The use of longer-term tactical spray fallows, which ‘spell’ paddocks into the winter growing season, are becoming increasingly popular with grain growers in lower rainfall parts of Western Australia.
These extended fallows can reduce risks associated with seasonal variability, herbicide resistant weeds and growing non-profitable crops in poor years.
According to Grant Thompson, of Crop Circle Consulting, yield advantages can be as high as 0.5-1 tonnes per hectare for wheat and 0.5t/ha for canola. Herbicide savings can be about $15-50/ha.
The GRDC RCSN fallow trial site at Mingenew. Photo by Grant Thompson, Crop Circle Consulting.A
“By strategically knocking down weeds in fallow paddocks during the summer months or at seeding time - and keeping these paddocks clean from weeds until the next year’s sowing period - vital soil moisture for the next 18 months is conserved for the subsequent crop,” he said.
“This next crop should be healthier, have a lower weed burden, produce more grain yield and be more likely to generate a higher two-year gross margin than growing two low-yielding cereal crops.
“However, a clean spray fallow can be costly to set up in a low rainfall environment, especially if there are multiple winter and summer weed germinations, and there is also concern about reliance on glyphosate in this phase.”
To boost grower confidence in the system, the Grains Research and Development Corporation (GRDC) – through its Kwinana East and Geraldton Regional Cropping Solutions Networks (RCSNs), is supporting fallow trials providing local data about:
- The effectiveness of summer and winter weed control from a wide range of herbicides
- Crop tolerances to residual herbicides in the treated soil
- Grain yields and quality from growing crops to full potential on stored winter and summer rainfall
The trials were established in 2015 at Wyalkatchem, Mingenew and Mullewa and are being conducted by Mr Thompson and Quade AgriServices Landmark agronomist Bernie Quade.
They are investigating more than 20 knock-down and residual herbicide options and a range of new crop technologies to lift the profitability of longer-term fallows.
2015 trial results, other associated information and links to additional resources are available in the new GRDC Hot Topic Tactical spray fallow in the western region which can be found by searching ‘fallow’ here.
Grant Thompson, Crop Circle Consulting
08 9965 2521
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code