Cattle select against the invasive grass tall fescue in heterogeneous pastures managed with prescribed fire

Tall fescue (Festuca arundinacea) is a Eurasian forage grass extensively planted in the United States. However, an endophytic fungus in tall fescue, Epichloë coenophiala, causes health problems in cattle. We predicted that cattle prefer to graze alternative forages when available. We also predicted that cattle use tall fescue more intensively in recently burned areas, as fire can increase forage quality. We tested these predictions in four diverse‐forage pastures in Iowa, comparing use by cattle of tall fescue and four alternative forages (non‐fescue cool‐season grasses, native warm‐season grasses, non‐leguminous forbs and legumes) to their availabilities at the pasture scale. We also examined how tall fescue influences the distribution of grazing at a fine scale (0.1‐m² quadrats). Tall fescue was the most abundant forage (46% of plants), but composed only 26% of grazed vegetation. In contrast, legumes composed 12% of available forage but 25% of grazed vegetation. Other forages were used in proportion to availability. At a fine scale, total grazing frequency (proportion of plants grazed) was lower in quadrats containing abundant tall fescue, and higher in quadrats with abundant warm‐season grasses. Grazing frequency of tall fescue and other cool‐season grasses was greatest in recently burned quadrats, but total grazing frequency did not increase after burning. Our results show that although cattle graze tall fescue, particularly following burns, they limit their use of this grass. Given that tall fescue is underused, creates health risks for cattle, and degrades wildlife habitat quality, it may be advisable to reduce tall fescue in pastures.     

Herbage production and quality of a range of secondary grass species at five rates of fertilizer nitrogen application

The productivity of ten grasses was measured under six cuts per annum for 3 years and three cuts for a fourth harvest year in comparison with a perennial ryegrass (Lolium perenne) control. The grasses were Yorkshire fog (Holcus lanatus), two red fescues (Festuca rubra), creeping bent (Agrostis stolonifera), bent (Agrostis castellana), bent (Agrostis capillaris), smooth meadow-grass (Poa pratensis), crested dogstail (Cynosurus cristatus), sweet vernal (Anthoxanthum odoratum) and timothy (Phleum bertolonii). Another grass sown, rough meadow-grass (Poa trivialis), did not persist after the first harvest year. Annual N rates were 0, 120, 240, 360 and 480 kg ha^?1. Classified by DM production, the grasses grouped into: high (perennial ryegrass, Yorkshire fog and red fescue), intermediate (creeping bent, bent (A. castellana), crested dogstail and smooth meadow-grass) and low (bent (A. capillaris), sweet vernal and timothy. With frequent cutting, production ranking interacted with N rate: Yorkshire fog. red fescue and creeping bent were more productive than ryegrass at the 0 N and 120 N rates but not at higher N rates; crested dogstail and sweet vernal outperformed ryegrass at 0 N; ryegrass and smooth meadow-grass performed relatively better at moderate to high N. DM production of ryegrass was matched or exceeded by some of the other grasses during different parts of the season particularly at low N rates. Notable features from the 3-cut regime were the outstanding DM production of Yorkshire fog at all N rates and the poor production of bent (A. capillaris) and crested dogstail. High DM response to applied N in both cutting regimes was given by perennial ryegrass. smooth meadow-grass, red fescue cv. Boreal, timothy, crested dogstail and Yorkshire fog. N concentrations were highest in less productive grasses such as the bents and lowest in highly productive ryegrass and Yorkshire fog. Ryegrass was superior in digestibility to the other grasses, but especially to the red fescues, bents and smooth meadow-grass. The other grasses, especially Yorkshire fog and bent (A. capillaris) were superior to ryegrass in P, K and Mg concentrations, but not Ca. It is concluded that the annual and/or seasonal production of some of the secondary grasses at low to moderate N rates, e.g. the performance of Yorkshire fog and red fescue, warrant a reconsideration of their poor reputation, particularly within the context of increasing grassland extensification. Breeding to improve selected characteristics, such as digestibility in red fescue, seems justified. Assessment of the grazing and ensiling qualities of secondary grasses require further study.     

