Perennial Grass Pastures Research Articles

Texas Bluegrass Responses to Seeding Rate and Fertilization

ABSTRACT Texas bluegrass has potential as a cool-season perennial pasture grass for the south-central USA. Slow stand establishment in competitive environments is a limitation. Forage production of this grass increases with nitrogen (N), and rhizome growth increases with phosphorus (P). Stand responses by Texas bluegrass from three seed sources to seeding rate and a complete mixed fertilizer were assessed from 1997 through 2005 on a Louisiana Coastal Plain site. A linear response (R2 = 0.39, P ≤ 0.0001) to seeding rate in March 1998 persisted through 2005, even though stands at all seeding rates improved over time. Stands did not differ (P > 0.05) among seed sources. At only the higher seeding rates, rhizome mass increased with fertilization. Soil pH decreased with fertilization, and pH was positively correlated with the final stand rating in 2005. Direct stand responses to fertilization were not detected. Lack of competitive advantage, despite growth responses, and soil acidification with fertilization indicate that increased seeding rates and delayed fertilization may enhance initial establishment of Texas bluegrass in humid environments.

Discriminating the effects of agricultural land management practices on soil fungal communities

The structure of fungal communities was examined in soil subjected to 5 years of different agricultural land management and tomato production practices. Length heterogeneity polymerase chain reaction (LH-PCR) of fungal rDNA internal transcribed spacer-1 (ITS-1) regions was used to create genomic fingerprints of the soil fungal communities. Three years after initiation of land management practices, univariate analysis of genetic diversity failed to detect differences among soil fungal communities in plots managed organically, conventionally or maintained free of vegetation by continuous tillage (disk fallow). Genetic diversity was significantly higher in plots maintained as a perennial pasture grass ( Paspalum notatum var Argentine bahiagrass) or as an undisturbed weed fallow. The composition of soil fungal communities within organic, pasture grass or disk fallow plots were separated into unique clusters by non-parametric multivariate analysis of their Bray-Curtis similarity matrices, computed from the relative abundance of ITS-1 amplicons, while the composition of communities within disk fallow and conventional plots could not be distinguished from each other. Diversity of soil fungal communities was significantly reduced following the cultivation of tomato in year four when compared to the diversity in plots where tomato was not cultivated. Divergence in the composition of soil fungal communities was observed following the cultivation of tomato under all land management regimes except organic, where communities continued to remained clustered based upon similarities among their ITS-1 amplicons. Divergence in the composition of fungal communities became more pronounced following two major hurricanes (Francis and Jeanne, September 2004) except for communities in the organic and pasture grass plots. Following the completion of a second tomato crop in year 5, genetic diversity and richness was similar under all land management regimes except the pasture grass, where it remained significantly higher. By contrast, following two consecutive years of tomato production, unique but mutually similar compositions of fungal communities were detected only in plots subjected to the organic land management regime. This was supported by observations that fungal communities were dominated by a 341 bp rDNA amplicon fragment in all land management regimes except the organic. Cloning and sequencing indicated that the 341 bp fragment generated by LH-PCR had a sequencing size of 343 bp, which was most closely related to Fusarium oxysporum. Thus, land management practices that disturb or disrupt soil fungal communities will significantly reduce their diversity. However, the composition of soil fungal communities is more strongly influenced by land management practices and communities within an organically management system were more resistant to anthropogenic and meteorological disturbances.

Comparative defoliation tolerance of temperate perennial grasses

AbstractThe defoliation tolerance of cultivars of four temperate perennial pasture grasses, perennial ryegrass (Lolium perenne, cv. Yatsyn1), phalaris (Phalaris aquatica cv. Australian), tall fescue (Festuca arundinaceae cv. Demeter) and cocksfoot (Dactylis glomerata cv. Porto), was determined under controlled conditions over a period of 12 weeks. Undefoliated plants were compared with defoliated plants, where only half of one leaf was left intact at the initial defoliation, and leaf regrowth was harvested every 3–4 d. The growth responses measured were plant tiller number, dry weight, relative leaf regrowth rate, root:shoot ratio, sheath:stem ratio and specific leaf weight. All species showed morphological adaptations that potentially increased their ability to tolerate defoliation (e.g. increased allocation to shoot at the expense of roots and lower specific leaf weights) but cocksfoot was found to be the most defoliation‐tolerant and perennial ryegrass the least. The adaptation that favoured cocksfoot most strongly was high sheath:stem ratio, which, it is proposed, allowed it to maintain photosynthesis and a level of carbon supply sufficient to support regrowth throughout the experiment. The strategy of perennial ryegrass which favours leaf growth and leads to rapid leaf turnover rates made it particularly susceptible to defoliation under the conditions of this experiment. This highlights the likely importance of defoliation‐avoidance responses in explaining the well‐known grazing resistance of this species. Phalaris and tall fescue showed responses that were intermediate between the other two species. The importance of defoliation‐avoidance mechanisms and implications for grazing management are discussed.

