Controlled release delivers for potato grower

Of course, the add-on benefits of this change in fertiliser strategy for protecting the Great Barrier Reef in the region are also well recognised.

Mr Fritz is a fourth generation grower in the area, farming 240 hectares together with his wife, Judy, and parents, Gordon and Allison.

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Today they grow crisping potatoes and sugarcane under their M & J Produce brand, and have previously grown tomatoes, capsicums, watermelon, soybeans and peanuts.

Mr Fritz said the predominantly sandy soils on the property, which “you can’t stand on in summer’’, were good for growing and harvesting potatoes in winter.

He said the potatoes were grown from March-April through to November-December in 12-14 paddocks totalling about 80ha.

A further 80ha of land is left for spelling in the rotation and the remainder is devoted to cane production.

The family has been producing potatoes for Smith’s Crisps in Brisbane since the mid-90s, growing the company’s preferred varieties and meeting set production targets for different periods throughout seasons.

Cover crops are grown on the spelled land, with a final forage sorghum crop being mowed and allowed to regrow before being sprayed with Roundup and incorporated with a disc or speed till in preparation for the potato planting.

“We try to keep cover on the soil all the time to avoid erosion caused by wind or water. It stores some moisture and by ploughing it back in, it stores some residual nutrition and helps soil health,’’ Mr Fritz said.

The seed potatoes are sourced from SA, Vic and Charters Towers in Qld.

The family carries out a pre-plant fertiliser application of phosphorus with some trace elements, but without any nitrogen, and applies a compound fertiliser with the seed potatoes at planting.

The remaining nutrition is mostly supplied through the side dressing of Haifa Multicote Agri controlled release fertiliser (CRF) blends, sourced through Paul Warhurst at Sunfam in Bundaberg.

Based on 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.

Mr Fritz said they make up the CRF blends and apply them two to three weeks after planting.

They use a four-month release Multicote Agri fertiliser with 40 per cent coated potassium nitrate, 40pc coated sulphate of potash and 20pc magnesium sulphate, applied at 350 kilograms/ha, as well as a two-month release Haifa coated urea fertiliser applied at 150kg/ha.

The application rates can sometimes change depending on plant densities.

Mr Fritz said a lot of bulking up occurs later in the crop and that’s when the controlled release potassium nitrate “kicks-in’’.

They have also trialled the two-month release coated urea product in cane and were able to achieve similar production despite using 20pc less urea than traditional applications.

He said their sandy soil was prone to significant leaching.

“With a fall of over 75 millimetres, we could get a lot of nutrient loss. Throughout the crop, we could lose a lot of fertiliser by 90 days (after planting) – and we are not harvesting until 120 days.’’

“We did some work with a New Zealand company showing how different soil types hold different amounts of rainfall. Ours only holds 25mm before leaching, so with a 75mm rainfall event, we can lose 40-50 units of N.’’

He said they had been trialling CRF products the past five years and using the Haifa Multicote Agri fertiliser the last two seasons.

“The Haifa fertiliser has been the most consistent product and has handled the blending. Some other fertilisers have had different nutrient releases and can break down in the blending,” he said. 

Mr Fritz said he was also using Haifa’s CRF to avoid multiple fertiliser applications in the potato crops during the season.

“We might have been applying up to three applications with a spreader. Now we only apply cal (calcium) nitrate and boron about halfway through the crop – and we have two less products in the shed.’’

Yields of 15 tonnes per acre are targeted and last season, despite considerable rainfall that caused some damage, a yield of 14.8t/ac was achieved.

Mr Fritz said they also were now producing better sized potatoes, however this also could be attributed to improved seed potato quality.

Tony Grassick, who works for Mark and also grows potatoes on 25ha of leased land, follows a similar fertiliser regime.

He supplies his crisping potatoes under Mark’s contract with Smith’s Crisps

The Fritz family’s potato crops are watered via lateral and overhead travelling irrigators, with some trickle tape also used, drawing from underground water and dams on a couple of properties.

Lighter crops may receive 13 irrigations, with others up to 18 irrigations.

Up to 20mm is applied every four to seven days depending upon crop stage and weather conditions.