In vitro rumen simulated (RUSITEC) metabolism of freshly cut or wilted grasses with contrasting polyphenol oxidase activities

The study investigated in vitro simulated rumen metabolism of freshly cut and wilted cocksfoot [Dactylis glomerata; high polyphenol oxidase (PPO)] and tall fescue (Festuca arundinacea; low PPO). A 16‐vessel RUSITEC was used with the four treatment combinations: cocksfoot wilted (C_w); cocksfoot fresh (C_f); tall fescue wilted (TF_w) and tall fescue fresh (TF_f). Rumen liquor was collected from four fistulated dairy cows maintained on permanent pasture. The experiment ran for 12 d with sampling of effluent for rumen parameters [volatile fatty acids (VFA) and NH₃‐N] on days 10 and 11 at 0, 1, 2, 3, 4, 6, 8 and 24 h intervals. On days 9–12, gas production and composition were measured using a plastic gas collection bag attached to the effluent bottle. At the end of day 12, the grass residue and effluent from the vessels were collected and analysed for digestibility and lipid fractionation. Lipolysis was calculated as the proportional loss of glycerol‐based membrane lipid between the forage and residue. Polyphenol oxidase was higher (P < 0·001) in C_f than the other treatments; C_w was higher than both TF treatments, with no difference between TF_w and TF_f. The level of protein‐bound phenol (product of oxidation reaction) tended to be higher for C_w and TF_w than C_f and TF_f, (P < 0·1) and was higher for cocksfoot than tall fescue (P < 0·001). As an average across the day, NH₃‐N was lower (P < 0·001) in cocksfoot than tall fescue, despite the lower nitrogen concentration of tall fescue, and in fresh as opposed to wilted grass (P < 0·001). There was a trend (P < 0·1) for lipolysis to be lower in cocksfoot than tall fescue, and for both wilted treatments to be lower than the fresh (P < 0·05). Total VFA concentration was not different across treatments, although there were differences in molar proportions of individual VFA. Cocksfoot as opposed to tall fescue showed a small effect in lowering lipolytic and proteolytic activity (release of NH₃‐N), although other differences between the grasses other than just PPO activity such as lipase activity, diphenol substrate content and digestibility may have greater effects between the grasses confounding the effect of PPO.     

Forage biomass,soil cover,stability and competition in perennial grass–legume pastures with different Paspalum species

The short life span, irregular forage production and susceptibility to weed colonization of cool‐season grass–legume pastures are serious problems in grazing dairy systems in warm‐temperate regions. The inclusion of warm‐season species has the potential to mitigate these problems. In this study, we evaluated the effect of the inclusion of two warm‐season grasses with different growth habits on seasonal forage biomass, soil cover and weed colonization. Three different pasture mixtures were evaluated under grazing: conventional pasture (CP) [tall fescue (Festuca arundinacea), white clover (Trifolium repens) and birdsfoot trefoil (Lotus corniculatus)], CP with Paspalum dilatatum and CP with Paspalum notatum (CP + Pn). Forage biomass and soil cover were sampled thirteen times during a 3‐year trial, and sampling times were grouped by season for the analyses. The mixtures with Paspalum showed higher soil cover in the autumn, while in the winter CP had higher soil cover than CP + Pn. Competition with tall fescue was similar between mixtures with Paspalum, when considering biomass, but it was higher in CP + Pn when considering soil cover. The inclusion of P. notatum increased biomass during the autumn but decreased the mixture performance during winter by reducing tall fescue soil cover. The addition of a warm‐season grass species with a moderate competing ability like P. dilatatum is likely to avoid a negative impact on the cool‐season component of the pasture.     

