Autumn Grazing Research Articles

Tall Fescue Response to Nitrogen and Harvest Date for Stockpiled Grazing in the Upper Midwest

Tall fescue (Festuca arundinacea Schreb.) is a cool-season grass with physiological and morphological traits suitable for stockpiled grazing. The effect of late summer nitrogen (N) application was measured for yield and quality responses using four N rates (0, 25, 50, and 100 lb/acre) and three autumn harvest dates. Averaged across harvest date, linear increases of dry matter (DM) occurred in 1999 and 2000. In 1999, yield = 1747 + 15 × N rate (R 2 = 0.92, RMSE = 235) and in 2000, yield = 672 + 19 × N rate (R 2 = 0.96, RMSE = 202). Year by harvest date and year by N rate interactions were observed for yield because of above average rainfall in 1999 and below average rainfall in 2000. Forage crude protein (CP) and in vitro dry matter digestibility (IVDMD) increased as N rate increased, while neutral detergent fiber (NDF) decreased. Year by harvest date interactions were observed for CP, NDF, and IVDMD, and year by N rate interactions were observed for CP and NDF. Late summer N application increased DM yield and CP of the first cutting the following spring. Forage producers who apply late-season N can increase the quantity and quality of tall fescue forage available for autumn grazing. However, yield and quality losses can occur if harvest is delayed beyond October.

Nitrat-Austräge auf intensiv und extensiv beweidetem Grünland, erfasst mittels Saugkerzen- und Nmin-Beprobung II Variabilität der NO3- und NH4-Werte und Aussagegenauigkeit der Messmethoden

de

Divergent recurrent selection for seedling tiller number in Altai wildrye

Seedling tiller number is a possible selection criterion to improve seedling establishment of Altai wildrye, Leymus angustus (Trin.) Pilger, an important grass for autumn grazing of beef cattle in semiarid environments. Forty‐two half‐sib families selected for high seedling tiller number (HTN) and eighteen half‐sib families selected for low seedling tiller number (LTN) by four cycles of divergent recurrent selection were compared with four controls, Altai wildrye cultivars Prairieland, Eejay and Pearl, and crested wheatgrass (Agropyron desertorum (Fisch. Ex Link) Schultes), cultivar Nordan, on dryland and irrigated sites at Swift Current, Saskatchewan, Canada. Seedling tiller count, seedling height, tiller weight and seedling dry‐matter yield (DMY) were determined on two plants per plot and DMY was determined for each plot for 2 years post‐establishment. HTN half‐sib families had more, lighter and shorter tillers than LTN half‐sib families. There was a negative correlation (r=–0·42, P < 0·01, n=60) between seedling DMY and tiller number. HTN half‐sib families had higher DMY in post‐establishment years at the dryland site only. Seedling tiller number in Altai wildrye may be related to DMY at sites at which resource availability delays seedling establishment, but selection for HTN will not increase seedling DMY owing to concomitant changes in carbon allocation.

Demographic variation and population viability in Gentianella campestris: effects of grassland management and environmental stochasticity

Summary Transition matrix models were used to evaluate the effects of environmental stochasticity and four different methods of grassland management on dynamics and viability of a population of the biennial Gentianella campestris (Gentianaceae) in species‐rich grassland. Data were collected between 1990 and 1995. Continuous summer grazing, the prevailing management strategy in Scandinavian grasslands, resulted in high recruitment of new plants, mainly because litter accumulation was prevented and gaps were created by trampling. Trampling and repeated grazing, however, caused damage which reduced seed production. Lambda for the average matrix was c. 0.77, and a stochastic matrix model yielded an extinction probability for the total population of c. 0.08 within 50 years. Mowing in mid‐July (used as a conservation tool) increased seed production, but litter accumulation following re‐growth of the vegetation prevented establishment. Lambda and extinction risk were similar to continuous grazing. Mowing in October (another conservation tool) promoted recruitment because of low litter accumulation, but the seed output decreased because plant growth was impaired by tall vegetation. Lambda was 0.64, while the extinction probability was very high (c. 0.98 within 50 years). Mid‐July mowing followed by autumn grazing (the historical management regime) yielded high values for both seed production and establishment of rosettes. Lambda was 0.94 and the probability of extinction within 50 years was below detection level. Log‐linear analysis showed that the matrices differed significantly both between treatments and between years. The latter indicates environmental stochasticity, here caused by summer drought that increased the extinction risk. Lambda may be slightly underestimated because drought occurred in one out of five summers during the study period, which is high compared with the natural frequency. We conclude that traditional grassland management is more favourable for G. campestris than the methods that prevail in Scandinavia today. This indicates a serious conservation problem, because grazing has replaced traditional management in many of the remaining semi‐natural grasslands throughout Europe.

