Bermudagrass Pastures Research Articles

Allelopathic Effects of Cereal Rye on Weed Suppression and Forage Yield in Alfalfa

Cereal rye (Secale cereale L.) is widely used as cover crop because of its allelopathic effects and effectiveness in weed suppression. In the Southeastern US, rye is traditionally grown for winter grazing in dormant bermudagrass pastures, where alfalfa (Medicago sativa L.) is increasingly planted as a companion crop. The effect of cereal rye on alfalfa as a succeeding crop is not known. Therefore, the objective of this study was to evaluate the effect of cereal rye on alfalfa seedling emergence, growth, forage yield, and weed suppression in field conditions. Rye was planted in the fall (mid-October) and the biomass was harvested in spring (March) followed by disking and incorporation of the remaining stubble in the soil. Alfalfa seed was planted four weeks later. The experiment design was a split-plot design with the main plots being no-rye and after-rye and the sub-plots being alfalfa cultivars. Ten alfalfa cultivars were planted in three replications after-rye and three replications with no-rye as a previous crop. In the establishment year, weed density was significantly (p 0.01) among the cultivars planted in the after-rye block compared to the no-rye, with a seedling count reduction between 35% and 64%. Reduction in total dry biomass yield varied from 15% to 43% among the cultivars planted in the after-rye block. The results of this study also suggest that the allelopathic effect of rye on alfalfa may not persist beyond the establishment season, but the enormous yield reduction in the first production season may constitute a costly economic penalty in terms of forage production. There was variation in the response of different alfalfa cultivars to the effect of rye residue as indicated by the variation in the magnitude of reduction in stand count and forage yield. This warrants more research in multi-location trials with and without rye in order to establish whether there is genetic variation in alfalfa germplasm in their tolerance to cereal rye allelopathy.

Grazing management of mixed alfalfa bermudagrass pastures.

Rotational grazing management is commonly recommended to improve persistence of legumes interseeded into bermudagrass, but impacts on animal performance are poorly understood. Steers (n = 365, BW = 249 ± 22.9 kg) grazed mixed alfalfa (Medicago sativa L.)/bermudagrass (Cynodon dactylon [L.] Pers.) pastures (n = 10; 1.6-ha) with either continuous grazing (CONT) or rotational grazing (ROT) management over 3 yr. Initial stocking rate was set at 6.25 steers/ha. When forage allowance of CONT became limiting in mid-July each year, 2 randomly selected steers were removed from all pastures to maintain equal stocking rates in CONT and ROT. Rotational grazing pastures were divided into 8 paddocks with 3-d grazing and 21-d rest between grazing events. Initial, final, and interim (28-d) BW were collected following a 16-h removal from feed and water. Data were analyzed as a repeated measures experiment with completely random design using the mixed procedure of SAS (SAS Inst. Inc., Cary, NC) using pasture within treatment by year in the random statement. Across years, steer BW did not differ (P ≥ 0.47) at the midpoint or end of the grazing season. Daily BW gains during the early summer period tended (P = 0.10) to be 0.11 kg greater for CONT than ROT in yr 1, but did not differ (P ≥ 0.24) in yr 2 and 3. In the late summer, ADG was 0.15 kg less (P < 0.01) for CONT than ROT in yr 1, were not different (P = 0.23) in yr 2, and were 0.29 kg less (P < 0.01) for CONT than ROT in yr 3. Over the entire experimental period, ADG did not differ (P ≥ 0.67) in yr 1 or 2, but tended (P = 0.09) to be 0.10 kg greater for ROT than CONT in yr 3. Forage mass of ROT was greater (P < 0.01) than CONT throughout the grazing season. Because stocking rates were maintained at the same level, ROT pastures provided greater (P < 0.01) forage allowance during the grazing season than CONT explaining differences in ADG between treatments. Alfalfa stand percentage did not differ (P = 0.79) at the beginning of the experiment, but was less (P ≤ 0.03) for CONT than ROT at all other sampling dates. These data indicate that at equal stocking rates, ROT can maintain greater alfalfa persistence, forage nutritive quality, and forage allowance compared with continuous grazing and provided increased animal performance during the late summer when the alfalfa stand was reduced in CONT pastures.

