Summer ‘ideal’ for low carbon fertiliser plan

• Think about sulphur – not only nitrogen

• Nutrient efficiency at heart of decisions

• Consider decoupling for more flexibility

Growers and agronomists are advised to think more broadly when devising their fertiliaer plans for next season.

A wider view when it comes to organic and inorganic fertilise will ensure crops get the right nutrients, says Peter Scott, technical director at Origin Soil Nutrition.

The need to reduce the carbon footprint of food production and minimise potential environmental issues, means growers need to understand more than ever how to low carbon fertiliser practices, he believes.

“Use of inorganic nitrogen fertilisers is the single largest component of the carbon footprint of crop production and any attempt to decarbonise food production will need to address this.”

In a typical combinable crop, 50% of the carbon footprint is related to the production of the fertiliser in the first place and the other 50% is due to in-field emissions.

“But, around half of human dietary protein consumed globally is directly related to the use of inorganic nitrogen and in the west, this would be much more. The issue of nitrogen use goes to the very heart of sustainable food production.

“Green ammonia, where the hydrogen element of ammonia comes from water rather than gas, could play an important role in the future with regard to reducing the carbon footprint of manufacture, but we must also address in-field emissions.”

Nutrient efficiency

The pH of soil together with its organic matter content and structure plus other considerations such as drainage all impact on emissions, so better management is essential in the future, says Mr Scott.

“One of the biggest things we can do, and one of the most important benchmarks for delivering future sustainability full stop, is to focus on nitrogen use efficiency (NUE). The higher the NUE, the lower the N loss, but you have to measure it to manage it.”

Richard Ward, of crop nutrition specialists ICL Growing Solutions, says all arable producers need to think carefully about their sulphur and nitrogen plans for next year with a view to optimising NUE and reducing emissions.

“Summer is typically the time growers start to think about their fertiliser programmes for the following season so it’s a good time to make some key decisions.

“Nitrogen-based sulphur products lead to the release of ammonia into the atmosphere, so anything that can help reduce this will have a significant impact on a farm’s carbon footprint.

“While it’s easy to look at nitrogen in isolation, growers should not overlook the role of sulphur in the NUE and carbon equation.”

Focus on sulphur

Sulphur is a key element in ensuring the maximum use of applied nitrogen is made but it is also one of the most overlooked nutrients, with many growers thinking organic sources are sufficient to supply it but this far from the case.

“One of the options farmers should consider to improve NUE is separating their nitrogen and sulphur sources. Decoupling N and S can help maximise NUE and also allow you to choose the lowest carbon programme.

“There is a growing market for polysulphate as more farmers are seeing the many benefits of the product in helping achieve this. Other commonly used sulphur fertilisers are mainly nitrogen-sulphur (NS) products, often at fixed N to S ratio.

“As a zero nitrogen sulphur source, polysulphate allows you to achieve the appropriate sulphur application rate based on the crop need and you can then also add a specific rate of nitrogen to your crops.”

Prolonged benefits

One of polysulphate’s other key advantages is that it has a very high sulphur content at 48% SO3, while also containing 14% K2O, 6% MgO and 17% CaO, Richard Ward stresses.

“It’s a naturally occurring multi-nutrient sulphate fertiliser mined from the under the North Sea and processed into an easy-to-apply product with excellent physical properties and performance right up to the widest spread widths of 36m and more.

“As well as polysulphate being a non-nitrogen sulphur source, it also has a unique ‘prolonged release’ action.

“As plants can only take up so much sulphur at a time, this prolonged release enables roots to take up nutrients as and when they need it over the growing season with minimal risk of it being lost by leaching.

“In addition, polysulphate is UK produced, with minimal processing, low transport miles and high energy efficiency making it the lowest carbon footprint fertiliser available with just 0.0029 kg CO2 e per kg of product.”