Also, once the early-season supply shipment had run out, that was it, Ballance chief executive Mark Wynne said.
The Timaru plant would initially produce about 10,000 tonnes a year, with capacity to expand as demand grew.
South Island shareholders had told the co-operative they wanted local supply, he said after the plant was opened on Tuesday.
North Island sales were about 20,000 tonnes.
PhaSedN, a mix of the urea (nitrogen) product SustaiN, elemental sulphur and lime, was applied to pasture or crops in autumn.
Most South Island soils required a high sulphur input and PhaSedN had a slow-release product to complement the more immediate pre-winter nitrogen boost from SustaiN, Wynne said.
With farmers reviewing their fertiliser programmes because of tightening budgets, PhaSedN’s combined mix gave them flexibility on the time of other base nutrient applications of phosphate and potash.
PhaSedN was developed for sheep and beef farms in “hungry” terrain but the biggest users now were dairy farmers who had expanded into those areas.
The product was useful on farms, both dairy and hill farms, where phosphate levels were high but sulphur was still needed, he said.
The Timaru plant was Ballance’s second fertiliser manufacturing site in the South Island, added to the superphosphate facility in Southland.
Spring was typically a busy time for superphosphate but demand was stronger this season as farmers sought a pasture boost ahead of an expected dry El Nino weather pattern.
As it turned out, many areas had a lot of rain instead and grass growth had been prolific.
With this and continued falls in dairy prices, there might be a later start to the autumn fertiliser season, Wynne said.
