Calcareous soils are notoriously difficult to manage in terms of cereal production and are generally low-yielding. Early plant growth is slow and tillering is restricted, leading to low water-use efficiency (WUE).
Investigations into the cause of this problem— known initially as'sick wheat syndrome'— have indicated that phosphorus deficiency in wheat plants is almost universal on highly calcareous soils, despite soil tests that appear to indicate 'adequate' levels of extractable P.
Excerpted from 'Fluid Fertilisers —Will they make a difference?' in The Eyre Peninsula Farming Systems 1999 Summary*
Looking at fluid P
In response to this environmental limitation, Principal Researcher and Minnipa Agricultural Centre leader, Bob Holloway, and colleagues have been investigating a range of fluid P fertilisers in field trials.
In one trial, the fluid fertiliser produced 45 per cent more grain than the granular fertiliser at the same rate of phosphate. A further experiment indicated that 4 kg of P applied in fluid form
as as effective in promoting grain yield as 18 kg P/ha of granular MAP
"Liquids appear more efficient in dry years at low rates of application. They appear to be more accessible physically and chemically and promote early establishment, which is good for WUE," said Dr Holloway.
The results show promise for Wimmera and Mallee soils as well. However, optimum formulation, placement and delivery are still on trial. That's where the Mudges and several other farmers have picked up the reins in adopting the use of fluid fertilisers into broadacre farming.
Leon Mudge and his daughter Carolyn, who farm on calcareous soils at 'Maildaburra' nearWirrulla, last year extended their on-farm tests of liquid fertiliser to a whole-farm approach. They have a mostly mixed cereal cropping program (with some oilseeds grown when the season suits).
"The results from Bob's trials looked such that we felt that fluid fertiliser was the way to go in our soils and so we used it in our whole cropping program," Carolyn Mudge told Ground Cover. "We're certainly very pleased with the results in 2000. We spent the same on fertiliser as we would have with the granular method and we gained in yield."
Last year their Frame, Excalibur and Carnamah wheat averaged 1.4 t/ha. The Mudges spent $9,000 converting their seeder to apply fluid P and are still experimenting with delivery and storage materials and methods.
They are now collaborating on related nutrition research trials on trace elements, particularly zinc.
* The 2000 summary of project results is now available from Minnipa Agricultural Centre.