"These are different to our previous results," admitted Mark Stalham of Cambridge University Farm. "In the past, we’ve seen large differences created in bulk density and rootability in the top 50cm by destoning at different depths."
In a normal season, working at depth would cause compaction, he noted. "Depending on soil moisture, the optimum depth would be between 20-50cm. The wetter it is, the shallower you should work."
This year, however, there’s been no effect from destoning between 19 and 54cm deep, at similar planting depths.
"Ridge shape didn’t affect emergence either," he said. "Because it was so dry, the bulk density of the soil wasn’t increased by ridge compression. So again, there was no effect on emergence."
Organic matter is an important soil factor, as bulk density decreases as the organic content rises, he continued. "Fine, sandy and silty soils are more sensitive to structural degradation, so the organic matter content is critical."
These soils should have a minimum of 3.4% organic matter, he advised. "The cultivation window depends on the organic matter level in these sensitive soils. If it’s too low, damage will occur."