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Although perennial bioenergy crops provide a potential for soil C sequestration, high fertilizer inputs are required to sustain yields. Land application of bioenergy byproducts can be an effective strategy to reduce the use of inorganic fertilizer. This study examined the impacts of elephantgrass [Pennisetum purpureum (L.) Schum.] bioenergy cropping and conventional pasture on soil C and N responses. Treatments included (a) bahiagrass + 50 kg N ha−1 yr−1 (BHG), (b) elephantgrass + 50 kg N ha−1 yr−1 (E50), (c) elephantgrass + 50 kg N ha−1 yr−1 + fermentation residual (E50FR), (d) elephantgrass + 50 kg N ha−1 yr−1 + biochar (E50BC), and (e) elephantgrass + 250 kg N ha−1 yr−1 (E250). Soil C and N responses occurred mainly at the 0‐ to 10‐cm depth. Biochar resulted in the largest increase in soil C stocks at the 0‐ to 10‐cm depth (5.8 Mg C ha−1 in 2012 vs. 40 Mg C ha−1 in 2016), but no differences were observed among the other treatments. Conversely, greater soil N stocks at the 0‐ to 10‐cm depth were associated with the BHG (0.8 and 0.34 Mg N ha−1 for other treatments). Biochar favored N and C accumulation in the mineral‐associated (<53 μm) fraction, possibly from the accumulation of fine biochar fragments. In contrast, fermentation residual promoted C accumulation in unprotected light fraction. These results are supported by the δ13C signature and C/N ratios of the fractions. Results underscore the value of recycling biochar in bioenergy cropping systems as a means of improving C in coarse‐textured soils. [ABSTRACT FROM AUTHOR]

The ingrowth core method for measuring root accumulation has several advantages over sequential soil cores or mini-rhizotrons. However, current ingrowth core designs are not well suited for use with rhizomatous perennial forage species or when defoliation occurs during the measurement period. Our objective was to develop a modified ingrowth core device and to evaluate its use for measuring root-rhizome accumulation of a rhizomatous perennial forage in a hay management context. The modified ingrowth cores were constructed of 4-mm polyester mesh surrounding a 7.5-cm diameter cylinder constructed of cage wire. Field testing of the core design involved placing three ingrowth cores in each of four replicates of six treatments arranged in a randomized complete block design. Treatments consisted of six rhizoma peanut (Arachis glabrata Benth.) entries, and they were evaluated during 2017 and 2018. The ingrowth core design facilitated ease of placement, maintenance of core structural integrity throughout 100-d deployment periods, rapid location of cores using a metal detector at the end of deployment periods, and precision to detect differences among treatments. We conclude that this modified ingrowth core design is well suited for measuring root-rhizome accumulation rate of perennial forage species. [ABSTRACT FROM AUTHOR]

Bahiagrass (Paspalum notatum Flüge) 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. [ABSTRACT FROM AUTHOR]

Sand blackberry (Rubus cuneifolius Pursh) is a troublesome perennial weed in Florida rhizoma peanut (Arachis glabrata Benth.)-grass pastures. The degree to which it can be controlled by defoliation is not well understood. In 2011 and 2012, blackberry regrowth and persistence responses were assessed by clipping every 35 d to three stubble heights (8, 16, and 24 cm), with or without simultaneous removal of all leaf from remaining stubble. Blackberry dry matter harvested decreased linearly (12.8 to 8.5 g m-2) as clipping stubble height increased when remaining stubble leaf was removed, but there was a linear increase in blackberry harvested with increasing clipping stubble height (12.1 to 26.0 g m-2) if remaining stubble leaf was not removed. Across stubble heights, cumulative change in blackberry cover across the 2 yr was -15% units if stubble leaf was removed compared with +1% unit when leaf remained intact. As stubble height increased from 8 to 24 cm, blackberry cover increased linearly, both when stubble leaf was removed (-18 to 0% units, respectively) and when leaf remained intact (-12 to +17% units, respectively). In Year 1, blackberry stem density decreased 10 stems m-2 when stubble leaf was removed and 4 stems m-2 when leaf remained intact, but there was no effect of leaf removal in Year 2. Both clipping stubble height and removal of leaf mass affected blackberry regrowth and cover responses, suggesting that combining leaf removal by browsing animals with periodic close mowing will reduce blackberry cover, mass, and stem density. [ABSTRACT FROM AUTHOR]

