"BEING on L Plates" is how Kellerberrin farmer Matt Steber describes his foray into variable rate application of fertiliser on parts of his 7600-hectare farm.
But he’s hoping that a combination of researcher know-how and his comprehensive knowledge of individual paddock performance could net him more than $10/ha productivity improvement at very little cost.
Mr Steber runs a family operation of three properties with his parents, Lou and Lyn, wife Allie and four sons Rory, Thomas, Lachlan and Patrick.
The aggregation is predominantly grain-focused, including wheat, barley, lupins, canola and field peas with the remainder running about 1500 adult merinos.
Sitting on his harvester, listening to the computer mapping systems communicate with nine satellites and watching the canola run through the header, Mr Steber is also watching for visible variations in the paddock and thinking about how that might impact on next year’s crop.
"The trick is working out why some parts of the paddock don't perform," he says.
"Yield maps show which part of the paddock doesn’t perform but they don’t show why.
"Part of the answer is in soil constraints, but you need local farmer knowledge to add in information about frosting, or a different rotation two years prior, or even a problem at seeding time."
Variable rate technology (VRT) is the focus of a CSIRO, Floreat and Department of Agriculture and Food WA (DAFWA) precision agriculture project funded by the Grains Research and Development Corporation (GRDC),
The project is finding that there has to be significant yield and/or soil fertility differences on significant areas within a paddock, for VRT to pay.
While in WA those differences are common, the problem is determining how large, and where they exist in cropping paddocks.
VRT appears to be particularly suitable for Mr Steber’s country which is extremely variable, ranging from red morel soils to good tama sandplain. It’s predominantly sand over clay with good phosphate, but low pH on the lighter country.
Mr Steber is quick to point out however that the biggest problem is rain, with this crop receiving only 167 millimetres in a 320mm average annual rainfall zone.
He has always been interested in variable rate fertiliser, but the technology is now making it much easier to implement.
"I used to do it 15 years ago and manually adjusted from the tractor. I started doing yield mapping in 2004 then had access to 10 years of biomass imaging," he says.
"The variable soil types and biomass imaging showed variable plant growth across certain paddocks year after year.
"Very few paddocks have uniform soil type so trying to farm it all as one is rather difficult. Variable rate technology is one way we can manipulate some of the inputs to our soil type and production."
Mr Steber’s aim is not to reduce costs, but to farm smarter and improve productivity.
"My main reason for the variable rate approach is not to use less fertiliser, but attempt to use it smarter by trying to apply fertiliser inputs where the marginal rate of return is greatest," he said.
"If they are too costly to try and improve, I accept that and fertilise accordingly for a low yield.
"The fertiliser I save there, I put into the better parts of the paddock which I know will get a response from my higher inputs."
He applies fertiliser where the marginal rate of return is highest.
He says the higher that fertiliser and grain prices go, the greater the potential for increased margins from variable fertiliser rates.
"This year we used variable rate fertiliser and seeding on nine of our paddocks, mainly wheat and barley.
"We identified the poorer performing parts of the paddock and reduced inputs on those parts to put more inputs into the better performing parts; breaking paddocks into three zones: poor, average and high."
The basal rate goes on the median, the lower rate (25 per cent less) on the lower performing and the rest (25 per cent more) on the higher performing.
Where known frost risk is high, inputs including sowing rates are cut down on those parts to keep the vegetative growth down and the frost risk to a minimum.
Mr Steber says this year has been frustrating due to lower rainfall and he may not see the full potential. He says the practice is still a valuable, low cost strategy.
"All new headers now come with yield monitors and appropriate software to do application maps," he said.
"Once you have all the hardware talking to each other it’s relatively easy to identify the poorer performing parts of the paddock. The hard bit is determining what to do.
"Some people are out there trying to bring the poorer parts of the paddock up to the rest."
He says this can be done in certain instances but a lot of the time the poorer parts are very shallow soils or have subsoil problems that can’t be economically fixed.
"Given this, even $500/ha in fertiliser inputs would still not grow an average crop, so we need to accept that these areas will only ever grow below average yields, and fertilise accordingly.
"For example there’s certainly parts of the paddock now which will only ever grow 1t/ha so we might use four units of phosphorus and 10 units of nitrogen.
"On other parts of the paddock which can grow 4t/ha we might apply 12 units of phosphorus and 30 plus units of nitrogen at sowing."
Mr Steber is not sure whether the same potential for variable rate fertiliser exists for lupins as with canola, wheat and barley where grain prices and input fertiliser costs are higher.
But he does believe it’s a technology that will see rapid adoption now that GPS technology is so widely used.
"In a couple of year’s time, I believe I’ll be doing variable rate to all of the cropping here.
"I think it’s only a matter of time before this sort of thing grows exponentially and will become very widespread.
"If you go back a generation ago, growers fertilised on a farm basis with one rate covering the whole farm, then people fertilised on an individual paddock basis and we progressed to vary the rates for different paddocks."
He says the next step is for more farmers to farm to soil type within each and every paddock.
And as for improvements in productivity, Mt Steber says an improvement of ten dollars per hectare would be great.
"But I think in a good season we could do even better than that."
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