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The objective of this study was to evaluate the effects of different potassium (K) fertilization levels and defoliation intensities on performance of "BRS Zuri" guineagrass Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L Jacobs (syn. Panicum maximum Jacq.). Treatments were the factorial arrangement of three K fertilization levels: 0 (control), 40, 80 kg K2O/ha/harvest) and two defoliation intensities (10‐ and 20‐cm stubble heights), distributed in a completely randomized design with five replications. The experiment was conducted in Araguaina, TO, Brazil, from October to January, 2020–2021 and 2021–2022. Plots were harvested four times per year with 21‐day regrowth interval. The 40 and 80 kg K2O/ha/harvest fertilization levels had greater HA than the control (5490 vs. 3,440 kg DM/ha, respectively). There was a K fertilization level × stubble height interaction on tiller population. There was greater tiller population at 20‐ than 10‐cm stubble height at 40 kg K2O/ha/harvest; however, no effect of stubble height was detected at 0 and 80 kg K2O/ha/harvest. Plots fertilized with 80 kg K2O/ha/harvest had greater tiller population than 40 kg K2O/ha/harvest, which was greater than control. Forage harvested at 10 cm had greater crude protein (CP) than 20‐cm stubble height (mean = 11.4% vs. 10.8%). Tissue K concentration increased from control to 40 kg K2O/ha/harvest, but there was no difference between 40 and 80 kg K2O/ha/harvest (mean = 1.1% vs. 3.5%). The combination of 40 kg K2O/ha/harvest and 20‐cm stubble height may be a desirable management strategy to promote Zuri guineagrass productivity in tropical regions. [ABSTRACT FROM AUTHOR]

The geographical distribution of bermudagrass cultivars is limited by freezing events (<0°C), commonly associated with higher latitudes in the northern hemisphere. The lipid composition in the plant cell membranes is critical to promote persistence under freezing conditions. This study evaluated herbage accumulation (HA), nutritive value, and lipid biosynthesis of different bermudagrass cultivars in Ona, FL (27°26' N 82°55' W) and Marianna, FL (30o52' N 85o11' W), in 2 years. Treatments were five bermudagrass cultivars (Coastal, Tifton 44, Tifton 85, Jiggs, and Mislevy) distributed in a randomized complete block design with four replicates. HA was greater in Marianna than in Ona for all cultivars (p < 0.05). Mislevy and Jiggs had greater HA in Marianna than the others (p < 0.05), while all cultivars were similar in Ona (p > 0.05). There was no difference between locations or among the cultivars for crude protein and neutral detergent fibre, but bermudagrass cultivars had greater in vitro digestibility of organic matter (IVDOM) in Marianna than in Ona (p < 0.05). The concentration of unsaturated fatty acids increased in the northern latitude (Marianna; p < 0.05). Coastal had greater unsaturated fatty acid concentration than other cultivars (p < 0.05). Geographical location affects HA, IVDOM, and unsaturated fatty acid concentration of bermudagrass cultivars. The unsaturated fatty acid concentration plays a key role in acclimating bermudagrass to different thermal environments. Coastal showed great potential to tolerate chilling stress in Florida. Further studies may be developed to identify promising molecular markers for cold tolerance in bermudagrass. [ABSTRACT FROM AUTHOR]

