Polysulphate Reducing Sulfate Leaching

Reduces the Potential for Sulfate Leaching

Sulfur is an essential macro-nutrient so there is usually a need for fertilization. Like nitrate, sulfate is prone to leaching and needs be managed carefully to minimize that risk. Polysulphate, a multi-nutrient fertilizer mined at ICL’s mine in Boulby in the UK, helps reduce the risk of leaching due to its prolonged release characteristics.

In order to compare the rate of release of sulfate in soil from Polysulphate^® fertilizer with that from sulfate of ammonia, sulfate of potash and kieserite (all granular form), a soil column experiment was set up at the University of Nottingham, UK. The fertilizers, at equivalent rates of sulfur, were added to the tops of replicated columns of loam soil which had previously been leached. In order to determine how much sulfate became available each day from the different sources, the columns were leached (flushed) daily with de-ionised water, and the sulfate contents of the leachates were measured.

The chart illustrates the prolonged release characteristics of Polysulphate. All of the sulfate from the ammonium sulfate was released and recovered in the leachate within six days, compared to 12 days for sulfate of potash and 21 days for kieserite, whereas sulfate from Polysulphate was released for crop uptake into the upper soil horizon for about 50 days. These were extreme tests but they show that the release pattern of sulfate from Polysulphate matches the major growth period and demand of a crop. Unlike some other sources Polysulphate continues to supply the crop with sulfate even after heavy rainfall events following application.

Polysulphate is suitable as a source of sulfate for inclusion with multiple dressings of fertilizers over the season, but its particular strength is that it can be recommended as a single early dressing without causing a sudden high concentration of sulfate in the soil and with minimum risk of loss through leaching.