Pasture Renovation Research Articles

Subterranean clover in North Canterbury sheep pastures

The Hawarden basin is typified by dry, hot conditions over summer, which makes it difficult to retain ryegrass/white clover pastures on the lighter soils. These conditions have led to the introduction of better-adapted species such as the annual, subterranean clover. The mid-flowering cultivar 'Mt Barker' was first sown in the 1930s; then the earlyflowering 'Woogenellup' and late 'Tallarook' were used in the 1960s. The 'Mt Barker' type became dominant in these old pastures. The key factors for good subterranean clover growth were soil fertility (particularly P and S), space following dry summers for seedlings to re-establish, and moisture in the spring to maximise herbage yield. A visit to Australia in 1996 prompted the inclusion in new sowings of the late-flowering 'Leura' at high sowing rates (8-10 kg/ ha). It has taken 5 years for seed stocks to build to a level where we can identify good seedling strikes of 'Leura'. Two of the autumns over this period were very difficult and hindered normal establishment. Rainfall is erratic in North Canterbury, which affects the success of subterranean clover from one year to another. Dry summer conditions are optimal for subterranean clover strikes, as the pasture opens, and when the autumn break occurs, more than 2 000 subterranean clover seedlings/m2 can be produced. Autumn grazing management, when recovering from extreme drought, is critical because pasture must be spelled for 6 weeks to allow the subterranean clover to establish. However, if the autumn is wet, pasture cover must be controlled so that subterranean clover seedlings are not smothered. Set-stocking is best in spring to control pasture cover, but grazing should not be too hard during the flowering and seed set period. Subterranean clover seed yields of up to 250 kg/ha have been achieved from old pastures, but this is less seed than is produced under Australian conditions. Pasture renovation using the baker boot drill to re-introduce grasses and new cultivars of subterranean clover has been successful following very dry summers. Lamb growth rates have been excellent on subterranean clover-based pastures and these have increased the farm's meat production and reduced the cost of maintaining pastures. Key words: grazing management, North Canterbury, seedling establishment, seed set, subterranean clover

Using the recommended stocking density to predict equine pasture management

Best management practices for equine pastures include following the recommended stocking density, rotating, clipping, dragging manure, soil testing, and renovating as needed. Assuming these practices are implemented collectively, pasture resources can contribute significantly to annual forage needs. A survey was mailed to New Jersey pasture property owners in January 2000 to assess pasture management practices and determine the relationship between the recommended stocking density and individual management practices. Our survey indicates that many horse pasture managers follow individual recommendations, but generally do not implement multiple management practices. About 69% of survey respondents currently have between 0 and 20 horses. About 28% of respondents have between 6 and 10 acres of pasture, while only 20% have between 11 and 20 acres. Our analysis reveals a decreasing tendency to follow the recommended stocking density as horse numbers increase, but no difference as the number of acres of pasture changes. Our survey indicated that 66% soil test and about 45% fertilize every three years or greater while 50% lime pastures in intervals exceeding three years. The most commonly implemented management practice is mowing pastures (89%), while 54% of respondents rotate pastures. Despite the large proportion of managers that mow or rotate their pastures, there was generally only a small likelihood of these managers following the recommended stocking density and mowing, and no relationship between rotating and the recommended stocking density. Our results also indicate that at most about one-third of pasture managers have access to or own some piece of equipment used in pasture renovation or maintenance, although 92% make annual pasture expenditures. Consequently, pasture managers need additional information regarding the benefits of following best management practices to achieve the synergistic effect of multiple management practices on pasture productivity and persistence.

