Prioritising roots strengthens crops in saturated soils

Growers must focus on the role of critical nutrients such as calcium and magnesium alongside sulphur and nitrogen if they are to build the essential root mass needed to pull slow growing crops out of the cold, wet winter, says ICL agronomist Scott Garnett.

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 the growth and yield hoped for, he says.

“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.

“Soils across the UK are at saturation and although crops have established for the main part, they have not developed strong roots.

“Although soils are still wet and cold, this will change as we approach the summer months where 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.”

Essential building blocks

Polysulphate’s unique composition of 48% SO₃, 14% K₂O, 17% CaO and 6% MgO means that as well as addressing plants’ sulphur needs, it also provides the essential building blocks for rapid root growth, he points out

“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 contained, 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 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.

“In fact, phosphate uptake by plants correlates with root health and we consistently see 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 over 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.

“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.”

Prolonged nutrient release

Prolonged release characteristics are another important feature of Polysulphate, he adds.

“University of Nottingham trials 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.

“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.

“We believe there are multiple reason for using Polysulphate, from both environmental and productivity standpoints in any year, but in 2024 in particular, it could be a real life saver for crops.”