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e85050 Background: Paspalum dilatatum Poir. (common name dallisgrass) is a native grass species of South America, with special relevance to dairy and red meat production. P. dilatatum exhibits higher forage quality than other C4 forage grasses and is tolerant to frost and water stress. This species is predominantly cultivated in an apomictic monoculture, with an inherent high risk that biotic and abiotic stresses could potentially devastate productivity. Therefore, advanced breeding strategies that characterise and use available genetic diversity, or assess germplasm collections effectively are required to deliver advanced cultivars for production systems. However, there are limited genomic resources available for this forage grass species. Results: Transcriptome sequencing using second-generation sequencing platforms has been employed using pooled RNA from different tissues (stems, roots, leaves and inflorescences) at the final reproductive stage of P. dilatatum cultivar Primo. A total of 324,695 sequence reads were obtained, corresponding to c. 102 Mbp. The sequences were assembled, generating 20,169 contigs of a combined length of 9,336,138 nucleotides. The contigs were BLAST analysed against the fully sequenced grass species of Oryza sativa subsp. japonica, Brachypodium distachyon, the closely related Sorghum bicolor and foxtail millet (Setaria italica) genomes as well as against the UniRef 90 protein database allowing a comprehensive gene ontology analysis to be performed. The contigs generated from the transcript sequencing were also analysed for the presence of simple sequence repeats (SSRs). A total of 2,339 SSR motifs were identified within 1,989 contigs and corresponding primer pairs were designed. Empirical validation of a cohort of 96 SSRs was performed, with 34 percent being polymorphic between sexual and apomictic biotypes. Conclusions: The development of genetic and genomic resources for P. dilatatum will contribute to gene discovery and expression studies. Association of gene function with agronomic traits will significantly enable molecular breeding and advance germplasm enhancement.

Paspalum dilatatum, espécie de alto valor forrageiro, apresenta uma ampla variedade de biótipos, tendo formas sexuais e apomíticas. Os biótipos P. dilatatum anteras roxas e Torres são descritos como tendo reprodução assexual por apomixia, conclusão esta baseada apenas em análises citológicas do saco embrionário. O presente trabalho teve como objetivo confirmar o modo de reprodução destes dois biótipos, analisando a ocorrência de variabilidade entre plântulas-irmãs e entre endospermas, através de eletroforese de isoenzimas. Os sistemas de IDH, ME, PGM, SOD e GOT não foram informativos por não apresentarem polimorfismo intra-específico ou dentro de cada biótipo. Para o sistema das AMI, observou-se grande variação isoenzimática entre os endospermas de sementes de uma mesma linhagem, com ausência de variação entre as plântulas-irmãs, o que poderia sugerir a ocorrência de pseudogamia. Entretanto, para os sistemas das MDH e PER foi observado a ocorrência de variabilidade na progênie de plantas individuais, o que pode ser indicativo de segregação gênica e sugerir a ocorrência de reprodução sexual. Paspalum dilatatum is a plant species of high forage value with a wide range of biotypes, with sexual and apomictic types. Purple-anthered and Torres biotypes are described as apomictic based only on cytological analysis of embrionary sac. The present research aimed at analyzing the occurrence of variability among sib seedlings and endosperms of these biotypes through gel electrophoresis. Enzymatic systems of GOT, IDH, ME, PGM, and SOD were not informative because they did not show intra-specific or intra-biotype polymorphism. AMY revealed large isoenzymatic variation among endosperms from the same strain but without variation among sib seedlings. This could suggest occurrence of pseudogamy. However, for MDH and PER, the occurrence of variability among sib seedlings was observed, which can be indicative of genic segregation and suggests the occurrence of sexual reproduction.

Six vaches adultes munies d'une canule du rumen ont ete utilisees pour etudier, par la methode des sachets de Nylon, la cinetique de degradation des parois et de l'azote de prairies de Paspalum dilatatum soumises, au cours de deux saisons (ete et automne) a deux frequences de pâturage (pâturage frequent (F) : moins de 5 % de talles totales de Paspalum par m 2 etaient au stade de floraison ; pâturage peu frequent (PF) : plus de 60 % de talles totales par m 2 etaient au stade de floraison). La degradabilite theorique des parois varie tres peu selon les saisons (37,4 % versus 40,6 %). elle est un peu plus faible en ete. Pour l'azote, la fraction rapidement degradable (34,9 % versus 20,8 %) et la vitesse de digestion de la fraction lentement degradable (5,5 %.h -1 versus 4,1 %.h -1 ) sont plus elevees en automne, en raison probablement de la teneur en parois plus faible en cette saison. Pendant l'automne, la fraction rapidement degradable est superieure avec le pâturage PF. L'explication en serait la variation de la teneur en cette fraction (a) dans les differentes parties de la plante. La degradabilite theorique est aussi plus elevee dans le cas du pâturage PF et peut resulter de la fraction rapidement degradable. Pendant l'automne les prairies de Paspalum dilatatum soumises a un pâturage PF ont des degradabilites des parois (41,3 % versus 57,7 %) et de l'azote (72,1 % versus 80,7 %) plus faibles que celles sans Paspalum dilatatum. Ces differences peuvent s'expliquer par les caracteristiques morphologiques differentes des graminees C 3 et C 4 .

330 ##?$aThe effect of sward state and stocking rate upon leaf growth, senescence and consumption rates per tiller and upon the efficiency of herbage utilization in Lolium multiflorum (C3 annual grass), Paspalum dilatatum and Cynodon dactylon (C4 perennial grasses) within a native grassland continuously grazed by cattle under natural mineral and hydrie conditions was analyzed. Data of two complementary studies, one on leaf morphogenesis and the other on the effect of N fertilization on the dynarnics of herbage growth and utilization, are also presehted. Results demonstrated that leaf length (LL) and number of living leaves (NLL) per tiller can be adequately predicted by the association between leaf morphogenesis dynamics and temperature. However, canopy structure modified leaf appearance as weil as LL and NLL, the consideration of this plastic response being postulated as central to extend morphogenetic models of leaf growth to field conditions. Growth and senescence rates were generally not linked along the experimental cycle, this phenomena being particularly marked in the C4 grasses. The importance of such dynamics to optirnize the defoliation regime in complex plant communities under fluctuating temperatures is discussed. Results confirm that while the probability of defoliation (PDf) during the leaf life span (LLS) depends on stocking rate, the intensity of each defoliation is relatively constant. This supports that PDf and LLS constitute the main components that define the leaf proportion that will senesce and, hence, the efficiency of herbage utilization. Species selectivity analysis suggests that defoliation pattern results can be general to a wide range of species abundance. Evidences are presented on the positive effect of herbage growth increase upon the carrying capacity and the efficiency of herbage utilization. On this basis, the role of LAI and stocking rate as determinants of leaf tissue flows dynamics under continuous grazing are discussed., Les effets de l'état du couvert végétal (hauteur d'herbe et Indice Foliaire) et du chargement animal sur la croissance et la sénescence des tissus foliaires et leur consommation par les animaux ont été étudiés sur trois espèces représentatives des communautés végétales pâturées de la Pampa Humide en Argentine, Latium multiflorum, Paspalum dilatatum et Cynodon dactylon.Cette étude a été conduite en conditions naturelles, en pâturage continu avec des génisses. Les résultats montrent que la taille finale des feuilles (FLL) et le nombre maximum de feuilles vivantes par taille (NLL) peuvent être prédites par les lois de réponse de la morphogenèse foliaire à la température. Cependant, ces deux variables dépendent également de l'état du couvert végétal qui influence la vitesse d'apparition des feuilles (LAR). En situation de changement progressif saisonnier de la température les dynamiques de croissance et de sénescence foliaires sont apparues décalées. Les résultats confirment que la probabilité pour une feuille d'être défoliée avant sa sénescence est directement dépendante de la durée de vie des feuilles (LLS) et du chargement animal. L'absence de sélectivité marquée de l'animal vis à vis des espèces les plus abondantes permet de généraliser ce résultat à l'échelle de la communauté végétale. Enfin, ce travail confirme que toute augmentation de la vitesse de croissance de l'herbe, entraînant une augmentation du chargement animal se traduit par une augmentation importante de l'efficience d'utilisation de l'herbe produite par les animaux.

