Brachiaria 'Mulato II' is a hybrid brachiaria grass with superior nutritive value when compared with other warmseason grasses. The performance of 2 new brachiaria grass hybrids was compared with that of Mulato II in terms of herbage accumulation, nutritive value and ground cover in a series of experiments. In Experiment 1, Mulato II and lines BR02/1752 (now cv. Cayman) and BR02/1794 were harvested at 3-and 6-wk regrowth intervals in South Florida. Mulato II had greater herbage accumulation and ground cover than Cayman and BR02/1794, while Mulato II and Cayman had greater in vitro digestible organic matter (IVDOM) concentration than BR02/1794. Regrowth interval did not affect herbage accumulation and ground cover but herbage harvested at 3-wk intervals had greater nutritive value than 6-wk regrowth. In Experiment 2, Mulato II had similar IVDOM and CP concentrations to but greater herbage accumulation, ground cover and plant density than Cayman in North-Central Florida. In Experiment 3, Mulato II and Cayman plots were grazed at 2-, 4-or 6-wk intervals, and herbage accumulation and nutritive value were similar for both cultivars. Herbage nutritive value decreased and ground cover increased linearly as regrowth interval increased from 2 to 6 wk, and Mulato II had greater ground cover than Cayman. The new hybrids displayed no production or nutritive value advantages over Mulato II; regrowth intervals of less than 3 wk should be avoided to maintain Brachiaria hybrid stands in this subtropical environment. ResumenEl híbrido de braquiaria Mulato II es un cultivar (cv.) con valor nutritivo superior al de otras gramíneas de clima cáli-do. En la Florida se compararon, en 3 experimentos, 2 nuevos híbridos de braquiaria: las líneas BR02/1752 (ahora: cv. Cayman) y BR02/1794, con cv. Mulato II, en términos de producción de forraje, valor nutritivo y cobertura del suelo. En el primer ensayo, conducido en el sur de la Florida y con intervalos de corte de 3 y 6 semanas, el cv. Mulato II presentó mayor producción de forraje y cobertura que el cv. Cayman y la línea BR02/1794, mientras que los cvs. Mulato II y Cayman presentaron mayor digestibilidad in vitro de la materia orgánica (DIVMO) que la línea BR02/1794. El intervalo de corte no afectó la producción de forraje y la cobertura pero en los cortes cada 3 semanas el valor nutritivo fue mayor que en los cortes cada 6 semanas. En el segundo ensayo, conducido en el centro-norte de la Florida, Mulato II presentó valores de IVDMO y concentración de proteína cruda similares a cv. Cayman, pero mayor producción de forraje, cobertura y densidad de plantas. En un tercer ensayo, también en el centro-norte de la Florida, los cvs. Mulato II y Cayman fueron sometidos a pastoreo cada 2, 4 y 6 semanas. Aquí, la producción de forraje y el valor nutritivo de ambos cultivares fueron similares. El valor nutritivo disminuyó mientras que la cobertura aumentó en forma lineal a medida que el intervalo de pastoreo aumentó de 2 a 6 semanas; el cv. Mulato II tuvo mayor cobertura que el cv. Cayman. ...

‘Jiggs’ bermudagrass [Cynodon dactylon (L.) Pers.] is a productive forage in the southeastern United States; however, there is limited information on grazing management of this bermudagrass ecotype. The objective of this study was to test the effects of different stocking rates on animal performance and herbage characteristics of Jiggs pastures. The experiment was conducted in Ona, FL, from May to August 2011 and 2012. Treatments were three stocking rates, 3.0 (low), 7.5 (medium), and 12.0 animal units (AU = 450 kg liveweight [LW]) ha−1 (high). The animals received 10 g kg−1 LW concentrate supplement daily during the experimental period. Heifer weight was recorded every 28 d and herbage parameters were measured every 14 d. There was a linear decrease (P < 0.01) in herbage mass (HM, from 3.8 to 2.4 Mg ha−1), light interception (from 94 to 71%), forage height (from 17 to 9 cm), and herbage allowance (HA, from 2.3 to 0.4 kg dry matter kg−1 LW) with increasing stocking rate. There was no effect (P > 0.10) of stocking rate on herbage nutritive value. Jiggs ground cover decreased (P < 0.01) from 95 to 39% with increasing stocking rates. Heifer average daily gain decreased (P < 0.01, from 0.7 to 0.3 kg d−1) and gain per hectare (P = 0.01, from 692 to 1064 kg ha−1) increased as stocking rate increased. Despite greater gain per hectare with increasing stocking rate, continuously stocked Jiggs should not be grazed below 17‐cm stubble height during the growing season to maintain the stand.

The objective of this study was to evaluate the effects of monensin supplementation on animals receiving warm-season grass with limited supplementation. In Exp. 1, treatments were a factorial combination of 2 stocking rates (1.2 and 1.7 animal unit [AU] [500 kg BW]/ha) and supplementation with monensin (200 mg/d) or control (no monensin) distributed in a complete randomized design with 3 replicates. Thirty Angus × Brahman crossbred heifers (Bos taurus × Bos indicus) with initial BW of 343 ± 8 kg were randomly allocated into 12 bahiagrass (Paspalum notatum) pastures and supplemented with 0.4 kg DM of concentrate (14% CP and 78% TDN) daily for 86 d. Herbage mass (HM) and nutritive value evaluations were conducted every 14 d, and heifers were weighed every 28 d. There was no effect (P ≥ 0.97) of monensin on HM, herbage allowance (HA), and ADG; however, animals receiving monensin had greater (P = 0.03) plasma urea nitrogen (PUN) concentrations. The stocking rate treatments had similar HM in June (P = 0.20) and July (P = 0.18), but the higher stocking rate decreased (P < 0.01) HM and HA during August and September. Average daily gain was greater (P < 0.01) for the pastures with the lower stocking rate in August but not different in July and September (P ≥ 0.15). Gain per hectare tended to be greater on pastures with the higher stocking rate (P ≤ 0.06). In Exp. 2, treatments were 3 levels of monensin (125, 250, and 375 mg/animal per day) and control (no monensin) tested in a 4 × 4 Latin square with a 10-d adaptation period followed by 5 d of rumen fluid collection and total DMI evaluation. Blood samples were collected on d 4 and 5 of the collection period. Ground stargrass (Cynodon nlemfuensis) hay (11.0% CP and 52% in vitro digestible organic matter) was offered daily. The steers received the same supplementation regimen as in Exp. 1. Total DMI was not different among treatments (P = 0.64). There was a linear increase (P ≤ 0.01) in propionate and a tendency for decreased acetate (P ≤ 0.09) concentrations in the rumen with increasing levels of monensin; however, there was no effect (P ≥ 0.19) of monensin levels on ruminal pH and ruminal concentrations of butyrate and ammonia. In addition, there was no effect (P ≥ 0.73) of monensin levels on plasma concentrations of glucose, insulin, IGF-1, and PUN. In summary, monensin supplementation effects were not detected at either stocking rate and may not be effective in increasing performance of beef cattle grazing low-quality warm-season grasses with limited supplementation.

Core Ideas Bermudagrass K fertilization affects forage characteristics. Bermudagrass K fertilization effects are influenced by N fertilization. K fertilization is crucial to increase belowground reserves of bermudagrass. Adequate supply of potassium (K) is an important factor that can affect bermudagrass [Cynodon dactylon (L.) Pers.] production and persistence, particularly in soils with limited nutrient holding capacity. The objectives of this study were to (i) evaluate the effects of different nitrogen (N) and K fertilization strategies on Jiggs bermudagrass herbage accumulation (HA), root–rhizome mass, and K concentration and accumulation in above‐ and belowground tissue; and (ii) identify the critical minimum tissue K concentration below which bermudagrass HA is reduced. The experiment was conducted in a greenhouse at Ona, FL, from August to December, 2014 and 2015. Treatments were a factorial combination of three N (0, 45, and 90 lb/acre) and four K2O fertilization levels (0, 18, 36, and 72 lb K2O/acre, the equivalent of 0, 15, 30, and 60 lb K/acre) after every harvest, distributed in a completely randomized design with four replicates. Herbage was harvested every 6 weeks, and root and rhizome mass determined at the end of each year. There were no effects of K fertilization on HA and root–rhizome mass when no N was applied; however, Jiggs HA and root–rhizome biomass increased linearly with increasing K fertilization levels at 45 and 90 lb N/acre. For these N levels, HA increased with tissue K concentration up to 1.4%. Root and rhizome K concentrations decreased linearly with increasing levels of N. Conversely, root–rhizome K content increased with increasing levels of N fertilization. Potassium fertilization increased HA and root–rhizome mass of Jiggs bermudagrass; however, the responses were influenced by N fertilization levels.