Nitrate leaching and pasture production from different nitrogen sources on a shallow stoney soil under flood-irrigated dairy pasture

The leaching of nitrate (NO3–) in intensive agricultural production systems, e.g. dairy pastures, is a major environmental concern in many countries. In this lysimeter study we determined the amount of NO3– leached following the application of urea, dairy effluent, urine returns, and pasture renovation to a freedraining Lismore stony silt loam (Udic Haplustept loamy skeletal) growing a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture. The study showed that NO3–-N leaching losses ranged from 112 to 162 kg N/ha per year, depending on the amount and forms of N applied and pasture conditions. Nitrate leaching under the urine patches was the main contributor to the N leaching loss in a grazed paddock. Nitrate leaching losses were lower for urine applied in the spring (29% of N applied) than for urine applied in the autumn (38–58%). The application of urea or dairy effluent only contributed a small proportion to the total NO3– leaching loss in a grazed paddock. Pasture renovation by direct-drilling may also have caused an increase in NO3– leaching (c. 31 kg N/ha) in the first year. Modelled annual average NO3–-N concentrations in the mixed recharge water in the acquifer were significantly lower than those measured under the rooting zone due to dilution effects by recharge water from other sources (3.9 v. 13–27 mg N/L). Herbage nitrogen offtake and dry matter yield were higher in the urine treatments than in the non-urine treatments. groundwater, denitrification, mineralisation, grazing, forage.

北海道で実施された草地転換の成否に及ぼす雑草問題

北海道で実施された草地転換の成否に及ぼす雑草問題

Influence of panicle fragment size on ant seed-harvesting and seedling recruitment in Phalaris aquatica

Successful seedling recruitment events in sparse stands of the grass Phalaris aquatica (phalaris) are rare. A major contributing factor to this situation is the seed-harvesting activity of ants. In recently developed cultivars of phalaris, the seed is retained within the glumes of the floret and is shed in a seed-retaining panicle fragment. We tested the hypothesis that seed contained in panicle fragments was less likely to be harvested by ants than naked seed and that this would be reflected in increased seedling recruitment. Observations of ant seed-harvesting activity and records of seedling recruitment following dispersal of seed and panicle fragments onto field plots were made at Canberra, Australian Capital Territory, and Tamworth, New South Wales, over 2 years. In the second year, the effects of 2 pasture renovation treatments (sheep-grazing and shallow-discing) on seedling recruitment from seed and panicle fragments were examined. Averaged over the 2 localities, 4% of large-sized (>10�florets), 13% of medium-sized (5-10 florets) and 27% of the small-sized (2 or 3 florets) panicle fragments were harvested in a 24 h period by ants (mainly Pheidole spp.), compared with 83% of the naked phalaris seed. The effects of panicle fragment size on recruitment were variable depending on site in the first year and the interaction of site and renovation treatments in the second year, but contrary to expectation, recruitment often was not higher in panicle fragment treatments than in seeded treatments. Seedling recruitment at Canberra (a hardsetting sandy loam) was lower (22 plants/m2 from naked seed and 15 plants/m2 from seed in panicle fragments) because of the competition from existing vegetation and germination of subterranean clover from the seedbank, than at Tamworth (a self-mulching red chromosol; 179 plants/m2 from naked seed and 118 plants/m2 from seed in panicle fragments), where seedling recruitment was also significantly increased by the sheep-grazing renovation treatment. At Tamworth, a larger seedbank was recovered from plots of oversown panicle fragments compared with plots oversown with naked phalaris seed. This suggested that protection of seeds in panicle fragments over the summer months on the Tablelands of New South Wales would increase the time over which phalaris seeds are available for recruitment. Further work is needed to test seedling recruitment in panicle shattering v. non-shattering phalaris populations and to define the conditions under which the seedbank contained in the panicle fragments can be exploited to improve stand persistence.

Physical sod suppression as an alternative to herbicide use in pasture renovation with clovers