Chilling is a limiting factor for plant growth and distribution, affecting photosynthesis in several ways, namely, the content and quality of pigments, gas exchange rates and key enzymes activity, e.g. Rubisco and PEPC (1, 2). There are some plants able of cold-acclimation through changes in their metabolism resulting in an improved performance under the new growth regime (1, 2, 3). Paspalum dilatatum Poir or Dallis grass, a pasture C4 gratnineae, has been reported as being a semi-tolerant plant to cold (4). Dallis grass grows spontaneously in Portugal, and, as previously reported, maintains physiological activity during the whole year (5).

Many studies have analysed plant responses to flooding or drought separately, without addressing the relations between plant resistance to each of these factors. In this paper, we compare the responses to drought and flooding under glasshouse conditions of three populations of Paspalum dilatatum, a perennial C4 grass dominant at different positions along a topographic gradient in the flooding pampa of Argentina. Our results showed that flooding effects on yield were negative on an upland, null on an intermediate, and positive on a lowland population, whereas drought reduced yield equally across populations, showing that resistance to flooding was not related to resistance to drought at a population level. Drought decreased height and aerenchyma, and increased the proportion of roots, while flooding had opposite effects on these traits. The responses of the single clones that made up each population showed a positive relation between the resistances to both factors: along the ecocline formed by 58 clones, those more resistant to drought were also more resistant to flooding. In addition, the combined resistance of each clone to both factors was negatively related to yield at field capacity, (i.e. the most resistant clones were less productive) and unrelated to the proportion of roots and aerenchyma. This result agrees with predictions of Grime's plant strategy theory and differs from a few previous studies, which showed negative relations between the resistances to flooding and drought among genera and species.

SUMMARY: Virulent ovine footrot was transmitted accidentally to a group of 23 adult Merino sheep (flock B) after holding for 1 hour in sheep yards, which earlier the same day had contained another flock (flock A) with < 1% prevalence of sheep with footrot lesions. Sheep in flock B were rendered susceptible to virulent footrot by grazing 600 mm high unimproved pasture dominated by paspalum (Paspalum dilatatum) and kangaroo grass (Themeda australis) during warm, humid and wet weather. In addition to moisture, interdigital abrasions caused by the pasture might have predisposed the interdigital skin to infection with Dichelobacter nodosus.

Waterlogging is a common feature in some natural grazed grasslands of Argentina. Phosphorus is the most limiting element. The response of two representative grasses, Danthonia montevidensis and Paspalum dilatatum, to waterlogging and application of phosphorus and nitrogen fertilizer, was studied in a pot experiment. Both species tolerated waterlogging and both increased their herbage production when waterlogged, especially when phosphorus fertilizer was applied.

Perennial ryegrass (Lolium perenne L.) is the dominant forage grazed by dairy cows in Australia; however, poor persistence has led to an increasing interest in alternative forages. This study was conducted to identify more productive and/or persistent perennial forage species than perennial ryegrass. We evaluated 15 perennial forages under optimum irrigation (I1) and 2 nominated deficit irrigation (I2, 66% of irrigation water applied to I1; I3, 33% of irrigation water applied to I1) regimes, over 3 years at Camden, NSW (34°3′S, 150°39′E), on a brown Dermosol in a warm temperate climate. The forages were: perennial ryegrass, cocksfoot (Dactylis glomerata L.), phalaris (Phalaris aquatica L.), prairie grass (Bromus catharticus M. Vahl), tall fescue (Schedonorus phoenix (Scop.) Holub), kikuyu (Pennisetum clandestinum Hochst. ex. chiov.), paspalum (Paspalum dilatatum Poir.), birdsfoot trefoil (Lotus corniculatus L.), lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), strawberry clover (Trifolium fragiferum L.), sulla (Hedysarum coronarium L.), white clover (Trifolium repens L.), chicory (Cichorium intybus L.), and plantain (Plantago lanceolata L.). Under non-limiting conditions of water and fertility, tall fescue, kikuyu, and prairie grass had the highest mean annual yield over the 3 years of this experiment (24.8–25.5 t dry matter (DM)/ha), which was significantly greater (P

The objective of this study was to quantify the grazing preference of dairy cows for eight grass, four legume and two herb species in eight seasons over 2 years. All species were grown at the same site, under the same climatic conditions, and with soil moisture and nutrient availability being non-limiting to plant growth. The forage species evaluated were cocksfoot (Dactylis glomerata cv. Kara H0265), perennial ryegrass (Lolium perenne cv. Bronsyn), short rotation ryegrass (Lolium multiflorum cv. Concord), fescue (Festuca arundinacea cv. Advance Maxp.), phalaris (Phalaris tuberose cv. Holdfast), paspalum (Paspalum dilatatum cv. Poir. Common), kikuyu (Pennisetum clandestinum cv. Whittet), prairie grass (Bromus willdenowii cv. Matua), lucerne (Medicago sativa cv. Sceptre), persian clover (Trifolium resupinatum cv. Maral), red clover (Trifolium pretense cv. Astred), white clover (Trifolium repens cv. Kopu II), chicory (Cichorium intybus cv. Grouse) and plantain (Plantago lanceolata cv. Tonic). The 14 forage species treatment plots were laid out in a completely randomised block design with three replicate blocks. The treatment plots were around the circumference of a circle so that the three cows used in each test had unbiased access to all forage species within the blocks. The tests comprised observing the forage being grazed at 10-s intervals for 1 h. The cow preference was recorded as time (min) spent grazing on each forage species. Three Holstein Friesian dairy cows of similar dominance were selected and had grazed all 14 forage species before tests. Cows were fed to requirements before each test so that they would be selective in choice of forages. The most preferred species over the whole year was prairie grass followed by kikuyu and then white clover, despite the fact that kikuyu was not available in winter. Fescue was the least preferred grass species. The mean grazing times for prairie grass and kikuyu during the 1-h test periods of grazing was 11.6 and 10.5 min, respectively. White clover and lucerne were the most preferred legumes (9.6 and 9.0 min, respectively), whereas chicory and plantain were little consumed (3.5 and 3.2 min, respectively). A prediction equation comprising water soluble carbohydrates (WSC%) and nitrate-nitrogen [NO3-N (g/kg DM)] over all seasons and forage species accounted for more variation in cow preference than any other single or combination of variables measured: cow preference [time (min) on plots] = 1.86 + 0.67 WSC% – 1.9 NO3-N (g/kg DM) (r2 = 0.76; s.e. = 2.22; n = 109). The results indicate that the relative palatability of forages can be reasonably well predicted from WSC% and NO3-N concentration, having a positive and negative effect on cow preference, respectively. The prediction equation was improved for groups of species if neutral detergent fibre (NDF%) was included: grasses, cow preference [time (min) on plots] = 24.5 + 0.42 WSC% – 1.31 NO3-N (g/kg DM) – 0.39 NDF% (r2 = 0.87; s.e. = 1.62; n = 57); legumes, cow preference [time (min) on plots] = 3.02 + 0.98 WSC% – 2.15 NO3-N (g/kg DM) – 0.08 NDF% (r2 = 0.92; s.e. = 1.38; n = 36); and herbs, cow preference [time (min) on plots] = 19.41 + 0.22 WSC% – 1.74 NO3-N (g/kg DM) – 0.69 NDF% (r2 = 0.53; s.e. = 1.81; n = 19).

