Spading trials frost finding in western region

Higher canopy temperatures identified in WA spaded trial plots


Agronomy
'Walyoo' farm manager Mark Drake, left, and Department of Primary Industries and Regional Development researcher Giacomo Betti. PHOTO Evan Collis

'Walyoo' farm manager Mark Drake, left, and Department of Primary Industries and Regional Development researcher Giacomo Betti. PHOTO Evan Collis

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Trials find frost implications from claying and spading in water repellent sandy soils.

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SNAPSHOT

  • Owner: Lawson Grains
  • Manager: Mark Drake
  • Property name: 'Walyoo'
  • Location: Regans Ford, Western Australia
  • Size: 5600 hectares
  • Grains: Canola, barley, lupins and wheat
  • Soil types: Deep yellow sands with some pale sands in weaker areas and some patchy sandy gravels
  • Soil pH: 4.3 to 5.9 at 50 centimetres and 5.5 to 7 at the surface
  • Annual rainfall: 600 millimetres (long-term average)
  • Growing season rainfall: 430mm (long-term average)

When corporate farming group Lawson Grains went on a quest to improve water repellent sandy soils on a property at Regans Ford, in Western Australia, little did the company know that - together with local researchers - it would potentially stumble across a partial solution to the devastating effects of frost.

In October 2016, Lawson Grains 'Walyoo' farm manager Mark Drake, and his consultant Erin Cahill, came across this finding after noticing spaded plots, in a Department of Primary Industries and Regional Development (DPIRD) managed trial, appeared to look better immediately after a frost event, compared to all other treatments.

While the effect of frost on crop yield and its relationship to floret sterility is not yet clear, what was found was that spading altered crop canopy sufficiently to reduce floret sterility in barley by 20 per cent in a replicated experiment.

What made the results at 'Walyoo' even more interesting is that this part of WA's grainbelt is not highly prone to frost.

And Mark hadn't been aware the trial plots were in a particularly frost susceptible area on the property.

Starting in 2016, the GRDC-invested trials run by DPIRD on 'Walyoo', at Regans Ford, were originally investigating the impact of claying at various rates, plus incorporation methods, to reduce water repellence in sandy soils.

These trials are just one of a set of three trials run in the West Midlands region investigating ways to reduce water repellence in a range of soil types, including deep yellow sand, deep pale sand and sandy gravel.

Sandy soils

'Walyoo' farm manager Mark Drake, left, and Department of Primary Industries and Regional Development researcher Giacomo Betti. PHOTO Evan Collis

'Walyoo' farm manager Mark Drake, left, and Department of Primary Industries and Regional Development researcher Giacomo Betti. PHOTO Evan Collis

DPIRD soils research scientist Dr Giacomo Betti, who has been managing the trials, says water repellent sandy soils are common throughout the region and growers are increasingly searching for ways to overcome this major yield constraint.

But, he says, after severe frost events in 2016, the trial at Regans Ford is now also investigating the impacts of claying and spading on canopy air temperatures, particularly during the most frost sensitive periods of flowering and grain fill.

Sixteen treatments in the experiment include applications of locally sourced clay-rich subsoil at nil, 100 tonnes per hectare, 150 t/ha and 200t/ha, with each clay treatment applied and/or incorporated in four different ways:

  • No tillage
  • Spaded
  • Spaded at half speed
  • Ploughed with an off-set disc.

So far, the results are indicating that spading (alone or with clay spreading) and increasing rates of clay spreading significantly reduce the severity of soil water repellence in the deep yellow sands at 'Walyoo'.

Dr Betti says when the 2016 frosts occurred, he took the chance to consider reduced frost damage as an important finding of the trials.

"We collected samples from the treatment plots and with the DPIRD frost research team assessed floret sterility, which basically meant we counted the florets of the barley to see how many were sterile out of the total," he says.

"To our surprise, we found that in the treatments with spading, regardless of the amount of clay, 60 to 65 per cent of the florets were still good, but in the control treatment, only 40 per cent, or even less, were good."

It is suggested that spading, with or without a clay application, may have some relationship to frost damage.

"The idea that claying is a technique that may help to reduce frost damage is emerging, perhaps because it keeps more water in the soil and therefore increases its ability to store more heat during the day and then release it at night," Dr Betti says.

"But in this situation, spading alone appeared to reduce the impact of frost, regardless of clay application, and this is the first time we have seen this happen."

To our surprise, we found that in the treatments with spading, regardless of the amount of clay, 60 to 65 per cent of the florets were still good, but in the control treatment, only 40 per cent, or even less, were good - DPIRD soils research scientist Dr Giacomo Betti

While the 2016 trials were planted to barley, which showed obvious signs of the frost, lupins were planted in 2017, which made it more difficult to assess the frost damage.

As such, Dr Betti installed loggers to monitor air temperatures near the canopy.

Despite not being considered a frosty area, there were several hours from the end of August to early October in 2017 that were below zero degrees Celsius.

"When we assessed the data, we found that, again, the control site, (no clay and no incorporation) canopy had more hours below zero degrees C than the treatment with spading, with or without clay," Dr Betti says.

Wheat results

DPIRD frost research team leader Dr Ben Biddulph. PHOTO Evan Collis

DPIRD frost research team leader Dr Ben Biddulph. PHOTO Evan Collis

In 2018, the trial was planted to wheat and, again, the canopy air temperature monitors showed the ameliorated plots experienced less time below zero degrees than the control plots.