Supplements or conserved forage are often used to overcome forage quantity deficits for beef cattle, but stockpiled forage can be more economical. Limpograss [Hemarthria altissima (Poir.) Stapf & C.E. Hubb.] is the best available species for stockpiling in Florida because it is productive in autumn and maintains greater digestibility than other grasses at advanced stages of maturity. New limpograss hybrid breeding lines have been developed, but they have not been tested under stockpiling. Three limpograss breeding lines (1, 4F, and 10) and the most-used cultivar, Floralta, received 50 or 100 kg N ha-1 at initiation of stockpiling and herbage accumulated for 8, 12, or 16 wk. Entry 4F had greater herbage accumulation (7.3 Mg ha-1) than Entries 10, 1, and Floralta (6.1, 6.0, and 5.4 Mg ha-1, respectively). Entry 4F also had greater in vitro digestible organic matter (IVDOM) concentration (530-594 g kg-1) than Entries 1 and Floralta, but 4F was not different from Entry 10 (519-531 g kg-1) after 12 and 16 wk of accumulation. As stockpiling period increased from 8 to 16 wk, herbage accumulation increased from 5.3 to 7.4 Mg ha-1, dead material proportion increased from 1 to 10%, and herbage crude protein (CP) decreased from 44 to 32 g kg-1. Limpograss hybrids 4F and 10 are superior to Floralta for stockpiling, stockpiling period should not be longer than 12 wk, and protein supplement will be required to achieve satisfactory animal performance on stockpiled limpograss. [ABSTRACT FROM AUTHOR]

Cultivar Tifton 85 bermudagrass (Cynodon spp.) is often propagated using stolons, but the planting rate required for successful establishment varies under different soil conditions and on‐farm irrigation management. In the sandy soils of the U.S. Gulf Coast, desiccation of planting material can occur rapidly even under irrigated conditions due to variable on‐farm irrigation management, and few studies have evaluated stolon planting rate effects under these conditions. The objective was to assess the effect of stolon planting densities on establishment of Tifton 85. Treatments in this 2‐yr field study were five planting rates including 1120, 1570, 2020, 2470, and 2920 kg ha−1 arranged in four replicates of a randomized complete block design. Increasing planting rates increased bermudagrass frequency, ground cover, and dry matter harvested and decreased weed cover. All treatments had >80% bermudagrass frequency of occurrence and ground cover 3 mo after planting in 2011, but the three greatest planting rates achieved 80% frequency at 40 days after planting (DAP) compared with 68 DAP for the other treatments. In 2012, no treatment reached 80% frequency or ground cover until 118 DAP. The lowest stolon‐planting rate had 38% weed cover in April the year following planting compared with <15% for the three greatest planting rates. Independent of the year, the three highest rates presented greater cumulative herbage harvested than the lowest densities. These data suggest that planting rates of 2000 kg ha−1 or greater will likely be required to achieve rapid and successful Tifton 85 establishment in sandy soil environments. [ABSTRACT FROM AUTHOR]

Blackberry (Rubus fruticosas L.) can be a weed in rhizoma peanut (Arachis glabrata Benth.)- grass pastures. Goats (Capra hircus) have provided effective control of Rubus spp. in other environments, but their efficacy has not been tested in legume-grass swards in this context. The objective was to evaluate rotational stocking by goats alone or with cattle (Bos spp.) for blackberry control. Treatments stocked at 2.6 animal units (AU) ha-1 included a cattle-alone control, goats alone, concurrent stocking of cattle and goats, sequential stocking of cattle followed by goats, and sequential stocking of goats followed by cattle. The final treatment was concurrent stocking at a stocking rate of 3.5 AU ha-1. Goats grazed blackberry readily, but cattle avoided it. Blackberry selection was greatest when goats followed cattle sequentially. The blackberry proportion of total biomass increased 10% when cattle grazed alone but was reduced 11% with goats alone and 13% with mixed concurrent grazing at a high stocking rate. Treatments including goats resulted in reductions or smaller increases in blackberry mass than for cattle alone. Goats alone or with cattle resulted in greater removal of blackberry leaf and in reduced height and stem density than cattle alone. Goats reduced the blackberry contribution more than cattle, but it was not eliminated from initially heavily infested pastures across 2 yr of grazing. A greater goat stocking rate or a combination of grazing and mowing may be needed for complete eradication. [ABSTRACT FROM AUTHOR]

'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. [ABSTRACT FROM AUTHOR]

Choice of stocking method may impact soil, plant, and animal responses. This 3-yr study evaluated stocking method effects on animal behavior and soil nutrient concentration in 'Pensacola' bahiagrass (Paspalum notatum Flügge) pastures. Stocking methods were continuous stocking and rotational stocking with 1-, 3-, 7-, and 21-d grazing periods and a 21-d resting period. Responses were measured in three zones based on distance from shade and water (Zone 1, 0-8 m; Zone 2, 8-16 m; Zone 3, >16 m). Indices were calculated to weight number of dung and urine events and time spent by cattle in a zone by the proportion of the total pasture and paddock area represented by that zone. Indices were most uniform (~1) across zones for rotational stocking with short grazing periods and generally increased linearly in Zones 1 and 2 with increasing grazing period. Except for N, soil nutrient concentration was not affected by stocking method. In zones closest to shade and water, soil nutrients accumulated for all methods in the surface 8 cm but not in the 8- to 23-cm layer. Air temperature, wind speed, and temperature-humidity index explained 49% of the variation in time cattle spent under shade, confirming the importance of the environment in animal behavior. In warm environments, structural features of stocking method (e.g., the position of shade and water) have a greater effect on animal behavior and distribution in the landscape than do stocking density-mediated effects on competition for forage. [ABSTRACT FROM AUTHOR]