A range of forage legumes including Trifolium repens, T. pratense, T. subterranean, T. dubium, Medicago sativa, Lotus species, Ornithopus sativus, forage grasses, including Lolium perenne, L. multiflorium, Bromus wildenowii, Festuca arundinacea, Dactylis glomerata, Agrostis tenuis, Phalaris aquatica, Holcus lanatus, Phleum pratense and Paspalum dilatatum and one herb, Cichorium intybus were compared for their tolerance to aluminium in soil. P. dilatatum a hardy and persistent C4- grass had the highest Al tolerance ratio (Al500/Al50) of the 19 species screened. B. wildenowii, a species that requires well drained, moderately fertile soils to be productive also demonstrated greater tolerance to Al than the other grass species. Addition of 500 ppm of Al to soil (KCl extractable Al of 1.35 meq.) was an effective level for separating the grass and legume species as 6 of the remaining 7 grass species fell into the next most tolerant cluster. Of the legumes, O. sativus showed greater tolerance than any of the Lotus species and T. subterranean. T. dubium, a small leafed, annual legume found in low fertility environments, along with the herb C. intybus were the most sensitive species to added Al.

The objective of the research described here was to compare the milk production from paspalum (Paspalum dilatatum Poir.)-dominant swards with milk production from perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.)-dominant swards. Eight experiments were conducted over a 2-year period, during which half the cows grazed pastures that had been established for more than 15 years (old pasture) and were dominated by paspalum in summer, while the remaining cows grazed pastures sown within the previous 2–3 years (new pasture), which were dominated by temperate species. Groups of four to five lactating Friesian cows grazed either old or new pasture and were either unsupplemented or were offered ~5 kg DM/cow.day of a high energy supplement (75% barley and 25% wheat). The hypothesis was that milk production would be greater from cows grazing new pastures than old pastures (at common pasture allowances), but that marginal milk responses when cereal grain-based supplements were fed would be greater when cows grazed old pastures; this was only partially supported. Milk yields were generally greater when cows grazed new pastures, but in six out of eight experiments, the advantage was only ~1 kg milk (100 g fat plus protein)/cow or less. In these six experiments, the difference in metabolisable energy density between the pastures was 0.7 MJ/kg DM or less. When concentrates were fed to supplement grazed pasture, there were seasonal variations, but similar marginal responses in milk production were recorded on both pastures throughout the study.

To study the adaptation of the C4 plant, Paspalum dilatatum, to the climate conditions of the centre of Portugal, some physiological parameters, related to photosynthesis, were determined. Measurements were made from January to July 1988. The rates of photosynthesis and transpiration increased significantly during the summer, while the chlorophyll content fluctuated from March to July. The activities of PEPC and NADP-ME were measured at 32 and 15°C. At both temperatures, there was a significant drop on the activity of PEPC, during the hottest months. The activity of NADP-ME was constant during the study.

A field experiment was established in northern Victoria in the autumn of 1999 to quantify the effects of renovating a 15-year-old irrigated perennial pasture which had a high paspalum content [>40% dry matter (DM)] in summer. The treatments were: (i) control, the existing pasture; (ii) oversown, in which the existing pasture was grazed, topped and direct drilled; and (iii) resown, in which the existing pasture was sprayed, cultivated and sown with a new pasture. The grass species used in both renovation treatments were perennial ryegrass, Italian ryegrass and tall fescue. The treatments were grazed by dairy cows when the perennial ryegrass had reached the 2.5–3 leaf stage. Grazing of the resown tall fescue coincided with the resown ryegrass in years 1 and 2, but in subsequent years, resown tall fescue was grazed at a rising plate meter height of 80 mm. All treatments were grazed to a residual pasture height of 40–45 mm, as measured with a rising plate meter. Pasture consumption (measured as DM removed by dairy cows), in vitro DM digestibility (in vitro DMD) and crude protein (CP) contents were measured. Oversowing increased pasture consumption over the 4-year period, compared with the control, by an average of 1.1 t DM/ha.year when oversown once with perennial ryegrass and by 1.6 t DM/ha.year when oversown annually with Italian ryegrass. This increase occurred principally during the winter–spring period for pastures oversown with both perennial (0.7 t DM/ha) and Italian (1.6 t DM/ha) ryegrass. Oversowing with perennial or Italian ryegrass did not affect the in vitro DMD or CP content of the pasture on offer. These results show that oversowing with either perennial or Italian ryegrass is a viable means of increasing pasture availability over winter and spring from perennial pastures consisting of a mixture of perennial ryegrass, white clover and paspalum. Pasture consumption in the first 12 months after resowing was 3.5–4.1 t DM/ha lower from the resown than from the control pasture. This was because of two fewer grazings in autumn–winter and to reductions in pasture consumption of 20% in spring and of 40% in summer. These reductions would add considerably to the cost of resowing through increasing the need for supplementary feeding. Pasture consumption from the resown perennial ryegrass pasture in years 2–4 was, on average, the same as the control, although it was higher during winter and spring and lower during summer. Pasture consumption from the resown tall fescue pasture in years 2–4 was, on average, 2.5 t DM/ha.year higher than that of the resown perennial ryegrass pasture, with most of this increase occurring in summer and autumn. The resown pastures had higher in vitro DMD and CP contents than the control with little difference between the resown perennial ryegrass and tall fescue pastures. These findings show that tall fescue is a viable alternative to perennial ryegrass when resowing pastures. The use of nitrogen fertiliser did not affect the in vitro DMD or CP contents of the pasture on offer but allowed an increase in DM consumption, with this increase being greater for the control and oversown pastures than for the resown pasture.

A field experiment was established in northern Victoria in the autumn of 1999 to quantify the effects of renovating a 15-year-old, irrigated perennial pasture with a high paspalum content. The treatments were: (i) control, the existing pasture; (ii) oversown, the existing pasture grazed, topped and direct drilled; and (iii) resown, the existing pasture sprayed, cultivated and a new pasture sown. The grass species used in both renovation treatments were perennial ryegrass, Italian ryegrass and tall fescue. The treatments were grazed by dairy cows. The botanical composition, tiller density and plant frequency are reported in this paper. Oversowing with either perennial or Italian ryegrass increased the sown grass content by an average of 4–8% DM, and by up to 20% DM during winter and spring, but did not affect the average white clover, volunteer species or dead contents. Oversowing did not affect the sown grass or paspalum tiller densities but annual oversowing with either perennial or Italian ryegrass increased the ryegrass plant frequency and, in 2 of the 4 years, reduced the white clover growing point density. Resowing increased (P < 0.05) the content of sown grasses (by 12% DM for perennial ryegrass and by 20% DM for tall fescue) and white clover (by 8% DM) and decreased (P < 0.05) the content of volunteer species (by 18% DM) and, in years 1 and 2, dead material. The plant frequency of tall fescue increased over time (from 75 to 83% of quadrats), whereas that of perennial ryegrass declined (from 87 to 72% of quadrats). This resulted in the resown tall fescue having a lower (P < 0.05) white clover content and growing point density in years 3 and 4, and a tendency for a lower volunteer species content and tiller density in year 4, than the resown perennial ryegrass. Tall fescue is thus better able to resist the invasion of summer-active species and is less likely to require either oversowing or resowing than perennial ryegrass-based pastures. These results suggest that tall fescue should be considered as an alternative to perennial ryegrass when sowing pastures. The use of nitrogen did not improve the sown grass content, tiller density or plant frequency and will not therefore overcome problems resulting from a low ryegrass content.

