It is a common, but complex question for grain growers: Do I grow my farming business by purchasing more land, or by improving the hectares I already own?
The answer may come from an innovative co-investment by the Grains Research and Development Corporation (GRDC), the University of Southern Queensland and the Department of Agriculture and Fisheries (DAF) endeavouring to provide growers with the cost benefits of improving or ameliorating soil to boost both farm productivity and long-term land value.
The 'Economics of ameliorating soil constraints in the northern region' project is a five-year research initiative being led by the University of Southern Queensland with six trial sites across Queensland and northern New South Wales. These sites are managed by the DAF and the University of New England (UNE).
GRDC Soils, Agronomy and Nutrition Manager – North, John Rochecouste said the project's initial aim was to investigate strategies to overcome two key constraints, compaction and sodic soils, which commonly affect broadacre cropping paddocks across the two regions.
"The difference with this research is we want to understand if it is possible to make permanent or long-term improvements to correct compaction and sodic or dispersive soils," Dr Rochecouste said.
"Once we understand what is needed to overcome these constraints permanently, we can develop economic tools to accurately assess the whole-of-farm business impact.
"This economic analysis will consider soil amelioration costs and yield gains, as well as the overall improved productivity of the land, so growers – and importantly their financiers – can then evaluate soil amelioration as a capital investment on-farm."
Dr Rochecouste said the project was ambitious, but important because it put to the test well-established soil improvement practices and scientific knowledge in an economic way to assist growers make significant farm business decisions.
Researchers presented the first year of project findings at recent GRDC Grains Research Updates in Narrabri and Dalby. A recording of the presentation is available.
University of Southern Queensland researcher Stirling Roberton said the initial work focused on whether a soil profile could be 're-engineered' so it was not constrained physically and chemically.
As part of the research, trial sites have been established across Queensland and NSW assessing 13 treatment combinations to test surface (zero to 20cm) and subsurface (20-50cm) amelioration strategies to remove soil constraints. Extensive soil testing has also been carried out across the trial sites to ensure constraints have been accurately identified and to allow for targeted amelioration.
Dr Rochecouste said some of the amelioration treatments had generated significant industry interest because of the 'unorthodox' rates being used in the research.
"This research is testing, evaluating and determining the cost-benefits of treatments that growers couldn't afford unless they knew it was going to be economically viable," he said.
"For example, we tested the effectiveness of gypsum at 15 tonnes per hectare (t/ha), compared with high-rate feedlot compost, and lucerne pellets at 10t/ha. We also tested elemental sulfur applications as a way of dissolving calcium carbonate to produce gypsum in-situ and lower alkalinity.
"These rates were calculated based on each trial site's specific soil constraints and were theoretically sufficient to permanently correct soil constraints and achieve a long-term improvement in land productivity and thus increase the land's capital value."
Dr Roberton said the high rates had been designed to address soil constraints on areas within paddocks identified as most likely to benefit and generate long-term yield gains and permanent improvements to soil quality.
"Most highly constrained soils require significant capital investment, particularly when you consider the cost of deep ripping for compaction, combined with high rates of amendments needed to fix dispersive soils," he said.
First year results across all sites showed substantial yield gains, but researchers acknowledge ongoing work will be critical in determining the consistency and longevity of specific soil amelioration treatments.
As an example, DAF senior research scientist David Lester reported that at Millmerran (a Queensland trial sites) yields increased by 25 per cent or 1.25t/ha and similarly at Drillham (Queensland) grain yields increased by 60 per cent or 1.25t/ha after high nutrient treatments.
"But what these trial sites also proved was the 'blanket-applications' of ameliorants across a paddock was not economically feasible," Dr Roberton said.
"So, growers will need to diagnose soil constraints accurately and use yield maps and other tools to ensure they are only investing in treatments in the areas of their paddocks that offer the best potential for improvement.
"However, what we really need to find out, on behalf of growers, is what is needed to permanently overcome soil constraints and then assess whether these solutions are economically viable for northern grain growing businesses when they are viewed as capital investments on-farm."
Dr Rochecouste said results from the ongoing soil amelioration project would be shared widely with industry, with growers also involved in on-farm case studies to support the economic analysis.
For the latest information on the project go to the GRDC 2021 Update paper on Amelioration for sodicity – deep ripping and soil amendment addition across NSW and Queensland. A recording of Stirling Roberton's presentation on soil amelioration from the 2021 GRDC Grains Research at Dalby is also available.
For GRDC resources to assist with economic decisions, soil amelioration and amelioration processes go to:
