New Zealand average surface temperatures have increased by 0.7 °C since 1871. In the last quarter of the 20th century, more prevalent west to southwest flows occurred, accompanying a higher incidence of El Niño events. This resulted in annual rainfall decreasing in eastern areas of the North Island. As well as the global warming signal, interannual to decadal climate variability is a strong feature of east coast dryland climates. The El Niño-Southern Oscillation, (ENSO), through El Niño/ and La Niña episodes, drives climate variability seasonally. The recently described Interdecadal Pacific Oscillation (IPO) shifts climate every one to three decades and changes precipitation averages in these areas. These features of the climate system leave east coast dryland farming open to considerable climate variability. Records of potential soil moisture deficit (PSMD) around Napier and Ashburton show that significant PSMD developed in these regions by 1 December, in 50 to 85% of years with severe deficits in 20 to 55% of years. These deficits build as summer progresses. El Niño events intensify, whilst La Niña episodes normally ameliorate these conditions on seasonal time scales. The IPO climate shifts significantly change the dryness of the soil of these areas, with the transition from negative to positive phases increasing PSMD by 35 to 50 mm. Climate change over the next few decades will be driven by the underlying trend of global warming. For New Zealand, this will be a warming of about 0.2 °C per decade. The latest scenarios and climate model results indicate that westerly circulation is likely to strengthen over New Zealand, with a drying of east coast climate in the order of 10% by 2080. These will cause an increase in PSMD in the order of 20 to 30%. ENSO and IPO variability will be a continuing feature of New Zealand climate in coming decades. East coast dryland farms experience substantial climate variability. As climate warming continues in the decades of the 21st century, these areas will become increasingly stressed as potential evapotranspiration (PET) rates increase, particularly when the IPO next changes phase and during El Niño events. Climate forecasting is an exciting new technology that will give farmers early warning and increase preparedness for dry seasons ahead, allowing them to make key strategic decisions. A mixture of new and traditional technologies will also assist, such as intercropping and use of seasonal climate forecasting. Despite this, dryland farming systems are likely to become increasingly limited owing to low rainfall and high potential evapotranspiration rates.
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(112 KB)Basic forage legume morphology and development are described with reference to white, red, subterranean and caucasian clovers, lotus and lucerne, with emphasis on characteristics that relate to persistence in dryland environments, including crown formation, contractile tap roots and rhizomes. The range of structural variation is considered in detail by comparing development of plants with two extreme growth forms, i.e. white clover, which has branching horizontal growth and nodal roots, and lucerne and caucasian clover, which have vertical growth, permanent crowns and deep tap roots. Emphasis is placed on carbon allocation strategies during establishment and the inevitable compromise between shoot and root growth, which results in slow seedling establishment of the tap-rooted species, and on the effect of nodal roots as competitive sinks for carbon, which affect tap root development and longevity in white clover. The influence of storage tissues and the number of viable buds on regrowth following drought, overwintering and grazing is discussed together with the impact of variations in flowering shoot formation. All existing growth forms are seen as having evolved as compromise solutions to the problem of combining maximum growth rates with optimum drought tolerance. The possibility, or otherwise, of being able to combine rapid establishment, involving maximised leaf production, with development of a persistent deeply penetrating tap root is considered in light of present understanding. Key words: carbon allocation, dryland environment, forage legume, morphology, nodal roots, persistence, root:shoot ratio, seedling establishment, tap roots
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(247 KB)The different perspectives or concepts involved in developing legumes for dryland pastoral systems is commented on in relation to: N-fixation versus animal feed; root nodule bacteria requirements; large introduced legume flora compared with indigenous; species niche in relation to environmental gradients of moisture, temperature, fertility, and grazing; species adaptation along the decreasing fertility gradient from fine-root nutrient scavenging grasses, N-fixers, mycorrhiza, and proteoid roots; interaction of N- fixation with soil organic matter; establishment; determinants of pastures legume composition; and the possible role of allelopathy. Key words: dryland, environmental gradients, legumes, N-fixation, pasture composition