Dealing with nitrogen in subtropical Australia: Seven case studies in the diffusion of ecotechnological innovation

This paper describes seven case studies in which ecotechnological approaches are being used to reduce the discharge of nitrogen to the environment in three local government jurisdictions in the moist subtropical zone of eastern Australia. Both technical performance and factors relating to acceptance of the technologies are examined. Three of the technologies have survived early setbacks to achieve increasing acceptance. Composting toilets and reed beds (sub-surface flow wetlands) have achieved takeoff in the on-site wastewater context in the Lismore City Council area where the level of adoption (based on 2004–2005 figures) for both technologies was approximately 30% of newly approved systems. In both cases, the level of adoption has been favoured by local scientific studies which have confirmed claims regarding technical performance and by regulations which encourage the reduction of nitrogen discharge to the environment. Free water surface (FWS) wetlands are installed as polishing devices at three of the 10 sewage treatment plants (STPs) in Lismore and the adjoining Byron and Richmond River Shires. Early problems arising from inexperience at design, construction and management of these wetlands have been overcome as local familiarity has increased. This confidence has been a factor in the decision to support a major upgrade to the West Byron constructed wetland system and to install a further three wetlands locally. A further two technologies each have one full-scale system in operation. A 24 ha multipurpose wetland regeneration project for effluent polishing and transpiration, acid sulfate soil management, wetland regeneration, and carbon sequestration, recently installed at the end of the West Byron STP treatment train, is reducing total nitrogen concentrations from approximately 4–1 mg/L. A landfill leachate treatment system incorporating pond, macrophyte zones, horizontal flow gravel filter and single pass sand filter is reducing NH 4-N and TKN concentrations by 95% and 84%, respectively. The final two technologies described are associated with the reuse and/or treatment of municipal wastewaters. The annual crops hemp and kenaf have both exhibited high N uptake rates in irrigated crop trials. However, their short growing season has resulted in rejection as production crops at one STP in the Byron Shire. The recent realization that the perennial pasture grass Setaria sphacelata can perform the role of wetland macrophyte has given rise to the concept of the “wet-and-dry-land” cell. Still at the pilot stage, this ecotechnology may have application in areas with distinct wet and dry seasons.

Tolerance of perennial pasture grass seedlings to pre- and post-emergent grass herbicides

The tolerance of 5 perennial grasses during the seedling stage to pre- and post-emergent grass herbicides was examined in 3 glasshouse experiments. The perennial grass species screened were phalaris, (Phalaris aquatica L.), cocksfoot (Dactylis glomerata L.), wallaby grass [Austrodanthonia richardsonii (Cashm.) H.P. Linder], perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.). Wheat (Triticum aestivum L.) and subterranean clover (Trifolium subterraneum L.) were included as non-target species and annual ryegrass (Lolium rigidum Gaudin) and oats (Avena spp.) as representatives of typical weed species. Herbicides evaluated were fluazifop-p, tralkoxydim, diclofop-methyl, fenoxaprop-p-ethyl, fenoxaprop-p-ethyl + pyrazoline, sethoxydim, flamprop-m-methyl, quizalofop-p-ethyl, clethodim, simazine, imazethapyr, propyzamide, carbetamide, clodinafop-propargyl + cloquintocet-mexyl, propaquizafop, atrazine, trifluralin, triallate, pendimethalin, metribuzin, trifluralin + oryzalin, cyanazine, chlorsulfuron and triasulfuron. Herbicide phytotoxicity was assessed 15 and 30 days after post-emergent herbicide application using the European Weed Research Committee (EWRC) visual score of leaf damage (1 indicating no effect, 9 indicating all plants dead) and plant herbage yield depression relative to the unsprayed control. Plant responses to pre-emergent herbicides were assessed 45 days after sowing. Most herbicides were highly phytotoxic (EWRC score 4–9) to the perennial grass seedlings. However, atrazine, flamprop-m-methyl, imazethapyr, fenoxaprop-ethyl, and triallate caused less severe phytotoxicity (EWRC score 1–4) in phalaris, fescue, cocksfoot and perennial ryegrass from which they could be expected to recover, with yield reductions of between 0 and 45%, 30 days after spraying. Simazine caused yield losses of 20–50% in fescue, phalaris and perennial ryegrass which may be acceptable in swards with high weed burdens. Wallaby grass showed tolerance to flamprop-m-methyl, carbetamide, propyzamide and imazethapyr. Subterranean clover was tolerant of most herbicides with yield losses less than 20% except for the post-emergent herbicides simazine and atrazine, and the pre-emergent herbicides triasulfuron, metribuzin, cyanazine and chlorsulfuron where yield suppression was between 50 and 99%.

