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Volume 12 Issue 1, December 2014
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Pasture fertilization plays a vital role in the biological and economic successes of forage-based livestock systems. Sustainability of productive, warm-season perennial forage systems depends, to a major extent, on management–utilization strategies and pasture fertilization. As soil nutrient reserves are exhausted, forage production and nutritive value are reduced proportionally. Despite the vast scientific literature suggesting that warm-season forage crops can respond favorably to high levels of N fertilization, the increasing costs of commercial fertilizers and environmental concerns have prompted the need to reexamine optimum-efficient fertilizer levels, sources, and methods of application that can sustain economic pasture production. Because the fate of fertilizers applied to grassland systems is extremely complex and is affected by several factors, including application rate and timing, fertilizer source, and soil and environmental characteristics, it is critical to implement management strategies for soil fertility that integrate all the factors that affect fertilizer efficiency, sustainable forage production, and protection of natural resources. The primary objective of this review paper is to present some of the basic principles of soil-fertility management for warm-season perennial forages and fertilization strategies for sustainable pasture production.
Since first being discovered in southern Georgia in July 2010, the bermudagrass stem maggot (BSM; Atherigona reversura Villeneuve) has infested and damaged forage bermudagrass [Cynodon dactylon (L.) Pers.] throughout the southeastern United States. This review summarizes the available literature on the BSM and provides additional insight from other Atherigona spp. that are closely related to this exotic species. Additional research is underway to better understand the lifecycle of the BSM, confirm and quantify the degree of preference the BSM exhibits for the different bermudagrass varieties, and quantify the severity of damage in yield, quality, and aesthetics.
Inclusion of warm-season forage legumes in livestock grazing systems may increase forage quantity by maintaining the grazing season during dry periods and enhancing nutritive value. Two field experiments were conducted to evaluate forage yield and nutritive value of several warm-season legumes across different environments and soil pH levels in Oklahoma and Texas. The superior forage yield and nutritive value of Lablab purpureus (L.) Sweet ‘Rongia’ lablab and Vigna unguiculata (L.) Walp. ‘Iron & Clay’ cowpea, Glycine max (L.) Merr. ‘Big Fellow’, ‘Derry’, ‘Hutcheson’, ‘Laredo’, ‘Large Lad’, ‘Ozark’, and ‘Tyrone’ soybeans, and Glycine soja Siebold & Zucc. & max ‘Whitetail Thicket’ hybrid soybean in both near-average and below-average rainfall years indicate their potential for livestock production. However, further research on best management strategies, animal performance, and economics of these cultivars is warranted before being included in production systems.
Bermudagrass [Cynodon dactylon (Pers.) L.] cultivars with improved cold tolerance can be used for grazing in the U.S. upper south, but these bermudagrasses do not provide adequate growth for stocking until late May to early June. Length of the grazing season can be extended by interseeding bermudagrass with cool-season annual grasses; however, it is uncertain if competiveness of cool-season grasses will reduce yields and damage stands of bermudagrasses that are late in breaking dormancy. A plot experiment was conducted with ‘Wrangler’ bermudagrass to compare spring and summer herbage dry matter (DM) yields, percentage harvested yields relative to total spring or summer DM yields, and nutritive value among interseeded rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), wheat (Triticum aestivum L.), rye–wheat and rye–ryegrass mixtures, and bermudagrass-only plots. Rye and mixtures of rye with wheat or ryegrass had high total spring yields in both years whereas wheat yields were low in both years and ryegrass provided high yields in the first year and lower yields in the second. Bermudagrass-only plots consistently had the highest total summer yields, but any dampening of bermudagrass in interseeded plots occurred only in the first summer harvest. Results indicated that cool-season annual grasses can be interseeded into bermudagrass to provide grazing in the spring with high-quality forage.
The herbicide, Chaparral, has been shown to suppress seedhead development in tall fescue (Lolium arundinaceum) pastures and reduce the symptoms of tall fescue toxicosis in cattle. However, little is known about the logistics of herbicide treatment on tall fescue pastures. The objective of this study was to determine the effect of three rates of Chaparral on tall fescue pasture when applied at three times (October, March, and April) during the growing season. Chaparral reduced seedhead densities of tall fescue on all treatment dates, but the highest levels of suppression were achieved with a late-spring treatment, when tall fescue was in the early stages of reproductive growth. This treatment was also the least detrimental to tall fescue plant densities. Chaparral applied to vegetative tall fescue in the early spring had the least effect on seedhead densities but significantly reduced the density of tall fescue crowns. Other species of grass began to encroach into tall fescue stands following herbicide treatment during the fall and early spring. Delaying Chaparral until late spring may be more effective for producers because it may allow for greater control of seedheads with less loss in tall fescue and the potential for higher forage yields. There was some effect of suppressing reproductive growth of tall fescue with a fall treatment of Chaparral, but more research may be needed to evaluate its merit over a late-spring treatment.