Pest and Beneficial Arthropods in a ‘Tifton 85‘ Bermudagrass Field in North Central Florida

Summary Pest and beneficial arthropods were collected in a ‘Tifton 85’ bermudagrass pasture in north central Florida to assess their impact on forage production. The primary pests were Auchenorrhyncha (leafhoppers and spittlebugs), grasshoppers, grass loopers, plant bugs, fall armyworms, and stinkbugs. Major beneficial arthropods included spiders, damsel bugs, big-eyed bugs, and small possibly parasitoid wasps. The pest populations did not increase to obvious damaging levels during 35 d growing periods after the grass had been mowed to heights of 8 or 15 cm. Thus, pest arthropods probably can be managed by grazing or periodically mowing ‘Tifton 85’ bermudagrass.

Genetic evaluation of postweaning performance traits in Brahman and Brahman-influenced stockers grazing rye–ryegrass or bermudagrass pastures

ABSTRACT Growth of young cattle on forages and pastures has a major effect on the profitability of the stocker cattle industry. The objectives of this study were to estimate heritability of performance traits and additive genetic correlations of pairs of traits in Brahman and Brahman-influenced (0.25 or 0.5 Brahman) stocker cattle on rye (Secale cereale) + ryegrass (Lolium multiflorum) (RRG; n = 2,031) or bermudagrass [Cynodon dactylon (L.) Pers.] (BER; n = 1,322). Data from 1986 to 2014 at Overton, Texas, for BW, ADG, and BCS were analyzed for each stocking season. Main effects included stocking rate (3 levels), proportion of Brahman inheritance (3 levels on RRG: 0.25, 0.5, 1; 2 levels on BER: 0.25 and 1), supplementation status, and contemporary groups. Stockers receiving supplement were heavier (P

Invited Review: Management Strategies for Intensive, Sustainable Cow-Calf Production Systems in the Southeastern United States: Bermudagrass pastures overseeded with cool-season annual grasses and legumes

ABSTRACT Sustainability of cow-calf production in the United States has received increased attention during the past few years. The ever-increasing land values and ownership scenarios, redirected agricultural production objectives, and financial requirements for new ownership affects land use, livestock enterprises, and sustainability of the beef industry. Bermudagrass [ Cynodon dactylon (L.) Pers.] is the most sustainable and persistent warm-season perennial grass used for N-fertilized pastures in the southeastern United States. Management strategies that affect bermudagrass persistence and DM production goals include soil nutrient management, primarily N and K, and stocking rate, intensity, and duration. Overseeding bermudagrass with cool-season annual forages such as small grains, annual ryegrass ( Lolium multiflorum L.), or clovers ( Trifolium sp.) extends the active grazing period of pastures and provides the highest nutritive value of any forage class. Stocking strategies that incorporate the most adapted bermudagrass cultivars with soil type, soil nutrient availability, and use of cool-season annual forages provide the best options to achieve intensive forage utilization. Using stocking rates appropriate for forage utilization intensity objectives provides for enhanced gain per animal and gain per unit land area relationships. The economy of scale of operation, management objectives, and acceptable risk allow stakeholders to select their site-specific level of intensive cow-calf production. The most noteworthy aspects of bermudagrass pasture management have shown that the magnitude of forage mass can be immediately altered with implementation of levels of N fertilization and stocking rate to affect beef production per unit land area.

Performance of Heifers Grazing Bermudagrass Pastures Strip or Solid Seeded with Clovers