The interactive effects of management on the productivity and plant community structure of an upland meadow: an 8‐year field trial

Summary 1. Agricultural policy in the Pennine Dales Environmentally Sensitive Area in northern England aims to enhance plant species diversity in agriculturally improved meadows and return them to a ‘traditional’ species composition. The interacting effects of management on vegetation and productivity were tested in a split‐split‐split plot experiment. Three grazing treatments (autumn grazing with cattle and sheep, spring grazing with sheep, both regimes) were applied between 1990 and 98. Two fertilizer treatments (25 kg ha−1 N plus 12·5 kg ha−1 P2O5 and K2O, no fertilizer); three hay cut date treatments (14 June, 21 July, 1 September) and two seed addition treatments (no seed, seed of many species) were used within the grazing treatments. 2. By 1998, all the main treatments had produced small but significant changes to plant species diversity. A particularly large increase in diversity occurred with the combination of autumn and spring grazing, 21 July hay cut date and seed addition treatments. This change was achieved by an episodic rather than a regular increase in species over time. 3. Rhinanthus minor spread to most plots after its introduction as a constituent of the seed treatment. By 1996 it was particularly abundant in all treatment combinations that included autumn grazing, no mineral fertilizer and a July haycut. Populations of > 40 plants m−2 were associated with the lowest yields of hay. 4. ‘Unimproved‐traditional’ plant communities, mainly Festuca ovina–Agrostis capillaris–Galium saxatile grassland, occupied more than 66% of the trial area. Anthoxanthum odoratum–Geranium sylvaticum grasslands were most abundant in 1996, being primarily associated with the combination of autumn and spring grazing, 21 July and 1 September hay cut dates and seed addition treatments, over both fertilizer treatments. 5. Yields of herbage biomass initially declined over time in all treatment combinations. Lowest yields in most years were associated with the autumn and spring grazing, 14 June cutting date and no fertilizer treatments. 6. Management to increase the number of plant species in agriculturally improved mesotrophic grassland requires the joint implementation of appropriate cut date and grazing regimes, probably to provide regeneration niches, and the application of seed to provide species to fill these niches. The small amount of mineral fertilizer used in this experiment had a measurable effect, but was of lesser importance.

Performance of temperate perennial pastures in the Australian subtropics 1. Yield, persistence and pasture quality

Summary. Irrigated, pure stands of perennial ryegrass (Lolium perenne cv. Yatsyn), prairie grass (Bromus willdenodii cv. Matua) and tall fescue (Festuca arundinacea cv. AU Triumph) were compared with Italian ryegrass (L. multiflorum cv. Concord) under grazing in the subtropics of south-east Queensland. Pastures were fertilised with 50 kg nitrogen/ha . month as urea and annual dressings of 20 kg phosphorus/ha and 50 kg potassium/ha (as superphosphate and muriate of potash, respectively). There were 4 pasture treatments grazed by multiparous Holstein-Friesian cows at 3 cows/ha in a 1-week-on, 3-weeks-off rotation with 2 replicates and 3 cows/treatment block. Feed on offer was measured weekly and pasture quality, at the mid point of each of the 4 seasons. Detailed measurements on plant and tiller dynamics were recorded on fixed quadrats within the grazing areas from November to May in the second and third years. Yield of pasture on offer was greatest with prairie grass and the difference was most marked in spring and early summer. Yield of fescue was generally higher than that from the other 3 grasses in the autumn. In the second and third summers, the grass weed component in the 2 ryegrass, and to a lesser extent the prairie grass, pastures was greater than the sown grass component. Fescue generally produced forage lower in quality than the other 3 grasses although the differences were small in summer. The forage quality of Italian ryegrass was higher than perennial ryegrass in most seasons and for most attributes measured. Generally prairie grass had similar quality forage to the ryegrasses but at times it was as low as fescue. Fescue was the most persistent grass; it maintained a frequency of occurrence of 88, 56 and 71% in the first, second and third autumn periods, respectively, compared with 36, 37 and 21% for perennial ryegrass. To achieve these persistence figures, perennial ryegrass needed over-sowing in each autumn. Plant density and tiller numbers per plant fell in all grasses from November to May but the fall was significantly less in fescue than in other grasses. It was concluded that all 3 temperate perennial grasses demonstrated traits which were useful for subtropical dairy pastures. Fescue was the most persistent and the only grass which could sustain grazing in autumn. The performance of Italian ryegrass was as good as that of perennial ryegrass in the first year but fell substantially in the second and third years as the level of summer grass invasion suppressed the existing population and made oversowing increasingly less effective. Prairie grass produced the highest dry matter on offer under grazing, its forage quality was generally similar to that of the ryegrasses and it regenerated from self-sown seed.

