A move to controlled release nutrition is helping to limit nutrient losses and extra fertiliser applications for Bundaberg potato grower Mark Fritz. 

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. 

Mark 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. 

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

Mark 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.’’ 

Mark 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. 

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

 

PICTURED: Bundaberg potato growers Mark Fritz and Tony Grassick with Haifa Queensland Regional Agronomist Peter Anderson investigating the quality of a young potato crop.