Potato Review

T HE use of Polysulphate-based fertiliser products in the autumn is claimed to boost crop health, optimise uptake of mineralised nitrogen and minimise loss of valuable nutrients through drainage or run-off. But what is Polysulphate and how do we extract it? Polysulphate is the brand name for Polyhalite, a naturally occurring mineral rich in plant nutrients – potassium, sulphur, calcium and magnesium. It also contains trace elements such as boron and is approved for organic farming. It is a highly versatile, natural, multi-nutrient mineral which is low in chloride and crop safe, suitable for use alone or in blends and compound fertilisers. A recent webinar by ICL UK gave us an insight into this, delving into how it has been mined over the years and why it can provide a lifeline for soils. Furthermore, with the NFU and NFUS setting ambitious goal of reaching net zero greenhouse gas (GHG) emissions across British Farming before 2040, Polysulphate could help growers achieve these milestones, speakers told those who joined the briefing. Polyhalite is extracted by ICL UK at its Boulby mine in East Cleveland - the first Polyhalite: An unsung hero? Potato Review learns how a naturally-occurring mineral came to be mined in the UK and could play a key role in helping potato growers accommodate Government and industry demands. and only polyhalite mine in the world. The mine has been accessing and mining polyhalite since 2008 while ICL Boulby has been operating for 50 years and is the largest employer in East Cleveland, with around 600 employees on its books. In 2017 the mine achieved its first million ton milestone. Polysulphate products can play a key role in the farming industry’s drive to achieve net zero emissions and reduce the carbon footprint, according to ICL’s Agronomist Scott Garnett and its UK Business Sales Lead Howard Clark. Howard said: “Polysulphate has the lowest carbon footprint of any fertiliser at just 0.03kg CO2e/kg and we are working to reduce that further. It has a neutral pH and does not contain any nitrogen. Therefore, there are no losses to the environment and much less risk of losses through leaching. “It is a natural mineral and accepted by organic farming organisations. Therefore, it is a product that farmers seeking to become sustainable should consider seriously.” Crucial nutrient uptake Polysulphate has a prolonged nutrient release (up to 50 days) which results in the crop taking up the nutrients more efficiently over a longer period of time, with less leaching, according to Scott Garnett. Maximising the yield of plants is not dictated by the total resources available, but by the scarcest resource, and for the plant to maximise the benefit of residual and mineralised nitrogen in the soil, it especially needs potassium and sulphur, he said. Scott said: “Almost 90% of UK soils, both arable and grassland, are now deficient in sulphur, according to independent soil analysis results. But sulphur is crucial to uptake of available nutrients, particularly mineralised nitrogen, in the autumn.” Applications of phosphate and potash in England and Wales has declined over the past 25 years, with many soils now falling below the desired soil index level of 2. Regular, full analysis of soils is an important management tool to manage the risk of inadequate soil nutrients and maintain healthy soils. ICL trials prove that Polysulphate nutrients, when applied at planting with phosphate, further increase root and crop establishment. This has resulted in an increased yield of 12% in potatoes at harvest. Agronomist Scott Garnett Howard Clark, ICL UK Business Sales Lead The first and only polyhalite mine in the world at Boulby. “Polysulphate has the lowest carbon footprint of any fertiliser at just 0.03kg CO2e/kg and we are working to reduce that further.” 24 POTATO REVIEW SEPTEMBER/OCTOBER 2021 FERTILISATON