Five years of data gives insight into WA crop rotations

The results of the five-year Focus Paddocks project have provided industry with better insight into the agronomics and economics of paddock rotations across the Wheatbelt.

The project, supported by the Department of Agriculture and Food (DAFWA) and the Grains Research Development Corporation (GRDC), monitored the performance of 184 paddocks from across the Wheatbelt.

Department economist James Hagan said while there were individual years where a paddock may have produced a negative gross margin, on average over the five years every paddock delivered a positive return.

The results ranged significantly from $45 per hectare to $620/ha.

“Half of the paddocks retuned gross margins of between $170 per hectare per year and $350/ha/yr,” Mr Hagan said.

The best performing rotation across all agricultural regions included canola as the break crop of choice, with a rotation consisting of four years of cereal and one year of canola; or three years of cereal and two years of canola, consistently providing the greatest gross margins.

“Interestingly, in the majority of cases there were only minor differences between the gross margin returns of the best performing sequence and the second and third best rotations,” Mr Hagan said.

“In some cases there was a mere $20/ha difference in performance, which could easily be accounted for by better marketing, different chemical or fertiliser prices or any number of other factors not related to the agronomics of the rotations chosen.”

Cereals had a high level of inclusion in rotations, with 80 per cent of paddocks having three or more years of cereal over the five years.

Twenty one per cent of paddocks monitored by the project had rotations which only featured a combination of wheat and canola.

A further 13 per cent of paddock rotations included barley, in addition to wheat and canola, meaning a third of paddocks had rotations consisting only of cereals and canola.

Mr Hagan said the project had changed the way they viewed paddock rotation choices by growers.

“Coming into the project, we thought rotations would be driven primarily by disease and weed pressure, with the assumption being that once either of these constraints reached a certain level growers would swap to an appropriate break crop,” he said.

Mr Hagan said growers were much more proactive in their management than this initial assumption, with paddock rotations being managed to keep disease and weed burdens to very low levels rather than reacting to weed or disease build up.

“About 75 per cent of paddocks had weed numbers below 20 plants per metre square, while half were below five plants/m2,” he said.

“Likewise, 90 per cent of paddocks had either no or very low levels of disease, which remained fairly constant. However, detections of root lesion nematodes increased over the five year period, which growers will need to be mindful of with paddock rotation choices.”

A final report with key findings of the 2010-2015 project is scheduled for release in October this year.

Graphic: Distribution of Focus Paddock Gross Margins.

Wayne Parker, Department of Agriculture and Food, monitoring canola as part of the Focus Paddock project.

Media contacts: Jodie Thomson/Lisa Bertram  +61 (0)8 9368 3937