Using herbicides for sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate legume:grass ratios. Physical sod suppression methods could alleviate some of the problems associated with suppression via herbicide. A study was conducted in Québec, Canada, to investigate, as an alternative to herbicide, sod suppression by sheep grazing or mowing before and after spring no-till seeding of red clover (Trifolium pratense L.) or white clover (T. repens L.). Sod-suppression treatments included six physical suppression methods: mowing or sheep grazing, to 5 or 10 cm, at seeding and when the grass sward reached 30 cm during the first 2 mo of clover establishment, or similarly managed mowing or sheep grazing to 5 cm with an additional defoliation the previous fall. Additional treatments included suppression by herbicide (glyphosate [N-(Phosphonomethyl) glycine] at 2.6 kg a.i. ha–1) and two controls: sod-seeding with no sod suppression and no seeding. Among the physical suppression treatments, grazing and mowing to 5 cm resulted in highest clover densities, similar to those achieved via herbicide suppression. Red and white clover had similar plant densities. Yield components and total forage yields varied with sites. Clover yields tended to be higher with herbicide than under physical suppression treatments. However, increasing the severity of physical suppression increased clover yields. Weed encroachment was observed only with herbicide sod suppression. Unlike suppression with herbicide, physical suppression did not decrease total forage yields in the renovation and post-renovation years when compared with controls. Forage quality was increased in the renovation year by both physical suppression methods and herbicide when compared with unrenovated controls; but the increase was greater with herbicide suppression. Only the most severe of the physical suppression methods sustained increased forage quality in the year after renovation. Timely mowing or grazing as methods for suppression of grass sod during renovation with legumes appear to have potential, but cannot yet be recommended as alternatives to herbicide. Key words: Clover, forage, grazing, pasture renovation, sod-seeding

The yield, quality and irrigation response of summer forage crops suitable for a dairy pasture renovation program in north-western Tasmania

The yield and quality of perennial ryegrass, short-rotation ryegrass–perennial ryegrass mix, oats, millet, maize, rape, kale, pasja and turnips were determined over a 13-week summer period in 1995–96 and 1996–97. The experiment was conducted on the Elliott Research Station in north-western Tasmania (145˚E, 41˚S) and consisted of 2 irrigated and 2 dryland main plots. Within each main plot was a randomised complete block design with 9 forage crop subplots. Where forage is required through the summer, there is little advantage in establishing millet or oats over a spring-sown ryegrass pasture, mainly as the former still require replacement with permanent pasture in the autumn. However, if additional forage is required from late January then turnips are clearly superior to the other forages evaluated in all respects, apart from a low bulb crude protein (CP) content. Turnips responded significantly to irrigation, producing between 15 and 22 kg DM/ha.mm irrigation applied, with yields ranging between 7.9 and 10.6 t DM/ha dryland and between 13.5 and 14.4 t DM/ha under irrigation. The metabolisable energy (ME) and CP contents of turnips were 12.5 MJ/kg DM and 12.4% in the shoots and 13.4 MJ/kg DM and 7.0% in the bulbs, respectively. In comparison, the other fodder crops tested yielded between 4 and 6 t DM/ha under dryland conditions and between 5 and 7 t DM/ha under irrigated conditions. Turnips were most economic, costing on average A$120/t DM irrigated and $160/t DM dryland, while spring renovation to perennial ryegrass cost $385/t DM irrigated and $344/t DM dryland; clearly more expensive than purchased feeds for this period. These findings confirm the choice of many farmers that, of the species examined, turnips are the most suitable as a summer fodder crop, both irrigated or dryland, and integrate well with a pasture renovation rotation.

Achievements in Management and Utilization of Southern Grasslands

Grasslands in the humid southern USA are utilized primarily for grazing on improved pastures, most of which were developed since the 1930s and 1940s. Virtually all of these grasslands were developed from species introduced from other areas of the world. Major achievements in successful developing these grasslands, often on eroded cropland, were: (a) introduction of Kentucky 31 tall fescue (Festuca arundinacea Schreb.); (b) introduction of Pensacola bahiagrass (Paspalum notatum Flugge); (c) breeding of Coastal bermudagrass [Cynodon dactylon (L.) Pers.]; (d) fertilizer and lime use along with availability of low-cost N; (e) no-till planting of winter annual grasses; (f) pasture renovation with legumes; (g) herbicides for weed control; (h) recycling of agricultural wastes in forage production; (i) development of round hay baler; (j) controlled grazing; (k) discovery of the tall fescue fungal endophyte and its effect on livestock and the grass plant; (1) development of grazing-tolerant alfalfa; (m) improved cool season annual grasses and legumes for winter grazing; and (n) near infrared reflectance spectroscopy for rapid and low-cost forage analysis. Future areas of emphasis in improvement of these grasslands may include: (a) greater use of grazing-tolerant grasses and legumes; (b) stress-tolerant tall fescue with friendly non-toxic endophytes; (c) feed antidotes to the toxins of endophyte-infected tall fescue; (d) use of herbicide-and pest-resistant biotechnology genes in forage plants; (e) use of gypsum to alleviate subsoil acidity and improve rooting depth of aluminum-sensitive forage cultivars; (f) greater use of computers in information access and decision making by livestock producers; (g) greater use of forages for wildlife food; (h) breeding of pasture plants with greater winter productivity; (i) development of a perennial grass biomass energy industry for electrical generation and liquid fuel production. DOI:10.2458/azu_jrm_v53i1_hoveland

