Growing sweet potatoes better

Since changing his approach to production, sweetpotato grower Brodie Wolfenden has seen many benefits including increased yields, better water infiltration and water holding capacity of paddocks and he can now grow crops without the use of nematicides.

Agronomists from the Queensland Department of Agriculture and Fisheries (DAF) are working with growers like Brodie on the utilisation of nematode resistant cover crops to provide biomass and optimise fertiliser use, as well as retaining nutrients on farm and enhancing soil health.

Operating under the Wolfies Farms brand, Brodie has about 202 hectares (500 acres) under cultivation on his farm at Rossmoya, about 30km north of Rockhampton. Half is planted to sweetpotatoes with the other half a cover crop of nematode resistant jumbo sorghum.

Jumbo is an ultra-late flowering sorghum crossed to a sudan forage hybrid. Once grown, the crop is mulched and left to sit on top of the soil to break down naturally. The sorghum is left to reshoot and is often mulched a second time before the paddock is brought back into sweetpotato production.

``We are now able to grow the crop with no nematicides, which is fantastic,’’ Brodie said.

Adopting cover cropping meant turning away from the traditional practice of spraying to achieve bare fallow ground. The cover crop means the rootzone is shaded, stays moist and the soil is being used to actively grow.

"You have a better transplant survival rate for your sweetpotatoes and your crop grows better."

The farm has seen yield increases as well. Wolfies Farms is able to produce the popular Bellevue sweetpotato variety all year round. The variety's own nematode resistance also adds to the defence against the soilborne pests.

A multispecies cover crop was trialled but not maintained because of irrigation requirements to sustain it.  Jumbo sorghum however is dryland grown. The cover crop practice has also improved the water infiltration and water holding capacity of the paddocks.

``Water infiltration is a sign of healthy soils and healthy soils improve water holding capacity in the paddocks, and you're not watching that run-off into the creeks and swamps downstream."

That means less sediment, nutrients, chemicals and fertilisers heading out to the Great Barrier Reef, something which Wolfies Farms has gone the extra effort to ensure, by becoming the first sweetpotato growers Reef Certified through the Hort360 accreditation process.

In addition, Brodie has implemented controlled traffic through GPS guidance to ensure further care of the paddocks and soil.

The learning has not stopped for Brodie. He is currently trialling a soil ameliorant with organic compounds to better utilise fertilisers and looking into how to implement a more complete integrated pest management program using beneficial insects to further reduce pesticide use on the farm.