Conserving cool-season grasses as silage or hay remains a challenge due to the time required for field curing and the unpredictability of the weather. We compared the drying rates of three grasses with differing yield potential, morphology, and physical characteristics. Inflorescence-stage meadow fescue (Festuca pratensis Huds. subsp. pratensis [syn. Schedonorus pratensis (Huds.) P. Beauv.]), orchardgrass (Dactylis glomerata L.), and reed canarygrass (Phalaris arundinacea L.) were cut and swathed with field-scale equipment at 1100 h on three consecutive days of early June in each of 2 years. Moisture, drying rate, and nutritive value were measured hourly until 1600 h and over the same time frame during the following 2 days. Despite differences in leaf-to-stem ratio and windrow density, there were few differences in drying rate (mean of 0.229, 0.150, and 0.119/h on the first, second, and third days, respectively). In one year, meadow fescue had lower initial moisture content at harvest than the other grasses, potentially allowing earlier processing into silage on the first day of curing. Species will probably not have an impact on drying rate of cool-season grasses harvested at the same relative maturity.
Overseeding in bermudagrass (Cynodon dactylon) pasture is common to expand the harvest season in the southeastern U.S. coastal plain . Grasses are often utilized; however, using legumes would allow capturing nitrogen and extend the harvest season. Austrian winter peas (Pisum sativum, WP), crimson clover (Trifolium incarnatum cv. Dixie, CC), arrowleaf clover (T. vesiculosum Savi cv. Apache and Yuchi, AC), and hairy vetch (Vicia villosa cv. AU Merit, HV) were seeded into bermudagrass in a complete block design (four replicates in each of two seasons). Forage yield estimates were made before grazing by cattle and before bermudagrass hay harvests. Botanical separations and step-point analysis determined legume and bermudagrass contributions to the stand. Legumes yielded similarly (3842 kg/ha), with harvestable growth 6 to 10 weeks before bermudagrass alone. Compared to controls (no legume), HV and AC reduced bermudagrass hay yield (P < 0.05) and WP and CC did not. Crimson clover was the only legume that did not reduce the proportion of bermudagrass in hay. Late harvest of legumes exacerbated the decline of bermudagrass. Overseeding has the potential to increase harvestable forage; however, maturing legumes can have deleterious effects on bermudagrass. Crimson clover had the least negative impact and therefore might be the best suited of the legumes tested for overseeding.
Hairy buttercup (Ranunculus sardous Crantz) is a winter annual weed in southeastern U.S. pastures. Its potential toxicity and aggressive spring growth have made it a widespread concern among producers, especially in mixed grass-legume pastures. Few published studies have reported on its ecology or control. Furthermore, a lack of herbicide selectivity has historically been a problem when broadleaf weed control is needed in mixed grass-legume pastures. To address this issue, we compared multiple formulations of 2,4-D with imazethapyr, hexazinone, and aminopyralid + 2,4-D at December and February application timings for hairy buttercup control and white clover (Trifolium repens L.) tolerance. Dimethylamine, diethanolamine, and ester formulations of 2,4-D were effective in controlling hairy buttercup at 0.4 kg/ha. White clover cover was similar between all 2,4-D treated plots and the unsprayed control plots. Imazethapyr was also effective in controlling hairy buttercup. Hexazinone was not effective for hairy buttercup control and resulted in a considerable reduction in white clover. Aminopyralid + 2,4-D provided excellent hairy buttercup control but also eliminated clover cover. Herbicide treatments were very effective at both application timings. These studies indicate that hairy buttercup can be effectively controlled in mixed white clover/grass pastures with multiple herbicide options without reducing white clover populations.