Core Ideas Strip‐seeding of clovers into bermudagrass swards resulted in similar clover stand percentage compared with solid planting of clovers. Heifers grazing pastures that were strip seeded performed similarly to heifers grazing clovers that were seeded in solid stands. Red clovers persisted longer into the summer than either white or subterranean clovers. Red clover provided greater animal performance than white and subterranean clovers. Even though clovers can provide improved forage quality and reduced N fertilization when grazing stocker calves on warm‐season grass pastures, stand establishment remains a concern. The objective of this research was to determine if alternative methods of seeding legumes into warm‐season perennial swards could improve legume establishment. This research took place on 18, four‐acre mixed bermudagrass [Cynodon dactylon (L.) Pers.], crabgrass [Digitaria ciliaris (Retz.) Koeler], and dallisgrass (Paspalum dilatatum Poir.) pastures at the University of Arkansas Southwest Research and Extension Center Stocker Unit. Pastures were seeded in October of 2013 to white (Trifolium repens L.), red (Trifolium pratense L.), or subterranean (Trifolium subterraneum L.) clovers either in solid stands at the recommended rate (2.0, 8.0, and 11 lb/acre, respectively) or in four 0.25‐acre strips at twice the recommended seeding rate in a 3 × 2 factorial arrangement of treatments with three pasture replications per treatment combination. Growing heifers (n = 216; 614 ± 44.4 lb) grazed pastures from May to September 2014 and April to September 2015. Red clover was present later into the summer than white or subterranean clovers, but there were no differences due to seeding method. At the end of the grazing season, heifer bodyweight and gain was greater when grazing red clover than when grazing subterranean clover. Strip‐seeded clovers in only 50% of the pasture area provided similar stands to conventional solid seeding and equivalent animal performance. Red clover grew later into the summer grazing season and provided greater animal performance than white and subterranean clovers.

Using soybean hulls to meet dietary energy requirements of gestating cows having restricted access to poor-quality hay

Forage for grazing and hay may be limited during drought years, necessitating alternative feeding options. Co-product feedstuffs, such as soybean hulls (SH), may be a more economical means to maintain cows through such conditions. The objective of this study was to determine if SH could be used to meet the majority of the energy demands for cows in late gestation when access to hay was restricted to 1 h daily. Eighty-six gestating, spring-calving cows (527 ± 7.5 kg initial BW; 4.3 ± 0.27 yr of age) were allocated to 1 of 6 groups for a 68-d study beginning December 6, 2012. Three groups were given ad libitum access to medium-quality bermudagrass [Cynodon dactylon (L.) Pers.] hay. The 3 remaining groups were offered 6.4 kg of SH/cow daily and allowed access to a very-poor-quality, mature, mixed-grass hay for only 1 h daily. Each group was housed in separate 2.02-ha dormant bermudagrass pastures. Birth weight and dystocia scores were recorded, and calf performance was monitored through weaning. Representative bales of each hay were weighed to determine total hay offered. Differences in BW and BCS, and changes in these measurements during the study, were minimal between treatments (P ≥ 0.53). Calf birth weight, weaning weight, BW/d of age at weaning, and birth-to-weaning ADG did not differ (P ≥ 0.11) between treatments. Therefore, SH may be used as the major dietary energy component for cows in late gestation having access to hay for only 1 h daily without having adverse effects on the cows or their subsequent calves.

Insecticide Evaluation for Grasshopper Control in Bermudagrass Pasture, 2015*

Insecticide Evaluation for Grasshopper Control in Bermudagrass Pasture, 2015*

Including Legumes in Bermudagrass Pastures

Including Legumes in Bermudagrass Pastures

Nutrient Pools in Bermudagrass Swards Fertilized at Different Nitrogen Levels

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

Yearling Cattle Performance on Continuously Stocked ‘Tifton 85’ and ‘Florakirk’ Bermudagrass Pastures

Cynodon grasses are a major feed source for livestock in the US Gulf Coast region. Although continuous stocking is widely used for regional perennial grass pastures, there has been limited evaluation of animal performance on continuously stocked bermudagrass [Cynodon dactylon (L.) Pers.]. This 3‐yr experiment compared forage and animal performance on continuously stocked ‘Tifton 85’ (Cynodon spp.) and ‘Florakirk’ bermudagrass pastures using a variable stocking rate during summer (average of 159 d yr−1). Tifton 85 had greater herbage accumulation than Florakirk (average of 13.6 vs. 7.5 Mg ha−1 yr−1, respectively), in part because Florakirk percentage cover declined from 89% at initiation of the experiment to 35% after 3 yr. Change in cover of Tifton 85 over the same period was 93 to 90%. The Tifton 85 forage concentrations of in vitro digestible organic matter was greater than for Florakirk (563 vs. 523 g kg−1, respectively), but yearling cattle average daily gain did not differ between grasses (0.61 kg d−1). Greater herbage accumulation for Tifton 85 resulted in a greater average stocking rate than for Florakirk (6.4 vs. 3.8 head ha−1, respectively) at a similar herbage allowance of approximately 1.0 kg forage dry matter kg−1 animal body weight. Gain ha−1 was greater for cattle grazing on Tifton 85 than on Florakirk (638 vs. 358 kg ha−1, respectively). Tifton 85 was superior to Florakirk bermudagrass under continuous stocking in northern Florida because of its greater herbage accumulation, herbage in vitro digestible organic matter, average stocking rate, animal gain ha−1, and persistence.

