Backed by growing scientific evidence, Australian farmers like Andrew and Jenny Polkinghorne are making the switch from granular to fluid fertilisers, with great results.

"Since switching to fluid fertilisers in 2003, we have lifted our yield potential and changed the outlook of our farming enterprise," says Andrew Polkinghorne who farms north-east of Lock on the Eyre Peninsula in South Australia.

"Before we began to use liquid fertilisers, our yields were static at a frustratingly low level. If the profitability and viability of our business was to improve, then we had to increase our yields."

Today, Tuesday 21 September, at the first Australian Fluid Fertiliser Workshop being held in Adelaide, Andrew will share his experiences alongside five international speakers and a series of local experts.

Research by CSIRO, the South Australian Research and Development Institute (SARDI), and the Victorian Department of Primary Industries has shown fluid fertilisers work well on calcareous soils, frequently outstripping the performance of conventional solid forms of the same compounds at the same rate of application.

According to Dr Larry Murphy from the international Fluid Fertilizer Foundation (based in Manhattan, USA), data being developed by CSIRO scientists regarding the understanding of the soil chemistry and availability of fluid P sources is probably the best current research on the topic world-wide.

Research Director Mike McLaughlin explains, "We suspect crops find it easier to access phosphorus from fluid fertilisers rather than granular products on some soils."

Calcareous and acid soils are widespread across Australia and are commonly used for cereal production. But these soils can bind fertiliser phosphorus into forms unavailable for plant use.

In contrast, neutral pH soils do not fix phosphorus as strongly as alkaline and acidic soils and fluid fertilisers therefore do not seem to offer the same benefits over granular fertilisers on neutral soils.

When researchers supplied crops grown on calcareous soils with granular triple superphosphate in field trials, the amount of phosphorus in plant tissue was found to be critically deficient. "But when the same amount of phosphorus was applied in fluid form, plant growth increased by more than 40 per cent," says Dr McLaughlin.

"In calcareous soils, chemical reactions occur around phosphorus granules, which render much of the granular phosphorus unavailable for plant use," Dr McLaughlin continues. "So when granular phosphorus fertilisers are applied to grey or red calcareous soils, 10-20 per cent of the total phosphorus remains precipitated within the granules after five weeks and is therefore inaccessible to plant roots."

Fluid fertilisers progressively diffuse away from where they are placed within the soil, creating a larger volume of soil with elevated and available phosphorus levels and increasing the likelihood of roots coming into contact with the phosphorus.

The research is helping to explain why fluid fertilisers can have such an impact, even when soil tests indicate there is plenty of phosphorus (P) present.

Fluid fertilisers are widely used in the US. Dr Murphy: "With continuing industry and grower interest and considering the ingenuity of Australian crop producers, fluid fertilisers will continue to develop in Australia." But, he says, fluids have to make sound agronomic sense. The workshop is intended to offer useful and practical advice to help farmers improve crop nutrient management and profitability.