Achievements in management and utilization of southern grasslands

Grasslands in the humid southern USA are utilized primarily for grazing on improved pastures, most of which were developed since the 1930s and 1940s. Virtually all of these grasslands were developed from species introduced from other areas of the world. Major achievements in successful developing these grasslands, often on eroded cropland, were: (a) introduction of Kentucky 31 tall fescue (Festuca arundinacea Schreb.); (b) introduction of Pensacola bahiagrass (Paspalum notatum Flugge); (c) breeding of Coastal bermudagrass [Cynodon dactylon (L.) Pers.]; (d) fertilizer and lime use along with availability of low-cost N; (e) no-till planting of winter annual grasses; (f) pasture renovation with legumes; (g) herbicides for weed control; (h) recycling of agricultural wastes in forage production; (i) development of round hay baler; (j) controlled grazing; (k) discovery of the tall fescue fungal endophyte and its effect on livestock and the grass plant; (1) development of grazing-tolerant alfalfa; (m) improved cool season annual grasses and legumes for winter grazing; and (n) near infrared reflectance spectroscopy for rapid and low-cost forage analysis. Future areas of emphasis in improvement of these grasslands may include: (a) greater use of grazing-tolerant grasses and legumes; (b) stress-tolerant tall fescue with "friendly" non-toxic endophytes; (c) feed antidotes to the toxins of endophyte-infected tall fescue; (d) use of herbicide-and pest-resistant biotechnology genes in forage plants; (e) use of gypsum to alleviate subsoil acidity and improve rooting depth of aluminum-sensitive forage cultivars; (f) greater use of computers in information access and decision making by livestock producers; (g) greater use of forages for wildlife food; (h) breeding of pasture plants with greater winter productivity; (i) development of a perennial grass biomass energy industry for electrical generation and liquid fuel production.

Pasture Renovation and Grazing Management Impacts on Cool-Season Grass Pastures

Legumes have been shown to increase production in cool-season grass pastures. However, they are included in relatively few acres of pasture. A split plot experiment with six replications was conducted to evaluate the impact of pasture renovation and grazing management on forage production and species composition of cool-season grass pastures. Grazing management main plots were grazed to leave low (2-4 in.), medium (4-6 in.), or high (6-8 in.) residue levels. Main plots were intensively grazed (50 000-70 000 lb of cows per acre) five or six times per grazing season by lactating Holstein cows. Subplot pasture renovation treatments were (i) an untreated check, or sprayed with glyphosate and interseeded with (ii) alfalfa (Medicago sativa L.), (iii) red clover (Trifolium pratense L.) and birdsfoot trefoil (Lotus corniculatus L.), or (iv) graziers mix (a mixture of legumes and grasses). Areas that were grazed to leave low residue level produced less forage mass (4.7 ton/acre) than areas grazed to medium (5.4 ton/acre) or high (5.5 ton/acre) residue levels. When averaged across years and grazing management treatments, renovated areas produced 1.8 ton/acre (46%) more forage than the control. Of interseeded species, alfalfa, red clover, and orchardgrass persisted through the study (more than 25% of the dry matter in at least one of the pasture renovation treatments). By June 1998, thistle (Carduus and Cirsium spp.) was present in all treatments. Fewer thistle was present in areas that were grazed to leave low residue (10 sq yd) than high residue (18 sq yd) and in renovated areas (9 sq yd) than the control (22 sq yd). The additional forage produced as a result of pasture renovation cost from $8.07/ton to $12.81/ton. Tbis study indicates that pasture renovation can be a valuable tool for increasing forage production in cool-season grass pastures.

Experiences with vaccination and epidemiological investigations on an anthrax outbreak in Australia in 1997.