Productivity of tropical and subtropical grasslands is often limited by inadequate nitrogen (N) supply. Aeschynomene (Aeschynomene americana L.) is a warm‐season legume that may contribute as N input in grazing systems, but there is limited information about aeschynomene litter decomposition and N dynamics on pastures. The objective of this study was to quantify the effect of overseeding aeschynomene or applying N fertilizer to existing bahiagrass (Paspalum notatum Flüggé) on litter disappearance and decomposition rates. The study was conducted in Ona, FL, from October 2019 to May 2020 and October 2020 to May 2021. Treatments were the split‐plot arrangement of bahiagrass‐aeschynomene or bahiagrass monoculture (main plot) and N fertilization level, (0 [control] or 60 kg N ha−1) as subplot, distributed in a randomized complete block design with four replicates. The nylon bag technique was used to estimate organic matter (OM), N and carbon (C) disappearance, and lignin concentration for 184 days of incubation. Bahiagrass‐aeschynomene had greater OM disappearance (from 330 to 356 g kg−1 OM) and was driven by C disappearance. Nitrogen fertilization did not impact litter decomposition responses, except for C:N ratio. Overseeding aeschynomene is an effective management practice to increase OM decomposition and optimize nutrient cycling in warm‐season pastures. Core Ideas: Overseeding aeschynomene into bahiagrass increased organic matter and N disappearance litter decomposition.Nitrogen fertilization did not affect bahiagrass‐aeschynomene litter decomposition.Bahiagrass‐aeschynomene litter supported soil N mineralization. [ABSTRACT FROM AUTHOR]

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]

Sunn hemp (Crotalaria juncea L.) is a warm‐season legume often used as a cover crop; however, there is limited information about nutrient cycling of sunn hemp residue. The objective of this study was to evaluate the effect of sunn hemp genotype and residue management on plant characteristics, decomposition, and suppression of Fusarium, Pythium, Sclerotinia, and Sclerotium microbe species. Two field experiments were conducted in Ona, FL. In Experiment 1, treatments were the split‐plot arrangement of three sunn hemp genotypes (Ubon, Blue Leaf, and 'Tropic Sun'; main plot) and two biomass managements (removal or leaving the biomass on the field; subplot), distributed in a randomized complete block design. There was a greater biomass accumulation in 2019, but with no differences among genotypes (mean = 4,431 kg DM ha−1). Blue Leaf had greater N concentration than Ubon (23 vs. 19 g kg−1) and greater suppression of the Phytium populations than Ubon and Tropic sun in 2019 (0.9 vs. 2.0 colony forming unit g soil−1). In Experiment 2, the litter bag technique was used to estimate biomass and N decomposition. Treatments were the factorial arrangement of three genotypes and two residue management strategies (incorporated into the soil or placed on the soil surface). Sunn hemp biomass incorporation enhanced organic matter disappearance and N mineralization rate but leaving sunn hemp on the soil surface may result in a steadier N supply for the subsequent crop. Core Ideas: Sunn hemp genotypes differed in chemical composition.The genotype Blue Leaf most effectively suppressed Pythium populations in the soil.Sunn hemp residue management (surface vs. incorporated) affected decomposition.Genotypes did not differ in residue organic matter and N decomposition. [ABSTRACT FROM AUTHOR]

Land application of biochar as a soil amendment can be an effective strategy for reducing nutrient leaching while providing simultaneous benefits to soil health. However, biochar effects on soil nitrogen (N) and phosphorus (P) dynamics in biochar‐amended soils are poorly understood, particularly in Florida sandy soils receiving fertilizers. This study evaluated the effects of different biochar materials (particle size of 0.1 mm produced from pine (Pinus spp.) wood vs. ∼0.5–2 mm produced from fescue (Festuca arundinaceaSchreb.) grass, herein referred as "powder" and "coarse" biochar, respectively) and their application methods (surface vs. incorporated) on N and P leaching from soils amended with inorganic fertilizer or biosolids. Biochar materials were either mixed throughout columns of soil or surface applied at a 1% (w/w) rate. Columns were periodically leached over 6 mo to attain 138 ml (equivalent to ∼1 pore volume) of drainage in each event (total of ∼16 pore volume of leachate). Biochar materials exhibited modest affinity to retain ammonium (NH4+) but showed no ability to sorb nitrate (NO3–). Powder biochar incorporated throughout the soil reduced cumulative NH4–N, NO3–N, and total N mass leached (average of 25% reduction) relative to control (no biochar) treatments. Biochar materials acted as P sources and were ineffective in reducing leachate P. Biosolids generally resulted in significant lower risk of N and P leaching than inorganic fertilizer. Results suggested biochar ability to retain N and P in soils varies with biochar source, application method, and nutrient source. Biochar type and application method affected N and P dynamics in biosolids or inorganic fertilizer‐amended soils, but understanding the mechanisms requires additional study. Core Ideas: Fine‐textured biochar incorporated into the soil reduced leachate N losses.Biochars acted as P sources and were ineffective in reducing leachate P.Biochar type, application method, and nutrient source affected N and P leaching.Biosolids resulted in lower risk of N and P leaching than inorganic fertilizer. [ABSTRACT FROM AUTHOR]