'Tifton 85' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] is a highly productive warm-season grass, but it must be planted vegetatively using aboveground stems (stolons) or rhizomes. Use of stolons vs. rhizomes provides advantages of reduced cost, greater shoot production, and more planted area per hectare of nursery. However, establishment failures have been reported by producers under challenging environmental conditions common to the Coastal Plain region of the southeastern United States. Thus, strategies for harvesting and planting stolons need to be evaluated further. The objective was to assess the effect of stolon type (length and stolon position) and degree of stolon burial by soil (total or partial) at planting on Tifton 85 bermudagrass establishment. Partial burial of stolons at planting accelerated emergence and increased bermudagrass percentage cover and dry matter harvested at season end. Total burial resulted in only half as many shoots (3.5 vs. 7.8 m-2) as partial burial in 2011; total burial resulted in no emergence in 2012. Partial burial led to as much as 90% bermudagrass soil cover, while total burial provided 66 and 0% in 2011 and 2012, respectively. Also, partially buried stolons yielded 1000 kg ha-1 of forage more than totally buried in both years. This finding suggests the planting equipment should be set to achieve shallow planting, ensuring that some parts of the stolons remain uncovered. Stolon type is not as critical as the degree of soil cover on the stolons, which need to remain only partially but not totally buried. [ABSTRACT FROM AUTHOR]

Proper management of grassland ecosystems for improved pasture productivity can also enhance their potential to serve as sinks for anthropogenic carbon (C). We assessed the long-term (>22 yr) effects of grassland intensification (conversion of native rangeland to slash pine-bahiagrass silvopasture or bahiagrass-sown pasture) on above- and belowground C stocks in a subtropical ecoregion. Soil cores (0- to 30-cm depth) were collected from five equidistant quadrats (20 x 20 m) established along a diagonal transect within each of the experimental units. Root and aboveground biomass responses to grassland intensification were also evaluated. Management intensification resulted in increased soil organic C (SOC) stocks from 41 Mg ha-1 in the native rangeland to 62 and 69 Mg ha-1 in sown pasture and silvopasture, respectively. Additional C storage occurred in the live biomass of slash pine trees in silvopasture (58 Mg ha-1), while the C accruing to woody biomass in native rangeland (3 Mg ha-1) was lost after conversion to sown pasture. Conversion to tree-integrated silvopastoral ecosystem favored the sequestration of a more stable mineral-associated C fraction (41.8 Mg ha-1; ~200% increase) compared with the native rangeland. Ecosystem C was greater in silvopasture (144 Mg ha-1) and in sown pasture (83 Mg ha-1) relative to the reference native rangeland (69 Mg ha-1). This research supports growing evidence that increasing intensity of grassland management is beneficial for soil and ecosystem C sequestration in the long term; however, shifts in the allocation of C into ecosystem pools will likely have implication for biochemical cycling within this subtropical ecoregion. [ABSTRACT FROM AUTHOR]

This study compared the animal performance of beef calves stocked on bahiagrass (Paspalum notatum Flüggé) basal pastures (1.2 ha) without supplementation (Control) or with supplementation in the form of creep-grazed (0.12 ha) perennial peanut (Arachis glabrata Benth.) or cowpea [Vigna unguiculata (L.) Walp.] or a creep-fed concentrate. Twenty-four cow-calf pairs were assigned to two blocks. Cows weighed 559 ± 98 kg, averaged 5.5 ± 0.6 body condition score, and were 5 ± 3 yr old, and calves weighed 152 ± 32 kg and were 139 ± 27 d old. The first block had duplicate pastures for the control, cowpea creep grazing, and creep feed treatments whereas the second block had duplicate pastures for cowpea, perennial peanut, and the control treatments. Herbage mass of cowpea was greater than that of perennial peanut or bahiagrass in Weeks 2 to 4 in Year 1 and Week 4 in Year 2 and then declined. The neutral detergent fiber (NDF) concentrations of cowpea and perennial peanut were less than that of bahiagrass, and crude protein and in vitro true digestibility of cowpea were consistently greater than that of perennial peanut and bahiagrass. In Year 1, weaned calf body weights of creep-grazed or creep-fed calves were greater than that of the control calves and creep grazing cowpea or creep feed resulted in similar increases in Year 2. Calf average daily gain (ADG) was greatest for creep feed but did not differ among other treatments. Calf performance was improved by creep feeding concentrate followed by creep grazing cowpea. Benefits of cowpea on ADG were constrained by reduction in cowpea herbage mass and nutritive value during the grazing period. [ABSTRACT FROM AUTHOR]