Effect of supplementation of developing replacement heifers with monensin or bambermycins on gain and pregnancy rates

ABSTRACT Medicated feed additives have been shown to increase BW gain and decrease age at puberty; therefore, heifers were provided nonmedicated control (CNTRL), bambermycins (BAMB, Gainpro, Huvepharma Inc., Sofia, Bulgaria), or monensin (MON, Rumensin, Elanco Animal Health, Greenfield, IN) supplements to determine effects on growth performance and reproductive development. Spring-calving (block 1; n = 70 heifers; BW = 208 ± 21.7 kg; age = 231 ± 17.0 d) and fall-calving (block 2; n = 72 heifers; BW = 225 ± 31.7 kg; age = 276 ± 12.8 d) heifers were allotted to treatments [n = 4 groups in CNTRL and 5 groups in BAMB and MON (block 1), 4 groups per treatment (block 2)] by breed, BW, and source. Heifers in block 1 grazed tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] for 188 d; heifers in block 2 grazed bermudagrass (Cynodon dactylon) pasture and tall fescue for 161 d. The BW at breeding and ADG of CNTRL (323 ± 4.8 kg and 0.68 ± 0.0167 kg/d, respectively) was less (P ≤ 0.04) than medicated, yet MON (346 ± 4.6 kg and 0.73 ± 0.0163 kg/d) and BAMB (344 ± 4.6 kg and 0.74 ± 0.0163 kg/d) did not differ (P ≥ 0.69). Prebreeding reproductive tract scores (3.5 ± 0.60), cycling activity (61 ± 12.3%), and AI (30 ± 12.3%) and total pregnancy rates (82 ± 11.5%) did not differ (P ≥ 0.25) among treatments. This experiment indicates that BAMB and MON effectively increased growth performance of heifers but did not affect reproductive development or pregnancy rates.

Relationships between restricted residual feed intake of Brahman bulls measured in confinement and under different stocking intensities on Coastal bermudagrass pastures

ABSTRACT Efficiency of animal production is an important component of the beef industry. The research objectives of this 2-yr study were to (1) estimate residual feed intake (RFI) of yearling Brahman (Bos indicus) bulls grazing Coastal bermudagrass [Cynodon dactylon (L.) Pers.] using DMI measured with n-alkanes; (2) compare RFI under grazing (RFIg) with RFI determined in confinement under restricted feed intake at 2.8% of BW (RRFIc); and (3) assess the relationships of carcass traits and gastrointestinal tract anatomy to RFIg. Bulls RRFIc-phenotyped as efficient (n-RFI) and inefficient (p-RFI) in both 2009 and 2010 were assigned to 2 replicate pastures at either low or high stocking intensity (STK) for 60 d. In 2009 there was no difference (P > 0.3) between n-RRFIc and p-RRFIc for initial or final BW, ADG, DMI, or feed-to-gain ratio. There was an interaction of RFIg × STK (P = 0.043) for ADG in which p-RFIg bulls on low STK had the greatest gain. The p-RFIg bulls had the greatest DMI regardless of STK (P

Vasoactivity and Vasoconstriction Changes in Cattle Related to Time off Toxic Endophyte-Infected Tall Fescue.

