This season we have seen the price of granulated fertiliser go through the roof which has resulted in a proliferation of alternative approaches to soil fertility management. I thought I would go over some guidelines to how farmers can discriminate between the many systems on offer today, i.e. some of the rules for addressing the debate.

Throughout my career I have been involved in the evaluation of fertilisers from prescription type products at Mudamuckla through to carbon-based products at Tuckey. It’s important that farmers distinguish between fact, myths and down right marketing.

My 30 years of experience in trying to develop fertiliser recommendation systems, which are adapted to upper Eyre Peninsula, I have yet to see a fertiliser system consistently outperform those based on water-soluble phosphorus and nitrogen. The results of this independent research into a range of alternative fertiliser products are documented in the Farming Systems Research Summaries from 2002-2005.

Here’s where the marketing comes in, with comments like “the formulation of those products evaluated have changed since then” or “you need to use this stuff for a number of years before the system will benefit”, which obviously creates the perception of repeat business. Does this sound familiar?

We all know the value of retaining organic matter to enhance nutrient cycling, biological activity and soil stability. Adding charcoal to soils in sufficient quantities would make both the carbon content greater (if added at a high enough rate) and the colour darker, but it would not increase the soils fertility. To build up soil organic matter your need to add organic matter (plants) and reduce losses (cultivation). Carbon based fertilisers appear not to achieve organic carbon improvement.

I urge farmers to calculate the on-farm price per hectare of their traditional product and the suggested alternative and how much water-soluble nitrogen and phosphorus are applied per hectare in each. You can then compare the two nutritional systems or products and make you own judgement of what to use.

The next question to ask of an alternative product manufacturer is for their rate response curve for your soil type, as this will indicate if there is a yield advantage over doing nothing!

The many phone calls I’ve had recently have generally been on fertiliser rates and products with decisions on a “horses for courses” basis. We are all aware of the value of soil nutrient testing in the decision making process but if that’s not possible I suggest that this year a minimum phosphorus application rate of 6kg P/ha (18:20:00 at 30kg/ha) would not see you fall off a production cliff provided soil reserves of P are reasonable. Apply more nitrogen mid season if necessary. This year I would also be managing trace element requirements with seed dressings or foliar sprays.

Whether you invest your scarce dollars in short or long-term fertility is a personal decision, which can be made with the help of good advice from credible nutritional consultants.

Further information can be obtained from .

AUTHOR: Neil Cordon, Extension Agronomist, SARDI
CONTACT: Neil Cordon, Minnipa Agricultural Centre, Telephone 08 8680 6210