Early weaned beef calves (Bos spp.) grazing warm‐season grasses may benefit from increasing levels of rumen‐undegradable protein (RUP) supplementation due to the limited RUP supplied by the forage and their high nutrient requirements. The objective of this study was to test the effects of increasing levels of RUP supplementation on performance of early weaned calves grazing stargrass (Cynodon nlemfuensis Vanderyst) pastures. The experiment was conducted in Ona, FL, from May to August 2007 and 2008. Treatments were 1.5 g kg−1 body weight (BW) of three levels of supplemental RUP from soybean [Glycine max (L.) Merr.] meal (SBM) (350 g kg−1 RUP), Soyplus (SP) (600 g kg−1 RUP) (a modified expeller SBM) (West Central, Ralston, IA), or a 50:50 mixture of SBM and Soyplus (SBMSP) (475 g kg−1 RUP). Pasture size was 0.51 ha and four early weaned calves were assigned to each pasture. There was no effect of the treatments on mean herbage mass (HM; 2.7 Mg ha−1), forage crude protein (CP) (171 g kg−1), in vitro digestible organic matter (IVDOM) concentration (640 g kg−1), or calf average daily gain (0.56 kg d−1). Increased RUP supplementation did not affect forage dry matter intake (mean = 2.0% BW); however, there was a linear decrease in apparent dry matter digestibility from 640 to 600 g kg−1. Increasing levels of RUP supplementation may not increase performance of early weaned calves grazing stargrass pastures when forage CP is not limiting. [ABSTRACT FROM AUTHOR]

'Mulato II' [Brachiaria spp.] is a warm-season grass with excellent nutritive value adapted to tropical regions; however, its herbage production and persistence in subtropical locations is unknown. Grazing and clipping studies were conducted in 2008 and 2009 in Marianna and Gainesville, FL, respectively. The treatments for the grazing study were beef heifers (Bos spp.) grazing Mulato II, 'Tifleaf 3' pearl millet [Pennisetum glaucum (L.) R. Br.], or 'Hayday' sorghum-sudangrassgrass [Sorghum bicolor (L.) Moench] pastures on a continuous stocking rate. In 2008, there were no differences in herbage allowance (HA) (0.9 kg dry matter [DM] kg-1 live weight [LW]), average daily gain (ADG) (0.5 kg d-1), and gain per hectare (168 kg) among treatments. However, Mulato II had greater HA (2.0 vs. 0.7 kg DM kg-1 LW) and ADG (0.78 vs. 0.41 kg d-1) than Tifleaf 3 and Hayday and similar gain per hectare (302 kg) in 2009. The treatments for the clipping study were Mulato II, evaluated as an annual and perennial, 'Tifton 85' bermudagrass (Cynodon spp.), Tifleaf 3 pearl millet, and Hayday sorghum-sudangrass. In 2008, Hayday and Tifleaf 3 established more rapidly than Mulato II; however, Mulato II grew later in the fall. In 2009, the perennial treatments (Mulato II and Tifton 85) had overall greater herbage accumulation than the annual treatments. In the clipping study, Tifton 85 had greater ground cover than Mulato II perennial in 2009 (73 vs. 36%) and 2010 (73 vs. 12%). Mulato II may be used as a high quality, short-lived perennial warm-season grass in subtropical areas. [ABSTRACT FROM AUTHOR]

Sweet sorghum [Sorghum bicolor (L.) Moench] is a potential bioenergy crop that is capable of high biomass and sugar yields, but production for biofuel in the Southeast is not well understood. The present study examined the effects of planting date (three dates from mid-March to mid-June) on primary and ratoon crop fresh biomass, brix, and estimated sugar yield of three sweet sorghum cultivars ('Dale', 'Topper 76-6', and 'M-81E') grown at three sites from North (29° 24′ to South Florida (26° 40′. Across all treatments, primary crop fresh biomass, brix and estimated sugar yields were 70 Mg ha-1, 148 g kg-1, and 5.69 Mg ha-1, respectively. Primary crop yields were greatest for the two earliest planting dates (mid-March to mid-May), and for our southernmost site. The yield potential for ratoon crops was in general only about half as much as the primary crop across all years, sites, and cultivars for the earliest planting date. An exception, however, was ratoon crop yields at the southernmost site, which were in some cases equal to or greater than primary crop yields. Low primary crop brix values were found for all cultivars on the muck soils in South Florida compared to the other two sites, and for M-81E compared to Dale and Topper 76-6. These low brix values were correlated with greater fresh biomass production. Further research is needed on planting dates for optimizing primary and ratoon crop yields along with varietal development with improved ratoon crop yields. [ABSTRACT FROM AUTHOR]

Carbohydrate and N reserves are important for perennial grass regrowth after defoliation. The objective of this study was to quantify the effects of N fertilization on dynamics of reserve accumulation and utilization for regrowth of a C4 perennial grass. A field study was conducted at Gainesville, FL, on established 'Tifton 85' bermudagrass (Cynodon spp.) in 2006 and 2007. Treatments were N rates of 0, 45, 90, and 135 kg N ha-1 regrowth period-1. Total nonstructural carbohydrate (TNC) and N concentrations, leaf area index (LAI), and canopy carbon exchange rate (CER) were measured weekly during 28-d regrowth periods. Stem and rhizome TNC concentrations decreased with increasing N rate, ranging from 20 to 80 mg g-1 for stem and 45 to 145 mg g-1 for rhizome, and followed quadratic time trends, with minima between 7 and 14 d of regrowth, suggesting reserve utilization up to 2 wk after defoliation. Leaf, stem, rhizome, and root N concentrations increased with N rate. Leaf and stem N concentrations followed quadratic time trends, with maxima between 7 and 14 d of regrowth, and ranged from 15 to 50 mg g-1 for leaf and 10 to 40 mg g-1 for stem. Rhizome N concentrations were constant throughout regrowth. Canopy CER and LAI followed logistic time trends within each 28-d regrowth period, with upper asymptotes raised by increased N rate. Nitrogen fertilization increased TNC reserve utilization, LAI, and canopy CER, thereby increasing shoot regrowth at rates up to 90 kg N ha-1 period-1. [ABSTRACT FROM AUTHOR]