The common biotype of Paspalum dilatatum Poir. (dallisgrass) is a pentaploid obligate apomict and efforts to improve the grass have not been successful because of its asexual reproduction and irregular meiosis. An apomictic hexaploid biotype, known as Uruguayan dallisgrass, is a new source of genetic variation that may be useful in improving dallisgrass. As with common dallisgrass, improvement of this biotype via conventional breeding methods is difficult because of its apomictic reproduction. However, the use of tissue culture to produce somaclonal variation in the Uruguayan biotype has not been reported, and may offer a means for improving the species. The objectives of this research were to: (i) regenerate plants of Uruguayan dallisgrass through tissue culture, (ii) screen the regenerants for useful agronomic variation and evaluate their forage potential and nutritive value, and (iii) determine the genetic relatedness of the regenerants and their explant sources. In total, 178 plants, selected from 2372 regenerants in preliminary screening, were evaluated for forage nutritive value. Thirty-seven of these were planted into replicated field plot trials at two locations. None of these regenerants were superior to the Uruguayan biotype for forage nutritive value. However, two regenerants, 3440 and 3441, produced more forage than either the Uruguayan or common biotypes in evaluation tests for 3 years at one of the two locations. Data from AFLP analyses indicate genetic variation between two of the Uruguayan accessions and these two regenerants. This variation could account for the differences in forage yield between 3440 and 3441 and the Uruguayan accessions.

This study reports on the effect of oversowing perennial ryegrass (Lolium perenne L.) into a degraded perennial ryegrass and white clover (Trifolium repens L.) pasture to extend its productive life using various intensities of seedbed preparation. Sites in New South Wales (NSW), Western Australia (WA), South Australia (SA) and Tasmania (Tas.) were chosen by a local group of farmers as being degraded and in need of renovation. Control (nil renovation) and medium (mulch and graze, spray with glyphosphate and sow) renovation treatments were common to all sites whereas minimum (mulch and graze, and sow) and full seedbed (graze and spray with glyphosphate and then full seedbed preparation) renovation were imposed only at some sites. Plots varied in area from 0.14 to 0.50 ha, and were renovated then sown in March or April 2000 and subsequently grazed by dairy cows. Pasture utilisation was estimated from pre- and post-grazing pasture mass assessed by a rising plate pasture meter. Utilised herbage mass of the renovated treatments was significantly higher than control plots in period 1 (planting to August) and 2 (first spring) at the NSW site only. There was no difference among treatments in period 3 (first summer) at any site, and only at the WA and NSW sites in period 4 (March to July 2001) was there a response to renovation. As a result, renovation at the NSW site only significantly increased ryegrass utilisation over the whole experimental period. Ryegrass plant density was higher at the NSW, WA (excluding minimum renovation) and Tas. (excluding full renovation) sites 6 months after renovation but this was only sustained for 12 months for the minimum and medium treatments at the NSW and Tas. sites, respectively, presumably due to reduced competition from naturalised C4 summer grasses [kikuyu (Pennisetum clandestinum) and paspalum (Paspalum dilatatum)] in NSW. At the NSW, WA and SA sites, the original ryegrass plant density was low (

Arbuscular mycorrhizae (AM) can ameliorate the impact of disturbance on agroecosystem sustainability. The objective of this study was to describe mycorrhizal colonization patterns in contrasting grazing situations (exclosure and continuous grazing) and topographical positions (upland and lowland) in the flooding pampa (Argentina). We determined the mycorrhizal colonization of the community as a whole and of Dallis grass (Paspalum dilatatum Poir.), a highly palatable, dominant species. We characterized colonization by the proportion of root length occupied by fungi and their different structures. At the community level, there was higher total colonization in the grazed area than in the exclosure. In contrast, Dallis grass showed higher total colonization and higher proportion of vesicles and arbuscules in the exclosure than in the grazed area. For both levels, colonization was higher in the lowland than in the upland position. Differences were observed only in winter and spring, not in summer. Our results show that 1) continuous grazing is associated with an increase of mycorrhizal colonization at the community level and 2) community-level patterns of mycorrhizal colonization cannot be inferred from dominant species. To our knowledge, this is the first characterization of AM abundance at the plant community level under contrasting long-term grazing conditions in a subhumid grassland.

Question: Do warm season (i.e. mainly C4) grass species exhibit a higher water status than winter-growing competitors, (mainly C3 plants) and is this part of their competition ability? Location: Flooding Pampa grassland at Balcarce, eastern Argentina. Methods: Predawn leaf water potential was measured in five species: (1) three cool-season species: Festuca arundinacea, Lolium multiflorum and Stipa neesiana, and (2) two warm-season species: Sporobolus indicus and Paspalum dilatatum, throughout a summer season. The sensitivity of leaf growth to low water status was investigated in a greenhouse experiment where plants were grown in pots at three levels of water deficit. Results: The field study revealed strong differences of water status between the five species likely indicating large contrasts in soil water availability, irrespective of their photosynthetic metabolism. By contrast, the response of leaf elongation rate to predawn water potential was similar in all species studied. Species to which ...

Nine species of forage grasses (five C3 species and four C4 species) were planted in a controlled-environment glasshouse. The C3 plants were Festuca arundinacea Schreb, Dactylis glomerata L., Phleum pratense L., Lolium perennel L. and Poa pratensis L.; the C4 plants were Chloris gayana Kunch., Cynodon dactylon (L.) Pers., Paspalum dilatatum Poir. and Sorghum halenpense (L.) Pers. The number of major vascular bundles and minor vascular bundles, cross-sectional area, the area and proportion of sclerenchyma in a cross-section, thickness of leaf blade, and tensile and shear strength were investigated in order to determine the relationship between physical strength and anatomical characteristics. Physical strength and anatomical characteristics of leaf blades showed significant (P < 0.01) variation between species. Significant correlations were detected between tensile strength and cross-sectional area in forage grasses except Festuca arundinacea. Festuca arundinacea, Dactylis glomerata, Phleum pratense, Chloris gayana and Sorghum halenpense showed significant correlations of tensile strength with the number of major vascular bundles. Festuca arundinacea, Dactylis glomerata and Lolium perennel showed significant correlations of shear strength with cross-sectional area. Festuca arundinacea, Dactylis glomerata and Paspalum dilatatum showed significant correlations of shear strength with the number of major vascular bundles. The proportion of sclerenchyma in a cross-section showed poor correlations with tensile and shear strength. Thickness of leaf blade showed poor correlations with tensile and shear strength except in Dactylis glomerata. Physical strength and anatomical characteristics of leaf blades of the C3 group differed significantly (P < 0.01) when compared with the C4 group except for cross-sectional area. Tensile and shear strength showed significant correlations with cross-sectional area, sclerenchyma area and the number of vascular bundles when all nine species were treated as one group.

Common dallisgrass (Paspalum dilatatum Poir.) is an important forage grass in many subtropical regions induding the southeastern USA. The term dallisgrass is synonymous with the common biotype. There are other biotypes of this species but little is known about their forage potential. This study was initiated to evaluate accessions of five dallisgrass biotypes (common, prostrate, Torres, Uruguaiana, and Uruguayan) and 'Pensacola' bahiagrass (P. notatum var. saurae Par ) for forage yield, nutritive value, and persistence in southern Louisiana and southeastern Texas, and to determine the response and persistence of the superior biotypes under grazing. Three years of clipping data were collected at Baton Rouge, LA, and College Station, TX. Most of the Uruguayan accessions were equal or superior to common dallisgrass for yield and nutritive value and all had superior stand persistence. The Torres and Uruguaiana biotypes did not survive after the first harvest season. Forage production and persistence of prostrate dallisgrass and Pensacola bahiagrass were better than expected. Six superior accessions of the Uruguayan biotype and common dallisgrass were evaluated under grazing for 3 yr at Jeanerette, LA. After 2 yr of rotational stocking, an average of 90% of the Uruguayan and only 53% of the common dallisgrass plants survived. This was followed by one season of continuous stocking and the average plant survival decreased to 75% for the Uruguayan accessions and 33% for common. Because the yield and persistence of the Uruguayan biotype was consistently superior to that of common, Uruguayan dallisgrass could provide livestock producers in the southeastern USA with a viable alternative to common dallisgrass.