Previous research has indicated that serotonergic and α-adrenergic receptors in peripheral vasculature are affected by exposure of cattle grazing toxic endophyte-infected (E+; Epichlöe coenophialia) tall fescue (Lolium arundinaceum). The objective of this experiment was to determine the period of time necessary for the vascular effects of ergot alkaloids to subside. Two experiments were conducted to investigate changes in vascular contractile response and vasoconstriction over time relative to removal from an ergot alkaloid-containing E+ tall fescue pasture. In Experiment 1, lateral saphenous vein biopsies were conducted on 21 predominantly Angus steers (357 ± 3 kg body weight) at 0 (n = 6), 7 (n = 6), 14 (n = 5), or 28 days (n = 4) after removal from grazing pasture (3.0 ha; endpoint ergovaline + ergovalinine = 1.35 mg/kg DM) for 126 days. In Experiment 2, lateral saphenous veins were biopsied from 24 Angus-cross steers (361 ± 4 kg body weight) at 0, 21, 42, and 63 days (n = 6 per time point) following removal from grazing tall fescue pastures (3.0 ha; first 88 days endpoint ergovaline + ergovalinine = 0.15 mg/kg DM; last 18 days endpoint ergovaline + ergovalinine = 0.57 mg/kg DM) for 106 total days. Six steers (370 ± 18 kg body weight) off of bermudagrass pasture for the same time interval were also biopsied on Day 0 and Day 63 (n = 3 per time point). Additionally, in Experiment 2, cross-sectional ultrasound scans of caudal artery at the fourth coccygeal vertebra were taken on Days 0, 8, 15, 21, 29, 36, 42, and 45 to determine mean artery luminal area to evaluate vasoconstriction. In both experiments, steers were removed from pasture and housed in a dry lot and fed a corn silage diet for the duration of biopsies and ultrasound scans. Biopsied vessels used to evaluate vasoactivity were cleaned, incubated in a multimyograph, and exposed to increasing concentrations of 4-Bromo-3,6-dimethoxybenzocyclobuten-1-yl) methylamine hydrobromide (TCB2; 5HT2A agonist), guanfacine (GF; α2A-adrenergic agonist), and (R)-(+)-m-nitrobiphenyline oxalate (NBP; α2C-adrenergic agonist) in both experiments and ergovaline (ERV) and ergotamine (ERT) in Experiments 1 and 2, respectively. In Experiment 1, days off pasture × agonist concentration was not significant (p > 0.1) for all four compounds tested. In Experiment 2, GF, NBP, TCB2 and ERT were significant for days off pasture × agonist concentration interaction (p < 0.02) and vasoactivity increased over time. Vasoactivity to agonists was reduced (p < 0.05) when steers were initially removed from E+ tall fescue pasture compared to bermudagrass, but did not differ by Day 63 for any variable. Luminal areas of caudal arteries in steers grazed on E+ tall fescue relaxed and were similar to steers that had grazed bermudagrass for 36 days on non-toxic diet (p = 0.15). These data demonstrate changes in peripheral vasoactivity and recovery from vasoconstriction occur beyond five weeks off toxic pasture and 5HT2A receptors appear to be more dramatically affected in the lateral saphenous vein by grazing E+ tall fescue pasture than adrenergic receptors.

Persistence of Alfalfa Sod‐Seeded into Bermudagrass Pastures on Coastal Plain Soils

Alfalfa (Medicago sativa L.) production and persistence in the Lower South of the USA are dependent on climate, soil, and competition from warm‐season perennial grasses such as bermudagrass [Cynodon dactylon (L.) Pers.]. A 3‐year study was conducted at Texas A&amp;M AgriLife Research, Overton, to evaluate ‘Alfagraze’ alfalfa persistence on a Darco loamy fine sand (loamy, siliceous thermic Grossarenic Paleudult) when sod‐seeded at three row spacings (10, 20, and 30 inches) into a well‐established ‘Coastal’ bermudagrass pasture. Alfagraze was rotationally stocked with animal residence time from 5 to 13 d and deferment periods ranging from 18 to 27 d. In Year 1, during the first three grazing periods (1 April to 31 May), alfalfa was the dominant species (P &lt; 0.05). Thereafter, from 30 June to 3 October, bermudagrass was dominant (P &lt; 0.05). At the initiation of harvest in Year 2 (1 April), alfalfa dry matter (DM) was 1353, 783, and 690 lb/acre, respectively, at 10‐, 20‐, and 30‐inch drill‐row spacing prior to bermudagrass growth. At the end of Year 2 (3 October), alfalfa DM was 33, 10, and 0.90 lb/acre, respectively, at 10‐, 20‐, and 30‐inch spacings while bermudagrass DM was 1424, 1557, and 1080 lb/acre. At the beginning of Year 3, the percent stands of alfalfa were 14, 11, and 5%, respectively, for 10‐, 20‐, and 30‐inch spaced alfalfa plantings, while the respective percent stands of bermudagrass were 86, 89, and 95%. Under the climatic and sandy Coastal Plains soils of this vegetation region, Alfagraze was not persistent under grazing at any row spacing for more than 3 years when sod‐seeded into a well‐established Coastal bermudagrass pasture.

