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The present research is the second phase (2 yr) of a multiyear cow-calf project examining the effect of stocking method, i.e., continuous and rotational, and fixed stocking rate on beef-cattle production. Two sets of 4 adjacent pastures, each containing a mixed warm-season, perennial grass sod [common bermudagrass, Cynodon dactylon (L.) Pers.; dallisgrass, Paspalum dilatatum Poir.], were overseeded to ‘Marshall’ annual ryegrass (Lolium multiflorum) in the autumn of 2 consecutive years. Within each set of 4 pastures, 1 of the following grazing treatments was randomly assigned each pasture: rotationally stocked (8 paddocks) at a low, medium, or high stocking rate (RL, RM, and RH) and continuously stocked at a moderate stocking rate (CM). Low, medium, and high stocking rates were 1.25, 2, and 2.75 cows/ha. Brangus cow-calf pairs were stocked on treatment pastures in March 2004. Mean cow BW was greater for RL compared with RM (P 0.20) for the RM versus RH (522 kg) and the RM versus CM (530 kg) stocking-treatment comparisons. Calf-adjusted 205-d BW was similar for all treatment contrasts. Pasture weaning BW differed between the RL versus RM (P

The present research examines the effect of stocking method, i.e., continuous and rotational, and set (fixed) stocking rate on labor requirements, costs, and profits in cow-calf beef production. Two replicates of 4 adjacent pastures each, containing a mixed warm-season, perennial grass sod [common bermudagrass, Cynodon dactylon (L.) Pers.; dallisgrass, Paspalum dilatatum Poir.], were overseeded to ‘Marshall’ annual ryegrass [Lolium multiflorum (Lam.)] in the autumn of 2 consecutive years. Within each replicate of 4 pastures, one of the following grazing treatments was randomly assigned each pasture: rotationally stocked (8 paddocks) at a low, medium, or high stocking rate (RL, RM, and RH) and continuously stocked at a moderate stocking rate (CM). Labor activities, expenditures, sales, and equipment usages were recorded throughout the study. On a per-cow basis, total labor usage declined (P 0.90) and would not justify the additional labor associated with rotational grazing management.

The present research is the second phase (2 yr) of a multiyear cow-calf study employing fixed stocking rates and examining the effect of stocking method, i.e., continuous and rotational, and stocking rate on beef cattle production. Two sets of 4 adjacent pastures, each containing a mixed warm-season, perennial grass sod [common bermudagrass, Cynodon dactylon (L.) Pers.; dallisgrass, Paspalum dilatatum Poir.], were overseeded to ‘Marshall’ annual ryegrass (Lolium multiflorum) in the autumn of 2 consecutive years. Within each set of 4 pastures, one of the following grazing treatments was randomly assigned each pasture: rotationally stocked (8 paddocks) at a low, medium, or high stocking rate and continuously stocked at a moderate stocking rate. Low, medium, and high stocking rates were 1.25, 2, and 2.75 cows/ha. Brangus cows and their suckling calves were stocked on treatment pastures in March 2004. Stocking treatment affected prebreeding cow BW (P

Beef producers throughout the United States frequently are restricted to a fixed land area that varies considerably in carrying capacity throughout the year. Much of the research that has focused on stocking rate and methods (continuous, rotational) has failed to recognize the inability of most producers to use a variable stocking rate. Two sets of 4 adjacent pastures, each containing a mixed warm-season, perennial grass sod [common bermudagrass, Cynodon dactylon (L.) Pers.; dallisgrass, Paspalum dilatatum Poir.] were overseeded to ‘Marshall’ annual ryegrass (Lolium multiflorum) in the autumn of 3 consecutive years. Within each set of 4 pastures, one of the following grazing treatments was randomly assigned each pasture: continuous stocked at a low, medium, or high stocking rate (CL, CM, and CH) and rotational stocked (8 paddocks) at a high stocking rate (RH). Low, medium, and high stocking rates were 1.25, 2, and 2.75 cows/ha, respectively. Brangus cows and their suckling calves were stocked on treatment pastures in February 1999. Available forage mass tended to be greater (P = 0.10) for CL than CM in the late spring and was greater (P < 0.05) for CL than CM in the summer grazing season. Differences in forage nutritive value were largely associated with the stocking method comparison, favoring CH in the early spring (percent CP, percent in vitro true digestibility, and percent ADF; P < 0.01) and summer (percent CP and percent ADF; P < 0.01) grazing seasons. Cow-calf productivity, as measured by kilograms of calf wean weight per hectare, increased (P < 0.01) in response to increases in stocking rate, but was similar between the continuous and rotational stocking methods at the high stocking rate.

