Rainfall is generally not a significant problem for South Australian Wimmera grower David Kuchel, whose properties on either side of the SA–Victorian border experience reliable rainfall of about 450 millimetres per year. Soil variability, though, is another matter altogether.

David and his family have long struggled with extremely variable pH – from 4.5 to 7.0 in some areas, with acidity being a major limiting factor for production.

In recent years, paddock mapping of soil acidity levels has proved a game changer. David is now able to grow crops in paddocks where he previously could not, and enjoys increased yields due to much-reduced soil pH variability.

“We had identified pH as being the main instigator of poor crop growth, particularly in areas where legumes would not grow well. But in the early days, we were just walking around and using manual probes to identify areas that needed lime,” David says.

Lime spreading

He started by spreading lime at two tonnes per hectare in areas that had been identified as yielding poorly – and quickly saw benefits. “We did that for a couple of years, but there wasn’t much science to it. Then our agronomist told us about precision agriculture (PA) and grid mapping. Five years ago, we started doing that in just one paddock, and now we are doing 200 to 300ha a year.”

After soil testing in grid maps of all paddocks (eight soil probes in each 2ha grid), he now applies lime at rates of between zero and 6t/ha, with a target of achieving pH of 6.0 across the property. “We knew that the pH was low, but we didn’t know the rates of lime we needed to correct it,” he says.

“As it turns out, applying lime at 2t/ha was a waste of time, because it was either not needed in a particular area or a drop in the ocean compared to what was actually required.”

Apart from growing wheat, canola and faba beans, David runs 1600 ewes on irrigated country where lucerne seed is grown. He aims for yields of 6t/ha in wheat, 4t/ha in faba beans and 3.5t/ha in canola. “Last year was really good – we yielded 7t/ha for wheat,” he says.

I love growing the best crop possible, and soil variability was stopping me doing that.

As well as implementing PA and grid mapping, he switched to controlled-traffic farming on a 12-metre system about five years ago. “We’ve seen exceptionally good results from the changes we have made. We are now growing crops in places where we previously couldn’t, and our cereal yields have gone up too.

“It has taken the variability out of our paddocks and, in particular, we are seeing that the areas where we are putting the lime have become our highest-yielding.

“We are also seeing that soil-applied chemicals work better because of the higher pH, which leads to cleaner and better crops as well.”

David describes improving soil pH levels and variability as the “low-hanging fruit” of productivity improvement. “At a cost of about $34/ha for testing, it certainly provides the most bang for your buck,” he says.

“I love growing the best crop possible, and soil variability was stopping me doing that. Now I am getting rid of the variability, so my poor patches are as good as the good patches – and I can hold my head high that I am growing good crops.”