Effects of systemic fungal endophytes on the performance of meadow fescue and tall fescue in mixtures with red clover

A symbiosis between grasses and systemic fungal endophytes exists in both natural and agricultural grassland communities. Our objective was to examine the effects of systemic endophytes on the competitive ability of two agronomically important grass species: meadow fescue [Festuca pratensis (Huds.) syn. Schedonorus pratensis (Huds.) P. Beauv] and tall fescue [Festuca arundinacea (Schreb.) syn. Schedonorus phoenix (Scop.)]. Plants of meadow and tall fescue were grown for 48 days in replacement series of interspecific mixture with a legume (red clover, Trifolium pratense L.) in different nutrient environments in a greenhouse. Neither of the grass species gained endophyte‐promoted competitive advantage over red clover in grass–clover mixtures. Endophyte infection increased the growth of meadow fescue monocultures by 89% compared to endophyte‐free monocultures in high‐nutrient soils, but plant competition or the cost of endophyte infection to the meadow fescue decreased the yield in resource‐limited conditions. On average, endophyte‐infected and endophyte‐free meadow fescues produced 0·15 and 0·17 g, and 0·14 and 0·14 g dry biomass per plant in mixtures with red clover in high‐ and low‐nutrient soils respectively. In contrast to meadow fescue, endophyte‐promoted growth of tall fescue monocultures was not detected. Endophyte‐infected and endophyte‐free tall fescue monocultures produced 0·76 and 0·95 g biomass per pot, respectively, in the high‐nutrient environment. Endophyte infection can increase the performance of the host grass, but the positive effects depend on the host species, the species composition and soil nutrient availability.     

Mice find endophyte‐infected seed of tall fescue unpalatable – implications for the aviation industry

Bird strike is a significant problem for the aviation industry, caused in part by the attractiveness of the grass surrounding airports to birds. Endophyte‐infected grasses such as Avanex^® have been shown to reduce bird populations at airports through the production of secondary metabolites. These metabolites are unpalatable to herbivorous, omnivorous and granivorous birds and are known to reduce insect densities, thereby making the sown areas less attractive to insectivorous birds. Raptors also provide a bird‐strike threat which could be reduced by controlling mouse populations around airports. In this study, the effect of endophyte‐infected seed on mouse feeding behaviour has been investigated. By performing a choice trial offering diets containing endophyte‐infected and endophyte‐free tall fescue seed, it was shown that endophyte‐infected seed was less palatable to mice (P < 0·001 in a 14‐d trial). Furthermore, when diet positions were reversed, mouse feeding behaviour was modified to again select endophyte‐free material (P < 0·001 over a further 14 d). This result shows that endophyte‐infected grasses could not only be used in the control of bird populations but they also have the potential to control mouse populations which in turn would decrease the number of raptors. This use of endophyte‐infected grasses in areas surrounding airport runways shows great promise for the aviation industry.     

Pasture residue amount and sowing method effects on establishment of overseeded cool‐season grasses and on total annual production of herbage

Warm‐season pasture residue may create problems for no‐till overseeding with cool‐season grasses in the USA Southern Plains. Removal of residue to facilitate overseeding, however, represents additional cost and labour that may not be available on small livestock farms. Field experiments were undertaken to assess the effects of above‐surface residues of warm‐season pasture averaging 1·62, 2·48 or 3·36 t DM ha^?1 on establishment and herbage production of Italian ryegrass (Lolium multiflorum) or tall fescue (Festuca arundinacea) overseeded by broadcasting or by no‐till drilling into dormant warm‐season pasture. On average, no‐till drilling was more effective than broadcasting in establishing both grass species, but it was no more effective than broadcasting when used with the greatest amount of residue. Cool‐season grass production was increased by 0·16 when no‐till drilled, but combined yearly total herbage production of cool‐ and warm‐season grasses was increased by 0·07 when cool‐season grasses were established by broadcasting. Amount of residue at sowing did not significantly affect herbage yield of cool‐season grass, but increased residue in autumn resulted in a 0·16 increase in total herbage production in the year following sowing. Residue amount did not affect over‐winter survival of grass seedlings, and productivity benefits of increased residue are small compared with reduced harvest arising from underutilization of warm‐season pasture residue in autumn.     

