‘Listening, learning and responding’ is the mandate of GRDC’s National Grower Network and it was exactly what was practised at grower forums at Kalannie and Moorine Rock in August 2021.

The events were an opportunity for growers to learn about local and interstate GRDC-supported research on improving wheat yields in sodic and dispersive soils.

GRDC grower relations manager Jo Wheeler says these roadshows are a key means to raise the profile and awareness of GRDC’s research investments.

“We are able to facilitate direct researcher-grower interactions. It is a great way to share learnings from research and for some growers it may be the first time they have heard about the research addressing what might be a priority issue for them,” Ms Wheeler says.

“But equally it is a great way for GRDC to listen and learn from growers and for us to respond to their needs.”

This was the case when David Hall, a senior research scientist from the Department of Primary Industries and Regional Development (DPIRD) at Esperance, talked to the growers in attendance about his research on sodic and dispersive soils. Research experience on similar constrained soils was shared from across the country as Dr Ehsan Tavakkoli from the New South Wales Department of Primary Industries shared his NSW experience via a virtual appearance.

“We try and make these forums informal; attendees are able to chat with the presenting researchers as well as GRDC staff and Western Panel members,” Ms Wheeler says.

“It is an effective way in which GRDC can engage directly with its stakeholders to assist in developing locally relevant research, development and extension (RD&E) investments.”

As a result of these events, GRDC was approached by growers who were keen to have the GRDC-supported soils work by David Hall extended to their regions.

Identifying best bets

Mr Hall has been exploring the potential of a number of different amelioration interventions for managing sodic and dispersive soils, particularly on heavier clay soils and specifically to aid rainfall infiltration.

“We have been concentrating our research at a limited number of trials at Merredin Research Station with particular soil types and environments. The aim is to have detailed research trials in a wider range of environments than we currently have,” Mr Hall says.The aim of the work has been to retain water from rainfall in these soils as up to 40 per cent can be lost to evaporation due to poor infiltration.

“The poor structure, clay textures and low rainfall mean more water is stored closer to the surface in these soils, leaving it exposed to evaporation.

“We have been evaluating a number of amelioration options both in field trials and glasshouse work, including in-furrow gypsum application and the use of inorganic mulches such as sand and gravel.

These new trials will contain some of the emerging or ‘best-bet’ treatments that have the potential to boost yields on sodic soils and combine these with existing amelioration practices.

Gypsum is a widely used method of ameliorating dispersive sodic soils, but rather than applying blanket rates, recent research by DPIRD principal research scientist Dr Ed Barrett-Lennard has suggested that in-furrow applications of gypsum at low rates could be just as effective.

“Our research has shown that low rates of gypsum, 50 to 100 kilograms per hectare, applied in-furrow can increase barley grain yields on average by 0.5 tonnes per hectare – or 17 per cent – at Merredin,” Mr Hall says.

“While we are confident that this is occurring at the Merredin site and has also been observed in previous trials, we are less confident how this result might be achieved in other locations, as responses can be quite site-specific.”

Field trials have shown that on clay soils, unincorporated gravel and sand applied to the surface as mulches has been shown to increase yields by 0.4 to 1.4t/ha (17 to 66 per cent) in non-waterlogged soils at two locations at Ravensthorpe. Additionally, the ability of two centimetres of gravel to reduce evaporation has been demonstrated in controlled glasshouse experiments.

“Growers have also observed benefits from mineral and organic mulches in improving crop growth on sodic soils and are obviously keen to learn about the science to underpin this practice.

“Finally, we want to include a deep tillage treatment. Currently we do not recommend deeper tillage on sodic clay soils given that our results so far have not led to yield improvements.

“Despite this, farmers still deep-till their sodic soils given that the subsoil’s strength almost always exceeds limits for plant root growth. We want to either completely discredit deep tillage in sodic soils or understand the exceptions.”

Enlarged footprint

The enlarged footprint for this soils work will include three additional experiments being established in each of the following locations on growers’ properties: Geraldton (Devils Creek), East Kwinana (Moorine Rock) and Esperance (Grass Patch) port zones. These areas all have soil that is sodic, dispersive and has toxins at depth such as boron and salt (Table 1).

Table 1: Description of soil characteristics at Devils Creek, Moorine Rock and Grass Patch sites.

Source DPIRD

Table 2 shows the 12 treatments that will be applied, which are single or combinations of amelioration interventions.

“We intend to use a paraplow to more thoroughly investigate the benefit, or not, of deep ripping these challenging soils,” Mr Hall says.

Table 2: Amelioration treatments for expanded soils research. Gravel will be sourced from a local gravel pit.

Source: DPIRD

“This is essentially an experimental tool. It is a slant-legged tyne that operates at a 30cm depth, shattering the soil at that depth but without bringing clods or columns to the surface. This means that we will not bring possibly toxic soils to the surface.

There are mixed reports of the success of deep ripping of these sorts of soils. We want to determine – definitively – whether these soils will respond to deep ripping alone or combinations of deep ripping with other amelioration.

The additional trials will be run for two years and cropped to cereals in the first year and then to the growers’ rotation selection in the second year. Yield and plant analyses will be carried out each year. Economic analyses will also be carried out.

The enlarged footprint will be resourced with additional DPIRD personnel: Wayne Parker will oversee the Devils Creek site, Glen Riethmuller (Moorine Rock) and David Hall (Grass Patch), while Dr Geoff Anderson will collate and interpret the data.

“As some of the sites are co-located with other GRDC-supported DPIRD trials, this will give opportunities for field days where growers can inspect responses, meet with researchers and ask questions,” Mr Hall says.

More information: David Hall, 0447 914 013, david.hall@dpird.wa.gov.au

Read more: Mineral mulches improve water relations and yields on sodic clay soils.