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(187 KB)The dryland regions of New Zealand suffer from summer moisture deficits in the majority of years. These dryland regions have been developed along the same basis as other farming regions, with increasing fertiliser usage leading to more subdivision and higher stocking rates. Given the exposure to droughts, the production per head of these regions has been extremely variable. Historically, dryland farming systems have been based around breeding ewe systems with all lambs finished if the season allowed. Since the removal of all Government support during adverse events, in the early 1990s, farm systems have become considerably more diverse. Irrigation areas have doubled between 1985 and 1999 to approximately 500 000 hectares. Both sub clover and lucerne have been used extensively in dryland areas, but the main legume is still white clover. Farmers recognise the significant limitations in the ability of white clovers to cope with summer droughts, but have not been able to efficiently utilise other legumes, which require unique management to perform. There are a number of reasons for this. Looking forward, the five key roles that legumes have in dryland farming systems are, to persist within a general purpose pasture, to produce nitrogen, to improve summer feed quality, to improve year round quality feed through specialist crops and pastures and to provide specialist composite feeds (i.e. condensed tannins). With the increased diversity in farming systems, growers require a more diverse range of legumes from perennial species to annuals that will fit a short-term high feed quality niche.
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(120 KB)There are limitations to the production and persistence of white clover in drought prone regions. We report on the population dynamics of white clover during the summer/autumn drought of 2000. Seventeen paddocks were selected from Marlborough, Mid Canterbury, South Canterbury and North Otago on the east coast of the South Island, and Wairarapa in the North Island. The pastures were sown in 1998/99 and are comprised of ryegrass, tall fescue, cocksfoot or combinations of these as the grass base, with white clover included in the mix. White clover populations were monitored pre- and post-drought using tiller cores. The percentage of each region’s long-term mean rainfall received during the 6-month “drought period” had the largest influence on the presence of white clover in these pastures. Marlborough, with only 73 mm of rainfall during November 2000-April 2001 (23% of its expected rainfall) suffered a 95% reduction in white clover. Mid Canterbury, South Canterbury and North Otago, at 53-61% of expected rainfall had a 40-78% loss. In contrast, Wairarapa, with 303 mm of rainfall, lost only 8%. The rate of recovery was closely related to the magnitude of white clover loss during drought. In regions where large losses occurred, further sampling after 18 months showed little increase in white clover presence. Key words: drought, persistence, populations, seedling, Trifolium repens, white clover
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(97 KB)
Australian farming systems have traditionally relied on annual legumes such as subterranean clover (Trifolium subterraneum) and annual medics (Medicago spp.) in either short-term pastures in rotation with crops or permanent pastures to provide low cost biologically fixed N and a high quality forage for livestock. The role of legumes in farming systems is now being reassessed because of the recognition that their extensive use is associated with widespread soil acidification, loss of species diversity in native pastures and increasing dryland salinity. In the future, annual legumes are more likely to be sown in mixtures with deep-rooted perennial pasture species, both in permanent pastures and in rotation with crops, to improve hydrological balance in the landscape. As a result, there is a change of direction in annual legume selection and breeding programs within Australia with a greater focus on the ability of legumes to coexist with perennial species, as well as on characteristics such as an extended growing season and deeper rooting habit to exploit subsoil water. There is also a trend towards increasing the diversity of annual legume species sown in pasture mixes to better exploit paddock variation and variable seasonal conditions.