Sustainable grazing systems for the Central Tablelands of New South Wales. 3. Animal production response to pasture type and management

The main limitations for prime lamb production in the Central Tablelands of New South Wales are low availability of forage early in the growing season (late autumn–early winter) and low nutritive value in the summer. This paper describes the performance of a first-cross lamb breeding enterprise on 4 pasture types and 2 management systems over 4 years for the Central Tablelands region. The pastures studied comprised a traditional unfertilised naturalised pasture, a similar pasture fertilised with superphosphate, a sod-sown fertilised introduced perennial grass pasture and a sod-sown summer growing perennial, chicory (Cichorium intybus L.) pasture. Grazing management involved either continuous grazing or tactical grazing that combined a lower annual stocking rate with an optional summer rest to maintain perennial grass content above 50%. An additional area of chicory pasture was set aside for finishing lambs. Over the experiment stocking rates were increased each year as the pasture became established, with increases ranging from 1.5 ewes/ha for tactically grazed unfertilised natural pasture to 3.6 ewes/ha, for chicory and clover pasture. The feed quality v. quantity problem of summer and autumn was reaffirmed for each pasture type except chicory and the lamb enterprise appeared to be sufficiently adaptable to be promising. Ewes lambed in September and produced satisfactory lamb growth rates (about 280 g/day for twins) on the various pastures until weaning in late December. Thereafter, lamb growth rates declined as the pastures senesced, except chicory, reaffirming the feed quality v. quantity problem in summer and autumn of naturalised and sown grass pastures for producing lamb to heavyweight market specifications. Weaning liveweights (in the range of 32–40 kg) from grass-based pastures were high enough for only about 45% of the lambs to be sold as domestic trade lambs with the remainder as unfinished lambs. In contrast, the chicory and clover finishing pasture produced lamb growth rates of 125 g/day and quality large, lean lambs suitable for the export market. Vegetable matter in the late January shorn wool was insignificant and there was no significant effect of pasture on fleece weight, fibre diameter or staple strength. Position of break in staples of wool from chicory pastures differed from that of the other pasture types and warrants further study on time of shearing. It was concluded that a first cross lamb producing enterprise of suitable genetics was effective in producing trade and store lambs before pasture senescence, but the inclusion of a specialised pasture of summer growing chicory would create greater opportunities. In the unreliable summer rainfall region of the Central Tablelands, the area of chicory pasture needed to maintain lamb growth rates of >125 g/day, estimated from these results, is around 10 lamb/ha of chicory.

Effect of annual weeds on the growth of perennial grass mixtures in the alpine region of the Qinghai‐Tibetan Plateau

In the alpine region of the Tibetan Plateau, five perennial grass cultivars, Bromus inermis (B), Elymus nutans (E), Clinelymus nutans (C), Agropyron cristatum (A), and Poa crymophila (P) were combined into nine communities with different compositions and ratios, B+C, E+A, B+E+A, E+B+C, C+E+A, B+E+C+A, B+C+A+P, B+E+A+P and E+C+A+P. Each combination was sown in six 10 × 10 m plots with three hand‐weeded plots and three natural‐growing plots in a completely randomised design in 1998. Afield experiment studied the performance of these perennial grass combinations under the competitive interference of annual weeds in 3 consecutive years from 1998 to 2000. The results showed that annual weeds occupied more space and suppressed the growth of the grasses due to earlier germination and quicker growth in the establishment year, but this pattern changed in the second and third years. Leaf area indexes (LAIs) of grasses were greatly decreased by the competitive interference of weeds, and the negative effect of weeds on LAIs of grasses declined and stabilised in the second and third years. E+B+C, B+E+C+A, and B+E+A+P possessed relatively higher LAIs (P < 0.05) among all grass combinations and their LAIs were close to five when the competitive interference of weeds was removed. Grasses were competitively inferior to weeds in the establishment year, although their competitive ability (aggressivities) increased throughout the growing season. In the second and third years, grasses were competitively superior to weeds, and their competitive ability decreased from May until August and increased in September. Dry matter (DM) yields of grasses were reduced by 29.8–74.1% in the establishment year, 11.0–64.9% in the second year, and 16.0–55.8% in the third year by the competitive interference of weeds. B+E+C+A and B+E+A+P can produce around 14 t/ha of DM yields, significantly higher (P < 0.05) than the production of the other grass combinations in the second and third years after the competitive interference of weeds was removed. It was preliminarily concluded that removal of competitive interference of weeds increased the LAIs of all grass swards and improved the light interception of grasses, thus promoting the production of perennial grass pastures. The germination stage of the grasses in the establishment year was the critical period for weeding and suppression of weeds should occur at an early stage of plant growth. The grass combinations of B+E+C+A and B+E+A+P were productive and can be extensively established in the alpine regions of the Tibetan Plateau. Two or three growing seasons will be needed before determining success of establishment of grass mixtures under the alpine conditions of the Tibetan Plateau.

