Levelling out production variability with advanced tools and data is at the heart of Kym I’Anson’s farming system. Twelve years ago, when he started farming with his parents Murray and Ann, wheat yield in the same paddock could vary between two and five tonnes a hectare.
Since then, applying site-specific management has enabled the I’Ansons to reduce this variation considerably. In 2011 their average bread wheat yield was 6t/ha with all soil types performing consistently.
The picturesque landscape near Marrabel, South Australia, hides the mix of soil types that range from free-draining neutral to highly sodic to acidic soils prone to waterlogging.
The majority of soil across their 1300 hectares is red brown clay loam that is sodic and acidic (pH 4.0 to 5.5). However, almost every paddock contains patches of grey shale and deep black cracking soil. All of these perform differently.
Kym knew the addition of lime and gypsum would help, but that it would be wasteful to apply a blanket rate. “The grey shale required less lime and no gypsum, and the black soil requires neither. So using a blanket rate of gypsum would have wasted over 1000 tonnes of gypsum and lime,” Kym says.
With his wife Katie, Kym embarked on an extensive soil-mapping program, taking about one sample per hectare. In the past 10 years, three applications each of 2.5t/ha of lime have been spread on the red brown clay loam, plus 3t/ha of hi-ag gypsum. The grey shale has received one to two applications of lime, and the black soils none.
Using these different rates has saved Kym and Katie considerable money and time spreading, while also lifting the average soil pH to 5.8.
“We need to keep monitoring the soil to assess whether we have raised the pH sufficiently or if it is acidifying under our continuous cropping program,” says Kym.
The couple are now taking advantage of the availability of an on-the-go pH and electromagnetic (EM) soil mapping machine. Working with Dr Brett Whelan, the University of Sydney and Andrew Harding, Rural Solutions SA, they are assessing the machine and the quality of data produced.
The EM data is gathered between discs that penetrate the moist soil, while the pH is sampled from a surface sample. Every 20 metres the unit lowers a tube that collects soil over about a metre. The sample is then raised to the pH sensor and the result logged automatically. Kym is enthusiastic about the potential of this on-the-go monitoring.
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