The temperature in the ameliorated plots never fell below minus 4 degrees C, while the control plot spent more than two hours throughout the season at temperatures of minus 4 degrees C or lower.

"We have yet to understand the mechanisms behind this effect, but perhaps it is to do with the change in physical properties of the soil," Dr Betti says.

"Or it could be that the crop established much faster in the spaded soils, so the plants were healthier and bigger and better able to maintain a higher air temperature around the canopy."

AgVivo consultant Erin Cahill suspects the higher canopy air temperatures could be a result of total soil health.

"Overall, though, any crops planted into ameliorated soils, particularly after lime incorporation, will have a better chance of accessing moisture for good early establishment, and be a healthier plant to withstand stress, of any kind, right throughout the season," he says.

DPIRD frost research team leader Dr Ben Biddulph agrees these findings could be a result of a combination of many reasons and says improving soil health and increasing yield potential is a good start when it comes to combating the effects of frost.

Dr Biddulph has seen similar results in frost trials in frost-prone locations in the Upper Great Southern in 2014 and 2015 in collaboration with ConsultAG, but the results were inconclusive due to variable affects across soil types and landscape and not enough frost damage in those seasons.

"While we have seen this effect on ameliorated soils before, we are cautioning growers not to invest in spading in the hope that it may improve the crop's chances during a frost even," he says.

"At this stage, our data isn't suggesting that the economics will work just for this end result."

However, like Mr Cahill, he says many frost-prone sandy areas are also water repellent, meaning spading, or other soil amelioration techniques, could have a win-win benefit.

"The great news is the amelioration benefit is still there even when the sites get light to moderate frost damage," Dr Biddulph says.

GRDC has invested in a frost identification guide. PHOTO Evan Collis

GRDC has invested in a frost identification guide. PHOTO Evan Collis

For Mark and Lawson Grains, the outcomes from the trial will have a practical impact on the way the company farms these soil types in the future.

As a start, Mark believes the results are justifying the decision to invest in soil amelioration machinery, including a deep ripper and spader.

Since that purchase, Mark has deep ripped and spaded, with lime incorporation, 100 per cent of the sandy soils on 'Walyoo' in just three years, believing water repellence to be one of his biggest yield constraints, along with nutrient leeching.

"The data from these trials has allowed us to look at both the short-term costs and the long-term benefits of the work carried out so far," he says.

While he still isn't convinced the property is particularly frost prone, he has now identified at least 300ha that he considers at risk from frost damage, albeit minimal in most years.

While the unexpected trial result in regard to frost may be important for growers in more frost prone areas, Mark is focusing on the outcomes from the water repellence data to improve farm business performance.

He says most of the property suffers from soil water repellence at some level and even his gravel soils, which historically have been the most productive soils in the business, have been showing some signs of water repellence in recent years.

Slow germination

In 2017, due to the dry start and the small early rain events, germination was slow and staggered on these areas, which affected yields, Mark says.

The results from the trial also confirmed that the 2017 yields of the lupin crop were highly correlated to early plant establishment.

Mark believes these water repellent challenges haven't gone away, so he plans to one-way plough these gravel areas in coming years, which covers about 25 per cent of the property.

"While it isn't a wide-scale issue anymore, staggered crop germination still shows that when soils become highly repellent, the work required to return them to healthy, profitable soils is immense," he says.

The research results also showed the importance of on-row seeding in water repellent soils for the 2017 lupin crop.

In fact, in the control treatments, a significant difference in crop establishment was found between on and off-row seeding, with the latter having 65 per cent less ground cover when measured in August using aerial imagery.

But, with the addition of spading, the difference between on and off-row seeding was reduced to 15 per cent or less.

While it isn't a wide-scale issue anymore, staggered crop germination still shows that when soils become highly repellent, the work required to return them to healthy, profitable soils is immense - Lawson Grains 'Walyoo' farm manager Mark Drake

At harvest time, extensive hand harvesting by DPIRD researchers revealed lupins sown on the previous year's barley rows were yielding more than double those sown off-row in the control areas, but there was less than a 10 per cent difference between row placement on spaded treatments.

"So one of my focuses moving forward will be targeting the on-row placement," Mark says.

Continuing trials

Mark Drake and Dr Giacomo Betti with temperature monitoring equipment at 'Walyoo'. PHOTO Evan Collis

Mark Drake and Dr Giacomo Betti with temperature monitoring equipment at 'Walyoo'. PHOTO Evan Collis

Further GRDC-invested trials on 'Walyoo' are investigating the effects of deep ripping and how long these effects last in the sandy soils.

"In 2017, the last 1000ha of deep yellow sand on 'Walyoo' was ripped and spaded, so following on from this we have been ripping down to 600 millimetres, or deeper, depending on the depth of the hard pan, as and when required," Mark says.

"This second set of trials will guide us in regard to when we need to re-do this deep ripping and spading.

"But the data from the claying and spading trials has given us accurate information to be able to carry out cost-benefit analysis, which has showed us that that we are on the right track with our amelioration program."

Since removing much of the severe water repellence constraint, Mark says it is time to focus on time of seeding, soil health and fertiliser applications to further build soil quality and slow the return of non-wetting issues.

"It isn't always about changing soil health in one pass," he says.

"Input costs and margins have to be looked at with any of these trials. If a specific area can't or won't return profit, something needs to change."

More information: Dr Giacomo Betti, giacomo.betti@dpird.wa.gov.au

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