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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]

Nutrient cycling via livestock excreta is an important grassland ecosystem service. This study was conducted in 2016 and 2017 and determined nutrient excretion from cattle grazing three systems: (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) overseeded with rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N), (b) unfertilized bahiagrass overseeded with rye–oat–clover (Trifolium sp.) mixture (Grass+clover), and (c) rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture overseeded with a rye–oat–clover mixture (Grass+CL+RP). Urinary volume excreted in the warm season ranged from 122 to 182 L ha−1d−1, more than double that in the cool season (56–70 L ha−1 d−1). Urinary N concentration during the warm season was greater in Grass+CL+RP compared with Grass+N (4.4 vs. 3.1 g kg−1, respectively). In addition, fecal dry matter and organic matter output was greater for Grass+N than for steers grazing Grass+CL+RP during the warm season (3.8 and 3.2 vs. 2.8 and 2.2 kg hd−1 d−1, respectively). Total annual feces excretion concentrations of P, K, Mg, and N were greater in the Grass+N than in Grass+CL+RP system. The introduction of legumes increased the proportion of N returning via urine. However, when summed across seasons, total N excretion (feces and urine) was greater in Grass+N than in Grass+CL+RP (89 vs. 71 kg ha−1 yr−1), mainly due to the greater stocking rate in the former. Grass–legume systems receiving 34 kg N ha−1 yr−1 recycled 80% of the N recycled in the grass system receiving 224 kg N ha−1 yr−1, indicating the potential of forage legumes to add N to grasslands. Core Ideas: Nutrient cycling and ecosystem services could increase in grass–legume mixtures.The introduction of legumes could reduce N inputs in beef‐forage systems.The introduction of legumes in grass pastures increase the N available for plant absorption. [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]

Sunn hemp (Crotalaria juncea L.) is an annual legume widely used as cover crop; however, there is potential to use it as forage. The objective of this study was to evaluate forage characteristics of five sunn hemp genotypes (herbage accumulation, nutritive value, N fixation, and nematode control), and beef heifer responses (intake and digestibility) to sunn hemp dietary inclusion. Two experiments were conducted at Ona, FL in 2016 and 2017. In Experiment 1, treatments were the factorial arrangement of five sunn hemp genotypes (AU Golden, Crescent Sunn, Ubon, Blue Leaf and Red Mini) and two harvesting time (60 d after seeding or flowering) in a randomized complete block design. In Experiment 2, treatments were 100% sun hemp hay, 50% sunn hemp–50% bermudagrass [Cynodon dactylon (L.) Pers] hay, or 100% bermudagrass hay diets distributed in a completely randomized design. In Experiment 1, Crescent Sunn had the greatest herbage accumulation [15.2 Mg dry matter (DM) ha−1], N fixation (81 kg N ha−1), and nematode control (80% reduction). AU Golden had the greatest crude protein concentration at 60 d after seeding and flowering (155 and 162 g kg−1, respectively). In Experiment 2, increasing the proportion of sunn hemp in the diet decreased total forage DM intake (1.6, 1.4, and 1.2 as a % bodyweight with 0, 50, and 100% sunn hemp inclusion). Sunn hemp harvested 60 d after seeding is adequate to meet the nutritional requirements of most beef cattle categories but the genotype choice affects herbage accumulation and nutritive value. [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]

