AGGRESSIVE soil disturbance techniques designed to reshape the soil profile and overcome a range of underlying constraints are starting to pay dividends for an extensive cropping enterprise in Western Australia’s central wheatbelt.
Ty and Em Fulwood and Ty’s father, Ray, have been running a program to ameliorate the gravelly sand, gravelly loam and yellow sand soils on the 3400 hectares of cropping country they farm in the Meckering and Tammin districts east of Perth.
“The big picture is we are trying to make a business that is profitable in the medium to long term. We have some serious constraints in our business and a lot of them are to do with the soils. We have non-wetting issues, compaction and acidity,” Ty Fulwood said.
“If I can fix these early in my career and maintain a controlled traffic system then I should be able to reap the benefits over the medium to long term.”
Soil disturbance techniques
The Fulwoods have adopted a range of soil disturbance techniques such as deep ripping, topsoil inclusion and spading across their farming country, using them either individually or in combination, depending on soil type and the constraint they are trying to address.
Mr Fulwood said they had achieved good results on country that had been treated with a standard deep ripping to 35-40 centimetres in depth.
They had also been using topsoil inclusion plates to good effect in some paddocks. Fitted to the back of the ripping tynes, the opener plates run below the soil surface allowing topsoil and organic matter to be slotted deeper into the profile.
They had also used spading on some of the country using a rotary machine that partially inverts and mixes the soil to a depth of about 35cm.
“Anywhere which is a sand and not too loamy that we can rip, we try to rip. Anywhere where there is non-wetting soil we will try to rip and spade,” Mr Fulwood said.
Inspired by work conducted in WA’s northern farming areas, the Fulwoods have also introduced very deep ripping to a depth of 70cm in particular paddocks using a robust, deep delving machine.
“I use the delver on the lightest part of our farm. I thought if we can bring up a bit of clay before we spade we would be better off. Typically I won’t use that, but it is as good as we can do without resorting to claying,” he said.
“I am confident it will solve our non-wetting issues and we will get yield responses, but how long it will last I’m not certain.”
Mr Fulwood said soil amelioration techniques needed to be tailored to suit individual soil types and were not the answer across all their farming country.
“We won’t necessarily do the whole farm because a lot of our soil is shallow to gravel which we can’t really rip or spade. I think we will do up to 1500ha in total,” he said.
“We do some contracting work as well, so will probably do about 1000ha in contracting. With grain prices where they are, I’m hoping that will help the budget.”
All the soil inversion techniques have played a part in incorporating the 7500 tonnes of lime the Fulwoods have spread over their country in the last four years.
Soil type responses
Mr Fulwood said the biggest response to the amelioration work was on soil types that were badly damaged and heavily compacted. The benefit wasn’t as great on country that had been no-tilled for a long period and where machinery movement had been confined to a controlled traffic system.
“In most instances, the payback is in year one. But if we can get five to 10 years out of it I will be pretty excited,” he said.
“Economically, there are a few assumptions that go into it. You have to buy the gear, work out the repairs and maintenance, work out how many hectares you apply it to, sell the gear, and work out the return benefit you get over time.
“For me, I am happy to spend the money now with the anticipation it will improve our profitability and allow our business to move forward.”
Soil amelioration trials
The Western Australian Department of Agriculture (DAFWA) began running a soil amelioration trial last year on the Fulwoods’ farm.
DAFWA soils research officer, Stephen Davies, Geraldton, said the trial was one of a series throughout WA looking at soil amelioration and managing multiple constraints.
“On some soils the main constraint will be compaction, so deep ripping will be enough. On other soils you might have a combination of compaction, subsoil acidity and topsoil water repellence. We need to understand what amelioration approach will help us overcome all of those constraints,” he said.
“We have long term research that shows us that if we can overcome multiple constraints we get bigger and longer lasting benefits. One of the things we wanted to do at Ty’s was to take the range of amelioration approaches that are available and put them all together to see what some of the pros and cons of them are.”
Dr Davies said the trial on the Fulwoods’ farm was set up to look at a range of treatments from basic deep ripping to soil inversion.
“In a way, the question we are asking is: Is deep ripping enough or do we need topsoil slotting or go to the extent of changing the soil surface even more by inversion ploughing?” he said.
Results from the first year of the trial have shown:
Acidity: The soil pH is low in the subsoil layer 10 to 40cm deep. Lime on top can fix the topsoil but it takes a long time to change the pH of the subsoil. That has been a big driver to mix the lime in to get a more rapid response to the lime application.
Water repellence: Deep ripping on its own doesn’t modify the topsoil enough to change the water repellence. It requires either one way ploughing with a disc, spading or mouldboard ploughing to significantly remove the water repellence from the surface.
Compaction: All the strategic tillage treatments reduced the soil strength to the depth of the tillage. The deep ripper (delver) removed compaction to 50cm and beyond.
Yields: the site was sown late last year and the ‘control’ yielded 2.1 tonnes/hectare of wheat.
- Standard shallow deep ripping showed a yield response, but it wasn’t statistically significant.
- Deep ripping with topsoil incorporation gave a positive yield response of about 550kg/ha of extra yield.
- Standard deep ripping with spading gave about 750kg/ha extra yield.
- Anything with deeper ripping, either on its own or with topsoil slotting or spading, gave about 800kg/ha yield response.
- The ultimate mixing treatment with the very deep ripper, topsoil slotting and spading yielded just over 1t/ha of extra grain yield.
- One way deep ploughing with a disc plough produced about 700kg/ha extra yield.
Dr Davies said the results were only from one season of data and would have to be repeated over at least two more seasons to see if they could be sustained over time.
“We have yet to crunch the economics on it, but in a sense the disc plough or the deep ripping with inclusion plates and topsoil slotting would probably be two of the more profitable approaches because the initial cost is not so high. Some of the higher yielding responses have higher costs,” he said.
“In the end it will be about what lasts over time and what gives the biggest benefits over time.”
Links to GRDC papers:
Soil amelioration in Western Australia https://grdc.com.au/Research-and-Development/GRDC-Update-Papers/2017/02/Soil-amelioration-in-Western-Australia
Deep ripping https://grdc.com.au/GC126-DeepRipping