Seed dormancy, germination, seedling emergence, and survival of some temperate perennial pasture grasses in northern New South Wales

A series of seed and seedling studies was undertaken in northern New South Wales for the temperate perennial grasses phalaris (Phalaris aquatica cv. Sirosa and Australian), tall fescue (Festuca arundinacea cv. Demeter), perennial ryegrass (Lolium perenne cv. Kangaroo Valley), and 2 wallaby grasses (Austrodanthonia bipartita syn. Danthonia linkii cv. Bunderra and A. richardsonii syn. D. richardsonii cv. Taranna). Studies were conducted to determine the level of dormancy in freshly harvested seed and the time required to overcome it, effects of alternating daily temperatures on the germination of non-dormant seed, effect of time-of-sowing on seedling emergence (2 studies) and survival, levels of seed production and soil seedbanks, and the effect of litter cover and soil type on the emergence of Sirosa phalaris seedlings.Grass species, time, and their interaction all had a significant effect (P &lt; 0.05) on both dispersal unit and caryopses germination. One month after harvest, germination of caryopses was lower (P &lt; 0.05, 2 and 1%, respectively) for Taranna and Bunderra than for Sirosa (79.5%). In March 1993, germination of the 2 wallaby grasses was also lower (P &lt; 0.05) than that of Sirosa. Dormancy of freshly harvested seeds of Sirosa was mainly associated with the structures surrounding the caryopses (7.7 v. 79.5% mean germination), but for Taranna and Bunderra it was related to physiological dormancy of the caryopses.Germination levels that were not significantly different to the maximum occurred for temperature ranges of 35/30–15/10�C [Sirosa (commercial)], 35/25–15/10�C (Australian phalaris), and 35/30–15/05�C (Kangaroo Valley ryegrass). In contrast, maximum germination of wallaby grasses only occurred for Taranna in the temperature range 25/20–20/10�C, and for Bunderra at 25/15 and 20/15�C.Seedling emergence in the field was episodic, occurring on only 3 occasions from 1993 to 1996. No seedlings of Sirosa phalaris, Demeter tall fescue, or Kangaroo Valley ryegrass were successfully recruited, but Taranna and Bunderra successfully recruited new plants from natural seedfalls. Whereas seed production of the perennial grasses studied was relatively high (~10 000 seed/m2 in 1992), soil seedbank levels were much lower (generally &lt;1000 seeds/m2). These data were used to indicate the likely successful establishment of sown perennial grasses or by regeneration from natural seedfall.

The response to moisture and defoliation stresses, and traits for resilience of perennial grasses on the Northern Tablelands of New South Wales, Australia

A field experiment was conducted to study the effects of defoliation and moisture stresses on perennial pasture grasses and to identify traits associated with their resilience. The experiment, conducted near Armidale on the Northern Tablelands of NSW, studied 4 introduced perennial grass species (Phalaris aquatica, Festuca arundinacea, Dactylis glomerata, and Lolium perenne) and 2 native grass species (Microlaena stipoides and Austrodanthonia richardsonii) subjected to 3 moisture regimes (non-stress moisture, moderate drought, and severe drought) and 2 defoliation intensities (severe and moderate). Basal area, herbage mass, phenological growth stage, nitrogen concentration, root mass, and rooting depth were compared over 2 independent 6-month periods: spring–summer (1 September 1994–28 February 1995) and summer–autumn (1 December 1994–31 May 1995). Multiple regression was used to determine which traits were important for determining plant resilience.The differences between species and their respective responses were evident in the traits measured. In general, basal area tended to increase over summer and show little change during autumn. Severe defoliation stimulated plant growth, resulting in higher harvested herbage mass than from those moderately defoliated. Reproductive development was suppressed by severe drought and reduced by moderate drought. Severe defoliation suppressed flowering of Dactylis and Lolium at both drought intensities, compared with moderate defoliation. Phalaris, Festuca, and Austrodanthonia were the deepest rooting species during spring–summer, and Dactylis the shallowest. All species had similar rooting depths during summer–autumn, with those under severe and moderate drought having the deepest and shallowest rooting, respectively.Carbohydrate reserves and basal area were important traits for determining plant resilience during spring–summer. During summer–autumn, maintaining basal area and plant biomass through moderate grazing was important for resilience.

