Updates to uncover what is underpinning crop yield gaps

Author: | Date: 09 Feb 2018

A National Paddock Survey project supported by GRDC investments has found the average difference between actual and potential wheat yield in the western region can be as much as 1.3 tonnes per hectare. Further results will be presented at the GRDC Grains Research Updates in WA. PHOTO: GRDC

Grain growers in Western Australia will have a clearer idea of the key barriers preventing them from achieving optimum crop productivity following the release of a major national study into yield gaps.

Key findings from the National Paddock Survey, carried out by Birchip Cropping Group and CSIRO with Grains Research and Development Corporation (GRDC) investment, will be unveiled at the upcoming GRDC Grains Research Update, Perth and discussed at the GRDC Regional Grains Research Update at Darkan.

These events will be held at Crown Perth on February 26-27 and the Darkan Shire Hall on February 28. Registrations can be made on the GIWA website or the GRDC website. Alternatively, contact convenor the Grain Industry Association of WA (GIWA) on 08 6262 2128 or researchupdates@giwa.org.au

The National Paddock Survey assessed the size and variation of the yield gap on 250 paddocks from leading farms that represented a range of rainfall and soil conditions in the GRDC’s western, southern and northern regions.

Analysis showed the average difference between actual and potential wheat yield in each region respectively was 1.3, 1.2 and 1.1 tonnes per hectare.

Researchers describe the yield gap as the difference between actual yield achieved by the grower and water limited yield potential, which is the maximum possible yield able to be grown using the optimal sowing date, current varieties and nutrients (and with limited effect from pests, diseases and weeds).

National Paddock Survey project lead researcher Dr Roger Lawes, of CSIRO Agriculture and Food, said a combination of factors was underpinning the yield gap discrepancies.

“It is not one thing, rather it is a combination of agronomic and seasonal factors,” he said.

“For example, yield gaps are higher when the growing season rainfall is higher and a variable cropping sequence, reduces the yield gap.

“Insufficient crop nitrogen contributes to the yield gap and the presence of weed and disease also contribute.”

Dr Lawes said the research indicated the extent of the yield gap could be reduced through more targeted nitrogen management and crop rotation, but multiple interacting factors would still influence the final outcome on-farm.

“In the western region, growing season rainfall was the most important variable to explain the yield gap, followed by the amount of nitrogen and the previous crops in the sequence,” he said.

“In the southern region, the amount of applied nitrogen, the previous crop and root health score were most important, and in the northern region, it was growing season rainfall, applied nitrogen and root health score.”

The survey highlighted that in the western region, 46 per cent of wheat paddocks achieved between 80 per cent and 100 per cent of yield potential. In the south, this was 38 per cent and in the north it was 43 per cent. In WA, incidences of disease and pests were typically low.

Growers were often unable to capture the extra yield on offer in the high rainfall zones, but given the risks associated with targeting high yields, that is understandable, according to Dr Lawes.

He said, although more research was needed to better understand individual yield constraints in paddocks, achieving water limited crop potential was possible for a broad range of growers cropping on all soil types and rainfalls.

Contact Details

For Interviews
Dr Roger Lawes
CSIRO Agriculture and Food
147 Underwood Avenue, Floreat, WA 6014.
08 93336455

Melissa Williams, Cox Inall Communications

GRDC Project code: BWD00056