Rolling the dice on rotation risks at Updates
Growing break crops in a well-managed way can significantly and consistently boost the yields and profits of subsequent wheat crops in good seasons and reduce overall farming risks.
That has been the finding of economic modeling and analysis - using long term Western Australian crop sequence data - by researchers from the CSIRO’s Sustainable Agriculture Flagship and Department of Agriculture and Food (DAFWA).
Results from this project, funded by the Grains Research and Development Corporation (GRDC), were presented by CSIRO’s Roger Lawes during a crop rotation session at the 2015 Agribusiness Crop Updates, hosted by the GRDC and DAFWA at Crown Perth on February 24 and 25.
Dr Lawes said an analysis of 30 years of data from across the WA grainbelt using the crop and economic modelling systems APSIM and LUSO indicated there was a 0.6 tonne per hectare average yield benefit in wheat crops grown after a lupin break crop and 0.4t/ha benefit following canola, compared with wheat grown after wheat.
He said it showed yield benefits of up to 0.4t/ha could persist into the third year of wheat crops following lupins in the rotation.
“These findings highlight the value of considering break crops to stack the odds in your favour for getting a substantial wheat yield benefit in following years,” he said.
“The higher wheat yields are driven by control of soilborne diseases and weeds during the pasture or break crop phase.”
Dr Lawes said agronomic practices in one year influenced the biotic stresses and nutrient requirements of the crop in the following year and to reach optimum yield potential, paddocks needed to be set up to perform well.
“This means thinking about your paddock or farm over an extended period of time,” he said.
Using APSIM and LUSO modelling to generate 100 years of wheat, canola and pasture yields (based on a Kojonup location) - and repeating simulations thousands of time - CSIRO and DAFWA researchers found the use of break crops increased the chances of higher profits compared with continuous wheat sequences across a three-year rotation.
After a full three-year sequence, the probability of a canola-wheat-wheat rotation making a profit was 86 per cent, a pasture-wheat-wheat rotation was 84 per cent and a wheat-wheat-wheat rotation was 74 per cent.
Dr Lawes said the probability of making a $500 per hectare profit after three years was 55 and 50 per cent for canola-wheat-wheat and pasture-wheat-wheat respectively – but the continuous wheat sequence was about half of that, at just 24 per cent.
“We found the first wheat crop in a continuous wheat sequence could increase costs and depress yields in the second and third year wheat crops and, therefore, reduce the probability of these subsequent wheat crops making a profit,” he said.
“A crop rotation with break crops was more likely to break even after three years and more likely to be extremely profitable than continuous wheat plantings.”
Dr Lawes said, in practice, when considering crop sequences, growers and advisers should consider the odds of their individual whole cropping system - and each enterprise in that system - making a profit.
“These odds need to take into account the vagaries of the season, commodity prices and the manager’s ability to realise the potential yield of each enterprise,” he said.
For more information about and to register for the Agribusiness Crop Updates visit the Grain Industry Association of Western Australia website or contact the Grain Industry Association of WA office on 08 6262 2128.
More localised information on this and other research will be provided at Regional Crop Updates. For information about these events go to the GRDC Updates page or the DAFWA regional crop updates webpage.
Dr Roger Lawes, CSIRO
08 9333 6455
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code CSA00029