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(207 KB)Legume productivity in dryland pastures is often less than 10% of the total annual growth and dominated by annual species. White clover content of these pastures is often less than 5% because the period of potentially most active growth coincides with that of low soil moisture levels. Therefore variations in summer rainfall have a dominant effect on the white clover content of the pasture in the following spring. Predictive relationships for white clover content are presented. Attempts to introduce alternative legumes into dryland hill pastures have generally been unsuccessful because of the harsh climate during late spring–summer and competition from resident species. It is unlikely that further research will change this situation. This paper compares improved legume productivity from dryland pastures with the use of N fertiliser as options to increase winter and spring pasture growth for increased economic gain. To optimise productivity and summer persistence of resident legumes, grazing management, especially in spring, must aim to avoid accumulation of surplus grass that will shade associated legumes. During winter and early spring, when soil moisture is adequate, pasture growth in dryland hill pastures is limited by inadequate soil nitrogen (N), due to low legume content and N fixation, even where soil phosphorus (P) is at moderate to high levels. Consequently, pasture responds well to applied N fertiliser. At Waipawa in Hawke’s Bay, the magnitude of response to N fertiliser was inversely related to the legume content of the pasture and so was greatest (e.g. up to 47 kg DM/kg N) on steep north aspects with little clover, and much less (8-17 kg DM/kg N) on easy slopes. In winter, N fertiliser offers reliable and significant increases in pasture growth. To optimise economic returns from the additional pasture dry matter, winter stocking rates could be increased. However, a simulation study showed that the maximum economic benefit would be obtained by maintaining ewe numbers and increasing fecundity to produce more lambs. Key words: hill country, legumes, nitrogen fertiliser, pastoral dryland
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(191 KB)In North Island hill country, a number of environmental and management factors interact to limit the performance of herbaceous legumes in pasture swards. Summer-autumn moisture stress appears to be the dominant influence, particularly because of its irregularity. Legume performance is a function of establishment success, persistence and productivity. Long-term persistence of genotypes in particular should be a primary focus in the development of new germplasm. Secondary to this is the importance of improving herbage productivity and quality. We present evidence for this view from field studies of white and subterranean clover, as well as preliminary examinations of other legume species. Key characteristics contributing to enhanced persistence are prostrate growth forms with high numbers of growing points below the grazing horizon; nodal rooting and root tolerance of low soil pH; flowering patterns that are timed to avoid the dry period, yet sufficiently flexible to cope with the unpredictability of that period; and seed mechanisms that protect against “false strike” following shortlived summer rains. Key words: clover, hill country, legumes, persistence, summer-dry
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(128 KB)This review covers the history of subterranean clover (Trifolium subterraneum) and its present occurrence in New Zealand; a review of research and conclusions to be drawn from this; and examines past and future research directions. Subterranean clover has been important in terms of area of use in New Zealand since the late 1930’s. Today it makes a significant contribution to pasture production on steep, north-facing North Island hill country where effective rainfall is low, and in other areas where soil moisture drops below wilting point for between 2 weeks and 5 months of the year. Research has identified the superiority of cultivars possessing a compact, ground-hugging habit of growth, and flowering late, in late October – early November, for use in North Island hill country. In drier areas, more research is needed to identify superior cultivars, although there is evidence that lines in the mid-season or early mid-season flowering groups may be appropriate. A major problem for the use of subterranean clovers in New Zealand is the slow breakdown of hardseededness. About 7 M ha of land in New Zealand is mapped as being subject to slight to severe moisture deficit (an area which could with advantage support subterranean clover), but further research is needed to identify appropriate cultivars for 4.8 M ha or more of this area. Key words: history, New Zealand, research, Trifolium subterraneum
