Three seasons of UK trials have shown that using a combination of urease and nitrification inhibitors can not only improve efficiencies and reduce environmental impact but can boost soil fungal activity.

The trials were carried out on Agril's nitrogen-stabilising product Liqui-Safe, with Verdesian Life Sciences and build on research at the John Imes Centre, NIAB TAG, Wessex Water and Campden BRI as well as Agrii Technology Centres and iFarms.

This has highlighted marked increases in Nutrient Use Efficiency (NUE) from the stabiliser's combination of urease and nitrification inhibitors. These have led to improvements in crop yield, quality, labour and machinery use, claims Agrii, as well as environmental benefits.

The aim of the research has been to understand the science behind key elements of crop management and apply it in the most effective ways, says Agrii nutrition technical manager, Torn Land.

"We've been working with the technology behind Liqui-Safe for more than 10 years now through a sister product, Enhance. Replicated trials across a wide range of crops highlighted how it increases NUE of urea fertilisation —measured in higher yields and milling wheat N contents — and in enabling the number of passes to be manipulated."

Tom explains that Liqui-Safe's urease inhibitor slows down the rate at which urea is converted to ammonia in the soil, which reduces ammonia losses to the atmosphere from standard urea ammonia nitrogen (UAN) liquid fertilisers by as much as 25%.

In parallel, its nitrification inhibitor delay s the bacterial conversion of ammonium to nitrate to more closely match crop uptake. This has led to a halving of atmospheric nitrous oxide (N20) emissions in some cases, together with reductions of between 14% and 54% in soil nitrate leaching, depending on conditions.

More recent trials have also shown a 10% increase in mycorrhizal fungi colonisation in the soil, compared with standard UAN applications.

No adverse effects have been found on earthworms nor aquatic organisms even at 10 times the recommended dose rates. Tom points out that Liqui-Safe degrades to carbon, hydrogen and oxygen in the soil.

"Liqui-Safe brings both key components of improved liquid urea NUE together," he explains.  "It's based on natural organic acids, giving it a better environmental profile than traditional inhibitors. What's more, we believe it offers liquid fertiliser users the ability to avoid tying up sprayers during critical fungicide and PGR timings and reduces the need for fertiliser applications during the window where scorch is more prevalent.
So, our most recent trial work has explored the extent to which Liqui-Safe could allow the number of passes to be reduced."

Conventional three-split application trials undertaken by NIAB TAG at Morley in 2019 showed a wheat yield improvement of 7.4% from including Liqui-Safe, together with an uplift of 0.6% in grain protein.

Alongside this, iFarm strip trials found no difference between wheat performance from standard three-application farm regimes and those applying all the N with Liqui-Safe in a single early season pass in either 2018 or 2019.

These results were confirmed in replicated Agrii field trials with Skyfall during last season's very dry spring and early summer. Here, the standard treatment without Liqui-Safe was 200kg/ha of nitrogen balanced with sulphur applied in late-March, early April and mid-May. There was no discernible yield difference where the same total balance was applied with Liqui-Safe at just the first and third timings.

However, applying all the nitrogen with the stabiliser at the first timing alone raised yields by over 9% from an average of 10.8 t/ha to 11.8 t/ha — a margin over input costs of more than £110/ha.

"Applied at a standard 0.5% by volume, it improves the efficiency of UAN utilisation and means an average 4% cereal yield increase can be expected from current nitrogen application strategies, with similar gains in other field crops. Alternatively, you can maintain yield with lower overall levels of N use," notes Tom.