Performance of temperate perennial pastures in the Australian subtropics 2. Milk production

Summary. Milk production from irrigated, pure stands of perennial ryegrass (Lolium perenne cv. Yatsyn), prairie grass (Bromus willdenodii cv. Matua) and tall fescue (Festuca arundinacea cv. AU Triumph) were compared with that achieved from Italian ryegrass (L. multiflorum cv. Concord) over 3 lactations of multiparous Holstein–Friesian cows at Mutdapilly in south-east Queensland. Pastures were fertilised with 50 kg nitrogen/ha . month as urea and annual dressings of 20 kg phosphorus/ha and 50 kg potassium/ha (as superphosphate and muriate of potash respectively). There were 4 pasture treatments grazed at 3 cows/ha in a 1-week-on, 3-weeks-off rotation with 2 replicates and 3 cows/treatment block. Cows grazed the pastures day and night from May to November. Over summer, cows grazed the pastures during the night and were fed supplements (silage in the first lactation, and lucerne hay in the second and third lactations) during the day because there was no shade available in the irrigation areas. In autumn, the animals were removed from the ryegrass and prairie grass pastures for 8 weeks to allow seedling re-establishment, either by oversowing (ryegrasses) or natural reseeding (prairie grass). Cows continued to graze the fescue pastures at night during autumn. All cows received a ration of 4 kg/cow of a grain–minerals mixture in the first lactation and 5 kg/cow in the second and third lactations. Milk production from perennial ryegrass was higher than from fescue in the first lactation and Italian ryegrass in the second and third lactations. Prairie grass gave similar milk production to perennial ryegrass in all 3 years. In the third year, perennial ryegrass, prairie grass and fescue gave similar milk production. Milk quality from the 4 grasses was similar except in the third lactation when the lactose content of milk from perennial ryegrass pastures was lowest. There were also small and inconsistent differences in milk component yields between the 4 grasses. Liveweight changes were small except in the second lactation when the cows grazing fescue lost weight relative to the other treatments. Mean liveweight at calving increased over the 3 lactations. It was concluded that all 3 temperate perennial grasses demonstrated useful traits for use in subtropical dairy pastures. Perennial ryegrass produced the most milk from the lowest amount of dry matter on offer. Prairie grass produced similar milk yields to perennial ryegrass, was well eaten by cattle and was self regenerating. Although fescue was slower to establish and needed more intensive management to control maturity, it was the most persistent and was the only grass to provide autumn grazing. In the second year this attribute resulted in a lower requirement for supplementary feeding. Fescue produced the highest gross margin in the second lactation and was only marginally less than prairie grass in the third. The performance of Italian ryegrass was as good as that of perennial ryegrass in the first lactation but fell substantially in the second and third lactations as the level of summer grass invasion increased.

