Soil explorers' journey into the deep
GroundCover™ Issue: 117 | Author: Rebecca Thyer
The Ground Cover Matchmaker series looks at groundbreaking researcher–grower collaborations; in this instalment we profile the work of researcher Dr Yash Dang and Queensland grower Neville Boland in exploring and managing subsoil constraints.
Senior research fellow Dr Yash Dang
About two decades ago, soil researchers considered soils in the northern region to have few issues to hinder crop growth. But that was before people starting digging.
“Twenty years ago we just tested the surface of soils,” recalls University of Queensland senior research fellow Dr Yash Dang. “Unsurprisingly, we didn’t find many problems.”
However, growers were starting to encounter subsoil issues and this became the starting point for extensive research into salinity, sodicity and other constraints – fields of inquiry that opened up new research frontiers.
Yash says an early example was chickpea productivity. Growers were finding the crop grew well one year, but not the next, even when conditions remained the same.
This grower query alone has led to vital northern soils research for Toowoomba-based Yash, and a close working relationship and friendship with grain grower Neville Boland.
Across Queensland properties from Moonie to Goondiwindi, Neville and his wife Penny have been involved in projects to identify and manage subsoil constraints and assess strategic tillage effects, and are today involved in a new project on soil sodicity.
Yash says his relationship with Neville began in 2002 following a Grower Update at Billa Billa, Queensland: “Nev mentioned specific issues on his farm, which led to some tests and the result turned out to be high surface and subsoil sodicity and high subsoil chloride. He offered to collaborate with us and since then we’ve worked together to identify and manage subsoil constraints across the region.”
Neville says he was interested in volunteering a paddock for research. “We had some chickpeas that didn’t grow well,” he says. “I’d moisture-probed the paddock and found sufficient water and wondered why.”
Growers in the northern region rely on stored soil moisture for crop growth, with some soils able to store 200 to 250 millimetres of water. However, subsoil constraints can restrict crop roots’ ability to access this water.
So, the pair’s first collaborative project, which began in 2002, aimed to identify the main limitation in soils where multiple constraints were present.
It was not an easy task given subsoil constraints can vary spatially across the landscape and within the soil profile, and have complex interactions with each other.
However, two constraints – salinity and sodicity – were being identified often, and management options were tested.
“When you have a high degree of exchangeable sodium on top of the soil, as in sodic soils, it impedes water infiltration,” Yash says. Applying gypsum improves this by flocculating soil, leading to better infiltration.
For example, in soils with moderate surface sodicity, applying gypsum at 2.5 tonnes per hectare showed improved yields.
Happy with the trial results, Neville applied gypsum across the farm at 2.5t/ha and, over four years, increased profit by $207/ha in a wheat/chickpea/wheat/sorghum rotation (Figure 1) and increased plant-available water capacity by 15mm. Over four years, gypsum also reduced sodium chloride (salts) in the soil profile by 115t/ha.
“Most of the response was in the second crop and carried on for a few years after that,” Neville recalls.
Working together on subsoil constraints led to another research area – using electromagnetic (EM38) mapping to spatially identify subsoil constraints, better target gypsum applications and therefore reduce costs – and the development of a ‘toolkit’ for growers to identify areas with subsoil constraints.
Yash says another benefit of this early collaboration was the speed with which research results reached growers: “Nev’s a very innovative grower and is well respected. Other growers listen to him and they became very interested in our work early on because of him. Many growers looked to him when their own chickpeas were not performing well. He mentioned the gypsum trial and others decided to use the results of our research to ameliorate soil sodicity on-farm.”
When hard-to-kill and herbicide-resistant weeds, such as fleabane, became a major problem for growers, northern grains research branched out into strategic tillage. Neville again volunteered his time and land.
“Nev knew his own farms might not be the best for strategic-tillage work and suggested his father’s farm, where hard-setting soils were causing deteriorating weed control,” Yash says.
Strategic tillage research, which also occurred at four other sites in the northern region, showed that one or two cultivations in a no-till farming system caused little damage to biological activity, organic matter levels or crop yield and helped with weed control and, in some years, disease management.
Yash says the potential negative effect from tillage – reduced soil moisture – did not adversely affect productivity in 2012, most likely due to good rainfall between tillage and seeding and during the growing season. However, it highlighted the importance of tillage timing and taking the seasonal forecast into consideration.
This year, the pair is collaborating once again on two new GRDC-funded projects to improve the productivity of sodic soils.
Yash says, with up to 60 per cent of cropping lands being sodic and 75 per cent of soils with more than one constraint, management options are complex.
Yash will lead the two-pronged project to identify ways to manage sodic and magnesic soils and to improve yields on these soils.
“Nationally, sodicity, according to one estimate, costs $1.03 billion a year in lost production. Our aim is to develop a national framework to improve the long-term profitability of these soils.