'Tifton 85' bermudagrass (Cynodon spp.) has been widely adopted as a forage and hay crop and is being considered as a cellulosic ethanol feedstock. The objective of this study was to evaluate the effects of N fertilization rate on Tifton 85 regrowth dynamics. A field study was conducted near Gainesville, FL, on established Tifton 85 in 2006 and 2007. The treatments were N rates of 0, 45, 90, and 135 kg N ha-1 regrowth period-1. Tissue mass, leaf:stem ratio, and tiller number and mass were measured weekly during 28-d regrowth periods. Leaf mass followed logistic time trends with the upper asymptote varying between 50 and 225 g m-2 depending on N rate and season (summer and autumn). Stem mass lagged behind leaf mass for 7 to 14 d, subsequently following linear or quadratic time trends to reach between 75 and 300 g m-2 by 28 d. Increasing N rate from 0 to 135 kg ha-1 period-1 increased tiller mass at 28 d from 1.5 to 3 g tiller-1 in summer and 1 to 1.5 g tiller-1 in autumn. Leaf:stem ratio increased to 1.0 within 14 to 21 d, followed by a subsequent decrease. Rhizome and root mass were not affected by N fertilization. Increasing N rate primarily affected mass and proportion of above-ground plant parts, with little effect on mass of below-ground parts Nitrogen nutrition index values were similar whether calculated from samples taken to a 10-cm stubble height or from samples taken to the soil surface. Regrowth was not enhanced by N rate beyond 90 kg N ha-1 regrowth period-1. [ABSTRACT FROM AUTHOR]

Coastal wetland pastures in Hawaii are based on naturalized hilograss (Paspalum conjugatum Bergius) and paragrass [Brachiaria mutica (Forssk.) Stapf] growing primarily on moderately acid (pH 5.4) to mildly alkaline (pH 7.8) and mildly calcareous (<50 g kg-1 CaCO3 equivalent [CCE]) Aquepts and Aquolls. Nutrient concentration, distribution, and P retention dynamics have not been quantified for these ecologically important grazing lands. Soil and forage samples were collected from three pastures at each of six sites, with three sites representing each grass. In addition, pastures at one of the hilograss sites were subjected to zonal sampling with zones determined by distance from shade and drainage ditch borders (animal lounging areas). Soil total N, and exchangeable K and Na accumulated in shaded areas, and forage N, δ15N (‰), and K tended to follow a similar distribution. Across sites hilograss had very high and probably toxic S concentrations (5.6 to 11.0 g kg-1) for cattle (Bos spp.) compared with paragrass, which had S concentrations (1.9 to 4.0 g kg-1) within the expected range for tropical forage grasses. Across sites and the 0- to 15- and 15- to 30-cm soil depths, satisfactory predictive relationships (n = 54) were obtained between dissolved (<0.45-sm pore diameter) molybdate-reactive P (DRP) desorbed from soil in a water extract (DRPWE) and Olsen extractable P (POLSEN) and the oxalate extractable molybdate-reactive P (RPOX) saturation index (PSIOXRP). Oxalate extractable Al (AlOX) was a more important component of PSIOXRP than oxalate extractable Fe (FeOX), which could be omitted. [ABSTRACT FROM AUTHOR]

Despite evidence that forage crops can access P from the Bh horizon, routine soil testing focus only on P concentrations in the top 15 cm. We evaluated the role of the Bh horizon on the overall P budget for 2 yr in a bahiagrass (Paspalum notatum Flügge) pasture grown on a Spodosol. Treatments consisted of three P rates (0, 5, and 10 kg ha-1) arranged in a completely randomized design with each plot receiving a basal application of 56 kg N ha-1 and 47 kg K ha-1. Phosphorus application had no effect on bahiagrass P uptake (P = 0.2). Average P mass leached below the 45-cm soil depth was 0.08,0.08, and 0.09 kg P ha-1 for the 0, 5, and 10kg P ha-1 treatments, respectively. In 2007, the net balance of P in the Ap horizon was -10.8 kg P ha-1 for the control and -0.8 kg P ha-1 for the 10kg P ha-1 treatment. The same treatments had net P balances of-6.6 and 7.2 kg ha-1 in 2008. When soil P held in the Bh horizon was included in the P budget computation, the net P balance was positive for all treatments including the control. Results indicate that soil P concentrations were sufficient to maintain bahiagrass production with no additional P fertilization required. Phosphorus held in the Bh horizon is a significant supply of P to low-input pastures growing on Spodosols in Florida and should be considered in nutrient management programs for perennial grasses. [ABSTRACT FROM AUTHOR]