THE SPECIES PREFERENCES OF GRAZING HORSES

Palatability studies of 29 species of grasses, legumes and herbs, and two seeds mixtures, were conducted using three replicates of each species. Crossbred ponies and a few Thoroughbreds were obserred and timed for a total of 260 hours grazing. The results were analysed and sbowed small statistical differences between replicates, between tbe 2 years observed and between horses; and highly significant differences (P<0.001) between certain species. The most palatable was a clover-rich mixture. Tbe pasture varieties of perennial ryegrass were significantly more palatable tban S24, and as palatable as timothy and cocksfoot Alta tall fescue, crested dogs tail and wild white clover were palatable. Some herbs, red clover, brown top, red fescue and meadow foxtail were tbe least palatable. Dandelion, ribgrass and yarrow were palatable herbs.     

Identification,ecological evaluation and phylogenetic analysis of non‐symbiotic endophytic fungi colonizing timothy grass and perennial ryegrass grown in adjacent plots

Non‐systemic endophytes coexist with grasses and produce positive or negative effects for the host. In agricultural grasses, endophytes such as Epichloë spp. (formerly: Neotyphodium spp.) enhance the biometric parameters and agricultural value of grass biomass and seeds. Some endophytic fungi produce active substances that exert a negative influence on grass‐fed livestock. There is a general scarcity of studies investigating other endophytic fungi, the species composition of fungal communities, fungal species capable of colonizing different grasses and endophyte transfer between grass taxa. This study aims to fill in the existing knowledge gap by describing the relationships between fungal species and grass species. Timothy grass (Phleum pratense L.) is more readily colonized by endophytic fungi than perennial ryegrass (Lolium perenne L.), and the ratio of fungi isolated from the above species was determined at 3:1. Ecological indicators, especially diversity, were also higher in the fungal community colonizing timothy grass. The vast majority of the isolated fungi were ascomycetes. In addition, two Basidiomycota isolates and three Oomycota isolates (Phythium acanthicum) were also obtained from timothy grass. The most prevalent fungal species were Alternaria alternata, Microdochium bolleyi and Epicoccum nigrum. An analysis of minisatellite DNA regions revealed high levels of genetic polymorphism in A. alternata, whereas the remaining isolates were characterized by low levels of genetic variation or genetic homogeneity. The transfer of endophytic fungi between grass species was determined, which was one of the most important observations made in the study. The Sørensen–Dice coefficient reached 50%, which indicates that all fungal species isolated from perennial ryegrass are capable of colonizing timothy grass.     

Yield and nitrogen concentration of above- and below-ground biomasses of red clover cultivars in pure stands and in mixtures with three grass species in northern Europe

Three red clover (Trifolium pratense) varieties differing in productivity and winter hardiness, Jokioinen, Betty and Ilte, were sown in a 2‐year (2003–2004) pot experiment in pure stands and mixtures with the grasses, timothy (Phleum pratense), tall fescue (Festuca arundinacea) and meadow fescue (Festuca pratensis). Grass growth dominated until fertilizer‐N, applied when the stands were sown, was depleted. Timothy was the least competitive of the grass species. Red clover variety Ilte produced the highest dry‐matter (DM) yields. Variety Betty yielded less, but allocated as much biomass to the root and stubble (soil‐bound) fraction as variety Ilte. Variety Jokioinen allocated least to the soil‐bound fraction. While the root structure and the starch concentration of the crown‐root area were similar in all varieties, the high ratio of soil‐bound: harvested fractions could be a key to the higher winter survival and higher DM yields of Betty under field conditions. At the end of the experiment, 3–5 g N pot^?1 (49–81 g m^?2) had been harvested and 0·7–1·5 g N pot^?1 (11–24 g m^?2) was left in the soil‐bound fraction, amounts depending on the red clover variety and grass mixture, with pure clover stands containing the highest N amounts. Because of the high N concentrations in the biomass of red clover, the proportion of red clover and conditions prevailing during canopy and root death in mixed stands are crucial for N mineralization and incorporation into new growth.     