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(196 KB)
Red and white clovers are best adapted to areas with good soil fertility and adequate soil moisture (750 mm annual rainfall), particularly over summer (150 mm), and are therefore restricted to small areas such as the more fertile valley floors and lower shady slopes in dryland environments. To extend their range and aid survival in dry environments, grazing management and cultivar selection are critical. Continual grazing (set stocking) during spring leads to a dense grass pasture, providing protection from desiccation for white clover stolons in the following summer. White clover cultivars have an inbuilt plasticity that allows morphological adaptation to changes in grazing management. For instance, set stocking in combination with a small-leafed cultivar results in a reduction of plant size but an increase in the stolon population, leading to better plant survival through drought periods. Where drought leads to stolon death, reseeding becomes a viable mechanism for clover persistence, and grazing management has a major influence on survival of new seedlings. For red clover, there is evidence that ‘creeping’ types survive better than ‘crown’ types in hill country, but the scope for extending red clover into drier areas is more limited. Key words: cultivars, drought, dryland, grazing management, morphological adaptation, persistence, red clover, reseeding, summer rainfall, Trifolium repens, T. pratense, white clover
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(123 KB)A 5-year experiment was conducted under dryland conditions (mean annual rainfall 660 mm) on a Wakanui silt loam at Lincoln University. The mean annual production of lucerne (20 t DM/ha) was greater than red clover and chicory (16 t DM/ha). The advantage of lucerne increased with time to 6 t DM/ ha in the final year, when the lucerne component of the sward was 94%, whereas chicory and red clover declined to 62 and 0% of their respective swards. The annual production advantage of lucerne was a result of higher growth rates in September and from December to May. The higher summer/autumn growth rates were attributed to a greater water extraction depth, giving lucerne access to more water during this time. The DM yield of all three species had a linear relationship with water use. These results are discussed in relation to the fitness of the three species for a dryland farming system, and how the performance of each would be expected to vary with differing soil type and rainfall situations. Key words: Cichorium intybus, extraction depth, Medicago sativa, Trifolium pratense, water use, water use efficiency
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(319 KB)Dry matter (DM) production of sown monocultures of Caucasian and white clovers was compared under irrigated and dryland (non-irrigated) conditions in their third year. Caucasian clover produced 11.9 t DM/ ha when irrigated and 9.4 t DM/ha under dryland conditions, and both treatments exceeded white clover by ~2.5 t DM/ha. This increase in yield reflected ~23 kg DM/ha/day higher production rates in spring and summer. During this period, production rates of irrigated treatments increased by 11 kg DM/ ha/day/oC for Caucasian compared with 8 kg DM/ha/ day/oC for white clover as mean daily air temperature increased from 8-16 oC. In late summer/autumn, production rates of Caucasian clover decreased more than white clover when air temperature dropped from 16-9 oC. Growth (photosynthesis) and development (leaf appearance) characteristics of each species were also examined. Leaf photosynthesis was ~6 ƒÊmol CO2/m2/ s higher for Caucasian than for white clover irrespective of measured air temperatures (7-28 oC) and soil moisture from 1.00-0.39 of water holding capacity (WHC, 512 mm to 1.5 m depth). Both clovers had similar ranges of optimum temperature (21-25 oC) and soil moisture (1.00-0.86 of WHC) for photosynthesis. These results could explain the observed higher production rates for Caucasian clover in spring and summer, under both irrigated and dryland conditions. Lower production rates of Caucasian clover in autumn may be attributed to a similar phyllochron (126 oCd), but higher base temperature (5 oC) than for white clover (1 oC), and hence a slower recovery to canopy closure post grazing. This study shows that Caucasian clover has potential to increase spring and summer legume production, in combination or as the sole legume species in both irrigated and dryland grass/clover pastures in lowland temperate environments of New Zealand. Key words: irrigation, photosynthesis, phyllochron, seasonal production, Trifolium ambiguum M. Bieb, T. repens