Use of an Experimental High-Magnesium Tall Fescue to Reduce Grass Tetany in Cattle

Grass tetany (hypomagnesemia) continues to be a problem for the livestock industry. An experimental cultivar of tall fescue (Festuca arundinacea Shreb.) selected for high Mg concentration, HiMag, was compared against four other cultivars for its ability to increase serum-Mg and reduce the risk of grass tetany. Forage from HiMag contained 22% more Mg, 18.5% more Ca, and 9% more P than other cultivars; K levels were not different. Regardless of cultivar, concentrations of Ca and Mg were lower while K and P were higher during the spring than the autumn. The tetany ratio [K/(Ca + Mg) on M c basis] was lower for HiMag than for other cultivars (1.34 vs. 1.65); all cultivars had a higher ratio during spring than autumn (1.91 vs. 1.31). In cattle (Bos taurus) grazing trials, blood serum from steers grazing HiMag contained 8% more Mg in autumn 1993 but was not different in spring 1994. Blood serum Mg was not different for cows (either dry or nursing calves) during autumn grazing, but approached significance (P = 0.09) during the spring 1995 calving season (2.32 vs. 2.07 mg/dL for HiMag vs.other cultivars). Except for differences between calves on HiMag compared with Kentucky-31 in autumn 1995 (58 vs. 43 Ib, respectively), animal weight change was not affected by cultivar. Normal forage Mg concentrations (>0.20%) and tetany ratios below 2.2 for all cultivars in every season except spring 1995 may explain the lack of consistent animal response. No clinical symptoms of grass tetany were observed at any time during these studies. However, the higher Mg concentration and lower tetany ratio suggest that HiMag could provide a means of reducing the incidence of grass tetany in livestock during periods when risk of the disorder is high.

Autumn-Grazed Orchardgrass-White Clover Pasture: Nutritive Value of Herbage and Lamb Performance

Performance of livestock grazing pasture is inherently variable. Pastures must be managed to optimize quantity and quality of herbage to meet the nutrient requirements of a specific class of livestock involved in a defined production goal. Consumer desires for healthier meat products have shifted the emphasis to lean, trim carcasses from livestock production systems using forage crops. The purpose of this study was to characterize herbage nutritive value changes in grass-legume pastures grazed during autumn and to compare growing lamb (Ovis aries) performance and carcass quality when grazing autumn pasture or fed concentrate in feedlot. Less crude protein (CP) from legume was available for use by grazers in 1992 than in 1991. Frequent clipping of autumn pasture resulted in herbage with greater nutritive value (lower neutral detergent fiber [NDF] and higher in vitro organic matter disappearance [IVOMD]) than more mature stockpiled herbage. A computer model of energy determined from acid detergent fiber (ADF) nutritive value and herbage mass data predicted greater potential for lamb growth on intensively managed (clipped) vs. stockpiled herbage. Lambs fed grain had greater (P ≤ 0.05) cumulative weight gain, average daily gain (ADG), slaughter weights, chilled carcass weights, dressing percentages, leg conformation scores, ribeye area (REA), fat over rib, quality grade, and yield grades than lambs grazed on autumn pasture. However, carcasses from lambs grazing pasture in autumn had 14% less fat and about 8% more protein than lambs fed grain. While total fat content of carcasses was lower for pasturegrazed than grain-fed lambs, saturated fatty acid composition and cholesterol concentrations in lean tissue were not different. Percentage legume in the sward may have influenced the proportion of individual fatty acids in lean and fat. Market weight lambs may be produced from botanically complex autumn pasture. Research Question Livestock performance varies on pasture probably as a result of fluctuations in forage plant nutritive value, herbage productivity, and botanical composition. Canopy management, as well as livestock genetics, can influence the variability. Our study characterized herbage nutritive value changes of grass-legume pastures resulting from grazing during the autumn growth interval. In addition, performance and carcass quality were compared for lambs that grazed autumn pasture or were fed concentrate in feedlot. Literature Summary Extensive knowledge of the dynamics of grass-legume swards exists for the cool-temperate, continental climatic zone of the eastern USA. Most of what is known about autumn management of cool-season forages has been obtained from studies of stockpiled, grass-dominated canopies with relatively limited information obtained under actual grazing conditions. Finishing lambs on forage rather than concentrate leads to relatively lean carcasses. Consumer desires for healthier meat products (e.g., less fat) have shifted the emphasis to leaner, trimmer carcasses from livestock production systems. Study Description An established mixed sward of orchardgrass and white clover growing in southem West Virginia was used. Growing lambs grazed either pasture or were fed concentrate in feedlot. Herbage nutritive value in pasture was monitored for 3 yr during the autumn grazing interval and lamb performance and carcass quality were determined in each of 2 yr. Applied Questions Did autumn grazing management of grass-legume pastures influence herbage nutritive value? Less crude protein was available for use by grazers in 1992 than in 1991 resulting primarily from less legume in the sward in 1992. Herbage of higher nutritive value (lower neutral detergent fiber and greater digestibility) was available from intensively managed (frequent clipping) canopies compared with that of stockpiled canopies. Did autumn pasture or concentrate feed influence lamb performance and carcass quality? Lambs fed concentrate had greater cumulative weight gain, average daily gain, slaughter weights, chilled carcass weights, dressing percentages, leg conformation scores, ribeye area, fat over rib, quality grade, and yield grade than lambs grazed on autumn pasture. Total fat content of carcasses was lower for pasturegrazed than grain-fed lambs, but saturated fatty acid composition and cholesterol levels were greater. Recommendation We are suggesting that market weight animals may be produced from mixed-plant-species autumn pasture. Results depend upon animal genetics and the subsequent potential for rapid and efficient gain on pasture, as well as carcass weight and composition desired by the market at any given time.

