WHILE the reduction in sweetpotato prices to growers has proved difficult for many, there’s no doubting the advancements with seed potato quality and nutrition technologies that have contributed to improved efficiencies, production and productivity in the industry.
Russell Mortimer, originally from Cudgen in NSW, where his wife’s family grew sweetpotatoes, has been growing them in the Hummock area, near Bargara in Queensland, for nearly 20 years.
The Mortimers source clean, virus-free sweetpotato tubers from Rockhampton, grow them out in separate beds and then plant the harvested cuttings over about 190 hectares of volcanic, heavy red soils, with the produce heading to markets in Sydney and direct to chain stores.
They also grow some other opportunity crops, including melons.
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A winter crop is planted from April-June and harvested in November-December, while a summer crop is planted in August-September and harvested from January.
Sorghum crops are grown prior to about a month of soil bed preparation for planting and, in recent years, controlled release fertiliser (CRF) has been used after previously using straight soluble products and carrying out side dressing applications of granular fertiliser.
Mr Mortimer said the aim was to get 70 per cent of crop nutrition requirements down at planting and while further applications had not generally been required for summer crops, they had supplemented the nutrition of winter crops with a NutraFeed soluble fertiliser blend.
These blends are based on the renowned Multi-K potassium nitrate fertiliser from Haifa to ensure the highest quality.
Soil testing is carried out from block-to-block and if there is some residual nutrition, the applicable nutrients in the CRF can be adjusted.
Sap testing has also helped to provide a nutritional baseline for the sweetpotato crops.
The Mortimers have been applying a Haifa Multicote Agri CRF containing 14pc nitrogen, 8.6pc phosphorus and 16.6pc potassium plus trace elements at 650 kilograms/ha. Sourced through Lindsay Rural at Bundaberg, it features 70pc coated nitrogen and potassium and 30pc uncoated, and has a four-month release period.
Using Haifa’s polymer coating technology, the Multicote Agri fertiliser releases nutrients into soils in a gradual manner according to soil temperature, matching plants’ requirements. It meets the strictest environmental regulations, with near zero nitrogen leaching.
Multicote Agri combines polymer-coated granules of nitrogen, phosphorus, potassium and boron, and non-coated, readily available nutrients.
It is available with a variety of nutritional compositions and release features.
Lindsay Rural Bundaberg account manager, Geoff Turner, said the 40pc coated phosphorus was particularly important for plant availability of the nutrient in the heavy soils, which were prone to locking up granular phosphorus applications.
Mr Mortimer said using the Haifa CRF was certainly a major benefit in times of heavy rainfall.
“If you get a lot of rain, you won’t lose it. We have had summer storms and recorded three to four inches overnight. With other fertilisers, you never know how much you lose,” he said.
“We also do lots of watering at crop establishment. We would be putting out 4.5 millimetres per day.’’
Mr Mortimer said using the Haifa Multicote Agri CRF was also more efficient, with less in-crop applications required, and it supplied the critical nutrition for the latest variety they grew, Orleans.
“The nutrition is very important for the Orleans variety because the vine can tend to go off a bit.’’
He said they noticed a real difference with their sweetpotato crops on the Haifa CRF 60-80 days after planting.
“You don’t get the sporadic growth and there is more consistent development and size.”
“Markets are looking for uniform shape, size, colour and minimal skin defects.
“The consistency of pack-out has been very good. The naked eye can pick up a 15pc improvement, so you have automatically had a productivity increase.
“We are getting more even tonnage and more into the marketable size.
“Previously, if we did 500-600 cartons pack-out we were over the moon. We are now around 1500-1800 of the 18 kilo cartons/acre,’’ Russell said.
- Copy supplied by Haifa.