Effects of continuous sheep stocking and strategic rest periods on the sward characteristics of binary perennial grass/white clover associations

Five binary perennial grass/white clover (Trifolium repens, cv. Menna) mixtures were evaluated over a 3-year period under continuous sheep stocking together with the imposition of a rest period for either an early or a late conservation cut; the experiment with plot sizes of 0·16 ha was replicated three times. The grass species and cultivars used were Merlinda tetraploid and Magella diploid perennial ryegrass (Lolium perenne), Prairial cocksfoot (Dactylis glomerata), Rossa meadow fescue (Festuca pratensis) and Goliath timothy (Phleum pratense). The greatest total lengths of white clover stolon developed in the meadow fescue (171·6 m m^?2) and timothy (151·9 m m^?2) associations compared with those in tetraploid perennial ryegrass (98·6 m m^?2), diploid perennial ryegrass (91·9 m m^?2) and cocksfoot (74·6 m m^?2) (s.e.d. 16·4, P < 0·001). On average, the proportion of white clover stolon that was buried was between 0·86 and 0·89 and this was more abundant in late than early season. Whereas timothy persisted, the persistence of meadow fescue was low under any of the managements tested and this was markedly reduced by the third grazing season. In the diploid perennial ryegrass sward, a late June to early August rest period for conservation enhanced white clover stolon length. An early April to late May rest period greatly reduced total white clover stolon length in both diploid perennial ryegrass and tetraploid perennial ryegrass associations (diploid perennial ryegrass-unrested 89 m m^?2, early rest 56·1 m m^?2, late rest 130·7 m m^?2; tetraploid perennial ryegrass - unrested 125·1 m m^?2, early rest 71 m m^?2, late rest 99·7 m m^?2; s.e.d. 19·19, P < 0·001). The numbers of white clover stolon growing points per unit stolon length were greatest when the sward was rested during late June to early August ?55·9 m^?1 stolon length compared with 45·7 m^?1 for an April to late May rest and 46 m^?1 in the absence of a rest (s.e.d. 2·59, P < 0·001). Likewise, the percentage of stolon above ground was greatest with the late June to early August rest ?15·78% compared with 10·61% for the April to late May rest and 7·69% for no rest (s.e.d. 1·569, P < 0·001). The complementary percentages of buried stolon indicate the important role this fraction has and the need to study stolon behaviour in grazing studies generally. It is concluded that, in relation to perennial ryegrass as a companion grass, meadow fescue and timothy allow better white clover development and cocksfoot less. However, other attributes have to be considered, for example the poor persistence of meadow fescue and the slower regrowth of timothy, both of which allow the invasion of weed grasses, or the lower acceptability of cocksfoot to livestock. The timing of the rest period before the conservation cut can influence white clover development considerably, but the effects differed with different companion grasses.     

Milk yield and nitrogen excretion of dairy cows grazing binary and multispecies pastures

Three grazing experiments were carried out in late spring (early lactation), summer (mid‐lactation) and autumn (late lactation) to compare the effects of perennial ryegrass cultivar or grass species, sown in binary or multispecies mixtures, on milk yield and nitrogen excretion of dairy cows. Replicated groups of multiparous Holstein Friesian × Jersey cows were offered either a control or high‐sugar perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea) base grass in a binary mixture with white clover (Trifolium repens) or in a multispecies mixture with additional legumes, bromegrass (Bromus willdenowii) and forbs. During each 9‐day experiment, botanical composition, milk production and faecal and urine composition were measured. Milk solid (MS) yield for the control ryegrass, high‐sugar ryegrass and tall fescue grass types averaged, respectively, 1.53, 1.64 and 1.70 kg MS cow^?1 day^?1 for a binary mixture sward, compared with 1.65, 1.54 and 1.53 kg MS cow^?1 day^?1 for a multispecies sward. Legume content influenced milk production more than the number of species present in a mixture. There was lower urine N concentration from a multispecies sward compared with a binary mixture. Urine N concentration of cows grazing the control ryegrass, high‐sugar ryegrass and tall fescue grass types averaged, respectively, 4.6, 5.3 and 6.8 g N L^?1 for a binary mixture, compared with 4.1, 3.9 and 3.9 g N L^?1 for a multispecies mixture. Feeding dairy cows on multispecies swards containing forbs presents an opportunity to reduce N losses without compromising milk yield.     

