Ground Cover Supplement : GC Supplement - Tactical cereal agronomy
5 Early sowing SOURCE: DR JAMES HUNT, CSIRO FIGURE 1 Development pattern of winter and slow-developing spring wheat varieties relative to mid-developing spring wheats. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Optimal flowering period Dec Mid-maturing spring wheat Slow-maturing spring wheat Winter wheat Emergence -- GS30 GS30-GS69 GS69-maturity Emergence -- GS30 GS30-GS69 GS69-maturity Emergence -- GS30 GS30-GS69 GS69-maturity Canola agronomy pays wheat dividends Canola has emerged as the dominant broadleaf break crop in Western Australia with about 1.3 million hectares sown across the WA wheatbelt during 2013 – more than four times the area planted in 2009. The canola growth has been driven by plant breeding advances, high returns and an ability to achieve good weed and soil-borne disease control in this rotation phase. Canola also provides benefits to the following wheat crop. Where cereal root pathogens are present, Department of Agriculture and Food, WA (DAFWA) trial data indicates a large yield benefit from a canola break to a following wheat crop. Weed control options, both herbicide and cultural, are strong in canola with this crop being used to reduce weed numbers. In light of the significant rise in canola plantings in WA, a GRDC-funded project ‘Tactical break crop agronomy in WA’ is developing canola agronomy packages for low and high-rainfall areas across the WA wheatbelt. The project will run for five years until 2019. The canola research spans the following areas: ¢ production of an annual canola variety guide for WA; ¢ development of an online canola seeding rate calculator; ¢ nitrogen amount and timing; ¢ seeding rate/plant density; ¢ sowing time and depth; ¢ precision seeding methods; ¢ row spacing versus yield; ¢ direct harvesting/shattering loss; and ¢ annual canola herbicide tolerance assessments. □ More information: Jackie Bucat, DAFWA, 08 9368 3481, email@example.com To download the latest canola variety guide for WA and the recently released seeding rate calculator visit: https://agric. wa.gov.au/n/4210 For a comprehensive summary of GRDC canola agronomy research download the recent Ground Cover Supplement on this topic: www.grdc.com.au/gcs117 MANAGEMENT OF EARLY-SOWN WHEATS Early-sown crops require specific management to achieve best results. ¢ Do not dry-sow slow-developing varieties (EGA WedgetailA, EGA EaglehawkA) as they will flower too late if not established early. There must be seedbed moisture and ideally some stored soil water to get them through to winter. ¢ If growing winter wheat (EGA WedgetailA) and not grazing, reduce seed rate (plant density) and defer nitrogen inputs until after GS30. ¢ Choose clean paddocks – winter wheats at low plant densities are not competitive with ryegrass and common root diseases are exacerbated by early sowing. ¢ Protect against diseases associated with early sowing – barley yellow dwarf virus (apply imidacloprid on seed backed up with in-crop insecticides at the start of tillering if aphid pressure is high) and Septoria tritici blotch in some areas (flutriafol on fertiliser and timely foliar fungicide applications at GS30 and GS39). Many slow-developing varieties also have poor resistance to stripe rust (flutriafol on fertiliser and timely foliar fungicide application at GS39). Flowering triggers Slow-developing wheat varieties have genes that prevent them from flowering quickly. Cold (vernalisation), heat (thermal time) and day length (photoperiod) interact with these genes to determine flowering time. COLD Wheat varieties with a vernalisation (cold) requirement will not flower until they have experienced a specific period of cold temperature (0°C to 12°C). Most spring wheats, including fast-developing varieties such as MaceA, have only a small vernalisation requirement, which is easily met during normal growing conditions. Winter wheats, such as EGA WedgetailA and Whistler, have a strong vernalisation requirement and therefore will not flower until they have experienced cold conditions. This means they can be sown very early and they will not flower until after winter. DAY LENGTH A day-length or photoperiod requirement delays flowering during short days and speeds up flowering during long days. Most mid and slow-developing spring wheats are photoperiod- sensitive. If photoperiod-sensitive wheats are sown too early their day-length requirement can be met in autumn and they will flower too early. HEAT Crops develop more rapidly under warm temperatures but this response differs between varieties. A thermal-time requirement is the amount of thermal (heat) time required by different varieties before they can reach critical growth stages. Cold, day-length and thermal time can act together or in isolation to slow development. For example, very-slow-developing European winter wheat varieties often have a strong vernalisation requirement along with a large day-length (photoperiod) requirement. On the other hand, other winter wheats such as Whistler have a vernalisation requirement but a weak photoperiod requirement and therefore develop quickly once their vernalisation requirement is met. ‘Fast winter’ varieties, such as Whistler, are likely to be the best adapted slow-developing varieties for most of the Australian wheatbelt.
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