Influence of Flue Gas Desulfurization Gypsum on Reducing Soluble Phosphorus in Successive Runoff Events from a Coastal Plain Bermudagrass Pasture.

Controlling the threat that pastures intensively managed with poultry litter (PL) pose to accelerating eutrophication is a major issue in the southeastern United States. Gypsum (CaSO) has been identified as a promising management tool for ameliorating litter P losses to runoff. Thus, research was conducted to elucidate gypsum's residual effects on P losses from a bermudagrass ( L.) pasture. Runoff events (60 min) were created using rainfall simulations. Treatments consisted of applying four flue gas desulfurization (FGD) gypsum rates (0, 2.2, 4.4, and 8.9 Mg ha) to bermudagrass fertilized with 13.4 Mg ha PL plus a nonfertilized check (no litter or gypsum) and 8.9 Mg ha FGD gypsum only as controls. Rainfall simulations (∼ 85 mm h) were conducted immediately, 5 wk, and 6 mo (i.e., at the end of growing season) after PL application to determine gypsum's effectiveness at controlling P loss over successive runoff events. The greatest dissolved P (DP) in runoff occurred immediately after PL application. Gypsum effectively reduced cumulative DP concentration losses (54%) compared with PL alone in initial runoff events. Gypsum reduced DP concentrations in succeeding runoff events also regardless of timing, suggesting that its effect is persistent and will not diminish over a growing season. Generally, maximum DP reductions were achieved with 8.9 Mg ha. However, it was surmised from this study that optimal P reduction in a bermudagrass pasture can be achieved with 4.4 Mg ha. Information ascertained from this study may be useful in aiding land managers making prescriptions for management practices that reduce DP losses from agricultural fields.

Replacing synthetic N with clovers or alfalfa in bermudagrass pastures. 3. Performance of growing steers

The objective of this study was to evaluate the performance of steers (n = 590, 263 ± 30.6 kg) grazing alfalfa (ALF, Medicago sativa L.) or a combination of white (Trifolium repens L.) and red (Trifolium pretense L.) clovers (CLVR) inter-seeded into bermudagrass (Cynodon dactylon L. Pers.) pastures compared with fertilisation with 0 (0N), 56 (56N), or 112 (112N) kg nitrogen (N)/ha (n = 4, 0.8-ha pastures per treatment) in north-east Arkansas (USA) over 4 years. The carryover N benefit of CLVR or ALF was compared with N fertilisation rates during the fifth year on performance of growing steers (n = 120; 235 ± 22.6 kg). Average daily gain increased with N application rate and legume pastures were similar to 56N; but liveweight gain per steer grazing legume pastures tended to be greater than 112N. Steer grazing days per hectare and liveweight gain per hectare were greater for ALF and CLVR than bermudagrass monocultures regardless of N fertilisation rate. Steer average daily gain, grazing days per hectare and liveweight gain per hectare for carryover N from legumes did not differ from 56N. These results indicate that replacing synthetic N by inter-seeding legumes into bermudagrass swards has the potential to improve individual animal performance and production per unit area and carryover benefits of legume N may be equivalent to 56 kg N/ha.

Replacing synthetic N with clovers or alfalfa in bermudagrass pastures. 1. Herbage mass and pasture carrying capacity

