When interviewed for a GRDC case study more than 10 years ago, Peter Luberda likened clay spreading to opening Pandora’s box. “There is no going back once you have spread clay and you may expose some unforeseen consequences,” Peter, who farms near Esperance, explained at the time.
Eleven years on, Peter is continuing to ameliorate the land he farms with his parents, but he is many years wiser and clearly keeps the Pandora’s box analogy front of mind. He remains keen to share what he learns.
“Adding clay is relatively expensive and time-consuming and, if done incorrectly, can result in negative effects that are difficult to reverse,” he says.
“But it is still the best means of managing problem, non-wetting soils that we have at present, when clay is only available at depth on the property, and our knowledge has certainly evolved over time.”
Peter now takes a much more strategic view of the property’s amelioration operation, which is undertaken in a whole farm context.
Pit management and paddock management go hand-in-hand, and have to be done with care.
It may take him up to a day to ameliorate between two and eight hectares. “It is time-consuming and punishing on you and your machinery and something you have to pay close attention to throughout all phases of the process.”
Clay pits are sprinkled all over the Luberdas’ land, mainly low in the landscape where the clay is present, identified through the use of a drill rig.
We have learnt from experience you need to put some thought into the location of pits so you do not have to constantly dodge them during crop operations, which can add significant stress.
Peter is equally thoughtful about how he extracts the clay, reserving any gravel excavated from the pits separately for future farm use. “The pit area left is as small as possible as it is land sacrificed for the improvement of a larger area.”
The clay used is generally kaolinite and is found at depths of between 90 centimetres and 5.5 metres and at 30 to 40 per cent. It is spread at a rate of 200 to 300 tonnes per hectare, incorporated to improve soil clay content up to eight per cent.
Peter has been able to maintain yield improvements from a base of 2.4 to 4.6t/ha over the years and attributes this to a host of factors including the ability to incorporate lime and gypsum at depth when incorporating the clay, increased organic matter and the subsequent improvement in biological activity seen with increased fungal activity and earthworms.
“The clay is like a blotting agent acting as a carrier for so many more crop productivity factors.”