Sustainable grazing systems for the Central Tablelands, New South Wales

Pasture degradation is a major issue in the high rainfall zone (&gt;600 mm) of temperate Australia. Characterised by a decline in the perennial grass component, this degradation is responsible for reduced livestock production and implicated in environmental problems, such as dryland salinity, through changed water-use patterns. This paper reports on a multi-disciplinary research program conducted at Carcoar in central New South Wales, one of 6 sites that comprised the Sustainable Grazing Systems National Experiment. The aim of the experiment was to develop more profitable and sustainable pasture systems by evaluating the impact of changes in the perennial grass component on animal production and water-use patterns. Tactical management strategies were evaluated on naturalised and sown perennial grass pastures and on chicory (Cichorium intybus), using a Merino ewe-based first cross lamb enterprise. Data presented showed that grazing deferment over summer, combined with reduced stocking rate, increased perenniality and reduced annual grass weeds compared with continuous grazing. Livestock performance, however, did not always follow trends in available perennial herbage mass. Naturalised and sown pastures were suitable for raising prime lambs, but only chicory had the capacity to finish lambs to market specification without supplementation. With respect to water-use patterns, sown perennial pastures were more successful than naturalised pastures in reducing leakage of water from the root zone, although this seemed to be related mostly to the abundance of the perennial grass in the pasture. From a sustainability perspective, continuously grazed pastures generated higher net cash flows, but had negative environmental impacts, whereas tactically grazed pastures had positive on- and off-farm impacts but lower net cash flows. The implications of these findings for incorporation into future management strategies for sustainable production in high rainfall environments are discussed.

Ground cover in temperate native perennial grass pastures. I. A comparison of four estimation methods

Studies were conducted to compare visual estimates of ground cover and canopy cover by both inexperienced and experienced observers and to compare those estimates with those from more objective methods in native pastures in the high rainfall, temperate rangelands of northern NSW. Ground cover and canopy cover of 60 quadrats was estimated using visual, mapped area, digital image analysis and photo point quadrat methods. Inexperienced observers were trained by estimating ground cover of reference quadrats. Differences between mean visual estimates of ground cover and canopy cover for experienced and inexperienced observers were not significant (P&gt;0.05). Mean ground cover estimates by the mapped area, digital image analysis and point quadrat methods were also not different from each other. The overall relationship between mean visual estimate and mean objective estimate of ground cover was non-linear (second order polynomial, R2 = 0.93), observers tending to underestimate in the mid-range (20 to 80%) of cover compared with objective methods. Mean visual estimate of ground cover was 73.7% compared with the mean objective estimate of 83.7%. Visual estimates of canopy cover (mean 34.6%) were highly correlated (R2 = 0.90) with those of the mapped area method (mean 34.3%) and the relationship was linear. Measurement of ground cover is a standard technique used in many pasture ecology and management studies and is increasingly being used by land managers to monitor pasture production and sustainability. Inexperienced observers were trained quickly and easily to estimate ground cover and canopy cover with sufficient accuracy to identify ranges of cover using visual estimation, indicating that the visual estimation technique should be suitable for estimating ground cover in land management research.

Ground cover in temperate native perennial grass pastures. II. Relationship with herbage and litter mass

Studies were conducted to examine the relationship between ground cover and herbage mass; ground cover and litter mass; herbage mass and litter mass, and, ground cover and total (herbage and litter) mass for two grazed, native pastures in the high rainfall, temperate rangelands of northern NSW. Ground cover was visually estimated by two experienced observers, litter (unattached plant material) was collected and herbage mass was estimated by harvesting to ground level in 30 quadrats (40 by 40 cm). Data were collected for 16 sampling times at the change of season and from spring 1997 to spring 2000 (a total of 465 quadrats at each site) and examined by regression analysis for the mean data for each level of ground cover and for data from individual quadrats. The relationship between ground cover and herbage, litter or total mass was logarithmic at each site. The logarithmic nature of the relationship reflected the occurrence of low herbage, litter and total mass even when ground cover was 100%. For the mean data, herbage and total mass accounted for 68–77% of the variation in ground cover, but for the individual quadrat data these variables accounted for 42–53% and 43–55%, respectively of this variation. Litter and herbage mass had a low correlation (R2&lt;~0.20) and for the mean data litter mass accounted for around 40–60% of the variation in ground cover, compared with 15–21% for the individual quadrats. Some seasonal differences in these relationships were apparent and these were attributed to the occurrence of annual forb and legume species that had different growth habits to those of the native perennial grasses. For these pastures the data indicated that herbage mass could not be used as a surrogate measure of ground cover or litter mass.