Development of a biofuel industry based on biomass will require large quantities of cellulosic feedstock. Among the proposals for acquiring this feedstock, without impacting other land uses such as food or forage, is the use of up to 50% of Conservation Reserve Program (CRP) land. Our objective was to determine CRP biomass production in northwestern Oklahoma and record the harvest impact on plant species composition, plant growth, and soil characteristics. Six CRP sites were harvested on three dates, early August, early October, and postfrost, for three consecutive years, 2004, 2005, and 2006. Three sites were Old World bluestem (OWB; Bothriochloa spp.) and three sites were native mixed species (NM). Across all years and harvest dates OWB produced 3790 kg ha -1 and NM produced 1920 kg ha -1 of dry biomass. Maximum yields were obtained at the October harvest for both OWB (4170 kg ha -1 ) and NM (2180 kg ha -1 ). There was no observed change in species composition or soil characteristics. Among all species evaluated, nitrogen, neutral detergent fiber, carbon, and ash concentrations varied significantly. Within NM, production of dry biomass among native grass species differed and ranged from 213 g plant -1 for big bluestem (Andropogon gerardii Vitman) to 14 g plant -1 for sand lovegrass [Eragrostis trichodes (Nutt.) Alph. Wood]. Biomass production consistently declined at all sites and for all harvest dates over the three harvest years, but the greatest decline in yield was for OWB.

Female beef calves not retained within the cow-calf enterprise are sold and moved through the same production phases as male calves to produce finished beef. The objective of this study was to compare the stocker and feedlot performance of beef heifers of different tropically adapted breed types. Calves were sired by Braunvieh (yr 1) and Wagyu (yr 2) bulls. Dams were Angus × Angus, Brahman × Angus, Senepol × Angus, and Tuli × Angus. Calves were born in the spring and weaned in the fall and shipped from Texas to Oklahoma for growth and finishing. Data were analyzed as a randomized complete block design using the GLM procedure. Year was confounded with breed of sire and was considered fixed. Year × dam breed was used as the error term. Rate of gain during the posttransit recovery period (0.57 ± 0.15 kg) and during the winter (1.05 ± 0.08 kg) and spring (0.31 ± kg) stocker phases were not different (P > 0.10) among the 4 dam breed types. At the end of the winter grazing period (approximately March 20), mean BW within each breed group was greater than 330 kg; at these BW, heifers could be exposed to bulls to create replacement females. Heifers not sold as replacements could be finished on pasture, using a combination of intensive early stocking management, followed by ad libitum access to an energy-dense ration on pasture in a self-feeder. Heifers from Angus × Angus and Tuli × Angus cows had greater (P < 0.05) marbling scores and QG than heifers from Brahman × Angus and Senepol × Angus dams when finished on the farm. In conclusion, heifer calves from dams with 0 or 50% tropically adapted breeding gained enough BW as stockers to be bred in March and marketed as replacement females. Heifer calves not sold as replacement females can be retained and finished on the farm to produce finished beef.

Excess perennial cool-season grass production can be harvested as hay for feeding later. Thus, a series of experiments were conducted to estimate DMI and digestibility of perennial cool-season grasses relative to an annual cool-season grass hay. In Exp. 1, wheat (Triticum aestivum var. Pioneer 2174), tall wheatgrass (Thinopyrum ponticum var. Jose), smooth brome (Bromus inermis var. Lincoln), and intermediate wheatgrass (Thinopyrum intermedium var. Manska) were harvested in the spring as high-moisture hay and fed to lambs. At feeding, all 4 hays contained more (P 0.10) among the hays used in this experiment. In Exp. 2, grasses were harvested as field-dried (DM >65%) hay from established stands of Jesup Max Q (Festuca arundinacea) and Nanyro (F. arundinacea) tall fescues, Harusakae meadow fescue (Festuca pratensis), and wheat (var. Pioneer 2174). Lambs fed wheat hay had greater (P < 0.05) DMI (69.3 g/kg BW0.75, respectively) compared with lambs fed Jessup or Nanyro (35.0 and 33.8 g/BW0.75), and lambs fed Harusakae hay had intermediate DMI (50.2 g/BW0.75). Digestibility of Jesup hay was greater (P < 0.05) than digestibility of the other 3 hays. Excess cool-season grasses can be harvested as high-moisture or field-dried hay, but harvested hays had greater concentrations of ADF and NDF and a lesser concentration of N than preharvest standing forage.

