ACCORDING TO Alison Frischke of the SA Research and Development Institute, fluid fertilisers are the most efficient forms of fertiliser to deliver phosphorus to crops grown in phosphorus-responsive calcareous soils in low-rainfall areas.
"They have been shown to outperform gran ular fertilisers at equivalent rates of phosphorus, but only on soils that respond to phosphorus," she said. " In other words, no difference in performance can be expected on soils that have adequate available phosphorus although, of course, there may be responses to other nutrients if they are limiting."
Ms Frischke was speaking at the annual conference of the SA No-Till Farmers Association, which was supported by growers and the Federal Government through the GRDC.
She said that in 2001 there was a very favourable finish and the difference in yields between fluid and granular fertilisers was narrower. The fluid fertiliser advantage appeared to be greatest in seasons with dry openings and/or early finishes, possibly because in these conditions, with lower soil moisture, phosphorus in granular form became more 'tied up' and less available to plants in calcareous soils.
Summarising other aspects of the research, which is being conducted with Bob Holloway and Dot Brace of the Minnipa Research Centre, Ms Frischke said:a phosphorus rate of 6-9 kg P/ha as fluid fertiliser on red and grey calcareous soils appeared to be the most cost-effectivebesides yield advantages, there were logistical and agronomic advantages that many fluid fertilisers could offer, including general handling, time of application and mixing nutrients for specific purposesfluid fertiliser in the form of ammonium poly phosphates had outperformed most other fluid fertili ser formulations, although seasonal and soil type interactions could influence product performance.
Program 4 Contact: Ms Alison Frischke 08 8680 6208; email email@example.com
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