Continuous cereal crops can be costly, model reveals
A model unveiled at the Australasian Soilborne Diseases Symposium highlights the cost to growers from yield losses caused by continuous cereal rotations, which are becoming more common in the Western Australian grainbelt.
CSIRO researcher Roger Lawes demonstrated the Landuse Systems Optimiser (LUSO) which evaluates the relative economic impacts of different crop rotations given weed, disease and nutrient pressures, in conjunction with crop prices.
LUSO was developed by Dr Lawes and Dr Michael Renton of The University of Western Australia’s (UWA) School of Plant Biology under a Grains Research and Development Corporation (GRDC) funded project also involving the Department of Agriculture and Food (DAFWA).
Dr Lawes said LUSO showed that yield losses of at least 10 to 20 per cent were commonly incurred when two consecutive cereal crops were grown, with additional losses from three or more consecutive cereals.
“LUSO demonstrates that, when weeds are controlled, all break crops result in better yields in the following cereal crop, compared with consecutive cereals,” he said.
“When prices for wheat are really high, it may be more profitable in the short-term not to grow a break crop, but you will produce nowhere near the potential yields and there may be long-term ramifications from growing consecutive cereals.”
Dr Lawes said LUSO was designed to provide insight for consultants to help them advise farmers on what crops they should grow, given previous paddock management history.
It was currently being used to interpret data from crop rotation trials conducted by the Facey Group, and further demonstrations to grower groups were planned for next year.
Dr Lawes said LUSO showed that crop rotation choices exacerbated the yield effects caused by seasonal conditions.
“In a year of good rainfall, wheat grown following a wheat crop might yield 2 tonnes per hectare, compared with 2.5t/ha for wheat following a break crop,” he said.
“In a dry year, a typical result might be 0.75t/ha compared with 1t/ha for these two scenarios.”
Dr Lawes advised growers to monitor the disease and weed status of their crops and to consider growing break crops at some point in the rotation.
He said he was concerned that some Australian farmers were growing more than three consecutive cereal crops.
The 7th Australasian Soilborne Diseases Symposium, held at The University of Notre Dame from September 17 to 20, is sponsored by the GRDC, the Australasian Plant Pathology Society, Curtin University, DAFWA and Bayer CropScience.
For information about the event visit www.asds7.org/
PHOTO CAPTION: Roger Lawes.
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Contact: Natalie Lee
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