NEW ZEALAND – Diggers are being used to invert volcanic soils to answer whether old soils grow more grass after farmer observations prompted field trials.
A three year “soil flipping” project on New Zealand’s north island is evaluating the performance of land buried in Galatea under successive pumice falls thousands of years ago.
Adding to anecdotal producer observations, the study confirmed the biggest difference was seen when soils were drying, giving desirable species better chance of survival.
The advantage may be up to four tonnes per hectare per year.
But soil flipping is not equivalent to irrigation – there are still limitations to pasture production and survival in extreme dry conditions, said Bill Adam, farm consultant with study funders DairyNZ.
Digging occurs to a depth of 0.8 to 1.8 metres, with grass growing trials being indicated by a pasture cutting experiment.
Now two years in, early trials from study funders DairyNZ suggest a two and a half year pay-off period.
A 40 per cent pay back was noted in the first year before the drought came and limited second year growth, explained DairyNZ.
Costs range from NZ$3500 - $5500 per hectare. The process means spray-out, digging, levelling, cultivation, regrassing and fertility reinstatement.
“Farmers in the area noticed where they mixed topsoil with subsoil, that pasture would always grow better during dry conditions,” said Mr Adam. “Otherwise they’re dealing with coarse, challenging summer-dry topsoils.”
He added: “Reinstating soil fertility was surprisingly easy – very little capital fertiliser was required above normal maintenance. pH and Olsen P levels were lower on flipped soils, but natural potassium (K) and sulphur (S) levels were generally higher.”
TheCattleSite News Desk