Pastures represent the major cropping system where biosolids are recycled in Florida, yet limited information is available documenting the agronomic benefits of biosolids recycling programs. A 2‐yr experiment evaluated bahiagrass (Paspalum notatum Flügge) responses to application of biosolids and inorganic fertilizer applied either alone or in combination with biochar. Our hypothesis was that biochar could alter soil N and P dynamics, thus, affecting crop nutrient use efficiency. Treatments were a factorial arrangement of four fertilizer sources (inorganic fertilizer, thermally dried Class AA biosolids, aerobically digested Class B biosolids, and anaerobically digested Class B biosolids; surface‐applied at 160 kg plant available N ha−1 yr−1) with or without biochar (applied at 1% wt basis). Bahiagrass total annual herbage accumulation was similar for biosolids and inorganic fertilizer treatments in 2017; however, inorganic fertilizer and aerobically digested Class B biosolids increased total annual herbage accumulation by as much as ∼29% relative to other sources in 2018. Biosolids and inorganic fertilizer increased bahiagrass crude protein (CP) concentration by as much as ∼22 and ∼39% in 2017 and 2018, respectively, compared to unfertilized treatment. No treatment effects were observed on in vitro digestible organic matter (IVDOM) concentration in 2017; however, in 2018 biosolids resulted in greater IVDOM than inorganic fertilizer. Data suggested no benefit of biochar on bahiagrass responses. Bahiagrass tissue mineral concentrations in both biosolids and inorganic fertilizer treatments were generally within sufficient range for optimum plant growth. Biosolids can be a viable alternative for sustainable bahiagrass production while reducing the dependence on inorganic fertilizer. [ABSTRACT FROM AUTHOR]

Increased grazing land management intensification through the selection of productive species and the use of N affects the amount and quality of C and N inputs to the soil. This study evaluated the short-term impacts of litter quality on litter decomposition and C and N distribution among soil size-density fractions. A 168-d litter bagmesocosm experiment and a 120-d incubation study evaluated the decomposition of three perennial species [rhizoma peanut (Arachis glabrata Benth., RP), bahiagrass (Paspalum notatum Flügge; BG), and sawpalmetto (Serenoa repens Bartr., SP)] on grazing land soils with contrasting C concentrations (3.4 and 18 g C kg-1; Buck Island Ranch and Ona, respectively). Soil did not affect litter decomposition. There was less remaining biomass at the end of incubation for RP and BG (58%) than SP (79%). Nitrogen immobilization occurred on SP litter, probably because of its high initial lignin/N and fiberbound N/N ratios (43 and 384 g kg-1 organic matter, respectively). Litter had no effect on soil C and N concentrations in size-density fractions; however, greater proportions of C and N (~47 and 59%, respectively) were found in the light-free fraction. Nitrogen addition promoted C and N accumulation in the mineral fraction. These results suggest plant litter chemical characteristics played a more important role on litter decomposition than soil C and N concentrations. Management intensification through changes in plant species and N fertilization had positive effects on C and N dynamics in coarse-textured soils, with enhanced decomposability of cultivated forage species relative to native vegetation. [ABSTRACT FROM AUTHOR]

Limpograss [Hemarthria altissima (Poir.) Stapf & C.E. Hubb.] is commonly used as stockpiled forage. Variation in forage characteristics during the stockpiling period may affect supplementation strategies. Our objective was to characterize herbage mass (HM) and nutritive value of different canopy layers of stockpiled limpograss under continuous stocking from January to March in 2014 and 2015. Treatments were two limpograss cultivars (Floralta or Gibtuck) and three canopy layers (below 25 cm [CL0], 25–50 cm [CL25], or above 50 cm [CL50]) sampled biweekly. Gibtuck had greater HM (6.1 vs. 5.5 Mg ha−1) and in vitro digestible organic matter (IVDOM, 490 vs. 440 g kg−1) than Floralta. Herbage mass was 4.2, 3.3, and 1.0 Mg ha−1 in January, 2.5, 3.2, and 0 Mg ha−1 in February, and 3.4, 0.3, and 0 Mg ha−1 in March for CL0, CL25, and CL50, respectively. The IVDOM concentrations were 380, 470, and 570 g kg−1 in January for CL0, CL25, and CL50, and 390 and 450 g kg−1 in February and 390 and 400 g kg−1 in March for CL0 and CL25, respectively. Leaf proportion in the canopy decreased from CL50 to CL0. To meet the nutritional requirements of beef cattle grazing stockpiled limpograss pastures, it is necessary to adjust the supplementation quantity and composition during the stockpiling period due to the variation in HM, plant‐part proportion, and nutritive value of the canopy. [ABSTRACT FROM AUTHOR]