As the bioenergy industry expands, producers choosing to shift current forage crop production to dedicated biomass crops can benefit from growing lower risk multipurpose crops that maximize management options. Hybrid forage sorghums (HFS) and sorghum–sudangrass hybrids (SSG) are capable of impressive biomass yields and tolerance to environmental stress. Multiple vegetative harvests (ratoon harvests) of sorghum are possible and there are photoperiod-sensitive sorghums that remain vegetative. However, the response of newer HFS and SSG cultivars to harvest management practices designed for forage or cellulosic feedstock production has not been fully investigated in all environments. The objectives of this study were to: (i) determine biomass production and quality characteristics of a genetically diverse range of HFS, SSG and sudangrass cultivars and evaluate their interaction with harvest system; and (ii) provide data to aid selection of sorghum cultivars for both forage and biofuel uses. Mean yield across all entries and years for a single late season harvest was 27.1 Mg ha−1 of dry matter per year. Mean total yield for a first harvest plus a ratoon crop was 25.5 Mg ha−1 of dry matter per year. However, entries varied for yield and interacted with harvest system. Mean caloric value was 16.5 Gj Mg−1 and modest differences were observed among cultivars evaluated. The best performing entry (cv. Tentaka) yielded 40.3 Mg ha−1 of dry matter for a single late season harvest, demonstrating the biomass potential of existing sorghum cultivars, specifically those possessing photoperiod- and/or thermosensitive genotypes.

Dallisgrass (Paspalum dilatatum Poir.) is an important pasture grass on moist fertile sites in warm climates, however, it is limited in use by periodic low seed quality and resulting erratic availability and establishment difficulties. Due to apomictic reproduction, common pentaploid dallisgrass has not been responsive to traditional plant improvement approaches. Recent research has shown potential for some improvement in forage production and plant persistence with apomictic hexaploid varieties of dallisgrass. Tissue-culture regeneration has been reported to produce somaclonal variation in seed germination of common pentaploid dallisgrass and has recently resulted in availability of potentially useful regenerants of hexaploid dallisgrass. Seed of selected plants from both field and greenhouse environments was evaluated in replicated germination trials to determine whether hexaploid tissue-culture regenerants responded similarly to regenerants from common dallisgrass and to determine whether regenerants expressing potential agronomic usefulness as indicated by preliminary observations differed in germination. The eight germination trials included 299 regenerants with 57 of these being duplicate entries among trials. Germination did not differ among sources of regenerants. Within sources germination differed among regenerants with a few individuals exceeding germination percentage of parent lines in one evaluation of greenhouse-produced seed. Individual regenerants with agronomic potential and high percentage seed germination were identified. The results demonstrate that tissue-culture regeneration can be used to produce improved germination in agronomically useful genotypes of apomictic dallisgrass and suggest that such potential may exist for other recalcitrant plant species.

Simulation models for plant species important for biofuel such as switchgrass (Panicum virgatum L.) can be used to make management decisions related to biomass productivity and related to environmental impacts such as soil erosion and changes in surface and groundwater quality. The present study was designed to evaluate the accuracy of simulation of switchgrass biomass production by the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model at sites in Texas, Arkansas, and Louisiana. We used multi-year field data for Alamo switchgrass yields at each of five sites to evaluate ALMANAC. The model realistically simulated mean switchgrass yields at each of the locations and the total variability of all the data pooled, but did not perform as well in accounting for the year-to-year variability within some locations. Sensitivity analysis showed that changes in runoff curve number (CN) and changes in maximum stomatal conductance (GSI) had variable impacts on simulated values among the sites. A 15% change in CN changed mean annual biomass yield from 0% to 16% depending on location. Changing GSI from 4 to 8 mm s � 1 changed mean annual biomass from 1% to 31% depending on location. ALMANAC shows promise as a tool to realistically simulate mean biomass yields and variability around the mean for multi-year runs of switchgrass at