Endophyte infection, nutrient status of the soil and duration of snow cover influence the performance of meadow fescue in sub-artic conditions

Neotyphodium endophytic fungi are beneficial for certain cultivated grass species by increasing the stress tolerance and herbivore resistance of their host plants. These grass endophytes have been widely studied in temperate regions. Endophyte-infected grasses are also cultivated in sub-artic conditions, but studies on the effects of endophyte infection on grasses under conditions of prolonged snow cover are scarce. A 2-year field experiment was conducted with two originally endophyte-infected meadow fescue ( Schedonorus pratensis ) cultivars. The growth and reproduction of endophyte-infected (E+) and endophyte-free (E−) plants of two cultivars at two sites, differing in nutrient status and duration of snow cover, were compared at the latitude of the Arctic Circle in Finland. Endophyte infection enhanced plant performance most at the site with the higher nutrient status and the shorter duration of snow cover. The difference in growth between E+ and E− grasses increased during the second growing season and was most pronounced in the reproductive investment of grasses, but the benefits of endophyte infection for reproductive mass were cultivar-dependent. At the site with the lower nutrient status, costs of endophyte infection on the vegetative growth of grasses were found. The results suggest that Neotyphodium infection may benefit meadow fescue in sub-arctic conditions but the extent of the effects is dependent on the cultivar and the environment.     

Changes in nutritive value and herbage yield during extended growth intervals in grass–legume mixtures: effects of species,maturity at harvest,and relationships between productivity and components of feed quality

There is a lack of information on the effects of companion species in grass–legume mixtures on herbage yield and quality changes during prolonged growth. Such information is relevant for harvest planning and estimation of consequences for feeding value of conserved feed when harvesting is delayed. Perennial ryegrass was sown with each of four legumes: red clover, white clover, lucerne and birdsfoot trefoil, and white clover was sown with hybrid ryegrass, meadow fescue and timothy. Effects of species composition on herbage yield, contents of N, neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin, ash and in vitro organic matter digestibility (IVOMD) were studied in entire herbage and in component species during 2 years in a small‐plot cutting trial in Denmark. In May and August, the dynamic development of components of feed value and their interrelationships were investigated by sampling at optimum harvest date (i.e., normal practice) ± 1 week (t = ?1 to t = +1). Herbage digestibility and contents of N and ash decreased while those of fibre compounds increased during the 2 weeks from t = ?1 to t = 1 in all species. In May, contents of ADF and lignin increased at a faster rate in legumes than in grasses; in August, NDF and ADF increased most quickly in legumes. Generally, N contents and IVOMD declined at similar rates in grasses and legumes, but, within each group, differences in yield and quality development occurred among species. The relationship between weekly growth rate and change in quality parameters differed among species and functional groups, i.e., grasses and legumes. Results are discussed in the context of quantifying the impact of delaying the harvest date of grass–legume mixtures and relationships between productivity and components of feed quality.     

