THREE years of research testing wheat sowing times at different elevations within a paddock shows that elevation has a big impact on the best variety choice (maturity related) and generally supports earlier than conventional sowing time for best yields at high and low elevation sites.
Agricultural Marketing and Production Systems (AMPS) led the GRDC-funded research. Agronomists Matt Gardner, Stephen Towells (AMPS), Jules Dixon (formally AMPS), with co-partners Greg Giblett and Sam Simons (Agromax) conducted the study.
Research areas at Gurley and the Liverpool Plains had elevation differences between top and bottom test sites in individual paddocks varying from 46 to 20 metres. Their effect on climate related to early (late April early May), mid (mid to late May) and late sowing (early June) were the main reasons for big variety and sowing time-related differences.
Both trial sites faced hot, dry springs in 2014 and 2015 and there were big benefits from early sowing. At the Liverpool Plains top site, delaying planting from late April to early June resulted in a 2.24 and 1.04 tonnes-per-hectare yield loss when averaged across six varieties. Despite a favourable 2016 spring, there was still a 1.34t/ha yield penalty for delaying sowing from late April to early June at the top of the slope.
Unlike the Liverpool Plains in 2016, there was no yield penalty in delaying planting dates from late April until early June at Gurley. In contrast in 2015, during a hot, dry spring, the same delay in planting resulted in a 1.88 t/ha yield reduction.
Temperature and frost numbers and severity (including length), despite relatively low altitude variation between top and bottom trial sites, resulted in very different variety performance sown at different times. Early sowing of quicker-maturing varieties commonly resulted in significant frost damage and yield loss on the lower elevation sites. At the top sites frost damage from sowing quicker-maturing varieties early was less.
Areas, if zoned for elevation and treated differently, can have yields boosted considerably by sowing earlier than generally appreciated – and particularly on lower areas choose slower-maturing varieties to reduce frost risk.
Matt Gardner believes in establishing the desirable flowering date for a given part of the landscape and then choosing varieties for their ability to flower in that window. For example at Gurley optimum flowering window was mid to late August for the top of slope in 2015 and 2016, but in 2016 (wetter/ milder) was longer, beginning early September.
In contrast optimum flowering for the bottom Gurley slope generally started 9-13 days later. Optimum flowering time for the bottom Liverpool site was 10-22 days later than the top. Optimum flowering on the Liverpool Plains for the top slope sites started at the beginning of September, while for the bottom it was mid September.
Assuming a wheat price of $250/t advantage from sowing early (late April) can increase profit by $260-$1155/ha. Relatively small elevation differences measure big climate differences.
Average minimum temperatures across all three years were 2.4 and 2.9°C lower at the bottom compared with the top at Liverpool Plains and Gurley respectively. Maximum temperatures were similar at both top and bottom. Most striking is that at bottom sites on average 32 extra frosts per season occurred. On average, also the time temperatures were at or below 0°C at the top compared with the bottom sites was much shorter. Mr Gardner says frost length can be a major factor of damage.
More detailed information is available from GRDC update seminars or email Matt Gardner – matt@ampsagribusiness.com.au
Next week. Big springs challenge grazing.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or phone (0428) 752 149.