Seed Germination and Dormancy in Eastern Gamagrass

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is an important native rangeland species and could be a more widely used perennial pasture grass. Stand establishment, however, is slow, and it can take 3 yr before a full stand is attained. Our objectives were to determine the caryopsis weight distribution, the relationship between caryopsis weight and percentage germination, the role of the cupulate fruit case in seed dormancy, and the force required to open the cupulate fruit case. Caryopses of ‘Iuka’ and ‘Pete’ eastern gamagrass were extracted from the cupulate fruit case by hand, individually weighed, separated into five weight classes, and germinated in a germination chamber. Differences in percentage observed germination and total potential germination at 7 and 14 d were attributed to caryopsis weight (P &gt; 0.05). No caryopsis weight × cultivar interaction occurred, suggesting homogeneity of slopes for cultivars (P &gt; 0.25). An artificial fruit case (band) was fashioned from an extruded plastic tube and a caryopsis placed inside to examine the role of the fruit case in germination. Germination of unbanded caryopses (44.8%) was significantly greater than banded caryopses (6.3%, P ≤ 0.01). A lever and fulcrum were used to find the force required to open the fruit case. We concluded that seed dormancy was likely mechanical for these cultivars. Under natural conditions, the integrity of the fruit case must be reduced before germination will proceed normally. Light, alternating temperatures, freezing and thawing, fire, rodents, and soil microorganisms, to name a few, may be involved in the decay of the fruit case.

Spatial Legume Composition and Diversity across Seeded Landscapes

Pastures typically have diverse landscapes, and resulting soil conditions and plant composition can vary within small area units. This study was performed to quantify the spatial variation in legume contribution to the plant community when seeded into established perennial cool‐season grass pastures. Pastures were interseeded with an 11‐legume mixture and divided into three stocking methods (continuous, rotational, and nongrazed), with each stocking method containing five landscape positions (summit, backslope, toeslope, opposite backslope, and opposite summit). Grass and legume components were sampled three times annually between 1996 and 1998. Backslopes had greater legume dry matter (DM) composition (161 g kg−1) than either summit (62 g kg−1) or toeslope positions (7 g kg−1), and total legume concentrations increased over years. Legume composition consisted mostly of red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and white clover (T. repens L.). Species richness and Shannon–Weiner diversity index (H’dm) for the legume functional group were also greatest on backslope landscape positions, especially in continuously and rotationally stocked pastures. Legume DM composition showed a positive linear relationship with legume species richness in continuous, rotational, and nongrazed pastures (r2 = 0.76). The H’dm showed a positive linear relationship with legume DM composition in only rotationally stocked paddocks (r2 = 0.88). The legume component at grazed backslope sites filled a niche left unoccupied by the grass component. Species and site recommendations for pasture improvement and management should be made based on landscape position and stocking method.

Seasonal differences in the soil water balance under perennial and annual pastures on an acid Sodosol in southeastern Australia

SummaryReplacement of native deep‐rooted grasses by shallow‐rooted ones has resulted in greater losses of water and nitrogen by drainage. To counter this effect we have tested the hypothesis that liming, and the conversion of annual grass pastures to perennial grass pastures, could improve the sustainability of grazing systems in the high rainfall zone (&gt; 600 mm per annum) in southeastern Australia, through better use of water and nitrogen. A field experiment consisting of sixteen 0.135 ha (30 m × 45 m) grazed paddocks representing four pasture combinations (annual pasture (mainly Lolium rigidum) without lime (AP–); annual pasture with lime (AP+); perennial pasture (mainly Phalaris aquatica) without lime (PP–), and perennial pasture with lime (PP+)) was carried out from 1994 to 1997 on an acid Sodosol (Aquic Hapludalf) in southern New South Wales, Australia. Measurements were made of surface runoff, subsurface flow (on top of the B horizon) and soil water content. The results showed that perennial grass pastures, especially PP+, extracted approximately 40 mm more soil water each year than the annual grass pastures. As a result, surface runoff, subsurface flow and deep drainage were at least 40 mm less from the perennial pastures. These measurements were further supported by a simulation of soil water deficit and deep drainage for AP– and PP+ paddocks, using 10 years' past meteorological records. Overall, the results suggested that well‐grown, phalaris‐based pastures could reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone.