Pintoi peanut (Arachis pintoi Krapov. & W.C. Greg.) is a warm‐season perennial legume with potential for use in grass–legume mixtures in Florida; however, limited information exists about its establishment in mixtures with bahiagrass (Paspalum notatum Flügge). The objective of this experiment was to evaluate the establishment of bahiagrass cv. "Argentine" and pintoi peanut cv. "Amarillo" as monocultures or mixture. The experiment was conducted in Ona, FL, from June to October of 2014 and 2015. Treatments were a split‐plot design of seeding strategies (bahiagrass monoculture, pintoi peanut monoculture or bahiagrass‐pintoi peanut mixtures; main plots) and two N fertilization strategies (30 or 80 kg/ha N; 30N and 80N; subplots), with four replicates. Measurements of plant density and frequency were taken every 4 weeks after seeding. Ground cover and herbage mass (HM) measurements were taken 112 days after seeding. Pintoi peanut ground cover was affected by seeding strategy × N level interaction. Ground cover was greater with 80N than 30N when pintoi was seeded in monoculture (3.6% vs 1.5% respectively) but not when it was seeded with bahiagrass (2.1%). There was no effect of seeding or N strategy on pintoi peanut proportion in HM (1.4%). Bahiagrass ground cover was not affected by seeding or N strategy (15.9%); however, its proportion in the HM was greater in 80N than 30N (12.1% vs 9.4% respectively). Mixed seeding did not negatively affect the establishment of bahiagrass and pintoi peanut and greater N fertilization levels improved some establishment parameters, with no negative effect for pintoi peanut. [ABSTRACT FROM AUTHOR]

Rhizoma peanut (Arachis glabrata Benth.) is a widely used warm-season legume in Florida. Ecoturf is a rhizoma peanut germplasm with superior nutritive value; however, there is limited information about the effects of regrowth interval on this characteristic. The objective was to investigate the effects of regrowth interval on in situ crude protein (CP) and dry matter (DM) disappearance of Ecoturf compared with the predominant cultivar 'Florigraze'. The experiment was conducted from July to October of 2014 and 2015. Treatments were a split-plot design of Florigraze and Ecoturf (main plots) harvested at regrowth intervals of 4, 8, and 12 wk (subplots), distributed in a randomized complete block design with four replicates. Samples of each treatment were incubated in two steers (Bos spp.) for 0, 3, 6, 9, 12, 24, 48, and 72 h, and DM and CP disappearance were fit to a nonlinear model. Ecoturf had greater CP concentration than Florigraze (193 vs. 168 g kg-1). There was no effect of genotype on in situ effective disappearance of CP (715 g CP kg-1); however, there was a quadratic effect of regrowth interval. Ecoturf had greater effective disappearance of DM than Florigraze only at 4 wk of regrowth (597 vs. 563 g kg-1). Dry matter and CP disappearance parameters may differ between Ecoturf and Florigraze. Harvesting at a regrowth interval of 8 wk or less may improve rhizoma peanut nutritive value. [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]