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(349 KB)Lotus corniculatus (lotus) contains condensed tannins (CT; 25–35 g/kg DM), which reduce the microbial degradation of forage protein in the rumen and increase amino acid absorption from the small intestine. In grazing experiments at Palmerston North during the 1990s, sheep grazing L. corniculatus had superior wool production, body growth and ovulation rates (OR) relative to sheep grazing lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne)/white clover (Tritolium repens) pasture. Polyethylene glycol (PEG) drenching studies showed that action of CT was responsible for a component of the increases in wool growth and OR, but not body growth, and increased milk yield in lactating ewes. The ‘Massey lotus’ programme moved in 2000 to Riverside farm in the Wairarapa, where L. corniculatus is more agronomically suited, and its integration into dryland farming systems is being studied. We aim to develop systems that increase animal productivity whilst also reducing chemical input, notably of anthelmintic drenches. In two experiments conducted over 12 weeks in spring, ewes and lambs grazing L. corniculatus without pre-lamb drenching had lower faecal egg counts (FEC) and lower dag scores than ewes and lambs grazing pasture. Also, liveweight gain (+44%), weaning weight (+26%) and wool production (+32%) were greater for lambs grazing lotus. Weaned lambs grazing L. corniculatus over 14 weeks in summer grew faster than those grazing pasture (298 cf. 201 g/day) when regularly drenched. Reduction of anthelmintic drenching reduced the growth rates of lambs grazing L. corniculatus, but at 228 g/day this was still much faster than those grazing pasture (187 g/day). Lambs grazing L. corniculatus with restricted anthelmintic grew slightly faster than regularly drenched lambs grazing pasture. In addition, ewes mated on L. corniculatus had greater ovulation rates, lambing % and weaning % (approximately 25%) than ewes mated on pasture. Lamb weaning weight was unaffected by the ewes grazing L. corniculatus during mating, but mortality rate during the period from birth to weaning was lower for lambs that were conceived when their dams were grazing lotus. Annual (dry matter) production under grazing averaged over two years (2000–2001), was 9.5 t/ha for L. corniculatus and 8.6 t/ha for pasture. The percentages of annual production that occurred in spring, summer, autumn and winter were 49, 40, 8 and 4%, respectively, for L. corniculatus and 55, 30, 9 and 6%, respectively, for pasture. L. corniculatus has potential as a specialist feed in dryland farming systems for use during mating to increase subsequent lambing percentage and to increase lamb growth while reducing anthelmintic use. The result is more lambs being drafted at an earlier age. Key words: agronomy, body growth, condensed tannins, dry matter yield, Lotus corniculatus, reproduction, sheep, withdrawing anthelmintic, wool growth
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(191 KB)
Winter active legumes are suited to the mild winter areas of New Zealand, where they provide high quality forage in late winter and early to mid-spring. Six winter active annual legumes, persian clover, balansa clover, sweet clover, hybrid serradella, subterranean clover, and Medicago truncatula, were sown in a randomised complete block design with four replicates. Their dry matter (DM) accumulation and grazing preference to young sheep were measured every 3-6 weeks from sowing on 6 April 2000 until 24 October 2000. Total ungrazed DM production ranged from 5 500 kg/ha (sweet clover) to 9 300 kg/ha (balansa clover) over this period. The seasonal pattern of growth varied significantly between species, as did hogget grazing preference, with persian, balansa, and subterranean clover most preferred. These six plant species are capable of producing large amounts of high quality dry matter, but at all grazings, preference was extreme (measured by the number of sheep preferring to graze any one of the species when given a choice of all six), which may indicate the limited usefulness of some species. Key words: accumulative yield, grazing preference, Medicago truncatula, Melilotus albus, Ornithopus sativus x compressus, seasonal growth, sheep, Trifolium balansae, Trifolium respinatum, Trifolium subterraneum, winter active legumes
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(129 KB)The low level of legumes in New Zealand hill pastoral systems is a recognized problem that is likely to affect sustainability. The relative importance of the factors that cause low legume abundance has not been sufficiently tested, especially on dry hill country. This paper reports the effects of grass suppression in two contrasting years in a summer-dry hill country site on the east coast of the North Island. Suppressing grass with haloxyfop herbicide (Gallant) in late autumn increased legume abundance by > 25% in both years, but the response patterns were strongly influenced by soil moisture status. Moist late spring and summer conditions produced 34% more legume growth in both ± herbicide treatments. Residual effects of grass suppression favoured white clover over subterranean clover growth under moist seasonal conditions. The control of grass growth in these hill swards improved legume abundance, but the overriding factor affecting legume content in the pasture was the level of soil moisture. Key words: grass suppression, haloxyfop herbicide, hill country, legume abundance, soil moisture, subterranean clover, summer-dry, white clover