A New Zealand temperate pasture is currently exposed to either ambient air or air enriched to 475 µbar CO2 using free-air CO2 enrichment (FACE) technology. Sheep graze the site regularly, which results in heterogeneity in nutrient return. To investigate leaf photosynthetic responses, leaf gas exchange characteristics and nitrogen (N) content were measured in two consecutive years in spring under standard conditions on Lolium perenne L. and Trifolium subterraneum L. and on Trifolium repens L. and Paspalum dilatatum Poir. in the second year only. Leaves of the three C3 species growing under FACE conditions had lower (up to 37% in 1998 and 22% in 1999) photosynthetic rates than leaves growing under ambient conditions, when measured at the same standard conditions of high light and 360-380 µbar CO2. Differences in photosynthetic rates were correlated with leaf N content and stomatal conductance when measured under these conditions. There was no difference in photosynthetic capacities between ambient or FACE grown P. dilatatum, a C4 grass. Photosynthetic N use efficiency (A/N) differed among species. For the C3 species A/N was on average 25% greater under FACE conditions and L. perenne had the highest (240 µmol CO2 mol N -1 s -1 ) and T. repens the lowest A/N (142 µmol CO2 mol N -1 s -1 ) under ambient CO2 partial pressure (p(CO2)). A/N of L. perenne was similar to that of P. dilatatum measured under ambient p(CO2) but 21% greater under FACE conditions. In the second year, leaf stable carbon isotope compositions (δ 13 C) were determined for P. dilatatum, L. perenne and T. repens to assess long-term responses of leaf transpiration efficiency. Using the difference in δ 13 C between ambient and FACE-grown P. dilatatum as a reference to difference in δ 13 C in ambient and FACE air, we concluded that the ratio of leaf intercellular to ambient p(CO2) (Ci/Ca) was similar between FACE and ambient grown L. perenne and T. repens.

Two grazing experiments tested the hypothesis that a cereal grain-based supplement, fed to cows that are in mid–late lactation and grazing low metabolisable energy and high neutral detergent fibre content paspalum (Paspalum dilatatum Poir.)-type pastures, will increase milk yield, but that this response will diminish with successive increments of supplement. A further objective of this research was to investigate some of the factors, such as altered rumen fermentation pattern, that might vary the point at which diminishing returns start to occur. Cows grazed irrigated perennial pasture at an allowance of either 25 (experiment 1) or 31 (experiment 3) kg of dry matter (DM) per cow per day in late summer–early autumn (mid–late lactation) and were supplemented with cereal grain-based concentrates up to 11 and 7 kg DM/cow.day in experiments 1 and 3, respectively. In experiment 1, there were 3 replicates of 6 treatments (3 cows in each treatment group) that involved the feeding of either 0, 3, 5, 7, 9 or 11 kg DM/cow.day of supplement for 50 days. Experiment 3 was conducted over 35 days. There were 2 replicates of 4 treatments (4 cows per treatment group) that involved the feeding of either 0, 3, 5 or 7 kg DM/cow.day of supplement. A further experiment (experiment 2), associated with experiment 1, examined the effects of offering cereal grain-based concentrates up to 7 kg DM/cow.day to dairy cows consuming 10 kg DM/day of herbage with a high paspalum content on aspects of rumen fermentation. Incremental responses of 40 g/kg fat-corrected milk (FCM) to increasing concentrate intake diminished with increasing concentrate intake, with the level of supplementation at which diminishing returns occurred dependent on herbage allowance and, therefore, herbage intake. At a supplement intake of 3 kg DM/cow.day, the response in FCM was 1.1 kg/kg concentrate DM in both grazing experiments. There were no further increases in milk production with additional increments of concentrates in experiment 3 where the pasture allowance was highest. In experiment 1, where concentrates were offered to a level of 11 kg DM/cow.day, and the pasture allowance was lower, diminishing returns were not as pronounced as in experiment 3 until the highest levels of concentrate intake. Substitution of supplement for herbage was a major factor in causing the diminishing returns in both experiments, but especially in experiment 3, where pasture intakes were higher. Milk fat content was significantly (P

The broad-scale factors determining the level of colonisation by arbuscular mycorrhizal fungi in irrigated permanent pasture were investigated using 10 pairs of dairy farms located in northern Victoria, Australia. Each pair consisted of adjacent farms, one under conventional management and the other under biodynamic management. Significant quantities of fertilisers were applied only to the conventional pastures and this was the major difference in inputs between the 2 management systems. Colonisation by arbuscular mycorrhizal fungi of white clover (Trifolium repens L.), perennial ryegrass (Lolium perenne L.) and paspalum (Paspalum dilatatum Poir.) was lower in the conventionally managed pastures than in the biodynamic pastures. On all farms, clover was more highly colonised than the grasses. The level of colonisation in clover exhibited a strong negative relationship with the concentration of phosphorus in the pasture shoots and a weak negative correlation with soil-extractable phosphorus. Similar relationships were evident for the grasses, but these were not as strong. Soil pH, soil organic carbon and the concentration of other soil nutrients (Kjeldahl nitrogen, sulfate, EDTA copper, EDTA zinc, chlorine, and exchangeable potassium, sodium, calcium and magnesium) and pasture shoot nutrients (chlorine, sodium, potassium, calcium, magnesium, manganese, copper, zinc, iron, nitrogen, sulfur and boron) could not account for differences in colonisation levels. On 3 farm pairs, colonisation levels by arbuscular mycorrhizal fungi were monitored over 3.5 years. Colonisation did not vary seasonally. It is concluded that phosphorus levels and host plant will be the major determinants of colonisation levels by arbuscular mycorrhizal fungi in perennial irrigated pasture-based agricultural systems.

This paper aims to provide information for farmers and their advisers to predict levels of substitution that might be occurring under various feeding conditions in northern Victoria. The approach taken involved compiling data from research conducted in northern Victoria and subjecting these to multiple regression analysis to define the key variables affecting substitution and marginal responses in milk production when concentrates are fed. A significant relationship was obtained between level of substitution (kg DM reduction in pasture intake/kg DM of concentrates eaten) and unsupplemented pasture intake (PI, kg DM/100 kg liveweight) when concentrates are fed. The regression relationship also included species composition of the sward being grazed (species: +1 grass, 0 clover), season of the year (season: +1 spring, 0 summer, –1 autumn) and concentrate intake (kg DM/cow.day). The equation is: Substitution = –0.34 + 0.16 ( 0.035) PI + 0.16 ( 0.053) species + 0.11 ( 0.024) season+ 0.03 ( 0.014) concentrate intake [100R 2 = 50.9 (P