Between January and February 1997, there was a severe outbreak of anthrax on 83 properties in north-central Victoria, Australia. Vaccination was used as a major tool to control the outbreak by establishing a vaccination buffer zone 30 km by 20 km. In all, 78, 649 cattle in 457 herds were vaccinated in a three week program. In the face of the outbreak, there was a delay before vaccination was able to stop deaths. In the 10 days following vaccination 144 cases of confirmed anthrax occurred and 38 cases occurred more than 10 days after vaccination. When all cattle on at-risk properties were revaccinated in October and early November 1997, there were only two confirmed cases of anthrax in vaccinated seven and nine month old calves in the following anthrax season. Investigations into the epidemiology of the outbreak were unable to establish a single major association for the spread of the disease by flies, biting insects, carrion scavengers, wind, manufactured feed, milk factory tanker routes, veterinary visits, animal treatments, movements of personnel between farms or burning of carcases. The weather conditions in the outbreak area were part of a long dry spell with periods of high daily and night temperatures, continuing high humidity over the period and higher than normal soil temperatures. It is possible that extensive earth works in the district involving irrigated pasture renovation and water channel and drainage renovation could have disturbed old anthrax graves. It is postulated that these works released spores that were dispersed in the preceding wet winter across poorly drained areas that formed the axis for the outbreak. The earth moving renovations establishing irrigation in the area were conducted in the late 1890s, and before the occurrence of anthrax outbreaks were recorded. The axis of the outbreak was the major stock route for cattle and sheep moving from southern Victoria to northern Victoria and southern New South Wales, and undoubtedly there would have been extensive anthrax outbreaks before vaccine became available in the 1890s. In respect of other outbreaks, the events in Victoria most resembled outbreaks of anthrax recorded in the United States of America in the 1950s, 1960s and 1970s.

Effect of pasture renovation on the size and composition of the germinable fraction of the seed pool beneath bent grass (Agrostis castellana) pastures in southern Victoria

This paper investigated the potential for propagation of grass weeds from seed by measuring changes in the size and composition of the germinable fraction of the seed pool beneath 4 bent grass (Agrostis castellana) pastures in southern Victoria during renovation. Soil samples, for the estimation of the seed pool by seedling emergence in the glasshouse, were taken from a control and a renovated pasture on 3 occasions during renovation at each of the 4 sites. The depth distribution of seeds in the top 0–100 mm was assessed by dividing collected soil samples into depths of 0–30 mm and 30–100 mm. The total germinable seed pool (0–30 mm) ranged from 17 620 to 83 540 seedlings/m2, as affected by the time of sampling. There were seedlings from 14 grass genera (12% contribution to the total seed pool), Juncus (60%), 4 leguminous genera (17%), and 22 other dicotyledonous genera (12%). The percentage change in the number of germinated seeds of grasses and dicotyledons between the first and second sampling was negative ( –7·3% to –31·4%) beneath renovated pasture, as opposed to a positive change (29·0–174·4%) beneath undisturbed pasture; this was attributed to the prevention of seeding due to the cultivation of the pasture associated with renovation. The percentage change in the number of germinated seeds of grasses and dicotyledons did not differ significantly between renovated and undisturbed pasture between the second and third sampling, which suggested that no more seed germinated in response to renovation. Re-distribution of germinable seed to lower depths (30–100 mm) with renovation was apparent for grasses and other dicotyledons, and would depress successful emergence of these seedlings. Renovation prevented re-seeding of weeds and buried surface seed, but did not significantly stimulate additional seed to germinate the following autumn after renovation. Weed seeds were still present in the soil seed pool after renovation, which indicated that these species could potentially germinate and establish in new pastures.

Evaluation of a novel adjuvant for use with glyphosate on perennial ryegrass

Glyphosate is used extensively for pasture renovation, with an organosilicone surfactant when treating ryegrass (Lolium perenne). The effect of a novel, non-silicone surfactant, Browndown Adjuvant, on the performance of glyphosate on perennial ryegrass was determined and compared to the organosilicone surfactant, Pulse. Spray retention, uptake and translocation of glyphosate were quantified. Comparative efficacy of spray treatments was determined in pot and field trials. Browndown increased the speed and quantity of glyphosate uptake, with no adverse effects on herbicide translocation. At the recommended rate (0.25% v/v), Browndown reduced spray retention compared to Pulse (0.1% v/v), but provided faster brown-out of foliage and equivalent herbicide efficacy on glyphosate-tolerant ryegrass in spring.

