Western Australia
March 30, 2015

Crop modelling work shows that dry sowing wheat in April can maximise whole-farm yields in Western Australia and minimise the likelihood of late-season heat stress, without significantly affecting frost risk. 

Despite heavy rainfall in parts of the WA grainbelt in March, dry sowing opportunities could exist in April if top layers of paddocks dry out. In fact, a dry seed bed with significant subsoil moisture could provide ideal conditions for dry sowing.

The modelling work is being conducted by CSIRO researcher Andrew Fletcher, as part of a project led by the WA No-Tillage Farmers Association (WANTFA) and funded by the Grains Research and Development Corporation (GRDC).

Dr Fletcher is using the Agricultural Production Systems Simulator (APSIM) model to simulate whole farm responses to dry sowing. The APSIM simulations are based on a wheat sowing program beginning on April 20.

“Using data from 54 seasons at seven sites across the WA grainbelt, the modelling work shows farm-level yield benefits of up to 35 per cent – or up to 0.5 to 1.2 tonnes per hectare - from dry seeding wheat before autumn rains, compared with wet sowing wheat after autumn rains,” he said.

“The research indicates that dry sowing could bring forward the effective germination date of wheat by about a week, without impacting on yields in many parts of the State.”

The modelling shows the biggest yield benefits from dry sowing wheat early are in:

• Heavy soils
• Drier locations
• The northern grainbelt
• Bigger cropping programs relative to sowing capacity
• Years with low to medium yield potential.

Dr Fletcher said the work shows that most of the yield increases from dry sowing occur when up to 33 per cent of a farm is dry sown.

“This is driven by both higher crop yields and an increase in the total cropped area – due to the increased area of land which can be sown in the ideal sowing window,” he said.

Dr Fletcher found a marked decline in the number of heat stress events during the grain fill stage for wheat crops dry sown early, compared with later wet sown crops, resulting in higher yields and better grain quality.

“The risk of heat shock fell from 25 to 14 per cent when wheat was sown dry, due mainly to a tighter flowering window compared with wet sowing of wheat,” he said.

The APSIM modelling found dry sowing leads to only a slight increase – of up to 4 per cent – in the area of wheat frosted during flowering, compared with late wet flowering, even in high frost-risk areas.

“Based on the APSIM data, it appears that the risks of frost are outweighed by the potentially higher returns of beating the risks of heat shocks,” Dr Fletcher said.

He recommended that growers use a range of wheat varieties for dry sowing to spread the flowering window, rather than using one variety only.

But very long-season wheat varieties should only be sown into wet soil, and not dry sown early.

“Early dry sowing of very long-season varieties can delay their germination, resulting in these crops flowering very late in the season, exposing them to a high risk of heat stress,” Dr Fletcher said. 

To help guide decisions on variety choice and sowing dates, growers can access the online tool Flower Power, developed by the Department of Agriculture and Food (DAFWA) with funding from the GRDC.

Flower Power predicts wheat flowering times and the risk of frost or heat stress in your location. The tool can be accessed for free via DAFWA’s website agric.wa.gov.au by searching for ‘flower power’.

Information about time of sowing is also available at the GRDC Wheat GrowNote which can be found at www.grdc.com.au/GrowNotes.
 

Website: http://www.grdc.com.au

Published: March 30, 2015