Regrowth, morphology and persistence of Grasslands Puna chicory (Cichorium intybus L.) in response to grazing frequency and intensity

Effects of different grazing frequencies and intensities on herbage production (on both a unit pasture and individual plant basis) and on persistence of chicory (Cichorium intybus L. cv. Grasslands Puna) were studied at Palmerston North, New Zealand (latitude 40°23′S) from November 1994 to November 1995. Three experiments were conducted on the same chicory stand, sown on 12 May 1994. The main grazing experiment had two grazing intensities, hard‐lax grazing (50‐ to 100‐mm stem stubble to mid‐January, and thereafter 100‐ to 150‐mm stem stubble) and lax grazing (100‐ to 150‐mm stem stubble), and three grazing frequencies (1‐, 2‐ or 4‐week intervals). A subsidiary plant survival experiment compared the survival of 120 marked plants in ungrazed and grazed treatments. A late autumn grazing experiment examined the effects on plant persistence in the following spring. The greatest herbage mass (leaf + stem) resulted from the 4‐week grazing frequency [9640 ± 874 kg dry matter (DM) ha−1], in which stem mass was reasonably low (1270 ± 410 kg DM ha−1), but was significantly higher in the 4‐week grazing frequency than 1‐ and 2‐week grazing frequencies (P < 0·01). Grazing intensity had no significant effect except on the average stem mass of individual plants when the hard‐lax intensity gave a lower stem mass (P < 0·01). There were no interactions between grazing frequency and intensity in herbage mass. Plant density declined by 35% over the growing season with the decline unaffected by grazing intensity or frequency during the season. Grazing in late autumn resulted in approximately 27% less plants the following spring. It was concluded that grazing management through the growing season cannot be used to improve persistence without compromising leaf growth rate, but that avoidance of grazing late autumn will improve the persistence of chicory.

Monthly fluctuations of worm burdens and hypobiosis of gastrointestinal nematodes of calves in extensive management systems in the Pyrenees (Spain)

Monthly fluctuations of worm burdens and arrested development of gastrointestinal nematodes in cattle from a mountainous region of Spain were studied. Fourteen previously helminth-naive calves grazed together with a herd of 120 cattle from May to November following the traditional extensive grazing system used in mountainous regions of Spain (permanent calves). Each month, throughout the grazing season, two helminth-naive calves (tracer calves) were added to the herd and allowed to graze for 4 weeks. Every 2 weeks, throughout the grazing period, faecal and blood samples from the permanent calves, and pasture grass samples for larval recovery were collected. Every 4 weeks, throughout the grazing period, two tracer and two permanent calves were removed from the herd and housed on concrete for 2 weeks before being slaughtered. The nematode parasite species identified from the animals were: Ostertagia ostertagi, O. lyrata, Teladorsagia circumcincta, Trichostrongylus axei, Cooperia oncophora, Trichostrongylus longispicularis, Capillaria bovis, Nematodirus helvetianus, Oesophagostomum radiatum, Chabertia ovina and Trichuris spp. O. ostertagi was the predominant species, followed by C. oncophora and T. axei. The highest numbers of worms recovered from the tracer calves were observed in May, June, September and November with average worm burdens of 4050, 3775, 2775 and 2825, respectively. These dates corresponded with 2 months of spring grazing in areas below 1000 m (May–June), the last month of grazing in areas higher than 1000 m (September), and the last month of autumn grazing in areas below 1000 m (November), respectively. The highest total worm burden (8000 worms per animal) was observed in the permanent calves in June after 2 months of grazing below 1000 m. The average total worm burden in the permanent calves during the study was 5825 worms per animal. As in other cool temperate regions of the Northern hemisphere, the highest percentage of larval inhibition was observed in autumn, with maximum levels of 63.4% for Ostertagia spp. and 89.3% for Cooperia oncophora. Similar inhibition levels were observed in parasites from both tracer and permanent calves, indicating that previous exposure was not the primary cause of larval inhibition.

