Ground Cover Supplement : GC Supplement - Pastures
GROUND COVER PASTURES 12 ANNUAL LEGUMES HERBICIDES ARE AN important tool for controlling weeds in pastures. However, farmers and agronomists face a complex matrix of herbicide decisions because product labels remain inadequate for new pasture species. A number of new pasture legume species such as biser- rula, serradella and gland clover have been released over the past decade with spectacular success, but information on their tolerance or sensitivity to herbicides was limited on release. Research on herbicide sensitivity is required to ensure appropriate management for higher and more stable legume content and in turn increased nitrogen fixa- tion and better performance of subsequent crops. This project is providing agribusiness with infor- mation about the relative herbicide tolerance of new pasture cultivars, including the tolerance of new species under development and yet to be commercialised such as Trigonella balansae and Trifolium spumosum (blad- der clover). Initially, screening activities were carried out across cultivars and a limited number of advanced breeding lines in field trials. This is now being comple- mented by extensive screening of germplasm in the glasshouse to identify useful sources of tolerance that might be included in future pasture legume improve- ment programs. Between 1997 and 2005, 11 replicated field trials supported by GRDC were carried out across a range of soil types and seasons. Trial sites were located in the northern and central wheat belt of Western Australia. At each site, pasture cultivars/lines were sown with a cone seeder and sprayed with a wide range of herbicide treat- ments, either immediately after sowing (PSPE) or at the three- to six-leaf stage. The impact of herbicide on pas- ture performance was visually assessed six weeks after the application of the post-emergent sprays. Plots were maintained in a relatively weed-free condition over the assessment period, but were not grazed. Overall herbicide tolerance varied widely between legume species. Although some herbicide mixtures can improve efficacy and broaden the spectrum of 2,4-DB (1.5L/ha) on ScimitarA burr medic caused leaf curling. Seeds, Stephens Pasture Seeds and Irwin Hunter Seeds. UranaA is a very vigorous crossbred variety suited to areas with annual rainfall of about 400 to 525mm and where the growing season extends to mid-October. It has a flowering time later than Dalkeith but earlier than YorkA and Seaton Park and is well suited to mixtures with these cultivars. UranaA is more hardseeded than these cultivars, with denser regeneration following a year in crop or a poor seed production season. It has very high herbage production potential, averaging 14 per cent more than Dalkeith over 21 trials (Figure 2). Marketing licence: Premier Seeds. CoolamonA is a more productive and persistent replace- ment for Junee with resistance to both known races of clo- ver scorch disease. It is a crossbred variety suited to areas with annual rainfall of about 500 to 700mm and where the growing season extends into November. CoolamonA has sufficient levels of hardseed for it to be grown in rota- tion with crops, provided cropping frequency is no more than one year in three. It is also suited to phase farming and permanent pastures. When averaged across 15 sites, CoolamonA had 11 per cent better regeneration density and produced 10 per cent more herbage in winter, 14 per cent more herbage in spring and four per cent more seed than Junee (Figure 3). Average regeneration density of CoolamonA was 12 per cent higher than Junee in the first three years after initial seed set. However, at one site (Wundowie, WA) where persistence was measured into the sixth season, CoolamonA had 58 per cent more seed- lings than Junee, and nearly eight times the density of the older cultivar Woogenellup (Figure 3). Marketing licence: a consortium of Premier Seeds, AusWest Seeds, Stephens Pasture Seeds and Irwin Hunter Seeds. NapierA is a late-flowering crossbred subspecies yannini- cum variety. It is a more productive and persistent, dis- ease-resistant replacement for Larisa and Meteora suited to waterlogged permanent pastures in areas with more than 750mm annual rainfall and where the growing season extends into late November. Its upright, vigorous growth makes it well suited to grazing by cattle or sheep and to fod- der conservation. Over eight trials NapierA averaged five per cent more herbage production in autumn, seven per cent more in winter, five per cent more in early spring and 15 per cent more in late spring than Larisa (Figure 4). Late spring production was also 46 per cent more than Trikkala. Seedling regeneration of NapierA was 127 per cent greater than Larisa and seed production was 61 per cent greater. Marketing licence: PlantTech. Dr Phil Nichols is a senior research officer (pasture science), Department of Agriculture and Food, Western Australia. GRDC Research Code UWA360 More information: Phil Nichols, 08 9368 3547, email@example.com Which herbicides for new legume species? PROJECT: HERBICIDE TOLERANCE IN ANNUAL LEGUME SPECIES. CLINTON REVELL, DAVID FERRIS AND CHRISTIAAN VALENTINE Gramoxone® (500ml/ha) applied midwinter to Prima gland clover (right) and control (left). Layout of a herbicide tolerance trial at Muresk, WA. Spinnaker® (70g/ha) on ScimitarA burr medic (left) and control (right). Raptor® (45g/ha) on CaliphA barrel medic (bottom), Orion sphere medic (centre), and CavalierA burr medic (top). Treatment (left) and control (right). Dual Gold® (500ml/ ha) on FrontierA balansa clover (right) and control (left).
GC Supplement - Growers sharing knowledge
GC Supplement - Subsoil constraints