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.

Core Ideas Bahiagrass pastures on soils with low K concentration may not respond to K fertilization. Tissue K concentration in bahiagrass is variable and dependent on fertilization levels. Bahiagrass tissue K concentration of 17 g kg−1 was related to the greatest herbage accumulation in plants receiving greater levels of fertilization. Bahiagrass (Paspalum notatum Flügge) is the most utilized forage for beef cattle (Bos spp.) in Florida, but there is concern that bahiagrass pastures are declining due to insufficient K fertilization. Two studies determined the effects of K and N fertilization on bahiagrass herbage mass (HM) and nutritive value in field plots (Exp. 1), and greenhouse (Exp. 2). At two locations from May to December 2014 and 2015, Exp. 1 evaluated the combinations of three N fertilization levels (0, 50 kg N ha−1 in May, or 50 kg N ha−1 in May and August) and two levels of K fertilization (0 or 42 kg K ha−1). Potassium fertilization did not affect HM, crude protein (CP), or in vitro digestible organic matter (IVDOM); however, tissue K concentration increased from 10.6 to 11.2 g kg−1 with increasing K fertilization. Plots fertilized with N had greater HM than the control, but there was no difference between plots fertilized in May only vs. those fertilized in May and August. Experiment 2 was conducted in a greenhouse in 2014 and 2015 with a factorial combination of three levels of N fertilization (0, 50, and 100 kg N ha−1) and four levels of K fertilization (0, 16, 33, and 66 kg K ha−1). There was a quadratic relationship between tissue K concentration and herbage accumulation (HA) and maximum HA occurred with tissue K concentration of 17 g kg−1. Bahiagrass tissue K concentration and response to K fertilization are variable and can be related to fertilization levels.

Quantifying spatial and temporal fluxes of phosphorus (P) within and among agricultural production systems is critical for sustaining agricultural production while minimizing environmental impacts. To better understand P fluxes in agricultural landscapes, P-FLUX, a detailed and harmonized dataset of P inputs, outputs, and budgets, as well as estimated uncertainties for each P flux and budget, was developed. Data were collected from 24 research sites and 61 production systems through the Longterm Agroecosystem Research (LTAR) network and partner organizations spanning 22 U.S. states and 2 Canadian provinces. The objectives of this paper are to (a) present and provide a description of the P-FLUX dataset, (b) provide summary analyses of the agricultural production systems included in the dataset and the variability in P inputs and outputs across systems, and (c) provide details for accessing the dataset, dataset limitations, and an example of future use. P-FLUX includes information on select site characteristics (area, soil series), crop rotation, P inputs (P application rate, source, timing, placement, P in irrigation water, atmospheric deposition), P outputs (crop removal, hydrologic losses), P budgets (agronomic budget, overall budget), uncertainties associated with each flux and budget, and data sources. Phosphorus fluxes and budgets vary across agricultural production systems and are useful resources to improve P use efficiency and develop management strategies to mitigate environmental impacts of agricultural systems. P-FLUX is available for download through the USDA Ag Data Commons (https://doi.org/10.15482/USDA.ADC/1523365).

Forage is the primary feed source for livestock in tropical regions and energy is one of the most important nutrients for ruminant nutrition. The effects of harvest management of Marandu palisade grass (Brachiaria brizantha cv. Marandu Syn. Urochloa brizantha cv. Marandu) on non-structural carbohydrate (NSC) concentrations were evaluated. A plot (Experiment 1) and a greenhouse study (Experiment 2) were conducted in 2013–14. In Experiment 1, treatments were the factorial arrangement of two harvest times and two vertical canopy layers (upper and intermediate), distributed in a completely randomized design with five replicates. In Experiment 2, treatments were the factorial arrangement of six harvest times and two morphological fractions (leaf blade and pseudostem). In both experiments, NSC concentration increased during the day. Upper and intermediate canopy layers had greater NSC concentration at 15.00 than 06.00 h during spring and summer. In addition, the magnitude of NSC increase was greater in the upper than intermediate canopy layer and in spring than summer. Marandu palisade grass shows greater digestibility in the afternoon than morning, representing an opportunity to optimize energy concentration through harvest management.