NEW recommendations have emerged for using Polysulphate-based fertiliser products this autumn for new winter-sown crops.

Polysulphate is the brand name for polyhalite, a naturally occurring mineral rich in plant nutrients – potassium, sulphur, calcium and magnesium – extracted by ICL UK at its Boulby mine, in East Cleveland. “Almost 90% of UK soils, both arable and grassland, are now deficient in sulphur, according to independent soil analysis results,” pointed out Scott Garnett, ICL’s Agronomist.

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“But sulphur is crucial to uptake of available nutrients, particularly mineralised nitrogen, in the autumn,” he added, pointing out that the product had genuine 'green' credentials.

Applications of phosphate and potash to arable land had 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, he said.

Based on commercial experience and trials since Polysulphate was launched in 2016, ICL UK can now recommend autumn applications to ensure efficient uptake of available nutrients. Trials on winter wheat had shown a 40% increase in phosphate uptake and 28% more nitrogen taken up.

In part, this efficient use of available nutrients was aided by the prolonged release of sulphur from Polysulphate-based products across some 50 days, compared to release over 5-10 days with products such as ammonium sulphate and sulphate of potash.

“After autumn treatment, crops develop larger and more robust roots. So they grow away faster in the spring and are able to produce higher yields and improved quality,” said Mr Garnett. “We recommend autumn and spring applications for winter crops. On average, arable yield increases have been 10% in cereals; 12% in potatoes; 13% in oilseed rape and 22% in peas.

“In grassland, we have seen an average yield increase of 11% plus increased dry matter and crude protein levels,” he added.

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ICL also believed its use had a part to play in the farming industry’s drive to achieve net zero emissions and reduce the carbon footprint. “Polysulphate has the lowest carbon footprint of any fertiliser at just 0.03kg CO2e/kg,” said Howard Clark, of ICL UK. “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.”