The increased cost of fertilizer and concerns about environmental impacts have led to a reduction in P use in grazed pastures in Florida; however, P fertilization may be necessary to sustain bahiagrass (Paspalum notatum Flugge) pastures. This study evaluated the impacts of reduced P fertilization on forage characteristics, soil and leachate P concentrations on bahiagrass pastures during 2007 and 2008. Treatments consisted of three P fertilization levels (0, 5, and 10kg P ha-1, applied as KH2PO4) arranged in a randomized complete block design with four replicates. Twelve 1.2-ha bahiagrass pastures were stocked continuously with a fixed stocking rate of two beef heifers [Bos sp; 380 ± 30kg live weight (LW)] per experimental unit. Forage was sampled at 14-d intervals for herbage mass (HM), crude protein (CP), and in vitro digestible organic matter (IVDOM) concentrations. Two suction lysimeters were installed at 60- and 90-cm depth to monitor leachate P. Phosphorus fertilization did not affect HM (4.4 Mg ha-1), herbage accumulation rate (HAR, 43 kg ha-1 d-1), CP (94 g kg-1), or IVDOM (500 g kg-1). Tissue P concentrations increased from 1.9 to 2.2 g kg-1 as P fertilization increased from 0 to 10 kg P ha-1. Soil P concentration in the Ap (7 mg kg-1) and Bh horizons (23 mg kg-1) and leachate P concentration (0.06 mg L-1) were not affected by P application. Despite the lack of yield response to P fertilization, P application at levels of 5 and 10kg P ha-1 showed no impacts on water quality. [ABSTRACT FROM AUTHOR]

Tifton 85' bermudagrass (Cynodon spp.) is an important forage in the southern United States, but its responses to the interaction of grazing frequency and intensity have not been studied. Sward persistence, herbage accumulation, and nutritive value were measured during 3 yr. Treatments were all combinations of three post- graze stubble heights (SH; 8, 16, and 24 cm) and three regrowth intervals (RI; 14, 21, and 28 d). Short SH (8 cm) with long RI (28 d) or tall SH (24 cm) with short RI (14 d) produced greatest herbage accumulation (11-15 Mg ha-1 yr-1). Lowest or nearly lowest herbage accumulation occurred with 14-d RI and 8-cm SH or 28-d RI with 24-cm SH (7.4-12 Mg ha-1 yr-1). Intermediate levels of RI (21 d) or SH (16 cm) produced consistent herbage accumulation regardless of level of the other factor. Nutritive value was primarily affected by RI, and P (3.1 to 2.8 g kg-1), crude protein (CP; 150 to 108 g kg-1), and in vitro digestible organic matter (IVDOM; 602 to 582 g kg-1) concentrations decreased as RI increased. Organic matter and nutrient mass of storage organs increased with increasing SH, but the 24-cm SH treatment exhibited greater reduction in percentage cover (-.43% units) than the other SH treatments (-.22% units) after 3 yr of grazing. These data indicate that intermediate levels of SH (16 cm) and RI (21 d) provided relatively high Tifton 85 herbage accumulation and nutritive value while minimizing negative impacts on persistence-related responses. [ABSTRACT FROM AUTHOR]

Early weaned beef calves (Bos spp.) can be raised on cool-season pastures in Florida but more information on protein supplementation is necessary to optimize the performance of those calves. The objective of this study was to evaluate the effects of three levels of rumen-undegradable protein (RUP) supplementation on performance of early weaned calves grazing annual ryegrass (Lolium multiflorum Lam.) pastures. The study was conducted in Ona, FL in 2007 and 2008, Treatments were 1.5 g kg-1 body weight (BW) supplementation of three levels of supplemental RUP, soybean meal (SBM, 350 g kg-1 RUP), Soy- plus (SP, 600 g kg-1 RUP, modified expeller soybean meal, West Central, Ralston, IA), or a 50:50 mixture of soybean meal-Soyplus (SBMSP, 475 g kg-1 RUP). Pasture size was 0.3 ha and four early weaned calves were assigned to each pasture. There was a linear increase in herbage mass (HM, from 1.9-2.1 Mg ha-1) and herbage allowance (HA, from 1.1-1.4 kg dry matter [DM1 kg-1 live weight, LW) with increasing levels of RUP. Increased RUP supplementation decreased forage dry matter intake (FDMI) and total dry matter intake (TDMI) in 2008 but there was no effect in 2007. There was no difference in average daily gain (ADG, 0.76 kg d-1) among treatments. Increasing the levels of PUP supplementation has potential to increase stocking rates of early weaned calves grazing annual ryegrass pastures. [ABSTRACT FROM AUTHOR]