Despite scientific evidence suggesting that warm-season grasses can respond favorably to K and P fertilization, the increasing costs of fertilizers limit the extent to which these nutrients are used in pastures and hayfields. Two field studies evaluated 'Jiggs' bermudagrass [Cynondon dactylon (L.) Pers.] and 'Floralta' limpograss (Hemarthria altissima Stapf. and Hubbard) herbage accumulation (HA), nutritive value, and persistence to reduced fertilization strategies during 2012 to 2014. Treatments were allocated in a split-plot design with N (90 or 180 kg N ha-1, bermudagrass study) or harvest frequency (6 vs. 12 wk, limpograss study) as the main factors and P (0, 8.7, and 17.4 kg P ha-1) and K (0, 33, and 66 kg K ha-1) levels as subplots. Bermudagrass HA increased linearly (up to 377% in Year 3) as K level increased. Similarly, K fertilization increased limpograss HA from 8.4 to 11.6 Mg ha-1 in 2013 and from 5.8 to 15.7 Mg ha-1 in 2014 as K levels increased from 0 to 66 kg K ha-1; however, no effect was observed in 2012. Bermudagrass HA and ground cover decreased from 2012 to 2014 in all K treatments. Conversely, decreases in limpograss HA and ground cover over time were observed only in the control (no K) treatments. Bermudagrass and limpograss crude protein concentrations generally decreased with increased K level. No effects of N or P were observed. Continuous aboveground removal without proper K fertilization is detrimental to bermudagrass and limpograss production and persistence. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilization affects grassland herbage accumulation and nutritive value, but its effect on the distribution of nutrients among soil and plant nutrient pools is less understood. This 2-yr study determined the effect of N fertilization levels of rotationally stocked ‘Tifton 85’ bermudagrass (Cynodon spp.) pastures on nutrient concentration and content in soil (top 20 cm), live root-rhizome mass, live herbage mass, and aboveground plant litter pools. Treatments were 50, 150, and 250 kg N ha−1 yr−1. Greater N fertilization increased N concentration in all plant nutrient pools and potassium (K) concentration in live herbage and plant litter, but plant-pool phosphorus (P) concentrations changed little across N levels. With increasing N fertilization, live herbage (118–159 kg ha−1) and plant litter (8–14 kg ha−1) K pools increased linearly, but the Mehlich-1 extractable soil K pool decreased linearly (182–139 kg ha−1); live herbage (50–92 kg ha−1), plant litter (30–49 kg ha−1), and root rhizome (63–95 kg ha−1) N pools also increased with increasing N fertilization. The proportion of K in various pools was affected more by N fertilization than were proportions of N, P, or carbon. Soil was the dominant pool for all nutrients, with the exception of K in pastures fertilized at the greatest N level. Increasing N fertilization increased the proportion of K and N contained in plant pools and decreased the proportion in soil. Although N fertilization affected quantity and proportion of nutrients in pools in Tifton 85 pastures, changes occurred to a limited extent, with the exception of plant and soil K pools. [ABSTRACT FROM AUTHOR]

Feedstock mineral composition influences suitability for conversion to energy and soil nutrient removal impacts fertilization and economics of production. However, few data are available on mineral composition and removal for perennial bioenergy grass crops, especially in the southeastern United States. This study was conducted at three locations in Florida comparing biomass yield, mineral composition, and mineral removal of sugarcane (Saccharum spp. hybrid), energycane (Saccharum spp. hybrid), sweetcane [S. arundinaceum (Retz.) Jesw.], elephantgrass [Pennisetum purpureum (Schum.)], giant reed (Arundo donax L.), and giant miscanthus [Miscanthus x giganteus (Greef and Deuter ex Hodkinson and Renvoize)]. Tissue ash concentrations were very similar among species at each site. However, mineral concentrations varied by site and species. Giant miscanthus had the least dry biomass yield (13.5 Mg ha-1), followed by giant reed (23.8 Mg ha-1), which had lower dry matter yield than the remaining species (35.3 Mg ha-1). Giant miscanthus contained less moisture than all other species at each site. Leaves accounted for only 23% of total biomass. Nitrogen, P, and K removals were highest for sugarcane, sweetcane, energycane, and elephantgrass and averaged 179, 41, and 279 kg ha-1 yr-1, respectively and lowest for giant reed (147, 20, and 157 kg ha-1 yr-1 ) and giant miscanthus (56, 12, and 46 kg ha-1 yr-1). Relatively high dry matter yields desirable for bioenergy production can be achieved using perennial grasses in the region, but moderate to high fertility inputs will likely be needed to sustain high production levels. [ABSTRACT FROM AUTHOR]