Comparison of Mehlich 3‐ and bray 1‐extractable phosphorus levels in a Starr clay loam amended with poultry litter

Two soil tests commonly used to characterize the availability of soil phosphorus (P) are Bray P1 (B1) and Mehlich 3 (M3) extradants. The objective of this investigation was to compare M3‐ and B1‐extractable P levels in a Starr clay loam (fine‐loamy mixed thermic Fluventic Dystrochrepts) amended with relatively low to high surface applications of poultry litter (PL). The following eight treatments were applied to the soil for pasture renovation in 1991 and 1992: 1) a control, 2) P application as monocalcium phosphate [Ca(H2PO4)2‐H2O], 3) P application as Ca(H2PO4)2‐H2O and nitrogen (N) application as ammonium nitrate (NH4NO3) and urea, and 4) five levels of poultry litter (PL) based on N content. The five P levels as PL were 56.6, 113.2, 169.8, 226.4, and 283.0 kg ha‐1 in 1991, and 49.2, 98.5, 147.7, 196.9, and 246.1 kg ha‐1 in 1992, respectively. Soil samples were obtained from the 0‐ to 5‐cm layer in the spring of 1992 and 1993 for extractable P determination. Levels of P extracted from all treatments by the M3 and B1 extractants were linearly correlated both years (r2=0.96 in 1991 and r2=0.99 in 1992). However, M3 extracted more P from the PL treatments, whereas B1 extracted more P from the control, P application, and N and P application treatments. Curvilinear relationships were obtained between P uptake and levels of either M3‐ or B1‐extractable P for the PL treatments (r2=0.713 for M3 and 0.663 for B1 in 1991 and r2=0.925 for M3 and 0.933 for B1 in 1992). These close relationships in 1992 between extractable P and uptake of P for the PL‐ treated soils indicate that both the B1 and M3 extractants could be used to evaluate excess P in PL‐amended soils.

Pasture renovation practices of farmers in the neotropical savannahs

Degradation of sown pastures in the neotropics is a well known but poorly documented phenomenon. The paper reports the results of a survey conducted in the eastern savannahs of Colombia to quantify farmers' reactions to perceived pasture degradation. The survey was conducted in an area of 23 644 km2. The sample consisted of 46 farms, which had 19 012 ha of Brachiaria decumbens pastures distributed in 374 paddocks. Of these paddocks, 196 had been sown with vegetative seed, and 281 had received modest rates of P fertilization at planting. Pastures sown on flat lands had younger modal ages (three years) and were renovated more frequently than those sown on hilly or dissected savannahs (10 years). These differences were probably a result of variations in infrastructure and relative stage of development of the two topographies, but slight differences in inherent soil fertility may also have played a role. We found no relationship between grazing management and frequency of pasture renovation. Implications for future research on pasture reclamation are discussed. © 1998 John Wiley & Sons, Ltd.

Use of goats as biological agents for the renovation of pastures in the Appalachian region of the United States

Much of hill-land pasture in the Appalachian region of the United States is dominated by herbaceous weeds and brush. Low cost, low input and environmentally acceptable reclama- tion procedures are needed to maintain the productivity of these pastures. This experiment evaluated the effectiveness of using goats ( Capra hircus hircus) alone (30 mature, brush does/ha) or cattle (Bos taurus) with goats (17 mature, brush does/ha + two to three steers/ha - 225 kg average live weight) to reclaim a pasture from an abandoned, overgrown 5.9 ha orchard left untouched for 15 years. Over four grazing seasons, managed defoliation resulted in a substan- tial increase in herbaceous vegetative cover in plots grazed by goats alone (65 to 86%) and by goats with cattle (65 to 80%) while vegetative cover decreased from 70 to 22% in the control plot. Similarly, the cover by grass species increased in the grazed plots (goats: 16 to 63%; goats + cattle: 13 to 54%) while averaging 10% in the control plot. Multiflora rose ( Rosa multiflora Thumb.) bushes were practically eliminated after four grazing seasons as quantified by an average reduction in height from 2.1 m to 0.6 m, and by the number of dead canes (stems) in both the goat (100%) or goat + cattle (92%) treatments. Results indicated that the foraging habits of goats resulted in the elimination of multiflora rose bushes and in a significant increase in desirable forage species.