Two experiments were undertaken in summer to investigate production responses by dairy cows offered paspalum (Paspalum dilatatum Poir.)-dominant irrigated pasture to the inclusion of protein supplements with different rumen degradable protein characteristics in cereal grain-based concentrates. In experiment 1, cows in mid lactation were offered limited amounts of herbage, at an allowance of 28 kg DM/cow. day together with 8.0 kg DM/cow. day of a pelleted supplement containing: (i) mainly barley and wheat; (ii) barley, wheat and canola meal; or (iii) barley, wheat and cottonseed meal for 35 days. The 3 supplements were formulated to have similar in vitro DM digestibilities. In experiment 2 aspects of rumen function were measured in 9 rumen fistulated lactating cows, individually fed indoors on paspalum-dominant herbage harvested daily with a finger bar mower. Cows were offered the same amount of supplements for 28 days. Pasture intakes were similar to those of the grazing cows in experiment 1. In experiment 1, there were no effects (P>0.05) of dietary treatment on herbage intake (10.2 kg DM/cow. day) or selection of nutrients from herbage. The concentration of crude protein in the total diet consumed was lower (P0.05) of dietary treatments on milk production (21.8 kg/cow. day), milk fat concentration (34.1 g/kg) or milk protein concentration (29.8 g/kg). Urea-N was higher (P

The study reported here compared the nutritive characteristics of the 3 most common irrigated perennial pasture species grown in northern Victoria as they regrew after defoliation at various times during the year. In addition, the relative influence of changes to the proportions of morphological components and the nutritive characteristics of the individual components on the quality of whole plants was examined. The nutritive characteristics of white clover (Trifolium repens cv. Haifa), ryegrass (Lolium perenne cv. Ellet) and paspalum (Paspalum dilatatum) were examined at weekly intervals on 4 occasions during spring–autumn, 1993–94. On each occasion, pastures were defoliated with a drum mower and allowed to regrow for up to 9 weeks; defoliation dates were 24 September, 26 November, 28 January and 25 March. The variation in estimated metabolisable energy [obtained from in vitro dry matter (DM) digestibility], crude protein and detergent fibre concentrations within species was significantly (P

During 1993–94, the nutritive characteristics of white clover (Trifolium repens cv. Haifa), ryegrass (Lolium perenne cv. Ellet) and paspalum (Paspalum dilatatum) were examined at weekly intervals on 4 occasions. On each occasion, they were initially defoliated with a drum mower and allowed to regrow for up to 9 weeks; dates of the 4 initial harvests were 24 September, 26 November, 28 January and 25 March. The objective of the part of a larger study that is reported here was to examine changes in macro-minerals of the 3 species as they regrew after defoliation, in order to start providing information for informed decisions on the need for supplemental minerals in northern Victorian dairy systems. The ranges in mineral elements recorded in this study were 0.16–0.43% for phosphorus, 1.18–3.41% for potassium, 0.26–1.49% for calcium, 0.20–0.54% for magnesium, 0.05–0.44% for sodium, 0.79–2.02% for chlorine and 0.15–0.37% for sulfur. A major reason for the large ranges was due to variations between the 3 species. White clover was richer in a number of minerals than were the grasses, particularly calcium, potassium and magnesium, although phosphorus was also generally higher. Perennial ryegrass had high sodium concentrations, which were probably related to high watertables, with the associated propensity for salinity problems, that are endemic in irrigated northern Victoria. It is suggested that, on the basis of the pasture on offer, phosphorus is the major mineral that can potentially limit milk production by grazing dairy cows in this environment, although possible deficiencies were also demonstrated for calcium, sodium and sulfur. Where a mineral has its highest concentration in the leaves, lax grazing management or the use of short pastures should result in higher concentrations in the pasture eaten than that on offer. Leaves were not always the richest source of a mineral although this was almost always the case for all minerals in ryegrass leaves. In white clover, phosphorus, calcium, magnesium and sulfur were more concentrated in the leaves than in the stem. In paspalum, calcium, magnesium and sulfur were more concentrated in the leaves. White clover stems had higher concentrations of potassium and chlorine than leaves, while with paspalum this applied to sodium and chlorine. It was concluded that the species composition of a pasture will have a large impact on the supply of minerals for grazing dairy cows, although the leaf : stem ratio, as determined by time since the last defoliation, will also have a role in determining whole plant composition.

Two experiments examining the effects of herbage mass and herbage allowance on the consumption of nutrients by lactating dairy cows were conducted on irrigated perennial pasture swards in northern Victoria. Experiment 1 was conducted in early lactation (spring) with a perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) sward at herbage masses of 3.1 (low) or 4.9 (medium) t dry matter (DM)/ha and herbage allowances of about 20, 35, 50 and 70 kg DM/cow.day. Within each herbage mass treatment, there were no significant differences between herbage allowance treatments in nutritive characteristics of pregrazing herbage. Daily DM intake increased linearly from 7.1 to 16.2 (low mass) or 9.9 to 19.3 (medium mass) kg DM/cow, as herbage allowance increased which was equivalent to 2.29 kg DM/t DM increase in herbage mass and 0.18 kg DM/kg DM increase in herbage allowance. This was associated with a decrease in utilisation of herbage from 35 to 23% and from 52 to 29%. Also, milk production increased linearly from 21.8 to 27.1 (low mass) or 24.7 to 32.0 (medium mass) kg/cow.day as herbage allowance increased. Experiment 2 was conducted in mid lactation (summer) with a paspalum (Paspalum dilatatum L.)-dominant sward at herbage masses of 3.0 (low) or 4.7 (medium) t DM/ha and herbage allowances of about 25 and 45 kg DM/cow.day and either 0 or 5 kg DM concentrate/cow.day. Within each herbage mass treatment, there were no significant differences between herbage allowance treatments in nutritive characteristics of pregrazed herbage. Daily DM intake increased by 0.13 kg DM for every 1 kg DM increase in herbage allowance. Over the 2 herbage masses, 2 herbage allowance treatments and 2 concentrate treatments, cows consistently selected a diet about 1.03 higher in in vitro DM digestibility and 1.24 higher in crude protein than that in the herbage on offer. Substitution rate increased from 0.20 to 0.42 (low mass) and from 0.34 to 0.44 (medium mass) kg DM reduction in herbage intake/kg DM of concentrates consumed, with increasing herbage allowance. Along with these changes, marginal returns to supplements decreased from 1.38 to 0.95 (low mass) and 1.07 to 0.97 (medium mass) kg milk/kg DM of concentrates with increasing herbage allowance. Dairy farmers should consider the effects of herbage allowance and herbage mass on intake, nutrient selection and milk production when allocating pasture to dairy cows. Herbage mass and allowance had a greater effect on intake in spring than in summer, principally due to the decline in nutritive characteristics that occurs in summer. Cows selected nutrients to varying degrees depending on the composition of the pasture sward and this selection may result in seasonal nutrient imbalances. Finally, it appears that the best use of supplements will occur when pastures are short in height because this will minimise substitution of supplement for pasture and maximise marginal returns in milk production.

