Varying fertiliser rates is a goal this season for one Western Australian producer as a way to start tackling uneven crop establishment in sporadic moisture-holding soils
The race to get the winter wheat in and up is an increasing challenge for Western Australian grower Nick Gillett, who farms 9000 hectares at Bencubbin, north-east of Perth.
The variables he must factor in are increasing each year, and he is not alone in facing this challenge. In the past, for example, seeding schedules took into account potential frost risk. Now they have to accommodate moisture management because dry finishes seem to have become a new ‘norm’.
Farm owners: Nick and Tryphena Gillett
Location: Bencubbin, Western Australia
Farm size: 9000 hectares of arable land
Farm manager: Nick Gillett
Rainfall: 310 millimetres (growing
Soil type: 50 per cent mallee; 30 per cent heavy clay; 20 per cent sand and gravel
Soil pH: from 4.5 to 8.5 (continuous liming program to reach a minimum topsoil pH of 6)
Crops: 5000ha wheat, 2000ha barley and 2000ha of fallow, canola and pasture
Nick says dry conditions at season’s end (late spring) can now be pretty much guaranteed, so for the farm to be profitable and sustainable, timely crop emergence under marginal conditions needs to be improved.
It is a broad-ranging issue with many options, which Nick investigated as part of his GRDC-funded Nuffield Australia scholarship during 2014.
He travelled to Canada, the US, France and the UK, plus Australia’s eastern states exploring moisture and its measurement, soil improvement, soil health and moisture retention, seeding machinery, breeding and seed treatment.
Since coming home and mulling over what he has seen, Nick has decided to address the farm’s spatial variability by using variable-rate technology (VRT) to apply fertiliser.
“There is a large spatial variation in crop establishment across the farm, even in the same soil type, because of patchy moisture-holding. We need to measure it and see what’s happening and then work out what we can do better to improve our results,” Nick says.
The first step is VRT: “A rewards program for areas doing well, VRT will help us better manage our soils.”
Nick has used real-time kinematic (RTK) autosteer for about a decade and has “dabbled” with VRT in the past. “But, I guess it wasn’t classed as a high priority and was overlooked.”
Yield data, collected since 2003 and from typical seasons, will be used for zoning, as will Precision SoilTech soil testing, nutrient analysis from CSBP (a division of Wesfarmers) and local knowledge, Nick says.
The decision to begin using variable fertiliser rates again was not taken lightly. It will involve upgrading software and rate controllers, plus time. “It will take more than a week to process yield maps and soil-test results to determine fertiliser and seed rates. It will be a stretch to get it all done in time.”
Nick feels it is an important step and one that will help improve margins.
As well as addressing variability via input management, Nick would also like to explore the intricacies of his soils’ moisture needs using measurement tools.
Tools such as the ones he saw in the US at Decagon Devices in Washington state could help better understand patterns of soil moisture loss and help tweak management plans – such as seeding depth, moisture-seeking decisions and even location – so soil moisture can be retained for longer.
“Decagon Devices supply all manner of soil-measurement instruments. Dr Gaylon Campbell, the owner and founder, is highly regarded for his achievements, such as supplying soil-testing equipment for the NASA Phoenix Scout mission in 2008,” Nick says.
Nick was also interested to learn how US cereal growers were seeding deep into the profile to ensure timely germination – a management option that breeding programs there were working to achieve.
In the Pacific North-West, winter triticale is seeded at depths of 150mm to ensure the crop emerges before the winter freeze.
US breeders consider coleoptile length in their programs, Nick says.
The coleoptile is the pointed protective sheath that encases the emerging shoot as it grows from the seed to the soil surface. For wheat to emerge successfully from the soil, the seed should not be planted deeper than the coleoptile length.
Nick sees coleoptile length as an important breeding trait for Australian conditions too.
“And not just its length, but strength too. It’s a trait that could benefit all producers … it would give greater resilience to waterlogging, chemical damage and other seedbed imperfections.”
Now he is back on the farm and working through not only the 2015 season, but also his Nuffield report, Nick’s mind is swimming with ideas about what may work on his farm. “Anything from revolutionary polymer seed coatings, polymer soil blankets, stripper fronts to retain more soil cover or seeding machinery modifications,” he says.
He says it will be a “work in progress” as he balances diminishing returns and the challenges associated with spasmodic rainfall.
Heat stress overtakes frost risk
Seeding decisions at the Gilletts’ Bencubbin property used to be made to minimise frost risk. Now they are made to reduce drought risk.
Together, dry conditions at the season’s end and diminishing growing-season rainfall have seen yields drop.
Nick says that if germination is delayed, profit is at risk.
“If germination is delayed, by say four or five weeks, it will reduce the time the crop has for reaching maturity. The wheat will be trying to flower and grain fill when the weather is hot and dry.”
The difference in conditions can mean the difference between a big profit and a “skinny” year.
“Without frost and in an average season, our wheat potential can be two to three tonnes per hectare if it is sown early and has germinated by mid-May. This compares to well below 1t/ha for crops emerging in late June and early July.”
Nick now plans to start seeding in early April, before the traditional Anzac Day (25 April) start. “This is regardless of soil moisture levels or the forecast,” he says.
“Our seeding-date start time is now governed by our ability to get the crop in and maturing at the right time to beat moisture stress at the end of the season. This has become more of an issue than frost. When frost was a significant threat, we were once comfortable spreading out the seeding window, but now drought stress is more guaranteed.”
Last winter grains season was a below-average one for the farm, with wheat yielding 0.9t/ha. “A very hot, dry August at the business end of the season did not help,” Nick says. “This is what we want to avoid by learning more about moisture and germination variability.”
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