Systematic performance trials have been conducted in several states for more than 20 yr to evaluate agronomic performance of annual ryegrass (Lolium multiflorum Lam.). Despite development and testing of many annual ryegrass cultivars, the first improved cultivar, Gulf, has remained one of 10 to 12 cultivars recommended for planting in the southeastern USA. Our objectives were to evaluate cultivar yield performance across 12 yr at five locations, to assess cultivar yield distribution within growing seasons, and to estimate cultivar yield stability (consistency of relative performance environments). Efficacy measures were early-season yield (total before 1 March), late-season yield (total after 1 March), and total annual yield. Overall means for all cultivars and individual cultivar performance (for common years) were compared with Gulf or Marshall. Neither location effects nor cultivar X location interactions were found. Cultivar and year effects, plus cultivar × year interactions were detected (P < 0.05) for all three yield responses. Mean early season yields ranged from 2.3 to 4.6 Mg ha -1 , with mean late-season yields ranging from 5.1 to 7.4 Mg ha -1 . No trend existed for mean total yield relative to Gulf or Marshall to increase over time in association with availability of newer cultivars. Given large yearly fluctuation in yields, it is apparent that unpredictable environmental factors, including climate and perhaps pests, are the primary determinants of annual ryegrass performance rather than differences in yield potential among cultivars. Thus, yield stability may be an appropriate selection factor to include among the criteria for development of improved annual. ryegrass cultivars.

Multiple-year alfalfa production on coastal plain soils has been limited due to problems associated with stand persistence and post-harvest handling. One proposed management strategy is to maximize first-year alfalfa yield and quality, placing less importance on multiple-year alfalfa production. The objective of this study was to compare the effect on first-year alfalfa of four harvest intervals based on morphological stage and three harvest intervals based on a fixed harvest schedule. Dry matter (DM) yields, crude protein (CP), neutral detergent fiber (NDF), and in vitro digestibility were measured. First-year alfalfa DM yield ranged from 9,880 to 13,230 lbs/acre when harvested by morphological stage and from 8,860 to 10,200 lbs/acre when harvested on a fixed schedule. Nutritive value measurements showed small, although inconsistent, improvement in forage quality when harvested at either an early morphological stage (10%) or a short fixed interval (4 weeks). With the adoption of balage harvest systems and high quality imported alfalfa hay often approaching $200 per ton, managing alfalfa as a high quality annual, with an expected yield of 5 tons/acre, should be an economically feasible option for many southern forage producers.

Differences among annual ryegrass (Lolium multiflorum Lam.) cultivars for weight gain of grazing steers have been reported, even though plot experiments suggest that forage dry matter yield among cultivars should not be a limiting factor. Likewise, forage nutritive value differences among cultivars have not been assessed. The objectives of this research were to evaluate differences in cumulative forage yield, yield distribution, and nutritive value among 'Gulf', 'Jackson', 'Marshall', 'Rio', 'Rustmaster', and 'Surrey' annual ryegrass. Plots were harvested six times beginning in December at approximate 30-d intervals during the 1997-1998 and 1998-1999 growing seasons. Nutritive value measurements included crude protein (CP), neutral detergent fiber (NDF), in vitro true digestibility (IVTD), and digestible NDF (DNDF). There were no differences among cultivars for cumulative forage yield (P = 0.99). However, for the January harvest, Surrey and Gulf averaged 1030 (±65) kg DM ha -1 , whereas Marshall yielded only 672 (±79) kg DM ha -1 . For the March harvest, yields of all varieties were similar and averaged 1350 (±95) kg DM ha -1 . At the May harvest, Marshall and Jackson yielded 1232 (±123) kg DM ha -1 , whereas Gulf yielded only 929 (±74) kg DM ha -1 . Crude protein concentration differed significantly among harvests with a general decrease from 260 to 120 g CP kg -1 as the growing season progressed. Similar declines in nutritive value occurred for NDF, IVTD, and DNDF. Trends in yield distribution and forage quality may indicate a need for cultivar specific recommendations based on intended forage need and season of use.