Perennial forage grasses have potential as cellulosic feedstocks. Outside storage as round bales is a likely mode of storage; however, little is known of storage effects. The objective of this study was to determine the effects of baled storage method on saccharification, namely the recovery of glucose and xylose, and production of inhibitors after dilute acid pretreatment and enzymatic hydrolysis. Mature switchgrass (Panicum virgatum L. cv. Alamo) was harvested in Fayetteville, AR and packaged in large round bales in October 2010. There were two baling times: one soon after cutting when there was no rainfall and the other after a rainfall event. The bales that did not receive rain were stored either in an open barn or unprotected in the field. Bales made from rained-on switchgrass were only stored unprotected in the field. Samples were taken from the windrows right before baling, and after a maximum 65-day storage period. Field storage increased lignin content in biomass relative to barn storage, but carbohydrate constituents were not affected. Field storage decreased production of hydroxymethylfurfural and increased production of furfural relative to barn storage. Results indicate that protected storage conditions for switchgrass biomass in round bales can lead to greater preservation of fermentable sugars and reduced production of the important inhibitor furfural.
Cover crops are becoming increasingly popular in place of fallow in many farming regions. In semiarid, high plains regions, being able to utilize these annual forages for beef cattle can be crucial to maintaining beef cattle herds. The objective of this experiment was to evaluate annual forage mixtures for dry matter production and diet quality for beef cattle in a dryland no-till crop production system. In a two-year experiment, spring-planted forage pea (Pisum sativum), oat (Avena sativa), and turnip (Brassica rapa) were compared to crested wheatgrass pasture (Agropyron cristatum) for grazing cattle. Overall, annual forage mixtures had greater forage digestibility than crested wheatgrass (66.1 vs. 51.6%) and greater crude protein (10.0 vs. 6.9%, respectively). Dry matter production was greater for the crested wheatgrass pasture in 2011 than for the annual forage mixture (0.97 vs. 0.55 ton/acre). However, in 2012 the dry matter production was similar for annual forage mixtures and crested wheatgrass pasture (0.74 vs. 0.76 ton/acre, respectively). This integration of crops and livestock may offer an economical approach to using land for both grain and cattle production, while providing some deferment of perennial grass pastures when needed.
Fibrolytic enzymes and microbial inoculants have the potential to improve fiber degradability. A 2 × 2 × 2 factorial experiment was conducted to determine the nutritive value, ruminal degradability, and degradation rates of wheat (Triticum aestivum L.) and oat (Avena sativa L.) pretreated with fibrolytic enzyme (xylanase plus cellulase: XC) or bacterial [Promote ASB (Lactobacillus buchneri and L. plantarum); PRO] inoculants at two maturities. Forage was harvested twice during the tillering stage (H1 and H2) and a third time as stover (H3). Forage from H1 had less neutral detergent fiber (NDF; 43.8% dry-matter [DM] basis) and acid detergent fiber (ADF; 31.2% DM basis) and greater in vitro true digestibility (IVTD; 78.5%) concentrations than H3 (69.0 and 45.3% DM basis, and 51.9%, respectively). The IVTD was greater for oat (55.0%) than wheat (50.7%). Chemical composition was not affected by inoculant; however, inoculant did affect ruminal degradability and degradation rates. Potentially degradable DM, NDF, and ADF and effective ruminal degradability were greater for wheat and oat at tillering. Treatment of oat or wheat with XC or PRO enhanced potential degradability and reduced undegradable fractions. Both XC and PRO may be used to degrade the fiber fractions of small-grain forage.
Research has suggested that eastern gamagrass (EGG) may be an effective alternative to chopped straw in the blended diets of dairy heifers and cows. Extension materials discussing appropriate fall management of EGG often recommend avoiding harvest within 6 weeks of first frost. However, previous research has shown that single-harvest dry-matter (DM) yields are not maximal by mid-August in central Wisconsin; most probably this occurs because of inadequate accumulation of growing degree days by that date. Our objectives were to evaluate DM yield, plant persistence, and nutritive value for EGG harvested at 15-day intervals between 1 August and 1 November. Yields of DM (2010 through 2013) increased with linear (P = 0.001) and quadratic (P < 0.001) effects across harvest dates, peaking at >6600 lb/acre (7392 kg/ha) on 15 September and 1 October. Overall DM yields varied with year but were greatest (P ≤ 0.001) during the final year (2013) of the trial (7099 lb/acre; 7951 kg/ha). The percentage of continuous row coverage also was assessed but was not affected by harvest date (P ≥ 0.218). In central Wisconsin, single-cut harvests of EGG timed as late as 1 October improved DM yields relative to August harvest dates without compromising plant persistence.