The objective of this study was to evaluate the effects of including alfalfa (ALF, Medicago sativa L.) or a combination of white (Trifolium repens L.) and red (Trifolium pretense L.) clovers (CLVR) inter-seeded into bermudagrass (Cynodon dactylon L. Pers.) on herbage nutritive value compared with monocultures of bermudagrass fertilised with 0 (0N), 56 (56N), or 112 (112N) kg nitrogen (N)/ha over four grazing seasons. In autumn, at the end of the fourth year and in the spring before the fifth grazing season, alfalfa and clover plants were killed and the carryover N benefit of CLVR or ALF was compared with N fertilisation rates during the fifth year. Across years, N fertilisation rate increased herbage mass and carrying capacity linearly; whereas herbage production from CLVR and ALF swards was equivalent to 56N, were greater than 0N and less than 112N. Herbage mass in CLVR and ALF swards was greater than fertilised bermudagrass swards in the spring and did not differ from fertilised bermudagrass in the early summer. In late summer herbage accumulation of CLVR and ALF swards appeared to decrease, limiting the herbage mass in the legume pastures compared with 56N and 112N. Carrying capacity of CLVR and ALF swards was greater than fertilised bermudagrass in the spring and early summer, but did not differ from fertilised swards in the late summer. The N benefit of including legumes in bermudagrass swards can alleviate the reliance on synthetic N fertilisation with little overall effect on pasture carrying capacity.

Replacing synthetic N with clovers or alfalfa in bermudagrass pastures. 2. Herbage nutritive value for growing beef steers

The objective of this study was to evaluate the effects of including alfalfa (ALF, Medicago sativa L.) or a combination of white (Trifolium repens L.) and red (Trifolium pretense L.) clovers (CLVR) inter-seeded into bermudagrass (Cynodon dactylon L. Pers.) on herbage nutritive value compared with monocultures of bermudagrass fertilised with 0 (0N), 56 (56N), or 112 (112N) kg nitrogen (N)/ha over four grazing seasons. At the end of the fourth year (during the winter), legume plants in ALF and CLVR were killed and the carryover N benefit on bermudagrass nutritive value was evaluated during the fifth year. Pre-grazing herbage of all pastures exceeded the dietary recommendations for growing steers to maintain 0.9 kg/day average daily liveweight gain for crude protein and total digestible nutrients, 118 and 617 g kg/DM, respectively. Post-grazing herbage in ALF was below 600 g/kg total digestible nutrients at all times during the grazing season, post-grazing total digestible nutrients of CLVR was below 600 g/kg during the late summer and autumn. Post-grazing herbage of monoculture bermudagrass pastures fell below 600 g/kg in the middle of summer regardless of N fertilisation. Carryover N benefits of legumes were similar to 112N in the early summer, but were not different than 0N and 56N during the late summer and autumn. Replacing applications of synthetic N in bermudagrass swards with inter-seeding of either clovers or alfalfa produce herbage with equivalent nutritive value to heavily N fertilised monocultures of bermudagrass during the early summer, and similar to moderately N fertilised in the late summer and autumn. The inclusion of legumes in bermudagrass swards can reduce the reliance on synthetic N fertilisation with little overall effect on herbage nutritive quality possibly decreasing environmental impacts of grazing production systems.

Genetic gain from selection and potential for improving alfalfa phosphorus uptake and removal from soils heavily amended with poultry litter

Alfalfa (Medicago Sativa L.) is increasingly adopted in the southeastern USA as a companion crop in bermudagrass (Cynodon dactylon L.) pastures, where poultry litter is excessively used as source of N fertilizer. This research explores the extent of genetic variation in phosphorus (P) accumulation and uptake in alfalfa germplasm grown in a soil heavily amended with poultry waste, and the expected genetic gain from selection for P accumulation and uptake. Eighteen commercial and experimental populations of alfalfa were evaluated in a soil, heavily amended with chicken litter. The soil pH was 6.8 and Mehlich-1 P content was 1039.7 kg ha−1. Significant genetic variation was observed in P accumulation, forage yield, and P uptake and removal (p < 0.01). Harvest dates effect was significant (p < 0.01), but little interaction of genotypes x harvest date. Narrow sense heritability estimates based on family-means were 0.50 for P concentration, 0.25 for biomass yield, and 0.74 for P uptake. Genetic gain from selection for forage yield based on family means was much higher than that of selection based on individual pots (40 vs. 16 %). For P uptake, gain from selection was 7 % higher using selection based on family means compared to individual pot basis (46 vs. 53 %, respectively). The data suggests that it is possible to make reasonable progress in improving P uptake in alfalfa by selection methods that take advantage of the additive genetic variation such as family selection, whether selecting indirectly for high forage yield or concurrently for P concentration and yield.