WA rainfall shift to change weeds and yields

Tim Scanlon WA DPI

Dryland croppers might face a problem of more weeds during the summer fallow due to irregular rainfall, according to WA research.

Researchers from the Department of Primary Industries and Regional Development at Northam and Merredin examined 85 sites and also found higher out-of-season rainfall might be disguising the severity of the ongoing growing-season dry in WA’s south-west.

Their study revealed rainfall declines of up to 20% during the growing season (April-October), but increases in out-of-season rainfall by up to 87.6% at sites in the study’s eastern region.

A chart from the central sites showing the shift in rainfall totals and patterns.
A chart from the central sites showing the shift in rainfall totals and patterns.

Analysis of wheat yield indicated reductions of 13.5% in the western region of the study sites and 9.90% in central region, while a small group of eastern sites had a potential yield gain of 8.9% arising from the increased out-of-season rainfall, the scientists reported.

Lead researcher Tim Scanlon said: “The eastern part of the WA wheatbelt is particularly sensitive to changes in rainfall as they are already lower rainfall environments. Following the shift in Indian Ocean sea surface temperatures in 1976, there was a change in rainfall for the annual cropping and pasture areas. A second shift in sea surface temperature occurred in 2000, and this work investigated what impact that change has had on rainfall in the eastern WA wheatbelt.

“However, the eastern wheatbelt area producers have actually managed to maintain average yields, albeit with greater year-to-year variability, thanks to their adoption of new technologies and management techniques.”

The other DPI researcher was Greg Doncon.

Source: Crop and Pasture Science 71(2) 128-133

Featured Image: Tim Scanlon WA DPI