THE subject was dome clays.
The venue was a soil pit at the Soils Masterclass day at Scaddan.
The obvious discussion was how to build soil fertility.
For Department of Agriculture and Food soil researcher David Hall all options were on the table but choosing the right one was the most difficult option.
His key presentation points gave a hint of the complexity of the subject:
p What is the yield gap we are trying to fix?
p When is a constraint limiting yield, as opposed to slowly metering our resources so that they are available at the end of the season?
p Which subsoils do we mix and modify and which do we leave alone?
p Which soils give a profitable response to ameliorants, such as gypsum?
p Are soils self-repairing under controlled traffic?
Speaking to farmers in the mandatory soil pit, Mr Hall described the paddock as one prone to lots of water-logging with lots of weeds.
The obvious question was how to make it more productive.
Deep tillage was regarded as one answer, introducing lime and gypsum and sowing a summer cover.
Delving was another suggestion but bringing up rocks (cracked domes) would prove messy.
Introducing long taproot plants was another suggestion but these would be restricted by the soil type.
Mr Hall admitted the dome clays were a challenging soil.
"The department is researching principles to ameliorate these soils but at the moment don't spend too much on them," he said.
Perplexingly, the history of the paddock showed that crops could yield three tonnes per hectare in a good year despite the inherent hardpans created by the domes (created over eons), which when broken comes off as thick plates.
"The best option may be to manage the paddock to its potential," Mr Hall said.
"Dome clays are very challenging."