Soil water dynamics,herbage production and water use efficiency of three tropical grasses: Implications for use in a variable summer‐dominant rainfall environment,Australia

In the moist mid‐latitudes of eastern Australia, soil water dynamics, herbage production and water use efficiency (WUE) were monitored during 2006–2008, for five perennial pastures: digit grass (Digitaria eriantha), Rhodes grass (Chloris gayana), forest bluegrass (Bothriochloa bladhii), native grass (Bothriochloa macra and Rytidosperma bipartita dominant), lucerne (Medicago sativa); and two forage crops: oat (Avena fatua) and sorghum (Sorghum bicolor). Ground cover formed more quickly in Rhodes grass and lucerne (>70% ground cover in 120 and 175 days after sowing [DAS] respectively) than in forest bluegrass and digit grass (245 and 365 DAS respectively). Values of maximum extractable water (MEW) for Rhodes grass and lucerne were similar (180–242 mm), while values for digit grass and forest bluegrass (129–175 mm) were equal to or greater than those for native grass, and two annual forage crops (77–144 mm). Lucerne expressed the maximum root depth (1.46 m), while values for the tropical grasses (0.96–1.39 m) were greater than native grasses and forage crops (0.87–0.96 m). Native grasses (6.5–12 t DM/ha) had the lowest herbage production, which resulted in values of WUE that were significantly less than most other treatments (16–21 vs. 23–43 kg DM ha^?1 mm^?1). Digit grass (33–34 kg DM ha^?1 mm^?1) had higher WUE compared with the other tropical grasses (20–27 kg DM ha^?1 mm^?1). The data collected here suggest that a forage system comprising digit grass, lucerne and forage oat would provide high production and WUE in this environment.     

EFFECTS OF WHITE CLOVER ON THE BOTANICAL COMPOSITION OF SWARDS OF RYEGRASS, TIMOTHY AND MEADOW FESCUE AND MIXTURES OF THESE THREE

Results are presented to show the effect of white clover (Trifolium repens) and of applied N on the hotanical composition of swards sown with perennial ryegrass (Lolium perernne), timothy (Phleum pratense), meadow fescue (Festuca pratensis) and mixtures of two and three of these species. White clover had a more favourahle effect on the growth of perennial ryegrass than on either timothy or meadow fescue both in terms of yield and in terms of tiller numbers. Tiller numbers of rough-stalked meadow grass (Poa trivialis) were increased and tiller numbers of Agrostis species were reduced by application of N and by inclusion of clover. Possible reasons for these effects are considered.     

The effects of clipping height and frequency on net primary production of Andropogon gerardii (C4 grass) and Bromus inermis (C3 grass) in greenhouse experiments

There are potential agronomic and environmental benefits from incorporating warm‐season (C₄) grasses into temperate pasture systems, usually dominated by cool‐season (C₃) grasses, but there is a lack of information on how frequency and height of defoliation affects C₄ grasses. Three greenhouse experiments were conducted under (i) spring, (ii) summer and (iii) spring + summer clipping regimes. In each experiment, the effects of clipping frequency (weekly and monthly) and clipping height (clipped to 5 and 10 cm) were determined on above‐ and below‐ground net primary production (ANPP and BNPP) and total and seasonal dry matter (DM) yield for Andropogon gerardii Vitman (big bluestem, C₄ grass) and Bromus inermis Leyss (smooth brome, C₃ grass). Six replicates per treatment were used. In all experiments, ANPP and BNPP of smooth brome was greater than that of big bluestem although during late summer months big bluestem had higher DM yields of herbage than smooth brome. There were different effects of frequency and height of clipping for both species on two similar measurements: total annual DM yield and ANPP, indicating that the ability to generalize about the effects of defoliation from ecological and agronomic grassland standpoints is questionable. Clipping effects on ANPP and BNPP were different for summer‐clipped pots than for spring, and spring + summer‐clipped pots, indicating that management could be tailored to meet specific agronomic or conservation goals.     