Length of rhizome and depth of burial affects the regeneration of bent grass (Agrostis castellana Boiss. et Reuter)

Renovation of pastures dominated by bent grass (Agrostis castellana), by killing the vegetation with herbicides followed by cultivation and re-sowing, according to current recommendations, can kill up to 95% of the bent grass. To improve the success of killing bent grass and reducing the likelihood of regeneration from rhizomes after renovation, the behaviour of rhizomes after fragmentation was studied in pots. Rhizomes were cut into different lengths (15, 40, and 100 mm) to contain 1, 3, and 8 nodes per section and planted at depths of 25, 50, 75, 100, and 200 mm in cultivated soil, with or without competition from establishing seedlings of perennial ryegrass and white clover. The proportion of bent grass shoots developing from buried rhizomes was reduced to <10% when rhizomes were broken into sections containing only a single node and buried at or below 75 mm. Even after 3 months burial, an average of 0, 0·2, and 0·4 nodes in 1-node, 3-node, and 8-node sections, respectively, were still viable after fragmentation and could potentially develop, should conditions change, ensuring regeneration. The presence of newly sown pasture did not affect either the development of nodes or the vigour of shoots of bent grass during the 3-month measurement period. Pasture production, however, was reduced with increasing bent grass shoot production such that 8-node sections buried at 25 and 50 mm produced up to 3 times more dry matter per pot than other pasture components, giving bent grass a competitive advantage.

The impact of commodity prices and seasonal conditions on the adoption of productive pasture technology during the final 18 months of the Grassland’s Productivity Program

Summary. Nineteen participants in the Grassland’s Productivity Program were surveyed in autumn 1997 to determine whether they had continued to adopt productive pasture practices during the final 18 months of the program. The objective was to determine whether changes in commodity prices in 1996, involving falls in wool and beef prices and increases in prime lamb prices, and unfavourable seasonal conditions, impacted on the continuing adoption of productive pastures by participants of the Grassland’s Productivity Program. Despite the less favourable market and seasonal conditions, the Grassland’s Productivity Program participants continued to increase their adoption of productive pastures, almost trebling the area of land under the productive pasture technology from mid 1995 to 1997. This was achieved by rationalising farm expenditure in ways to cope with the less favourable conditions. The first was to undertake more pasture manipulation instead of high-cost pasture renovation. The second was to maintain expenditure on phosphorus fertiliser but focusing the application on more productive pasture paddocks. As a result the stocking rate across the whole farm was only increased marginally (by 0.2 dse/ha) from 1995 to 1997. Nevertheless the participants predicted that they would increase their stocking rate by an average of 17% across their farms, from 10.9 to 12.7 dse/ha, by the year 2000. The continuing strong commitment to adopt productive pastures is highlighted by the future intention of over half of the Grassland’s Productivity Program participants (53%) to implement the technology over their whole farm. The remaining participants intended to have at least half their farm under productive pastures. There was no discernible difference between wool growers and prime lamb producers in achieving adoption intentions apart from the area of the farm that is sown to productive species. This indicates that a short-term change in enterprise profitability is not necessarily a major determinant of adoption of more intensive grazing practices by participants in this type of group-facilitated program.