The economics of temperate pasture systems on the central and southern Tablelands of New South Wales

Pastures are the basis of most forms of agricultural production on the New South Wales central and southern tablelands. Pastures occupy the bulk of the region's landmass and pasture-based livestock production annually contributes more than three-quarters of the regional gross value of rural production. Throughout the region, there is substantial variation in pasture composition, ranging from high quality introduced perennial grasses and legumes to pastures comprising mainly low quality native species. This paper examines the economics of the main categories of temperate pastures over a range of soil fertility-rainfall environments on the south-eastern tablelands areas of New South Wales. Using a linear programming model and discounted development budgets, the results demonstrate the strong influence of the environment on the economics of the individual pasture systems. The highest economic returns in both the short and longer-terms were to the introduced perennial grass pastures in most of the environments. Pastures based on introduced legumes and the high quality native species also generated sound economic returns, although there are recognised problems with the persistence of the legume pastures. Over time, the returns to the better quality native pastures compare favourably with the introduced legumes and are better suited to acidic soils than the perennial grasses. Low quality native species produced relatively poor economic returns in all environments and unfortunately, are the main pasture type in the region's less favourable environments.

Long-term change in the economic productivity of four major pasture categories on the south-eastern Tablelands of New South Wales

The perception of change or decline in the productivity of temperate pastures in south-eastern Australia is an important concern to livestock producers and pasture scientists. Much of this concern relates to reductions in the proportions of desirable species in the composition of pasture systems as a result of increased soil and weed problems. The purpose of this paper is to investigate trends in the long-term economic productivity of four categories of temperate pastures (all introduced pastures, introduced perennial grasses, introduced legumes and all native pastures) on the central and southern tablelands of New South Wales. The results provide evidence of economic productivity decline in the all introduced pastures category in relation to sheep production, but this has been due to productivity decline in the dominant legume component of the introduced pastures. In contrast, there has been strong growth in the economic productivity of the introduced perennial grass pastures. Abnormally high beef cattle numbers in the mid-1970s appear to have created an illusion of high productivity and subsequent decline in all introduced pastures. In contrast, the economic productivity of the native pastures which are the bulk of the region's grazing areas, has fallen substantially.

Response of texas bluegrass to season of nitrogen fertilization on the Louisiana coastal plain

Texas bluegrass (Poa arachnifera Torr.) has shown potential for use as a cool‐season perennial pasture grass in the southern Great Plains, where it occurs as a natural component of rangeland plant communities, and into the western Coastal Plain. Responsiveness of this grass to nitrogen (N) fertilization appeared to be limited to the spring growing period in initial evaluations in Louisiana. A field plot experiment was conducted to assess forage production and quality responses to season of N fertilization on the Syn‐1 population of Texas bluegrass. Winter forage production responses to 50 kg N ha‐1 were obtained in the 1997–98 growing season but not in 1998–99 after stands had been depleted by summer drought. Greatest yield increases resulted from spring N application, however, fall plus winter fertilization provided the most uniform distribution of forage through the cool season. Forage fiber fractions, in vitro digestibility, and crude protein were not affected by N fertilization. Both amount and distribution of Texas bluegrass forage, but not forage quality, can be manipulated by time of N fertilization.

