter mass for GN was also greater than LG (1,990 vs. 1,200 kg ha–1). Initial litter N concentrations for GN and LG were 26 vs. 23 and 21 vs. 20 g N kg–1 organic matter in summer and winter, respectively. Litter lignin concentration and C/N and lignin/N ratios remained relatively constant. At the end of incubation, remaining litter biomass ranged from 63 to 85%. Nitrogen disappearance was greater for GN than LG, averaging 43 vs. 19 kg ha–1 yr–1, respectively, due to greater herbage accumulation and litter mass for GN. We conclude that year‐round forage systems including legumes contribute important quantities of N via aboveground litter decomposition, but amounts are likely less than for grass systems receiving relatively large N fertilizer inputs. Core Ideas: Aboveground litter is an important nutrient pool in grassland ecosystems.Aboveground litter mass was greater for N‐fertilized grass–grass than legume–grass systems.Chemical composition of aboveground litter reflected partial decomposition.Greater litter N return in N‐fertilized grass systems is associated with greater C footprint. [ABSTRACT FROM AUTHOR]

Plant litter deposition and decomposition play important roles in grassland nutrient cycling. The objective was to evaluate plant litter responses and estimate the N returns via plant litter in contrasting grazing systems, since legume inclusion is hypothesized to result in similar quantities of N return compared with N‐fertilized grass systems. Systems were (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer with a mixture of N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N); (b) bahiagrass (no N fertilizer) during summer and a rye–oat–clovers (Trifolium spp.) mixture + N in winter (Grass+Clover); and (c) bahiagrass (no N fertilizer in summer) with strip‐planted rhizoma peanut (Arachis glabrata Benth.) during summer with a rye–oat–clovers mixture + N during winter (Grass+CL+RP). Litter mass was greatest for Grass+N during October (4,430 kg organic matter [OM] ha−1) and least for Grass+CL+RP in June (490 kg OM ha−1). Litter N concentrations were greatest in Grass+N (16 g kg−1), with similar N concentration for Grass+Clover and Grass+CL+RP litter (14 g kg−1). Contribution of C3 species to litter mass increased from May to July but decreased thereafter. Overall, there was a net return of 47 kg N ha−1 yr−1 via litter across the three systems, and litter decomposition was similar in the three systems. Inclusion of forage legumes during cool and warm seasons in grazing systems has the potential to return similar amounts of N through plant litter deposition as grasses receiving moderate levels of N fertilizer. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is a common practice for sustaining forage production in forage systems in southeastern United States. Warm‐season annual legumes may be an alternative forage to warm‐season perennial grasses that do not require N fertilization. Sunn hemp (Crotalaria juncea L.) is a fast‐growing, warm‐season annual legume native to India and Pakistan. The objective of this 2‐year study was to assess the herbage accumulation (HA), atmospheric N2 fixation (ANF) and nutritive value of sunn hemp. Treatments were the factorial arrangement of two sunn hemp cultivars ("Crescent Sun" and "Blue Leaf"), three seeding rates (17, 28 and 39 kg seed/ha) and seed inoculation (inoculated or non‐inoculated seeds), distributed in a randomized complete block design with four replicates. Crescent sun had greater HA (3,218 vs. 1764 kg DM/ha) and ANF (41 vs. 25 kg N/ha). Blue leaf had greater crude protein (CP) (188 vs. 176 g/kg) and in vitro digestible organic matter (IVDOM) concentrations (564 vs. 531 g/kg) than crescent sun. Non‐inoculated seed had greater CP than inoculated seed, 188 and 177 g/kg, respectively, and inoculation did not affect HA. Intermediate seeding rate (28 kg/ha) decreased HA (2002 kg DM/ha), while HA from high and low seeding rates (17 and 39 kg/ha, respectively) did not differ (2,863 and 2,615 kg DM/ha respectively). Planting non‐inoculated crescent sun at 17 kg/ha seeding rate is a feasible management practice to produce sunn hemp in subtropical regions; however, inoculation should always be recommended for proper establishment. [ABSTRACT FROM AUTHOR]

Overseeding warm-season legumes into warm-season perennial grass pastures may increase productivity and nutritive value of pastures in tropical and subtropical regions. The objective of this study was to investigate the effects of overseeding 'Amarillo' pintoi peanut (Arachis pintoi Krapov. & W.C. Greg.) into Jiggs bermudagrass [Cynodon dactylon (L.) Pers.] pastures grazed at different stubble heights. The experiment was conducted in Ona, FL, from June to October in 2014 and 2015. Treatments were a split-plot design of two sward types (bermudagrass monocultures or overseeded with pintoi peanut, main plots) and two postgrazing stubble heights (15 or 25 cm [SH15 and SH25], subplots) arranged in a randomized complete block design with four replicates. Pastures were mob stocked, with 28-d resting periods between grazing events. There was no effect of stubble height on pintoi peanut plant density (5.8 plants m-2), ground cover (5.8%), or proportion in the herbage mass (HM, 5.2%); however, proportion in the HM increased from 1.1 to 8.2% over 2 yr. There was no effect of sward type on weed ground cover; however, SH25 had greater weed ground cover than SH15 (53.4 vs. 18.2%). Herbage accumulation rate, crude protein, and in vitro digestible organic matter were not affected by sward type (23.4 kg ha-1 d-1, 101 g kg-1, and 431 g kg-1, respectively). Pintoi peanut proportion in the HM increased over time; however, it may take >2 yr to have a significant presence of pintoi peanut in the mixed sward. [ABSTRACT FROM AUTHOR]