Pasture response to fertiliser inputs under dairy grazing

Conversion of sheep and beef farms into dairy units has resulted in research on appropriate fertiliser rates and pasture species to achieve maximum productivity in minimum time. An onfarm trial involving five different mixtures of pasture species (based on fescue, prairie grass, an improved mixture, farmer mixture or original pasture), three rates of nitrogen as urea (0, 50 or 100 kg/ha of N applied half in March and half in August) and four rates of superphosphate (0, 250, 500 or 1000 kg/ha applied annually in March) was established in Canterbury on a Waimakariri sandy silt loam with border-dyke irrigation and an Olsen P of 5 pg/ml. The trial was grazed by dairy cattle as part of the general rotation; plots were not fenced individually. Pasture growth rates were measured pre- and post-grazing using a calibrated pasture probe. Botanical dissections ,were made seasonally and soil samples were taken annually. Pasture dry matter production was greatest from the prairie grass, "improved" mixture and the original pasture, involved often contain a high proportion of annual and perennial, low-producing species. Grass species, nutrient status and management have been identified as the limiting factors in dairy conversion (Kleyngeld & Kleyngeld 1992). Ryegrass and white clover are still the most common species used in pasture renovation (Maloney 1991). However, short-rotation ryegrasses are favoured by some dairy farmers, and in new dairying areas such as Canterbury, optimally producing species may differ from those used in the more traditional North Island dairying areas (Charlton & Belgrave 1992). Nitrogen (N) is recognised as a strategic tool for increasing grass production in winter-spring in summerdry areas (Thomsoneta/. 1991) as well as for extending the milking season for factory supply herds in Southland (Kleyngeld & Kleyngeld 1992). High rates of nitrogen (217 and 324 kg/ha per year) have been found to increase annual net herbage accumulation by 23 and 27%, respectively, in the Waikato, but clover content declined significantly (Harrisetaf. 1994). Maintenance fertiliser requirements have been related to desired stocking rate in the past, based on animal production system and soil type (Computerised Fertiliser Advisory System (CFAS), reaching 13 000,ll 000 and 16 000 kg/ha in years Cornforth & Sinclair 1984). Recently responses in milk one, two and three, respectively; production from yield have been recorded to very high rates (100 kg/ha- IT the fescue increased with time; the 'farmer' mix performed poorly. Nitrogen at 50 kg/ha was generally sufficient to produce maximum yield increases. Increasing superphosphate increased production; this effect decreased with time. Change in Olsen P reflected superphosphate inputs and after three years of differential superphosphate application the Olsen P status was 8, 14, 27 or 42 (corresponding to 0, 250, 500 or 1000 kg/ha superphosphate). Keywords: Bromus wildenowii, dairy conversion, dry matter production Festuca arundinacea, Loliumperenne, nitrogen, Olsen P, superphosphate

Studies on the control of water-dropwort (Oenanthe pimpinelloides) in South Australia

Water-dropwort (Oenanthe pimpinelloides L.), a tuberous perennial herb, is currently known in South Australia from only a single locality in the Mount Lofty Ranges. There is little information on water-dropwort control, and 2 experiments were conducted to assess the effects of sowing pasture, with or without presowing herbicides, on the control of this weed. Phalaris (Phalaris aquatica L.) and perennial clovers were successfully introduced into infested pastures by direct drilling in autumn. Water-dropwort regenerated from seed more densely in unsown plots than plots of established perennial pasture, suggesting that upgrading pastures may be a strategy to reduce the rate of spread by seed of this weed. A range of herbicide treatments applied to waterdropwort at the stem elongation stage in spring before autumn sowing of pastures provided effective shortterm control. The best short-term control was provided by glyphosate at 1440 g a.i./ha; metsulfuron methyl at 6, 12, and 36 g a.i./ha; and metsulfuron methyl at 12 g a.i./ha tank-mixed with glyphosate or 2,4-D amine at 720 or 1000 g a.i./ha, respectively. These treatments, and chlorsulfuron at 21 g a.i./ha, also significantly (P<0.05) reduced water-dropwort abundance (relative to untreated areas) for up to 18 months after sowing and initially improved the density of sown pasture species, but these improvements were not evident 14 months after resowing. Although prior season herbicide treatments controlled water-dropwort in newly sown pastures, 2 separate applications of herbicides, in May and October, gave no better control of water-dropwort than a single herbicide application in spring. Water-dropwort infestations do not appear to prevent successful direct drilling of phalaris and perennial clovers. Although pasture renovation did not provide long-term suppression of water-dropwort, the maintenance of vigorous pastures may reduce the rate of population growth from seedlings of this weed. Recropping restrictions may limit the role of chlorsulfuron for water-dropwort control in pasture renovation situations.