The conservation management of mesotrophic (meadow) grassland in Northern England. 2. Effects of grazing, cutting date, fertilizer and seed application on the vegetation of an agriculturally improved sward

The plant species number and composition, iind yield of herbage biomass of an agriculturally improved hay meadow were assessed after 4 years under various combinations of grazing, fertilizer applicution. cutting date and seed addition treatments in a replicated split‐plot design.Grazing treatments consisted of either autumn grazing with cattle and sheep, spring grazing with sheep or both regimes. Fertilizer application treatments consisted of either 25 kg ha−1 N plus 12–5 kg ha−1 P and K or no fertilizer. Cutting date treatments consisted of cuts on either 14 June, 2i July or 1 September. Seed addition treatments consisted of either no addition or sowing with a range of meadow species in the autumn. Data analysis was by correspondence analysis and analysis of variance.Species number decreased with fenilizer use and when the cutting date was 1 September. A range of species was affected by the main treatments and there were some first‐order interactions, mainly between cutting date and fertilizer application. Rhinanthus minor was particularly favoured by the seed addition treatment. Species attnbutes in the regenerative and established phase were related to treatments and their effect on species composition.The National Vegetation Classification communities were associated with particular treatment regimes. The 21 July cutting date favoured ‘improved’ over ‘unimproved‐traditional’ swards, with spring grazing favouring ‘unimproved‐traditional’ swards.Lowest yields of herbage biomass were associated with autumn and spring grazing, the 14 June cutting date and no fenilizer treatments. The fenil‐izer, 1 September cutting date and auiumn grazing treatments gave the highest yields.The implications of these results are discussed in terms of the conservation management required to return agriculturally improved mesotrophic grassland to a species composition similarto that of traditionally managed grassland.

Nitrogen and mineral composition of autumn‐grazed pasture

Abstract Grazing management in autumn can influence the botanical composition and productivity of a sward. Cycling of nutrients as a result of grazing livestock activity and variable canopy growth rates may influence mineral nutrient supply and demand in a dynamic canopy. An experiment was conducted to determine the influence of autumn grazing practices on the growth and composition, including minerals in terms of ruminant requirements, of a grass/legume sward. Paddocks were established and three replicates grazed by growing lambs for 30‐, 60‐, or 90‐d intervals beginning in late summer. Herbage samples were collected at the beginning of the grazing interval and at the end of each interval (closing date). Herbage mass, and nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and sulfur (S), as well as copper (Cu) and zinc (Zn) were examined in terms of the influence of sampling date, closing date, year, and the interaction of these factors from stockpiled and grazed canopies. Soil mi...

Competitive ability of two grass species: Anthephora pubescens and Eragrostis curvula. 1. Yield and biomass allocation

The possibility of growing Anthephora pubescens Nees and Eragrostis curvula (Schrad.) Nees together in mixed pastures was investigated as E. curvula could provide early spring grazing and bulk in summer, while A. pubescens could provide good quality grazing in autumn and winter. In monocultures as well as in mixtures, the yield of A. pubescens remained inferior to that of E. curvula. The values of the relative yield per plant and aggressivity obtained in the present study all indicate that A. pubescens is a poor competitor, while E. curvula is a strong competitor. In spite of the fact that some niche differentiation does occur when the two species are grown together, E. curvula would probably eventually eliminate A. pubescens as the latter is not easily established where competition from existing grass species is high. Aangesien Eragrostis curvula (Schrad.) Nees vroeë lenteweiding en massa in die somer verskaf, terwyl Anthephora pubescens Nees hoë-kwaliteitweiding in die herfs en winter lewer, is die moontlikheid ondersoek om hierdie twee spesies in gemengde weiding aan te plant. In monokultuur sowel as in mengsels het die opbrengs van E. curvula dié van A. pubescens oortref. Die waardes van die relatiewe opbrengs per plant sowel as aggressiwiteit het getoon dat A. pubescens 'n swak kompeteerder en E. curvula 'n sterk kompeteerder is. Ten spyte van die feit dat daar wel nisdifferensiasie voorkom wanneer die twee spesies in mengsels gekweek word, sal E. curvula waarskynlik op die lange duur A. pubescens elimineer aangesien laasgenoemde spesie moeilik vestig as dit met bestaande grasse moet kompeteer.

