DGT proves worth on calcareous soils
Author: Rachael Oxborrow | Date: 08 Feb 2018
Randall Wilksch runs a 3650-hectare cropping enterprise at Yeelanna on the Eyre Peninsula in conjunction with his brother and parents. The GRDC Southern Panel member is a big believer in the science of soil testing, and as a farmer with calcareous soils, he has found DGT for phosphorus particularly useful.
Traditional soil testing in the middle of summer may not be a particularly appealing job, but in most cases it produces data that help growers and their advisers apply the right nutrients where they are most needed, and get the maximum return on their fertiliser expenditure.
“Given our calcareous soils, we have found that Colwell P doesn’t actually provide data that makes sense in the field. It doesn’t correlate well to our other testing results and mapping,” Mr Wilksch says.
“Colwell P just doesn’t quite relate to the responses we’ve seen in the paddock.”
Mr Wilksch says recent DGT tests had shown some good correlation to what they already knew about their soils.
“We’ve gamma radiometric, EM38 and pH mapped the whole property trying to get a better handle on whether any of those give us an indication on soil fertility and depth, and yield potential,” he says.
“I think the Colwell P was a very a good test for most soils and a leap forward in its time, but I suspected there was probably more accurate testing around now for specific soils and DGT is one of those tests.
“We have also had deep soil nitrogen test results come back saying we don’t need to apply anything at all, but we’ve learned that we can’t grow a profitable crop without adding some fertiliser nitrogen.”
Mr Wilksch says many farmers had moved away from traditional soil testing towards yield mapping technology and analysing those for better grain production. However, he believes mapping should not be the only type of testing a grower relies on for nutrient decision making.
“You can see on a map with your agronomist how the soils vary across a paddock or farm and relate that to crop growth,” he says.
“Why wouldn’t you use this information together with soil testing data to make sure you’re putting your fertiliser budget towards the right nutrients and the parts of your farm where you will get the most bang for your buck?”
Randall Wilksch, firstname.lastname@example.org, 0427 865 051