New bahiagrass (Paspalum notatum Flügge) genotype PCA Cycle 4 is more productive than existing bahiagrass cultivars during the cool season, but it may not persist as well when defoliated frequently or to short stubble. Characterizing tiller dynamics forms a basis for understanding mechanisms of grass yield and persistence responses to defoliation. A 2-yr field experiment studied the effects of two stubble heights (4 and 8 cm) and two harvest frequencies (7 and 21 d) on tiller dynamics of diploid (PCA Cycle 4, 'Pensacola', and 'Tifton 9') and tetraploid ('Argentine' and Tifton 7) bahiagrass. Tiller number of highly persistent Argentine and Pensacola was unaffected by defoliation treatment and generally greatest among cultivars. Tiller number of Tifton 9 and PCA Cycle 4 varied by up to 970 and 730 tillers m-2, respectively, among defoliation treatments and was greatest with frequent harvests at short stubble. PCA Cycle 4 tiller mass was relatively low. Net tiller appearance rate was positive in spring and early summer, and was nearly zero or negative throughout the remainder of the growing season. This study showed that Tifton 9 and PCA Cycle 4 responded to frequent, close defoliation by increasing tiller number, but tiller mass was the least or not different from the least among entries tested. Very small tillers may indicate a weakening stand under frequent, close defoliation, and management practices such as rotational stocking may be necessary for PCA Cycle 4 to persist. [ABSTRACT FROM AUTHOR]

Bahiagrass (Paspalum notatum Flügge) is the most used forage for beef cattle (Bos sp.) in Florida; however, damage to bahiagrass pastures by mole cricket (Scapteriscus spp.) stimulated a search for other adapted grasses. The objective of this study was to test the effect of different stocking rates (SRs) on animal performance and herbage characteristics of 'Mulato' (Brachiaria sp.) and bahiagrass pastures. The experiment was conducted in Ona, FL, from May to September, 2007 and 2008. Treatments were three SRs (4, 8, and 12 heifers ha-1) and two forage species (Mulato and 'Pensacola' bahiagrass). There was a linear decrease in herbage mass (from 5.9 to 3.2 Mg ha-1) and herbage allowance (from 2.8 to 0.6 kg dry matter kg-1 liveweight) with increasing SR. Mulato had greater in vitro digestible organic matter concentration than bahiagrass (675 vs. 534 g kg-1) but similar crude protein concentration (130 g kg-1). There was a linear decrease in average daily gain (from 0.49 to 0.22 kg d-1) and a quadratic response of liveweight gain ha-1 as SR increased (190, 353, and 217 kg ha-1 for SRs of 4, 8, and 12 heifers ha-1, respectively). Mulato has potential to be an alternative forage to bahiagrass for beef cattle producers in Florida. [ABSTRACT FROM AUTHOR]

Nutrients cycle among pools within an ecosystem, and losses of nutrients to the environment accompany each transfer from pool to pool. Efficient recapture of nutrients by plants is critical in extensively managed grasslands if these swards are to persist. In intensively managed systems, the greatest contribution of efficient recapture of nutrients may be minimizing loss of nutrients to the environment and associated negative impacts. Regardless of management intensity, grassland management decisions should be informed by an understanding of the dynamics of nutrient cycling. A significant body of literature has emerged in recent years describing nutrient dynamics in warm-climate grasslands. In warm climates globally, grasslands are most often low-input production systems dominated by C4 grasses. These characteristics affect nutrient cycling, resulting in very different management challenges and opportunities than in higher input, C3-grass or legume-dominated, grasslands. This paper will focus on warm-climate grasslands. Within that context its objectives are (i) to describe the most prominent pools of C, N, P, and K, (ii) to discuss fluxes among nutrient pools, with emphasis on plant litter and animal excreta, iii) to describe the importance, management, and dynamics of soil organic matter, and (iv) to review the impact of grazing systems on nutrient cycling. [ABSTRACT FROM AUTHOR]

Early weaning of calves (Bos spp.) increases pregnancy rates of beef cows; however, there is little information on nutritional management of the weaned calf on pasture. This research evaluated the effect of concentrate supplementation level on performance of early weaned (90 d of age) beef calves grazing annual ryegrass (Lolium multiflorum Lam.)-rye (Secale cereale L.) mixtures on Adamsville (uncoated, hyperthermic, Aquic Quartzipsamment) and Pomona (sandy, siliceous, hyperthermic Ultic Alaquod) sands. Three levels of supplement (10, 15, and 20 g kg-1 of calf body weight [BW]) were evaluated in a completely randomized design with three replicates. The concentrate contained 146 and 700 g kg-1 of crude protein (CP) and total digestible nutrients (TDN). Pastures were rotationally stocked with a 7-d grazing and 21-d rest period. Two calves were assigned as testers to each pasture, and additional animals were used to maintain a similar herbage allowance across treatments. There was no effect of concentrate supplementation level on herbage mass, accumulation, allowance, or nutritive value. Calf average daily gain (ADG; 0.74–0.89 kg), liveweight gain (LWG) per hectare (950–1320 kg), and stocking rate (SR; 5.5–6.5 animal units [AU] ha-1) increased linearly, and forage intake decreased linearly (18–11 g kg-1 BW) as concentrate rate increased. Grazing time was 284, 230, and 234 mind-1 (linear and quadratic effects) for the 10, 15, and 20 g kg-1 BW supplement treatments, respectively. Feeding systems with modest levels of supplementation (10 g kg-1 BW) of calves grazing cool-season grasses are practical options for early weaned calves during winter in the southeastern USA. [ABSTRACT FROM AUTHOR]

