A focus on key nutrients could help to pull lethargic crops out of the cold, wet winter.
Without a strong root system to scavenge for nutrients and reach water as summer droughts take hold, no amount of fertilisers or other inputs will deliver vital growth and yield potential, says ICL agronomist Scott Garnett.
“With extensive trials showing a 35-40% increase in root mass resulting from use of the prolonged release multi-nutrient fertiliser Polysulphate, it’s undoubtedly an approach practically all crops currently sitting in the ground could benefit from.
“Although many soils are still wet and cold, this will change as we approach the summer months. A shortage of water is very likely and without a well-developed root system, plants will be under a lot of stress with lower yields and quality resulting.”
Building blocks
Polysulphate’s mix of 48% sulphur, 14% potassium, 17% calcium and 6% magnesium means it provides the building blocks for rapid root growth as well as addressing sulphur requirements, says Mr Garnett.
“The high sulphur content of Polysulphate is important in boosting nitrogen use efficiency (NUE) and improving the quality of crops – but the potassium, calcium and magnesium also play a key role.
“If you want to develop a good root system you need calcium, magnesium, phosphate and some trace elements and these are the main components driving mitosis and the cell growth required to build a good, strong and healthy root system.
“Phosphate is usually fairly abundant in the soil, but adding calcium and magnesium can really kickstart root growth and this holds true across a range of crops including wheat, barley, oilseed rape and maize.
Mr Garnett says phosphate uptake by plants correlates with root health – and ICL has consistently seen this rise by up to 40% after Polysulphate application.
“It’s also very visible in the physical root mass with markedly bulkier roots with more branching and much greater ability to utilise available water and nutrients. One more centimetre of root growth per plant touches an extra 130 tonnes of soil/ha.”
Significant benefits
Polysulphate can be applied from February through to April at a recommended rate of 100 – 150kg/ha of product. As well as improved NUE and better roots, the low carbon mineral has been shown to deliver significant other benefits, Scott Garnett explains.
“It’s a naturally occurring multi-nutrient sulphate fertiliser mined from under the North Sea and processed into an easy-to-apply product with excellent physical properties and performance right up to the widest spreading widths of 36.0m and more.”
UK trials with Polysulphate have consistently shown yield lifts of 5 – 8% in winter wheat and as much as 33% in oilseed rape with a clear 0.5t/ha advantage over the commonly used NS products, says Mr Garnett
“Compared to NS products, it also gives growers the opportunity to separate sulphur out from their nitrogen applications. In NS products, both nitrogen and sulphur are locked together in a fixed ratio and this can be a problem.
“If you want to meet the crop’s sulphur requirements using NS products, for example, you’re often also applying a sizeable amount of nitrogen which may not be desirable, especially in the current very wet soil conditions, when leaching can be an issue.
“Applying Polysulphate means you can apply the sulphur you need with the precise amount of nitrogen required, which is better for both the environment and overall production efficiency.”
“Polysulphate can be applied by itself or blended with nitrogen fertiliser to provide the precise N:S ratio for an individual growing situation and to help farmers achieve ‘little and often’ applications.”
Nutrient release
Trials by Nottingham University researchers have shown over 50% of the sulphur contained in Polysulphate is available in the first 12 days after application with the remainder released over the following 6-8 weeks.
This matches nutrient availability precisely to crop needs through the growing cycle, which is in contrast to traditional NS products, where 100% of the sulphate is released within just 5 – 6 days after application, says Mr Garnett.
“This sudden release not only means many of the applied nutrients will never be taken up by crops, it also increases the possibility of soil nutrient loss and potential environmental problems.
“Polysulphate also has the lowest carbon footprint of all equivalent fertilisers at just 0.034 kg CO2e which is less than 6% of the carbon footprint of nitrogen sulphur products.”