Grazing Evaluation of Bigalta and Floralta Limpograss

The use of limpograss [Hemarthria altissima (Poir) Stapf et C.E. Hubb.] as a pasture plant is a relatively recent development. Available cultivars possess distinctly different characteristics. ‘Bigalta’ limpograss has been widely planted on peninsular Florida Spodosols, but stand loss under grazing is common. A more persistent cultivar, ‘Floralta’, has recently become the most widely grown limpograss cultivar in Florida. When grown in the same pasture, Bigalta was heavily grazed by yearling steers (Bos indicus L. and Bos taurus L. spp.) before any noticeable grazing of Floralta occurred. A series of grazing trials was conducted to investigate relative forage quality and plant growth responses of the two cultivars under grazing. Eight 0.5‐ha pastures were established to provide duplicate treatments of two stocking rates on each cultivar. Three summer grazing trials and two autumn grazing trials were conducted. Patterns of grazing differed distinctly between the two cultivars with distinct patchy grazing on Bigalta and rather uniform grazing of the upper canopy of Floralta. Bigalta had higher in vitro organic matter digestibility (IVOMD) and crude protein (CP) than Floralta in most instances, with Bigalta at the light stocking rate averaging 520 g kg−1 IVOMD and 61 g kg−1 CP vs. 480 g kg−1 IVOMD and 51 g kg−1 CP for Floralta. Bigalta produced greater average daily gains (ADG) than did Floralta prior to deterioration of Bigalta stands with 0.5 kg ADG on Bigalta vs. 0.3 kg on Floralta in 1986 and 1987 trials. Bigalta stands deteriorated rapidly especially when subjected to the higher stocking rate, but extended deferment from grazing allowed some stand recovery.

Effects of autumn harvest date on the performance of white clover/grass mixtures in Nova Scotia

SUMMARYWhite clover (Trifolium repens L.) is well adapted to the cool moist climate of Atlantic Canada, where it improves digestibility and protein content in pastures, but little is known about its role in pasture stockpiled for autumn grazing in this region. The objectives of this study were to determine the effect of autumn harvest dates on dry matter yield and clover content in herbage mixtures. Two experiments conducted in Nova Scotia between 1985 and 1991 on two different soil types showed that the effects of autumn harvest dates were inconsistent from year to year. Herbage growth rates ranged from 11 to 41 kg/ha per day between early September and mid-October. Clover content was generally lower in August–early September than in November harvests and declined in subsequent years irrespective of harvest date or forage species. Kersey White and Sonja white clovers were the highest yielding cultivars. Crude protein declined in late autumn harvests whereas acid detergent fibre tended to increase, and there were differences between years. Forage quality was significantly better in tall fescue (Festuca arundinacea Schreb.) than orchardgrass (Dactylis glomerata L.)/white clover mixtures.

Managing replacement stock within the environment of the south--plant, soil, and animal interactions: a review.

The South extends from the Atlantic Coast and the Gulf of Mexico north through Virginia and Kentucky and west to the 100th meridian, which extends through Texas and Oklahoma. The soils, environment, and range of adapted forage species offer many and varied opportunities for designing forage-livestock systems for rearing replacement stock. Anti-quality factors of concern when using forages for replacement stock include the presence of Acremonium coenophialum (Morgan-Jones and Gams) in tall fescue (Festuca arundinacea Schreb.), phytoestrogens potentially in several species of Trifolium and Medicago, toxins in some species of brush that contribute to infertility, and imbalances of several minerals including Ca, P, K, Fe, I, Zn, Na, Cu, and Se. Systems should be designed to provide appropriate quality and quantity of forage to produce reproductively active female animals of the desired weight and condition for breeding at the target age, usually 15 mo for beef and dairy heifers and 8 to 9 mo for ewe lambs. Systems generally require sequence grazing of two or more forage species or mixtures to provide extended or year-round grazing opportunities. Stockpiling of tall fescue in the Upper South and use of cool-season annuals in the Lower South extend grazing in autumn, winter, and early spring. Successful systems coordinate plant growth potential with changing animal forage requirements for both quantity and quality of forage to achieve optimum growth rates for replacement stock.