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(137 KB)Many legumes have been trialled for establishment, persistence and productivity in the tussock grassland region of the South Island, New Zealand. This paper presents information on long-term persistence and growth based on a survey of surviving legume species from 45 previous plant accession trials, established over a range of sites and environments (predominantly dryland) throughout Otago and Canterbury. Sites were visited in January/February 2003 and identified plants were visually scored for several growth-related parameters. Most sites were open to stock grazing and all were affected by drought during the current growing season. Of the legume species that seed is not commercially available for in New Zealand, the most persistent and vigorous were: Lupinus polyphyllus, Trifolium medium, Coronilla varia, Dorycnium hirsutum, Melilotus alba and M. officinalis, Astragalus falcatus, T. canescens, D. pentaphyllum, and A. cicer. These plants may usefully supplement tussock grassland vegetation under environmental and management conditions including periodic drought and the moderate to light grazing experienced at most of the trial sites visited. This paper reviews growth and survival of those legumes, and provides a guide to species with potential for revegetation in dryland and semi-arid environments that warrant further research into site x management interactions and possibly commercial development. Key words: legume persistence, Otago/Canterbury, revegetation, tussock grassland
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(265 KB)A series of Trifolium ambiguum x T. repens hybrid populations has been developed at the hexaploid (four T. repens and two T. ambiguum genomes) and pentaploid (four T. repens and one T. ambiguum genome) level. When tested for effectiveness of symbiotic nitrogen fixation, the 6x and 5x hybrids nodulated with either T. repens or T. ambiguum strains of rhizobia but only formed an effective N- fixing symbiosis with a mix of T. repens rhizobia strains. When grown in the field, the 6x and 5x hybrid plants had a similar morphology to white clover in that the hybrids grew surface stolons (fewer numbers than white clover) and no underground rhizomes. The advantage of the 6x hybrid was deeper roots and a greater proportion of root, a characteristic considered important for greater drought tolerance and persistence than for white clover. The 6x hybrid indicated 55% of the seed production potential of white clover, but there was large variation between plants in all reproductive traits. The 5x hybrid showed poor levels of seed set. The growth pattern of the 6x hybrids in the field indicated lower herbage yield in the first year but improved performance compared with white clover into the second year. At this early stage, the hybrid breeding populations consist of unselected and novel hybrid combinations. Variations in growth and reproductive characteristics exist between hybrid plants, thus providing scope for improvement through selection and breeding. Key words: caucasian clover, interspecific hybrid, morphology, nitrogen fixation, seed production, white clover
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(132 KB)
Seed softening rates of subterranean clover (Trifolium subterraneum) are lower in cool-temperate environments than in typical Mediterranean areas, allowing the accumulation of large seed banks. These large seed banks should enable a pasture to selfregenerate following a year of cropping in which the pasture has been removed. To test this hypothesis, a 1:1 pasture/crop rotation system was established at three sites in southern Victoria, Australia, with subterranean, balansa (T. michelianum), Persian (T. resupinatum) and arrowleaf (T. vesiculosum) clovers. At Hamilton, pure subterranean clover herbage yields of up to 10 t DM/ha were obtained under grazing. This was followed by wheat grain yields averaging 7 t/ha with 12.7% grain protein over three seasons. After a year of dryland cropping, the pastures selfregenerated with more than 3 000 clover seedlings/ m2. At Gnarwarre and Streatham, all four clover species were well adapted to the pasture/crop rotation in terms of their seed-seedling dynamics, with the highest regeneration after cropping at 8 000 seedlings/m2 in balansa clover and the highest seasonal herbage production of 12.8 t DM/ha in arrowleaf clover. No nitrogen fertiliser was applied in the system. Key words: annual legumes, cool-temperate climate, crops, seed softening rates