Management strategies to enhance or preserve nutritive value of rhizoma peanut (Arachis glabrata Benth.) would be beneficial because high plant growth rates and adverse weather at harvest often result in low nutritive value for both pastures and hay along the coastal plain of the lower Gulf Coast. The objective of this study was to determine if a 30- or 60-d harvest frequency or 0, 110, or 220 kg N ha -1 fertilization could be managed to enhance crude protein (CP) yield and nutritive value of rhizoma peanut at three locations in Louisiana. Crude protein, neutral-detergent fiber (NDF), in vitro true digestibility (IVTD), and digestible NDF (DNDF) were measured on Florigraze' rhizoma peanut grown at three Louisiana locations in 1997 and 1998. Nitrogen fertilization increased CP yield approximately 80 kg ha -1 for the 110 and 220 kg N ha -1 treatments at two locations in I of 2 yr. Nitrogen fertilization affected nutritive value at two harvests at two locations in 1998 only. However, nutritive value was consistently lower for 60-d harvests than for 30-d harvests and was more consistent. Rhizoma peanut harvested in 1997 at 30-d intervals had 50 g kg -1 greater CP, 72 g kg -1 greater IVTD, and 40 g kg -1 greater DNDF coupled with 80 g kg -1 lower NDF than rhizoma peanut harvested at 60-d intervals. Likewise, there were seasonal influences on nutritive value. Responses in CP yield and nutritive value observed in this study were influenced more by environment (primarily rainfall) than by N fertilization and harvest management.

Optimizing feedstock production from switchgrass (Panicum virgatum L.) requires careful matching of genotype to environment, especially for southern U.S. regions. Nine genotypes from four combinations of ecotype and morphological type were harvested once yearly in autumn for 3 or 4 yr at five locations across Texas, Arkansas, and Louisiana that varied in latitude and precipitation. Genotypes were evaluated for dry matter yield (DMY), plant density, tiller density, lodging, and rust (caused by Puccinia spp.) infection. Genotype x environment (GxE) interactions were identified for most traits. Biomass yield of all genotypes tended to increase with latitude, but lowland morphological types may have been more sensitive than upland morphological types to differences in moisture availability. Yield (5.82 vs. 14.97 Mg ha -1 , respectively) and persistence (final stand density, 3.99 vs. 5.96 plants m -2 ) were lower for upland than for lowland genotypes, particularly at higher rainfall and more southern sites. Lowland genotypes were often able to compensate for stand thinning by increasing individual plant size, but upland genotypes were not. Lodging and rust scores were higher for upland than for lowland genotypes. Yield (13.65 vs. 9.75 Mg ha -1 ) and final plant density (5.58 vs. 4.95 plants m -2 ) were higher for southern than northern ecotypes. The southern-lowland combination exhibited the best yield and persistence over the study region, and genotypes within this group exhibited variability in yield among sites. Therefore, development of switchgrass cultivars for biomass production in the southern USA should focus on the southern-lowland genotypes.

Optimizing biofuel production and quality from switchgrass (Panicum virgatum L.) may require matching of ecotype and morphological type to environments, particularly in southern regions. Nine genotypes from four combinations of ecotype and morphological switchgrass type were harvested from 1998 to 2000 in five sites across Texas, Arkansas, and Louisiana that varied in latitude and precipitation. An additive main effects and multiplicative interaction (AMMI) method was used to evaluate genotype x environment interaction (G x E) patterns for traits important to biofuel production. Compared with upland genotypes across all site-years, lowland genotypes had greater lignocellulose yields (3.26 vs. 7.40 Mg ha -1 ), greater removal rates of soil N (41 vs. 83 kg ha -1 ) and P (6 vs. 12 kg ha -1 ), greater concentrations of moisture (394 vs. 452 g kg -1 ) and cellulose (388 vs. 394 g kg -1 ), and lower concentrations of N (6.3 vs. 5.7 g kg -1 ) and ash (48 vs. 40 g kg -1 ). Compared with northern ecotypes, southern ecotypes had greater lignocellulose yields (4.95 vs. 6.85 Mg ha -1 ), greater removal rates of soil N (60 vs. 76 kg ha -1 ) and P (8 vs. 11 kg ha -1 ), greater moisture concentrations (417 vs. 445 g kg -1 ), and lower ash concentrations (45 vs. 40 g kg -1 ). Lignocellulose yield paralleled dry matter yield (DMY) patterns. Switchgrass biofuel production efforts in the south-central USA should focus on improving DMY of southern lowland genotypes to maximize lignocellulose yields, but management factors may be more effective in optimizing moisture, ash, and mineral concentrations for combustion.