“And we want to achieve this by working in active partnerships with growers, grower groups and agricultural consultants. We want to identify the cropping systems best suited to the constraints of specific soils.”
Yash says the broad aims of the new project and those in the past have been to address global food security and farming’s legacy. “If we don’t manage these soils, what do we leave for our future generations?” He sees future soil research addressing acidity, alkalinity and compaction, but always in collaboration with growers like Neville.
More information:Dr Yash Dang,
07 4529 1245, 0427 602 099,
When Queensland grower Neville Boland heard a Toowoomba-based soils researcher talking at a Grower Update in the early 2000s, he decided to ask him about his chickpeas.
Although the crop seemed to have enough stored soil moisture to yield well, tonnages were hit and miss – one year they were good, another not so.
“Yash was talking about a GRDC-supported subsoil constraints project he’d started and I expressed an interest in volunteering a paddock,” Neville recalls.
That chat led to 13 years of collaboration between an innovative grower and soil specialist Dr Yash Dang, both keen to understand more about soils and how best to improve productivity.
Neville and Penny Boland have 5000 hectares of owned and leased land across three farms between Goondiwindi and Moonie in Queensland’s south, farming about 4000ha a year of dryland cotton, wheat, barley and sorghum.
The initial trial, prompted by the Grower Update, was held on the Bolands’ Billa Billa farm. It found areas of sodicity and salinity on-farm, which can restrict the crop roots’ ability to access stored soil water (chickpea crops are particularly susceptible to high chloride and sodicity).
It was a crucial discovery as growers in the northern region cannot always rely on in-crop rain for crop growth. “The moisture we’ve got in the soil is 80 to 90 per cent of what is available to our crop a lot of the time,” Neville says.
“Ensuring crops have the ability to draw that moisture out is the key to success, but back then we were really in the dark about subsoil constraints.”
To ameliorate sodic soils, gypsum was applied. By flocculating soil, gypsum improves soil sodicity and leads to better infiltration.
Neville used gypsum at rates of 2.5 and 5 tonnes/ha at a cost of $250/ha to $300/ha. He says it was profitable despite the high initial upfront cost.
“The yield response was about 0.5t/ha higher than normal on the chickpeas and about the same on the following wheat crop. We also got a good response on the following sorghum, although we didn’t measure it.”
The success of the research also led into another practice change on-farm – the use of electromagnetic (EM38) mapping and the beginning of precision-agriculture techniques.
The trial had used EM38 maps to identify areas on farm affected by salinity and sodicity. “The first EM38 mapping I saw done was by Yash. I realised the value in being able to identify those subsoil constraints and the year after began the process of mapping our three farms.”
Following the trial, Neville also applied gypsum to other areas of the farm with fairly high surface sodicity. “Most of the response was quite immediate in the first and second crops and carried on for a few years after that.”
The Bolands soon adopted variable-rate technology across their farms. “Visually it was easy to identify various soil types and it matched with our yield data.”
Neville now applies fertiliser to meet nutrient deficiencies. “As it’s been farmed for about 40 years now, we’re getting a response out of urea and nitrogen applications in the rotation,” he says.
The advent of hard-to-kill, herbicide-resistant weeds, such as fleabane, feathertop Rhodes grass and barnyard grass, saw Neville and Yash work together on strategic tillage trials, established in an attempt to reduce weed burdens.
The trials were run at several sites in the area, including at Neville’s father’s farm, where hard-setting soils showed deterioration from existing weed-control treatment. “We saw good weed control, but did have structural decline from the one tillage operation and that’s probably because the soil had low organic matter and textural contrast soil properties (dermosol),” Neville says.
“Once you get that decline and that hard-setting surface, it will affect the infiltration through the fallow management.” Neville and Yash say strategic tillage should be considered with caution in these situations.
Neville believes that he will only need to embrace the strategic-tillage option infrequently thanks to the success of the better residual chemicals in controlling problem weeds.
This year, Neville will collaborate once more with Yash on two new GRDC-funded projects on managing soils with sodicity and multiple subsoil constraints.
Neville sees an enormous benefit in being able to work closely with researchers such as Yash.
“Queensland’s a big state in a big country and as such sometimes research has to be fairly ‘broad brushed’ in its recommendations. So if you can get trials done on your farm, I think it’s great. I always encourage researchers to run trials on the farm. There is nothing better than doing it in your own paddock.”
Over the years, Neville and Yash have become good friends, calling on each other when in town and phoning now and then to talk things over.
Their belief in research and collaboration may have also influenced another budding scientist – the Bolands’ eldest daughter.
“Samantha is interested in science so I took her to a workshop at Gatton, Queensland, with Yash. Although she’s keen on veterinary science, I’m encouraging her to look at agricultural science too,” Neville says.
More information:Neville Boland,
GRDC Project Code ERM00003, UQ00081