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(127 KB)It is common to have a shortage of high quality summer feed on hill country farms in New Zealand, due to a deterioration of pasture growth during the drier months. Lucerne produces high quality feed during summer on lowland fields; however, its potential in hill country is unknown. This study measured the persistence of lucerne and evaluated its seasonal production relative to pasture. These results were then modelled for a typical sheep and beef farm to assess the potential benefits of including lucerne on the farm. Monthly growth rates of lucerne (six cultivars) and pasture were measured pregrazing, and lucerne viability was assessed at the end of the five-year study. Lucerne was successfully established and maintained on hill country for five years. On average, the total annual production of lucerne and pasture were similar, with only the highest yielding cultivar ‘Rere’ consistently outproducing pasture on an annual basis. Lower spring production of lucerne was compensated for by higher summer growth rates of 62 kg DM/ha/day, compared with 34 kg DM/ha/day for pasture. The extra summer feed from lucerne enabled a model farm that included 12.5% lucerne to carry more animals and produce lambs of heavier slaughter weight than on a pasture only basis. This gave a predicted increase in the gross margin of 3%. The impact of lucerne on other farms must be modelled individually to establish the best system to utilise the additional high quality summer feed. Key words: lucerne, modelling, quality summer feed
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(106 KB)Lotus corniculatus (Birdsfoot trefoil, ‘Grassland Goldie’) may have a role in dryland pastoral systems in New Zealand, but there is little information available on its production under sheep grazing in these conditions. Dry matter (DM) production of L. corniculatus was measured monthly for 2 consecutive years in a systems approach experiment comparing it with perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture in the Wairarapa on the east coast of the North Island. The total DM produced for 2 years was 8.5 and 10.5 t /ha for L. corniculatus compared with 7.3 and 9.9 t /ha for pasture. Also, the moderate concentration of CT (18- 29 g/kg DM) in L. corniculatus has been shown to increase sheep productivity (Wang et al. 1996ab; Min et al. 1999, 2001). This production advantage, combined with improved sheep performance, supports the potential use of L. corniculatus as a specialist forage in dryland areas. Key words: condensed tannins, perennial ryegrass, Lolium perenne, white clover, Trifolium repens, pasture.
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(94 KB)A barrier to the adoption of many dryland legumes by grassland farmers is the lack of supply and/or the high price of seed. Growers face a number of problems in growing dryland legumes for seed, including a high risk of crop failure; alternatives such as wheat, barley and perennial ryegrass seed are lower risk crops. Gross margins for legume seed crops (including white clover) indicate that they have low profitability, at present prices if yields are average. Pollination remains a serious limitation to production, especially for dryland crops that are not well pollinated by honeybees. Both internationally and in New Zealand there has been a major decline in seed production research in the last decade, and little new research has been published on seed production of a range of dryland legumes. Seed production issues limiting yield in a range of dryland seed crops in New Zealand are identified. The paper concludes with suggestions that may help overcome some of these limitations. Key words: economics, lucerne, production constraints, red clover, white clover
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(124 KB)Four annual clovers have become adapted to the dry and semi-arid grasslands in New Zealand. In the absence of competition from perennial clovers, which are adapted to sub-humid and humid environments, further spread is likely to continue. Annuals rely on high numbers of small and hard seeds for survival. Their germination is dependent on a combination of adequate soil moisture and favourable temperatures, with no evidence of a prechilling treatment required. For striated clover, germination results highlight their adaptation to cool moist autumn conditions during germination. The benefits of adventive clovers for N fixation (0.2-100 kg N ha-1) are greatest where sulphur fertiliser has been applied, the clover population is dense, and soil moisture ideal over several months, but may be nil in drought conditions. Key words: annual clovers, germination, nitrogen fixation, semi-arid grassland, Trifolium arvense, T. dubium, T. glomeratum, T. striatum