Summary. The hypothesis tested in the experiment reported here was that levels of substitution would be lower and marginal responses to supplementation higher in grazing dairy cows that were subjected to long, compared with short, treatment periods. Forty cows were fed irrigated perennial pasture which contained ryegrass (Lolium perenne), white clover (Trifolium repens), paspalum (Paspalum dilatatum) and weeds at a herbage allowance of about 40 kg dry matter (DM)/cow.day. Of the 40 cows, 20 were under continuous treatment for 6 months (2 October 1995 to 24 March 1996, inclusive) (long term), while treatments were applied to the remaining 20 cows every second month (short term). The second group of cows, therefore, commenced 4 weeks of treatment on 3 occasions, 31 October, 1 January and 26 February. The cows in the short-term treatments were re-randomised for each of their 3 periods in the experiment. There were 2 long-term treatments, one where pasture was fed alone and the other where the same amount of pasture was supplemented with 5 kg DM/cow.day of a 75% barley –25% wheat grain pellet. There were 2 replicates of each treatment and 5 cows per group. The second set of 20 cows was allocated to the same treatments on a short-term basis. When not under treatment, all cows in this second group were offered about 40 kg DM of pasture/cow.day plus 5 kg DM of barley–wheat. Cows ate less pasture when concentrates were fed although total DM intake increased (P0.05) by the length of time for which the cows were supplemented. Milk yield declined from November to March and concentrates increased production, but the interaction between period of the year and use of supplements was not significant (P>0.05). However, the milk responses associated with length of time under supplementation appeared to be different in March relative to the other periods. Although the marginal returns to concentrates in March were 0.9 and 1.3 kg milk/kg DM for short- and long-term supplementation, the marginal returns to feeding concentrates for short or long periods during November and January were the same (0.9 kg/kg DM). However, in terms of total DM intake, the average marginal response was lower (1.4 v. 1.9 kg milk/kg of additional total DM) for the short-term treatments. The trends in body condition for the long-term treatments through the experiment indicated that divergence between unsupplemented and supplemented cows occurred consistently throughout, resulting in 0.8 units difference in body condition score after the 6 months of treatment. It is suggested that it was the differences in body condition that were responsible for the variation in milk response towards the end of the experiment. It was concluded that, while the length of time under supplementation had no effect on intake variables or substitution, marginal responses to the long term use of concentrates eventually diverged from those obtained from their use for short periods, principally due to changes in the body condition of animals in the long-term treatments.

Summary. Three experiments investigating the effects of herbage allowance on the consumption of nutrients by lactating cows were conducted on irrigated perennial pastures in northern Victoria during summer and autumn. Experiment 1 was conducted in mid lactation (autumn–early winter) with perennial ryegrass [54% of dry matter (DM)]–white clover (22% of DM) pasture offered at allowances of 15, 20, 30 and 40 kg DM/cow.day. Herbage intake increased (P

1. Dry matter yield, leaf growth and population dynamics of turves taken from an old Lolium perenne/Trifolium repens-dominated pasture were studied in controlled environment rooms at CO 2 concentrations of 350 μmol mol -1 , 525 μmol mol -1 and 700 μmol mol -1 . Starting with September data the turves were subjected sequentially to the mean monthly temperature and photoperiod taken from long-term climatic data for the area of New Zealand where the pasture was located. Each temperature and photoperiod regime was applied for 21 days to provide 12 different simulated 'months' of environmental conditions. The experiment ran for 14 simulated months, with September and October conditions being repeated at the end of the first simulated 'year'. Mean photon flux density throughout was 500 μE m -2 s -1 . 2. The total quantity of herbage harvested was increased by 7% and 14% at 525 μmol mol -1 and 700 μmol mol -1 CO 2 , respectively. The increase in the amount of T. repens harvested by the end of the experiment was 63% at 525 μmol mol -1 CO 2 and 48% at 700 μmol mol -1 CO 2 . In contrast, neither the yield of C3 grasses nor the yield of the only C4 grass present, Paspalum dilatatum, was significantly affected by CO 2 concentration. The implications of this increase in the proportion of T. repens in temperate pastures at elevated CO 2 is discussed briefly. 3. With the exception of a small increase in the specific leaf area of T. repens, detailed measurements of leaf growth on marked tillers (L. perenne and P. dilatatum) and growing points (T. repens) showed no consistent effects of exposure to elevated CO 2 concentrations. 4. Differences in yield between CO 2 concentrations were mainly attributable to changes in the number and balance of population units. By the middle of the 'winter' conditions T. repens growing point densities at 700 μmol mol -1 CO 2 were more than double those found at 350 μmol mol -1 but total grass tiller densities were unchanged. Growing point densities were also more than doubled at 525 μmol mol -1 CO 2 compared with 350 μmol mol -1 but grass tiller densities were reduced significantly below those recorded in the other two treatments. The relationship between the stability of herbage production and population densities is discussed and the potential interaction between population density, elevated CO 2 and grazing considered. 5. Although exposure to elevated levels of CO 2 did result in large changes in population numbers, this did not happen immediately and so the yield response of this particular commuyity to CO 2 varied with time. The average yield increases recorded here at elevated CO 2 may therefore tend to underestimate those likely to be shown by communities that, at the population level, have become fully adapted to growth in a CO 2 -enriched atmosphere.

Summary. Thirty-six Friesian cows in late lactation, with an initial average daily milk yield of 15.4 kg/day, grazed pure white clover (Trifolium repens cv. Haifa) or paspalum (Paspalum dilatatum)-dominant swards for up to 6 weeks in autumn and were supplemented with maize (Zea mays) silage with or without barley grain, urea or cottonseed meal. Five groups of 4 cows were offered about 21 kg dry matter (DM)/cow. day of paspalum-dominant pasture. One group was unsupplemented while the other groups were offered one of the following supplementary feeding treatments: (i) 5 kg DM/cow of maize silage; (ii) 5 kg DM/cow of maize silage and 75 g of urea; (iii) 3 kg DM/cow of maize silage plus 2 kg DM of rolled barley; or (iv) 3 kg DM/cow of maize silage plus 2 kg DM of cottonseed meal each day. A further 4 groups of 4 cows were offered 21 kg dry matter/cow. day of white clover pasture, and the same supplement treatments, with the exception of maize silage–cottonseed meal. All cows were individually fed their supplement but they grazed the pastures as groups according to treatment. Cows offered white clover and no supplements ate 12.9 kg DM/cow.day of herbage and maintained milk production. All supplements increased total DM intake and improved milk production, to about 18 kg/cow. day, with a mean marginal response of 0.8 kg of milk per 1.0 kg of extra total DM eaten. There were no differences in production due to the type of supplement. Cows grazing paspalum ate less pasture, and levels of substitution of pasture by supplement were higher than when white clover was fed. Milk yields of the unsupplemented cows dropped rapidly and consistently with the cows virtually ceasing production. All supplements successfully arrested the decline in milk production, and to about the same degree; the marginal response to extra feeding was 1.4 kg of milk for each kilogram of additional total DM eaten.

Isolates of Fusariurn graminum from heads of Paspalum dilatatum infected with Claviceps paspali were compared with isolates from soil which had been identified as F. graminum or F. heterosporum on the basis of conidial characters in an earlier study. Differences between isolates were found only in the degree of pigmentation and in the length of macroconidia. Colony morphology, growth rates, and responses of growth to temperature and osmotic potential were similar in all isolates. It was concluded that all isolates belonged to a single species, F. heterosporum. Crossing experiments indicated that the fungus may be homothallic, although ascospores were rare under the conditions used. None of the isolates tested was toxigenic.

Turves of a Mollic Psammaquent soil were used in controlled environment rooms to examine the response of managed temperate pasture communities to 350, 525 or 700 p.p.m. CO2. Yield of herbage (regrowth over 3-week intervals) increased only slightly with higher C02; however, the botan- ical composition was markedly different. At elevated CO2 Paspalum dilatatum (C4) and Lolium perenne (C3) declined as a proportion of harvested yield despite a stimulation of single leaf photosynthesis that was comparable to that found in Trifolium repens, a species that increased in abundance. Changes in species composition were largely a consequence of C02-induced differences in axillary bud activity. Net primary productivity below-ground was stimulated by CO2. Soil C02-C production was greater in elevated CO2 treatments, and was consistent with a greater input of herbage and root mass and/or metabolites and of more readily decom- posable material. Levels of microbial biomass were un- changed, but enchytraeids were more abundant at elevated CO2. Tracking of 14CO2 into the various C pools also indicated a more rapid turnover of C at elevated CO2 but no change in pool sizes. No consistent effects on net mineralization of N were observed.