Warm-season grasses require N fertilization to achieve their full production potential; however, increased costs have limited the use of N by beef cattle (Bos spp.) producers. The objective of this study was to test the effects of two grazing frequencies (2 and 4 wk) on production, nutritive value, and persistence of 'Argentine' (tetraploid), 'Pensacola', 'Tift on 9', and 'UF Riata' (diploids) bahiagrass (Paspalum notatum Flügge) cultivars fertilized with 60 kg N ha-1 yr-1. The study was conducted in Ona, FL, from January 2010 to December 2011. Treatments were eight factorial combinations of two grazing frequencies (2 and 4 wk) and four bahiagrass cultivars. The four cultivars were grazed by beef cows (505±30 kg) for approximately 8 h to a 7.5-cm stubble height at 2- or 4-wk intervals. Diploid cultivars had greater herbage accumulation (HA) in the spring; however, Argentine had greater annual HA in 2010 and 2011. Plots grazed at 4 wk had approximately 50% greater HA than 2-wk grazing frequency. Argentine and Pensacola had greater root and rhizome mass than Tift on 9 and UF Riata when grazed every 2 wk, while Argentine had greater cover than any of the diploids when grazed at the 2-wk frequency. Results show that Argentine is a productive and persistent bahiagrass for beef cattle producers using limited N fertilization and frequent grazing in Florida. Decreasing grazing frequency is an effective management practice to increase bahiagrass HA and persistence, particular the upright-growing Tift on 9 and UF Riata. [ABSTRACT FROM AUTHOR]

The article discusses a study that assessed the impact of the application of an aluminum water treatment residual (Al-WTR) on phosphorus (P) in soil, leachate P concentrations, bahiagrass yield and nutritive value and forage responses. It describes the effect of soil disturbance due to the Al-WTR on P transport in soil. It also cites strategies for minimizing P losses from agricultural soils.

Effective options for reducing P losses from P‐enriched soils remain a major challenge, particularly in intensive agricultural areas. While different strategies have been shown to control P mobility (e.g., Ca‐ and Al‐based soil amendments and riparian buffers), they provide no means to reduce in situ soil P concentrations. The objectives of this study were to: (i) investigate the potential P‐removal capacity of four bioenergy crops (elephantgrass [Pennisetum purpureum Schumach.], sugarcane [Saccharum spp.], switchgrass [Panicum virgatum L.], and stargrass [Cynodon nlemfuensis Vanderyst]) grown on a manure‐enriched soil, and (ii) examine the impacts of crop P uptake on soil P concentrations and surface groundwater quality. Treatments were distributed in a completely randomized design with four replicates. The greatest dry matter yields were observed for elephantgrass (average of 46 Mg ha−1 yr−1) followed by sugarcane (average of 40 Mg ha−1 yr−1). Tissue P concentrations were greater for stargrass (∼4 g kg−1) than elephantgrass (3.2 g kg−1) or sugarcane (1.9 g kg−1). Elephantgrass showed the greatest cumulative P removal (420 kg P ha−1 during the 3‐yr period). Soil P concentrations in the Ap horizon decreased with time, while an increase in soil P concentration was observed in the Bh horizon. Elephantgrass resulted in the lowest leachate P concentrations (∼0.5 mg P L−1) at the 60‐cm depth. Crop species had no effect on leachate P at the 90‐cm depth. Growth of elephantgrass as a biofuel feedstock appears to be an effective approach for remediation of excess soil P. [ABSTRACT FROM AUTHOR]