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(186 KB)Three pure swards of subterranean clover were either (a) left ungrazed with a leaf area index (LAI) of 4.6, or (b) continuously grazed leniently to leave 1 600 kg DM/ha herbage mass equivalent to an LAI of 1.0, or (c) hard grazed to leave 1 400 kg DM/ha herbage mass equivalent to an LAI of 0.6 throughout the flowering period. These swards yielded 1 250, 320 and 70 kg/ha of seed, respectively. One intensive sampling during the middle of flowering showed that seed yield was positively correlated with plant weight, leaf area per plant, and area per leaf, specific leaf area and leaf area ratio. Grazing reduced numbers of both inflorescences and burrs and hence seed yield. Whilst reduced leaf area and plant weight may have also been partly responsible, under hard grazing, only 58% of potential reproductive sites were occupied which suggests that grazing animals also reduced seed yield by consuming these. It is recommended that continuous grazing during flowering and seed maturation should be controlled to leave at least 1 600 kg DM/ha of residual herbage mass, equivalent to an LAI of 1.0, if adequate seed is to be produced to be ensure the establishment of a high producing sward in the following growing season. Key words: flowering, grazing, herbage mass, leaf area, seed production, Trifolium subterraneum
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(111 KB)
Successful lucerne stand management requires balancing animal and plant requirements to produce crops of high quality and yield at times of high animal demand. Understanding the impact of environmental signals on crop growth and development can aid management decisions throughout the season. In spring, crops remobilise reserves from the roots to shoots and expand nodes accumulated through the winter, producing rapid stem extension and canopy closure as temperatures increase. The timing of spring defoliation should be based on crop yield and animal requirements rather than any specific developmental stage. Through spring and summer, crops should be rotationally grazed, with highest lamb live-weights achieved from 6–8 weeks grazing solely on lucerne. Summer crop production is dependent on rainfall and the plant available water content. During summer, grazing at the appearance of open flowers or basal buds is recommended as a compromise between maximum yield and quality. In autumn, the priority of assimilates allocation in the crop changes from above to below ground growth. To enhance the recharge of root reserves, an extended period of flowering is recommended in February or March. The time of flowering is dependent on the accumulation of thermal time and increases as photoperiod shortens. In periods of prolonged drought, lucerne herbage should be hard grazed and then spelled until the end of late autumn regrowth. A final hard grazing in June or early July, to remove overwintering aphids, should be followed by spraying 7–14 days later. Crops continue to develop nodes through the winter, and stands should be spelled until spring to ensure nodes are not removed by grazing, as this delays regrowth and reduces dry matter production. Key words: Flowering, grazing, herbicide, Medicago sativa, nodes, photoperiod, phyllochron, root reserves
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(164 KB)Seeds of five cultivars of subterranean clover, together with one of white clover, were sown in a wide range of temperature regimes under both controlled environment and field conditions. Results were consistent across temperature regimes and showed that the first trifoliate leaf emerged after 230 °Cd for all subterranean clover cultivars and 309 °Cd for the white clover cultivar. For subterranean clover, exponential leaf appearance commenced after 434 °Cd at the six total leaf stage. At this time, subterranean clover can be defoliated without causing permanent physical damage to seedlings. The field study at Lincoln University showed that subterranean clover that germinated in March produced 44 kg DM/ha/day for 158 days to yield approximately 7 000 kg DM/ha by mid-September. Subterranean clover that germinated in May produced 15 kg DM/ha/day for 120 days to yield only 1 800 kg DM/ha by mid September. These results are discussed in relation to the time of autumn grazing management for subterranean clover, including extrapolation to other climatic areas of New Zealand. Key words: herbage yield, phyllochron, seedling establishment, thermal time, Trifolium subterraneum, T. repens, white clover
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(145 KB)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
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