THERE is excellent evidence from NSW Department of Primary Industries (DPI) to suggest that compost boosts the health of blueberry plants and improves eating quality.
At a field day north of Coffs Harbour, in the heart of Australia’s blueberry growing district, growers were shown field trials of how compost can enhance plant performance.
As with nature there is no immediate improvement but a couple of years after application there is an indication that yield will improve by around 15 per cent, according to investigations conducted by NSW DPI soil scientist Justine Cox.
There are other benefits of compost. In heavy clay soils it loosens soil structure and in sandy loam it tightens the spaces between grains to better hold water.
She said the diversity of microbial activity in compost resulted in carbon compounds breaking down labile organic matter – stuff that would otherwise be lost – into stable humus which remained in the ground with a ‘long shelf life’.
But there is a trade-off when comes to cost.
Even at the incredibly competitive price of $22/tonne ex-freight from Biomass Solutions at Coffs Harbour, growers think twice about the benefits.
“No one doubts that compost is a good thing,” says blueberry industry officer with NSW DPI Phil Wilks. “But it comes down to an economic decision.”
One area of great concern is the effect of root rot or phytopthora which can flourish in the raised beds on which blueberry bushes grow. When it comes time to replant or replace with new varieties there is evidence of high failure rates.
For that very reason larger growers able to afford the extra expense are going over to hydroponically grown blueberry bushes in pots.
Those that cannot go that route let portions of their farms go fallow for two years to let the soil recover. Small growers, however, cannot afford the loss of income.
Mr Wilks says the cost of compost, at $2000/ha compared with losing a hectare of new plants at $2400 suddenly makes the economic decision more logical.
At replanting it could make sense to strip and level the mounds, applying compost before remounding, he said.
The extra microbial activity in the compost would help to compete with and control the harmful phytopthora.
Coffs Coast blueberry grower Russ Glover, Sandy Beach, has been using compost on his plant beds for six years. “I apply my compost with a tractor bucket and my anecdotal evidence says I get heavier yields and my insect pressure is reduced.”
