Issue 10 2016
Never let something precious slip away
With the arrival of October, the year of 2016 is seeping away towards its end. No-one likes to feel that anything - whether that’s a resource or even time itself - has been wasted. We can’t stop time slipping by but we can help farmers to stop sulphate seeping away beyond their crop roots’ reach.

Cutting losses
Leaching of sulphate in the soil is something that’s preventable. Leaching is the loss of plant nutrients from the root zone. Preventing sulphate leaching has several benefits:
  • Retains sulphates within roots’ reach
  • Boosts crop growth
  • Avoids pollution of groundwater
  • Saves the farmer money 
So far, many farmers and their advisors would agree, that all makes good sense. The important question is how does Polysulphate perform? Does the sulphate it contains stay in roots’ reach? How long?

An investigation into the rate of sulphate release from Polysulphate provides the answers to these questions.

Learning about leaching
To learn about leaching takes time and careful technique. An experiment to compare the rate of release of sulphate from Polysulphate compared with other fertilizers was set up at the University of Nottingham in the United Kingdom. It took the form of a soil column test where a series of tall glass tubes were filled with a soil sample - or microfield.

Each soil sample, a depth or column of loam soil, had previously been leached of soil nutrients. Then four different fertilizers - Polysulphate, ammonium sulphate, sulphate of potash and kieserite - were added to the tops of the soil. The fertilizers each contained equivalent rates of sulphur.

Then it rained. By rain, we mean that the researchers flushed the soils daily with de-ionised water and then measured the sulphate contents of the leachates - the water containing water soluble nutrients that drain out the bottom of the soil samples.

The results are significant.
The soil column apparatus
Unleashing not leaching

The chart shows that the sulphate in Polysulphate is released gently and over a prolonged period of time, for about 50 days. It is released where it’s needed, the upper soil level, for weeks.

Sulphate from other fertilizers is released much more quickly, too quickly for crop roots to be able to capture and use it.

With available sulphate in steady supply, the power of this essential macro-nutrient of sulphur to help crop performance is unleashed.
Release of sulphate: Polysulphate vs. other sources
Reining in the impact of rainfall

Yes, the experiment was an extreme test. But rainfall - even heavy rainfall - is not only unavoidable after fertilizer application, it is welcome to dissolve and move the nutrients where they are needed by crop roots.

However, especially with an early season application of fertilizer, a farmer runs the risk of rain leaching the sulphates away. Applying Polysulphate avoids that risk, that waste, and that detrimental effect on crop growth because, even in the face of heavy rain, a steady supply of sulphur is released.

Polysulphate fertilizer offers prolonged and gentle nutrient release: that’s a fact none of us should let slip through our fingers, whatever the time of year.
Further details are available in the leaflet Prolonged nutrient release pattern of Polysulphate fertilizer.
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Mined in the UK, ICL is the first – and only producer – in the world to mine polyhalite, marketed as Polysulphate™