Plant litter is an important nutrient pool in grassland ecosystems. Management practices affect litter quality and may affect nutrient dynamics in pastures by altering the rates of nutrient mineralization and immobilization. The effect of management intensity on litter decomposition and nutrient disappearance was evaluated in a litter bag study on continuously stocked ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) pastures growing on Pomona and Smyrna sands. Treatments were three management intensities: Low (40 kg N ha-1yr-1 and 1.3 animal units [AU, one AU = 500 kg live weight] ha-1 stocking rate [SR]), Moderate (120 kg N ha-1 yr-1 and 2.7 AU ha-1 SR), and High (360 kg N ha-1 yr-1 and 4.0 AU ha-1 SR). Litter relative decomposition rate (k) was greater for High (0.0030 g g-1 d-1) than Low (0.0016 g g-1 d-1). Litter N, acid detergent insoluble N (ADIN), and lignin concentrations were greater for High than the other intensities at the end of the 168-d incubation period because of faster decomposition of soluble compounds. Across management intensities, approximately one-half of litter N remaining at the end of the incubation period was bound to acid detergent fiber (ADF). Net N mineralization through 128 d of incubation was only 200 to 300 g kg-1 of total N. Increasing management intensity resulted in faster litter turnover and greater nutrient release, but nutrient release from litter was small and significant quantities of nutrients were immobilized even under the most intensive management. [ABSTRACT FROM AUTHOR]

Plant litter is an important pathway of nutrient return to the soil in grazed swards, but the effects of pasture management on litter mass and composition are not well understood. This research evaluated the effect of management intensity, defined in terms of N fertilization and stocking rate (SR), on litter mass, deposition rate, and chemical composition in continuously stocked ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) pastures growing on Pomona and Smyrna sands. Treatments were three management intensities: Low (40 kg N ha-1 yr-1 and 1.3 animal units [AU, one AU = 500 kg live weight] ha-1 SR), Moderate (120 kg N ha-1 yr-1 and 2.7 AU ha-1 SR), and High (360 kg N ha-1 yr-1 and 4.0 AU ha-1 SR). Greater management intensity resulted in less litter mass on the pasture early in the growing season and more litter mass later in the season. Rate of litter deposition was generally greatest for High and ranged between 23 and 40 kg organic matter (OM) ha-1 d-1 compared with 13 to 30 kg OM ha-1 d-1 for Low and Moderate management intensities. Increasing management intensity from Low to High resulted in greater litter N (14.1 vs. 22.9 g kg-1) and P (0.8 vs. 1.3 g kg-1) concentrations and lesser C:N (∼40 vs. 22), C:P (649 vs. 433), and lignin:N (5.8 vs. 4.4) ratios. More intensive pasture management was associated with greater litter deposition rate and litter quality than less intensive management, suggesting a larger nutrient contribution from litter in intensively managed swards. [ABSTRACT FROM AUTHOR]

Vaseygrass (Paspalum urvillei Steud) is a weed in environments where limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] is a productive pasture grass. The objective of this study was to determine grazing management and N fertilization effects on persistence of vaseygrass in limpograss pastures on a Pomona sand (sandy, siliceous, hyper-thermic Ultic Alaquod). Treatments were arranged in a split-plot experiment; combinations of grazing method (continuous vs. rotational) and stubble height (15 and 30 cm) were the main plots, and N fertilization (50 and 150 kg N ha-1) was assigned to subplots. Continuous stocking for two grazing seasons reduced vaseygrass cover by 15 percentage units (-3 units for rotational) and increased limpograss cover by 6 units (-8 units for rotational). A stubble height × N rate interaction occurred because at the shortest height and lowest N rate the decline in vaseygrass cover (15 units) and increase in limpograss cover (7 units) were most pronounced. After 2 yr of continuous stocking, vaseygrass stem-base mass was lower than for rotational stocking (12 vs. 23 g plant-1), and stem-base (0.40 vs. 0.78 g plant-1) and root (0.46 vs. 0.91 g plant-1) content of total nonstructural carbohydrate (TNC) were lower under continuous compared to rotational stocking, respectively. Grazing to a 15-vs. 30-cm stubble height resulted in lower vaseygrass stem-base mass (12 vs. 23 g plant-1) and TNC content (0.44 vs. 0.73 g plant-1). Continuous stocking reduced vaseygrass plant mass and density while limpograss cover increased, but careful management of stubble height is required to avoid subsequent invasion by other undesirable species. [ABSTRACT FROM AUTHOR]

This article focuses on the phosphorus (P) content in Hawaiian kikuyugrass pastures and examines the potential phosphorus release to water. Pasture systems in Hawaii are based primarily on kikuyugrass. More specifically, kikuyugrass is the most widespread pasture grass in Hawaii and is common in tropical highland and subtropical environments throughout the world. This species is highly efficient in utilizing soil P and deficiencies appear to occur only in very P-infertile soils. Relationships among kikuyugrass P concentration, animal P requirements, and various soil P determinations are needed to help identify source areas for implementing pasture management strategies to limit P loss via overt land flow. A total of 51 rotationally stocked kikuyugrass pastures with contrasting soil chemical properties were sampled. The current study suggests that while Hawaiian kilruyugrass pastures tend to be sufficient to high in forage P, potential soil P release to water only appeared to be a possible environmental concern for the mollisol and inceptisol sites.