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FERTILISER | 3 September 2009

New technologies a boon to fertliser decisions

The need to increase productivity is driving Yeelanna graingrower Randall Wilksch to try a new precision farming service and adopt technologies that make more efficient use of the costly commodity that is fertiliser.


Amongst other innovations, Landmark’s Precision Farming Service has assisted Randall in adopting variable rate technology this season. The aim was to make more efficient use of phosphate fertiliser applications. Looking forward he’s evaluating other technologies that could help him make more informed decisions about nitrogen application.


Randall and his family crop 3000ha of wheat, malt and feed barley, canola, faba beans, and lupins. They began yield mapping in 2000 in some paddocks and now have five years of consistent whole farm yield maps across their properties.


Like many growers, Randall didn’t have a clear idea about how he would utilise yield maps when he first started. However, the accumulated information has proven extremely valuable.


Randall is the current Vice President of SPAA (Southern Precision Agriculture Australia) and through involvement with this organisation has learnt how to best utilise the variable rate monitors and computer technology that adorn modern tractor cabins.


Landmark’s Precision Farming Service has used the yield maps to create zones that identify consistently average, below average and above average-yielding areas of each paddock.


Extensive soil testing carried out to “ground truth” the zone maps showed that low-yielding areas with a high gravel content contained greater amounts of phosphorus than high-yielding clay areas.


Landmark then used that information, along with more gained from several years of on farm trials, to develop variable rates for phosphate application and to adopt variable rate technology across the entire farm this year.


“If we put the same amount of fertiliser across the whole paddock, the better areas yield higher and therefore take more phosphorus out of the system.


“When we plot the high and low-yielding areas on a graph, the distance between the two lines becomes greater and greater over time. We’ve kept mining phosphorus out of the clay soils, and putting more into poorer soil.


“We needed to stop that,” Randall said.


“We’ve been noticing the increasing difference in phosphorus levels across paddocks and we want to better utilise our fertiliser by putting it where it’s going to be used.”


“We’re still putting the same amount of fertiliser on, but being more efficient about it.


“So we’ll be spending more money in areas that are going to yield more grain and less in areas that aren’t.”


He said Landmark’s Precision Farming Services and SPAA are also helping him to make the next important decision, which is whether to calculate fertiliser rates using an average of yield maps collected over a period of time; or set the fertiliser rate so that it only replaces what was removed from the soil in the previous year.


“In a dry year, the crop takes less out and in a better year it takes more,” Randall said.


“We have five years worth of yield maps, but the last three years were below-average with a very low spring rainfall. Those poor finishes have put a big bias on the overall average of those maps. So at the moment, I’m leaning toward basing my decisions on what happened in the previous year rather than the average.”


The Wilksch’s have a long history of involvement with on-farm trials and are always open to new ideas.


Landmark is currently investigating permanent soil moisture probes, GreenSeeker and satellite crop biomass imaging technologies on their property to evaluate their potential benefits. Randall is hopeful these technologies will enable him to make more economically-sound decisions about nitrogen fertiliser application.


The soil moisture probe continuously measures soil moisture at various depths. Knowing how much moisture is in the soil and at what depth should enable more informed decisions about late application of nitrogen fertiliser, without relying solely on weather forecasts, which can be unreliable.


“It will give us an idea of how much moisture is in the soil profile later in the season, so we can work out whether it’s worth putting more nitrogen on,” he said.


Another Landmark tool to assist in nitrogen application decisions is satellite and GreenSeeker technology. It is used to measure biomass and greenness of the crop.


By mapping the vegetative index and cross-referencing with yield maps at the end of the season, it can be determined whether greenness and biomass of the crop early in the year correlates with final yield.


If this proves to be the case, then satellite GreenSeeker information could be confidently used to formulate variable rate application of nitrogen fertiliser.


Connected to a spreader, GreenSeeker has the ability to vary nitrogen rates according to crop biomass and greenness as it goes along.


Randall said the aim was to use these technologies to make better utilisation of fertilisers and therefore farm more profitably.

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