Effects of Grazing on Nesting by Upland Sandpipers in Southcentral North Dakota

Grazing by livestock is often used to reduce litter, improve plant vigor, and alter plant species composition, but additional information is needed on the effects of these management practices on uplandnesting birds. Thus, we conducted an experimental study of the effect of grazing on nest density and nest success of upland sandpipers (Bartramia longicauda) in southcentral North Dakota from 1981 to 1981. Our experimental design consisted of 4 treatments and 1 control, each applied to 1 field in each of 3 study areas. The treatments represented options available to grassland managers: spring grazing, autumn grazing, autumn-and-spring grazing, season-long grazing, and control (ungrazed during the study). Nests (P = 342) were found by searching study areas with a cable-chain drag

Conserving the species-rich meadows of Europe

Owing to changes in agricultural practices throughout Europe, with greater emphasis on intensification, traditionally managed hay meadows have become scarce. Their loss has also meant the loss of species diversity. One of the few areas of Europe where traditional management is still practised is in Northern Spain. The hay meadows of Northern Spain can be defined as semi-natural, species-rich communities that are maintained by one or more factors which are under the direct control of man. The traditional management to which they are subjected has led to a high species diversity. For centuries the meadows have been important to man in supporting cattle during the winter. There is now little need for further increase of production. However, the importance of the need for conservation of species diversity and protection of ecologically sensitive areas is now recognised. Although the biological richness of the hay meadows is well known, few studies have been made of the effects of different traditional management regimes on the diversity and floristic composition of these grasslands. A survey was carried out to examine the effects of traditional management on the floristic composition, diversity and production of these meadows. The area studied is situated in the Valdeón valley, northwestern Spain (Cantabrian Mountains) and consists of a deep valley in which arboreal vegetation is represented by beech ( Fagus sylvatica) forests. The survival of semi-natural habitats and traditional forms of management and also the low use of chemical fertilisers compared with Northern Europe are the most important reasons for the richness of these habitats. In this study, cutting for hay once per year, non-irrigation non-manuring and grazing in autumn was correlated with high species diversity. The future conservation of these habitats will depend on the formulation of support to continue with traditional management practices.

Grazing Management Effects on Aeschynomene Seed Production

Aeschynomene (Aeschynomene americana L.) is a warm-season annual legume; to persist from year to year, its stands must regenerate from seed. Autumn grazing management must balance the need for seed yield with livestock needs for quality herbage. Aeschynomene was grown in pasture association with ‘Floralta’ limpograss [Hemarthrla altissima (Poir.) Stapf & C.E. Hubb.] on a Pomona sand (sandy, siliceous, hypothermic Ultic Haplaquod) in 1987 and 1988. Our objective was to measure the influence of three postgrazing stubble heights (SH) and four closure dates (CD, the times when autumn grazing was discontinued) on legume pod yield and amount of herbage left ungrazed at season end. Aeschynomene pod yield per plant and per hectare decreased as SH decreased from 24 to 8 cm, and as CD was delayed from 1 wk before to 2 wk after first flower. Ungrazed plots yielded 350 and 500 kg of pod ha−1 in 1987 and 1988, while the earliest CD and tallest SH treatment yielded 90 and 180 kg ha−1. Pod yield declined with delayed CD because inflorescences per plant, pods per inflorescence, and pod weight decreased. Most pod yield components tended to decline with decreasing SH, but no significant differences were detected. Though pod yields were highest with early CD and tall SH, ≈50% of total herbage produced for these treatments remained ungrazed at season end. Thus, contribution of aeschynomene is reduced during a time when perennial grasses do not meet the nutrient requirements of grazing animals. Because taller SH leaves more ungrazed herbage, a potentially useful compromise between high seed yield and maximum forage utilization is to graze aeschynomene closely (8−16 cm), but to end autumn grazing before flowering. Additional utilization may be possible if grazing is resumed after most pods are mature, but nutritive value of this later herbage generally is low.