New research suggests Western Australian grain growers should focus primarily on matching inputs to growing season rainfall, and that modifying inputs based on stored sub-soil moisture has relatively little effect on wheat yields.
Led by CSIRO researcher Steve Milroy, the Grains Research and Development Corporation (GRDC) funded project suggests WA growers should not significantly adjust crop inputs at seeding time based on stored sub-soil moisture from summer rainfall.
On-farm trials in WA’s northern agricultural region showed stored water contributed only 9 to 19 per cent of water used by wheat crops.
The project ‘Increasing water use efficiency in the northern sandplain region of WA’ aims to help WA growers make more productive use of water and maximise profitability by investigating the effects of different inputs and treatments on crop yields.
Dr Milroy said the WA results contrasted with research findings in south-eastern Australia, but were consistent with previous WA research.
“While further work is needed to quantify these early on-farm trial results, it appears it is most important for WA growers to match inputs to in-season rainfall because out-of-season rainfall may not contribute much to wheat yields,” he said.
“In very dry years like 2010, sub-soil moisture becomes more valuable, but nevertheless growers should not significantly change inputs at seeding time based on summer rainfall.
“Sub-soil moisture makes only a small contribution to yields in normal to good years.
“This is because WA soils have relatively little water holding capacity and 75 to 80 per cent of rainfall is received in the growing season.
“Controlling summer weeds is important in maximising wheat yields, but there is no evidence that different stubble management practices over summer have much effect on yields in WA.”
The on-farm trials were conducted in conjunction with the Liebe Group, the Mingenew Irwin Group and the North East Farming Futures group.
Paddock trials were conducted on deep sandy soils on Stuart McAlpine’s property at Buntine, red loams on Jon Holmes’ farm at Mingenew and red loams on Gary Collins’ property at Morawa.
