Ground Cover Supplement : GC Supplement - Tactical cereal agronomy
3 Early sowing Early sowing shows national promise Taking advantage of rainfall events in March and April using early-sown, slow-developing wheat varieties can increase crop yield with very little initial investment By Dr James Hunt GRDC-FUNDED RESEARCH IN New South Wales has demonstrated that slow- developing varieties sown early yield more than mid to fast varieties sown later when they flower at the same time. The research has now been extended into Western Australia, South Australia and Victoria. WESTERN AUSTRALIA Even with WA's Mediterranean climate, modelling suggests slow-developing wheat varieties could increase whole- farm wheat yield when sown early to take advantage of March--April rainfall. Trials in 2014 examined whether slow-developing varieties (Table 1) sown early could yield as well as or better than fast-developing varieties such as MaceA sown during their optimal window in the WA environment. Based on one year of data, the winter wheat Whistler appears adapted to WA and when sown in mid-April it yielded as well as or better than MaceA planted in late May in three out of four trials. Whistler is unique among Australian cultivars in that its development is slowed by a strong vernalisation (cold) requirement, but it will flower rapidly once this is satisfied. This development pattern is very well suited to early sowing in lower-rainfall wheat- growing areas across southern Australia and WA. A variety such as Whistler would enable WA growers to take advantage of early planting opportunities across a broad sowing window (late March to early May and earlier if used as a dual-purpose crop). Whistler's stable flowering date would also reduce frost risk associated with early sowing. Unfortunately, inferior quality classification and poor availability of seed of slow-developing varieties, particularly Whistler, will limit uptake of this practice in WA. However, several major breeding companies have started selecting for winter wheats with a similar development pattern to Whistler, and varieties with likely WA adaption are three to four years from release. SOUTH AUSTRALIA Like WA, sowing earlier than is currently practised requires varieties not widely grown in SA and which are much slower to mature, either because they have a strong vernalisation (cold) requirement (winter wheats) or a strong photoperiod/ day-length requirement (slow-developing spring wheats) (Figure 1, page 5). Most wheat varieties grown in WA and SA are mid to fast-developing. When sown at their optimal times, all maturity rankings will flower during the optimal period in a given environment when the risks of frost and drough/heat are minimised. Winter wheats have a very flexible sowing window and if well adapted will flower during the optimum period in a given environment from a broad range of sowing dates. Despite a frosty July and August 2014, the highest yields in most SA trials came from mid-April sowings, with the mid-developing wheat variety LongReach TrojanA being the stand-out performer. Adding LongReach TrojanA to a MaceA cropping program brings TABLE 1 Wheat varieties used in early-sowing experiments in Western Australia. Variety Maturity Comments EGA WedgetailA Winter (strong vernalisation, moderate photoperiod) The early sowing and dual-purpose standard in southern NSW and an excellent grain-only option. May be too slow in most of WA. Default classification of APW in WA and APH in NSW. Whistler Winter (strong vernalisation, weak photoperiod) Slightly faster than EGA WedgetailA and with a more erect plant type. Potentially better suited to WA but has poor grain quality classification (default classification of AGP in WA and ASW in NSW/Victoria). Quite susceptible to stripe rust (MS-S). EGA EaglehawkA Very-slow-developing spring (moderate vernalisation, very strong photoperiod) Photoperiod-sensitive spring wheat that will flower at the same time as EGA WedgetailA from a mid-April sowing but hits GS30 about three weeks earlier, and is therefore not as suited to grazing. Default classification of APW in WA but APH in NSW. LongReach LancerA Slow-developing spring (moderate vernalisation, weak photoperiod) New release with adaptation to the same latitudes in NSW as WA wheatbelt. Very low vigour and excellent grain quality. Default classification of APW in WA but APH in NSW. MagentaA Mid-developing spring (moderate vernalisation, weak photoperiod) WA variety undervalued as it is rarely sown early enough to achieve yield potential. Probably suits late April--early May planting (similar to YitpiA). Classified as APW. MaceA Fast-developing spring (weak vernalisation, weak photoperiod) WA main-season benchmark and in the trial as a control from a mid-to-late May sowing. Classified AH. AH = Australian Hard; AGP = Australian General Purpose; APH = Australian Prime Hard; APW = Australian Premium White; ASW = Australian Standard White SOURCE: DR JAMES HUNT, CSIRO the start of the sowing window forward by about 10 days. Based on one year of data, a mixed wheat program using LongReach TrojanA and MaceA would enable growers to sow earlier and achieve higher yields (16 per cent in 2014) than they could with MaceA alone sown in its optimal window. The winter wheat EGA WedgetailA is the variety most suited to a very early sowing in SA; however, even sown early it still yielded less than MaceA planted in its optimal window. For growers in frosty SA environments wanting to sow before about 20 April, EGA WedgetailA is so far the safest option evaluated in the trials, but yields are likely to be less than MaceA sown in its optimal window. NEW SOUTH WALES Growers in southern NSW have sown early with slow-developing varieties since the release of the first semi- dwarf winter wheats from the NSW Department of Primary Industries Wagga Wagga breeding program in 1983.
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