AN emerging agronomic toolset to assess impact of variable factors across the Wheatbelt has shown plot trial research results may not entirely reflect what is happening on the ground in the low rainfall zone (LRZ).
CSIRO principal research scientist Roger Lawes told the Grains Research and Development Corporation (GRDC) Grains Research Update in Perth last week the toolset had been used to analyse flow-on benefits of different crop rotation break strategies in terms of subsequent wheat crop yield increase.
Dr Lawes said for the past four years the CSIRO has been statistically monitoring 10,000 paddocks in the Wheatbelt LRZ using a toolset developed as part of the CSIRO's Digiscape Future Science platform.
The toolset is also an extension of a joint project with the CBH Group to monitor WA grain production and deliver data to CBH in near real time, as the season progresses, to help it schedule its operations and of the CSIRO's component of the GRDC-funded National Paddock Survey aiming to measure the size of the yield gap.
Satellite mapping of the Wheatbelt, combined with overlays of digital paddock and crop identification, were coupled with data from a variety of sources - including Bureau of Meteorology (BoM) rainfall and temperature and data on crop yields and crop management from farmers and agronomists to create a ongoing seasonal library of information.
Apart from simply monitoring seasonal differences between regions, the toolset can now be used to monitor individual farms and the effectiveness of crop management strategies on those farms compared to the strategies used on neighbouring farms.
"We can now identify individual paddocks across the Wheatbelt and by layering information such as rainfall, soil type, fertiliser regimes and cropping history - what the rotations were, time of sowing et cetera - we can build up a picture of each paddock to try to understand what is happening there," Dr Lawes said.
"We can extract the wheat yield for wheat paddocks and then look at the history of their management.
"We've monitored 10,000 wheat paddocks a year in the LRZ (for four years), so we had 40,000 paddocks all up to look at and the history of rotations for those.
"It enabled us to start doing some simple analytics on paddocks, that would normally take an enormous amount of grower survey work, a lot of driving around and a lot of field inspections."
The analytics showed wheat after a cereal break is the most common management practice in the LRZ, with 41pc of wheat crops grown after a cereal.
Next most common was wheat after pasture, with about 30pc of the area following that management strategy.
"Then you get what is considered a traditional break, either a wheat after an oil seed, wheat after a pulse or wheat after a fallow," Dr Lawes said.
"So a massive area of the LRZ -nearly 80pc - has wheat after a cereal or wheat after pasture, so this begs the question, what sort of effect are farmers getting from these different rotation choices?
"Is it any different from what we see when researchers conduct a break crop trial or a crop rotations trial?"
Dr Lawes said DPIRD research in the LRZ indicated the "average break crop effect" is between 600 and 700 kilograms per hectare after a pulse or canola crop.
However, he said the CSIRO's analytics showed wheat after canola in the LRZ only generated about 180kg/ha improvement over wheat after wheat.
With a fallow break, the improvement over continuous wheat cropping was about 170kg/ha.
Other research described had indicated improvement after fallow in an experimental situation, but not necessarily in the LRZ, was "more like one tonne per hectare in a three-tonne environment", Dr Lawes said.
"We're actually only seeing a fallow benefit on average just equivalent to canola.
"So already we are starting to see a discrepancy between what researchers can report to achieve and see and what farmers are achieving through the same management strategy.
"We are also seeing a similar yield improvement with pulse and legume break crops of about 150kg/ha.
"So when a break of some sort is used in the LRZ benefits are coming through, but perhaps not quite to the level the research community might think is achievable."
Figures Dr Lawes showed, indicated that from 150 millimetres of rain in the growing season to 200mm, wheat after cereal and wheat after pasture provided least yield benefit in the follow-on crop.
Wheat after pulse and wheat after oilseed provided most yield improvement up to 200mm of rain in a growing season, but in wetter areas or in wetter years beyond 200mm, a fallow break or oilseed break crop produced the best follow-on benefit.
Wheat after cereal remained the least effective break irrespective of rainfall.
"The interesting one is pastures (showing a 60kg/ha yield improvement in a subsequent wheat crop) -the yield benefit following pasture is not that great, in fact not significantly different from wheat following a cereal," Dr Lawes said.
"There's an incredible amount of research showing that well-managed, weed-free legume pastures that are not overgrazed do give you a wheat yield benefit following, but that is not coming through in this (CSIRO analytics).
"This would suggest that maybe the pastures that are being managed might have some potential for improved management to realise that break effect that should transfer - at least according to the experiments that have been done - to the follow up yield."
Dr Lawes said the toolset ultimately had the potential to cut the cost of agricultural research by reducing the need to run many localised trials which are expensive.
Conversely, it could help determine whether a trail result is likely to be applicable to a particular area or farm, he said.
"It means we can test agronomic packages - I've used crop rotations as an example of what we can do right now - but we can bring in other factors like fertiliser regimes and time of sowing to explore how an agronomic package would work on your farm," he said.