Towards more sustainable pastures: lessons learnt

The Temperate Pasture Sustainability Key Program (TPSKP) was established across south-eastern Australia to test the hypotheses that an improved perennial grass content in pastures would result in fewer weeds, better water use (and hence lesser impacts on soil salinity), and lower soil acidification rates. Grazing tactics were seen as a means to enhance or maintain the perennial grass content. Soil and water sustainability experiments in summer and winter dominant rainfall environments showed fewer weeds, improvements in water use and less acidity under perennial versus annual grass pastures. Further work is needed to determine if these gains are sufficient to make perennial grass pastures sustainable in the long-term as some nitrate leakage still occurred at the winter rainfall site. Indicators were developed to rate the sustainability of treatments within experiments. A subset of these indicators was common across experiments and could readily be used by farmers to provide an initial assessment of the soil and water sustainability of their pasture systems. These are: the mineral nitrogen at the bottom of the root zone (40–60 cm); soil pH at the surface and bottom of the root zone and perennial grass content by species. Managing pastures through droughts is a critical aspect of grazing management in Australia. Experiments within the TPSKP demonstrated that perennial grasses survived during drought when maintained above critical lower biomass values. These values ranged from 0.5 to 1.5 t DM/ha depending upon species. Over all experiments, there was general support for the view that maintaining a higher level of biomass in pastures resulted in more sustainable systems. Twenty-three grazing experiments using an open communal grazing design showed that most perennial grasses were sensitive to grazing at some stage in their seasonal growth cycles. The exceptions were inconclusive for several reasons e.g. the grazing pressure may not have been high enough at those sites to elucidate any effects; they occurred where the perennial grass content was less than 10% or exceeded 70%, of the sward; or were confounded by interactions between species where the species under study was not dominant. After taking these exceptions into account, it was then possible to determine where grazing tactics could be expected to work. Species differed in their response to grazing. Some perennial grasses were more sensitive to grazing during periods of stress (e.g. dry summers) than when actively growing (e.g. cocksfoot), while the reverse applied with others (e.g. phalaris). Of the grasses sensitive to grazing when actively growing, sensitivity of some was largely confined to the reproductive period (e.g. perennial ryegrass). Across most experiments, continuous grazing resulted in either a decline in or no net benefit to, the perennial grass content. Microlaena stipoides was the only species to respond to increased grazing pressure — this only applied in spring. The experiments clearly showed that tactical rests were an important tool for grassland management. The effects recorded were predominantly expressed through impacts on vegetative growth and survival of existing plants. Short-term experiments and dry seasons did not enable recruitment processes to be studied. Within pastures, grazing tactics can influence many species. The challenge is to use the TPSKP outcomes to develop strategies that optimise the composition of these swards. Due to the short-term nature of these experiments the results were evaluated within a conservative framework and often simply on the absolute level of parameters. Techniques need to be developed to more effectively monitor the process (i.e. rates of change), rather than the consequences (i.e. ends). The information gained in this program needs to be incorporated into practical strategies for better management of pastures and tested at a commercial scale. The TPSKP was one of the largest, coordinated pasture programs ever attempted. Some major outcomes were the experience gained by a large number of grassland scientists in running such programs, the development and acceptance of standardised measurement protocols and a much stronger network among grazing systems scientists committed to achieving improved management systems.

Soil factors affecting the sustainability and productivity of perennial and annual pastures in the high rainfall zone of south-eastern Australia

A field study was carried out in the high rainfall zone (HRZ, &gt;600 mm p.a.) of southern Australia from March 1994 to August 1997 to test the hypothesis that sown perennial grasses and liming could make the existing pastures more sustainable through better use of water and nitrogen. The site, on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales, was typical of much of the HRZ grazing country in southern New South Wales and north-east Victoria. The experiment consisted of 4 replicate paddocks (each 0.135 ha) of 4 treatments: annual pasture (mainly ryegrass Lolium rigidum, silver grass Vulpia spp., subterranean clover Trifolium subterraneum and broadleaf weeds) without lime, annual pasture with lime, perennial pasture (phalaris Phalaris aquatica, cocksfoot Dactylis glomerata and subterranean clover T. subterraneum) without lime, and perennial pasture with lime. Soil pH (0–10 cm) in the limed treatments was maintained at 5.5 (0.01 mol/L CaCl2), compared to 4.1 in the unlimed treatments. The pastures were rotationally grazed with Merino ewe or wether hoggets at a stocking rate which varied with the season, but was 10–25% higher on the limed pastures [14.8–17.3 dry sheep equivalent (dse)/ha] than the unlimed pastures. One replicate set of pasture treatments was intensively monitored for surface runoff, subsurface flow (at the top of the B horizon), water potential gradients and ammonium volatilisation. Other measurements of nitrogen inputs, transformations and losses were made on all paddocks. In a normal to wet year, surface runoff, subsurface flow and deep drainage (&gt;180 cm depth) were about 40 mm less from the perennial than the annual pastures. The reduction in deep drainage under the perennials was about one-third to one-half (20–29 mm/year). The smaller loss of solution NO3– from the perennial pastures (up to 12 kg N/ha.year) suggested soil acidification under perennials was reduced by about 1 kmol H+/ha.year. Denitrification and volatilisation losses of N were small (1–12 kg N/ha.year). Nitrogen fixed by subterranean clover (above ground parts) ranged from 2–8 kg N/ha in the drought of 1994–95 to 128 kg N/ha in a normal year (1996). The soil-pasture nitrogen balance was positive for all treatments and averaged 76 kg N/ha.year over 2 years. The abundance of introduced and native earthworms increased from 85 to 250/m2 in the limed pastures between 1994 and 1997. Introduced species, such as Aporrectodea trapezoides, were especially responsive to lime. Animal production per hectare was 10–25% higher on pastures with lime. Critical gross margins per dse were lowest ($16/ha) for a long-lived perennial pasture (&gt;15 years), and highest ($20/ha) for a short-lived perennial (5 years). Overall, there were substantial benefits in animal production, improved soil quality and water use from establishing perennial grass pastures with lime on these strongly acid soils.