Over-summering grasses were collected in the south-west of Western Australia in 1991 and 1992 and tested by ELISA using serotype specific polyclonal antibodies for presence of barley yellow dwarf virus (BYDV) serotypes MAV, PAV and RPV (1991) or MAV, PAV, RPV and RMV (1992). In 1991, 33 samples from 33 sites were tested and MAV was detected in four of 12 samples of Pennisetum clandestinum found infected with BYDV. Presence of MAV was confirmed by retesting these samples using MAV specific monoclonal antibodies. In 1992, 802 samples from 16 grass species were collected from 579 sites in six regions. BYDV was detected in 214 (27%) samples at 178 (31%) sites. MAV was found in 50% and RMV in 38% of infected samples. Both were found either alone or in mixed infections with each other or with PAV and/or RPV; all four serotypes were found in 18 (8%) infected samples. The most important hosts were four perennials: Cynodon dactylon, Eragrostis curvula, Paspalum dilatatum and P. clandestinum. Eight other perennial and five annual grass species were also infected. MAV was most commonly found in C. dactylon and P. clandestinum and RMV in P. dilatatum. All four serotypes were present in the six regions sampled, but the relative proportions of the serotypes found varied from region to region. This paper represents the first extensive survey of MAV and RMV serotypes of BYDV in over-summering grasses in Australia. Aphid species found during this survey infesting over-summering grasses were Rhopalosiphum padi,R. maidis and Hysteroneura setariae. In the Mediterranean type climate of the south-west of Western Australia, BYDV and aphids on over-summering perennial grasses constitute the main reservoir of infection and means of spread to cereal crops. Factors favouring grass survival over summer result in increased cereal crop infection.

Changes in total biomass and botanical composition in a native pasture of the Flooding Pampa in the Salado River Basin (Province of Buenos Aires), under 3 grazing systems: spring-summer rest (November, December, and January); fall rest April, May, and June), and continuous grazing were evaluated from October 1979 to August 1981. A variable stocking rate based on available forage was used. Total aboveground biomass was periodically sampled to ground level and separated into dead and green components. The green biomass was subdivided into individual species. Total aboveground biomass averaged 4,600 +/- 445 kg . ha-1 and 3,750 +/- 120 kg . ha-1 for the spring-summer rest treatment during the first and second years, respectively. In the same period, warm-season species increased, principally due to an increase in dallisgrass (Paspalum dilatatum Poir.) and bluestem (Bothriochloa laguroides Herter) biomass. Total aboveground biomass yield was 2,000 +/- 170 kg . ha-1 during the fall rest treatment, and cool-season species such as Poa spp. and Stipa spp. increased. In general, continuous grazing at a moderate intensity resulted in total aboveground biomass of about 2,000 kg DM . ha-1 throughout the experimental period. Contributions of warm-season and cool-season species did not change. Only West Indies smutgrass (Sporobolus indicus (L.) R. Br.) increased under continuous grazing.

Six Friesian steers (300 kg liveweight) were prepared with rumen and abomasal cannulae, and fed three artificially dried grasses at three levels of organic matter (OM) intake and at two stages of maturity. The grasses were paspalum (Paspalum dilatatum), oats (Avena sativa) and kikuyu (Pennisetum clandestinum). The apparent digestion of organic matter (OM) in the whole tract decreased with increasing maturity for all grasses. The proportion of OM digested in the rumen was greater for paspalum and kikuyu than oats, and increased with advancing maturity for paspalum and kikuyu. Microbial nitrogen flow from the rumen was 26 and 25 g/kg of OM apparently digested in the rumen for paspalum, 32 and 36 for oats and 25 and 14 for the early and late maturity kikuyu. The true degradation of grass protein in the rumen was between 0.70 and 0.80 for all three grasses, at all three feed intakes and for both stages of maturity of the grasses. Total rumen pool size was less for oats than paspalum or kikuyu. The retention time of particles and fluid in the rumen increased with decreasing feed intake for oats.

Twenty-two accessions of Paspalum dialatatum Poir from Argentina, Brazil, South Africa, Natal and Uruguay, an Australian commercial line and I1 Australian ecotypes were screened for resistance to Ascochyta paspali. Disease incidence ranged from 0 to 81%. Purple anthered plants which included 11 Australian ecotypes were all susceptible, but 2 accessions were more resistant than the local commercial line. All except 1 of the yellow anthered accessions were highly resistant, but the one considered to be susceptible was more resistant to disease than the purple anthered accessions. A. paspali was re-isolated from symptomless yellow anthered accessions indicating that limited colonisation had occurred. The yellow anthered character appeared to be a useful indicator of resistance to A. paspali.

(...)Crossability between Paspalum dilatatum (F) and P. urvillei was low (1.2%).(...) Crossability between P.dilatatum (V) and P. urvillei was 19.3%.(...) Fertility was investigated for six P. dilatatum (V) × P. urvillei F 1 hybrids and seed set ranged from 0.3 to 18.8% among them. Seed set increased in the F 2 and backcross progenies. Some backcross plants exhibited similar seed set as the parental species. Findings from this study strongly implies that gene exchange between tetraploid P. dilatatum biotypes and P. urvillei is possible

Small swards of 14 grasses of tropical origin (Cynodon dactylon, Digitaria spp., Paspalum dilatatum, Pennisetum clandestinum, Setaria spp.) and 6 of temperate origin (Dactylis glomerata ‘Grasslands Apanui’, Festuca arundinacea, Lolium perenne ‘Grasslands Nui’ and ‘Grasslands Ruanui’, Phalaris spp.) were established in the field at Palmerston North, After planting in late spring, herbage samples were taken during January through May of the following summer, dissected into lamina, sheath, and remainder (culms, stems, stolons), and analysed for total nitrogen, soluble sugar, starch, and in vitro digestibility. Proportion of lamina was 58–96% for the temperate grasses and 31–76% for the tropical grasses. Proportion of sheath was 5–20% for temperate and 22–36% for tropical grasses; and for the remainder fraction 0–22% and 2–44% respectively. Total nitrogen content of the lamina was higher than that of the sheath and remainder fractions. There was no clear distinction between temperate or tropical spec...

Net herbage increments (NHI) and botanical composition were measured for 3 years on pasture grazed rotationally by cattle and subjected to the following treatments: no conservation of herbage; annual silage cut; and annual hay cut. While pasture was being rotationally grazed, i.e., outside the 9 weeks closing-up period, haying led to a progressive decline in NHI. A similar trend, but much less marked, was observed on the silage treatment. The main causes for the decline in NHI in the hay paddocks are thought to be the formation of reproductive tissue and the high temperatures and light intensities at and following harvest. Ensiling depressed the proportion of paspalum in the sward, whereas haying depressed both paspalum and ryegrass.

Twenty-four genotypes each of ‘Kangaroo Valley’ ryegrass, ‘Grasslands Manawa’ ryegrass, and ‘Demeter’ tall fescue were grown in competition with ‘Kangaroo Valley’ ryegrass, Manawa ryegrass, tall fescue. Phalaris luberosa, and Paspalum dilatatum under dryland and irrigated conditions. Basal diameter and height of individual plants were measured in the swards on three d'ltes, and, from a sample of cut and weighed plants, plant weights were estimated. All three grasses showed genotype × harvest interactions. There were no significant genotype × competition interactions, although competition effects on the mean size of plants of the grass species were large, and this effect varied with harvest. Regression analysis of genotype × environment interaction showed that a significant part of the interaction was accounted for by differences between slopes of the linear regressions of genotype yields against environment means. Logarithmic transformation did not reduce the overall genotype × environment intera...