Stockpiled forage for grazing during fall and winter can reduce winter feed costs for livestock producers. Tall fescue is used successfully as stockpiled forage in areas of the Midwest and Southeast. In the Southern Great Plains, drought conditions limit production, resulting in summer-active variety stand failure and summer-dormant variety persistence. This study compared the stockpiled production and nutritive value of summer-dormant type to summer-active type tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]. The yield and nutritive value of stockpiled summer-dormant tall fescue were similar to that of summer-active tall fescue. At the end of the study, severe drought occurred in the area, resulting in summer-active failure but summer-dormant persistence.
The climate in the upper Midwest is noted for extreme weather events that greatly increase the risk of alfalfa (Medicago sativa L.) winter injury. An electronic survey was sent to alfalfa producers and crop consultants in Minnesota, Wisconsin, and Iowa with the goal of providing a retrospective assessment of the causes of alfalfa winter injury during the winter of 2012–2013. Almost all alfalfa producers who responded to the survey observed some winter injury, and a majority of crop consultants indicated more than 2001 acres had been affected in among their clients. A majority of crop consultants and alfalfa producers indicated that they perceived that freezing rain during the winter of 2013 combined with the dry fall of 2012 and the lack of snow cover caused alfalfa winter injury. Along with weather events, management practices also affected the incidence of alfalfa winter injury, with the lowest occurrences of winter injury observed in fields that had 13 or more inches of alfalfa regrowth. The results from the survey confirm that alfalfa winter injury was probably caused by a combination of weather events and management decisions.
Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] responds to N fertilization; however, data are limited on N management options for the claypan soils of the eastern Great Plains. A field study was conducted from fall 1986 to spring 1990 to determine the effects of N fertilizer timing (100% in fall; 67% in fall, 33% in late winter; 33% in fall, 67% in late winter; and 100% in late winter), placement (surface broadcast, surface band [dribble], and subsurface band [knife at 4 inches]), and rate (75 and 150 lb acre−1) on tall fescue sampled in April to simulate “early-grazing” and then later in May for hay yields. The soil was a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf), which is a typical claypan soil of the area. Fescue sampled in mid-April yielded more when all or 67% of the N was applied in the fall, placed on the surface, and at 150 lb N acre−1. Crude protein in April samples was greater with knife placement in the fall, whereas digestibility was less with knifing when part or all of N was applied in late winter. Hay harvest yields were greatest when N was knife-applied at 150 lb acre−1 in both fall and late winter. In contrast, hay quality was generally improved with late winter and surface applications. Optimum N management will depend on producer goals to graze the forage early, to feed the hay to their own cattle at a later time, or to sell excess hay to others.
Quantifying botanical composition is important for evaluating the effects of management on legume content and of legume content on pasture yield and quality. The standard for measuring botanical composition is hand separation of clipped samples. An alternative is taking point counts of botanical components on photographs of the pasture. The latter was tested on a rotationally stocked pasture, with photos taken at 24 random sample areas, areas clipped at ground level, and samples hand separated into grass, legume, and forb fractions. Photos were evaluated with a grid in Microsoft PowerPoint. Point counts were calibrated to hand-separated values using linear regression. Grass and legume point-count components were not significantly different from hand-separated values (P = 0.05) but underestimated the forb fraction. Calibration regressions had R2 values ranging from 0.45 to 0.98. The precision of this technique is dependent on the number of photos per pasture, the number of points counted per photo, and the number of paired samples taken for calibration. In cool-season grass–clover pastures, 12 or more photos per pasture and 100 or more points per photo are a good balance between photo number and points per photo. For calibration, 12 or more paired samples should be used. Photo point counts appear to be a practical method of measuring grass, legume, and forb components in rotationally grazed pastures.
As the prices of nitrogen fertilizers rise, there is increased incentive to grow legumes for fixing nitrogen and improving forage quality in pastures and hay meadows. From a management perspective, it is important for managers to be able to estimate legume content in the stand. In research, clipping and hand separation is the standard method for measuring legume content. However, this method is impractical for farm managers. Another option is visual appraisal of the percentage surface covered by legumes. The objective of this photo reference guide is to provide a tool that pasture managers can use to assess legume content as it is related to legume cover. For each photo, the area within the quadrat was clipped and hand separated to determine the actual legume content. These photos represent a range of legume content across two ranges of forage mass. By using these photos to help estimate legume content, forage managers should be able to increase the accuracy of their visual estimate of legume content in pastures and aftermath meadows.
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