Growth rate and nutritive value of sown tropical perennial grasses in a variable summer‐dominant rainfall environment,Australia

Growth rate, proportion of leaf and stem and nutritive value of sown tropical perennial grasses have not previously been documented for the dryland, frost‐prone summer‐dominant rainfall region of eastern Australia. An experiment was conducted in northern inland New South Wales with Chloris gayana (Rhodes grass) cv. Katambora and Digitaria eriantha (digit grass) cv. Premier, and compared to Sorghum bicolor ssp. bicolor x S. bicolor ssp. drummondii (forage sorghum). The grasses were harvested every 2 or 6 weeks and fertilized at five rates of nitrogen (N; 0–300 kg N ha^?1) over two growing seasons (September–May), 2006–2007 and 2007–2008. Growing season rainfall was below median for both years of the experiment and growth rate was highly variable, reflecting variable rainfall. Sorghum generally had the highest growth rate. Digit grass generally had higher growth rates than Rhodes grass, was more responsive to growing season rainfall, commenced growth earlier and had a longer growing season. Nitrogen application extended the growing season of both perennial grasses. Growth response to N application was minimal when rainfall was low and response following significant rainfall was higher for fertilized than unfertilized grasses. In general, the proportion of green leaf was greater than green stem, although the proportion of stem increased when defoliation interval increased. Nutritive value of the perennial grasses was higher in leaf than stem and declined during the growing season. Differences between the grasses were slight, but indicated that fertilized digit grass defoliated at 2‐week intervals had higher growth rate and nutritive value than Rhodes grass.     

Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management

There is increasing interest in tall fescue (Festuca arundinacea Schreb.) in Western Europe and elsewhere, mainly because of its better drought resistance and yield potential compared with perennial ryegrass (Lolium perenne L.). Important drawbacks of tall fescue, compared with perennial ryegrass, are its lower digestibility and voluntary intake. Mixtures of both species might combine the advantages of each, and species interactions may eventually lead to transgressive overyielding. We compared the agronomic performance of tall fescue, perennial ryegrass and tall fescue–perennial ryegrass mixtures, as pure‐grass swards or in association with white clover (Trifolium repens L.). Tall fescue–perennial ryegrass mixtures differed in the proportion and ploidy of the perennial ryegrass component. Yield, feed quality and botanical composition were measured in the 3 years after the sowing year. We found significant effects of ploidy of the ryegrass variety and of the proportion of ryegrass in the initial seed mixture on the botanical composition of the swards. Nevertheless, all swards were dominated by tall fescue at the end of the experiment. No overyielding of the mixtures compared with that of single‐species swards was found, but feed quality was intermediate between that of the single‐species swards. Mixed swards had better drought resistance than L. perenne and higher feeding quality than F. arundinacea swards.     

Potential of the indigenous desert grasses of the Arabian Peninsula for forage production in a water‐scarce region

Indigenous perennial grasses are widely distributed in the Arabian Peninsula. Their survival under limited rainfall and grazing suggests a potential role as grassland species and for rehabilitation of degraded rangelands. Forage productivity, seed production and water‐use efficiency (WUE) was determined over 2 years for four indigenous grasses: buffel grass (Cenchrus ciliaris L.), dakhna (Coelachyrum piercei Benth.), da’ay (Lasiurus scindicus Henr.) and tuman (Panicum turgidum Forssk.) together with one exotic species, rhodes grass (Chloris gayana Kunth) in the central region of the United Arab Emirates. Three irrigation treatments were used: R1 (1858–6758 m³ ha^?1 year^?1), R2 (929–3379 m³ ha^?1 year^?1) and R3 (464–1689 m³ ha^?1 year^?1). Buffel grass had the highest dry‐matter (DM) yield under all irrigation treatments. The average DM yield of buffel grass was 14·6 and 15·1 t ha^?1 in the 2 years which was significantly higher than that for the other grasses with dakhna having the lowest DM yields. The WUE of 0·7 and 0·8 kg DM m^?3 in the 2 years for buffel grass was significantly greater than for the other grasses. Buffel grass showed the highest increase in WUE in both years when the irrigation was reduced from treatment R1 to R3. The results suggest that the desert grasses of the Arabian Peninsula, such as buffel grass, could be useful grass species in reducing the use of scarce irrigation water provided that seed production can be increased.