Grassland trial confirms sulphur application as an economically valuable input 

Applying fertilisers enhanced with selenium and sulphur has been shown to boost levels of selenium in grassland by up to five times, and to increase grass yield by up to 11%, during a Farming Connect trial.

Three Farming Connect demonstration sites took part in the project to establish the effectiveness of using fertilisers enriched with selenium and sulphur.

Independent grassland and soil specialist Chris Duller, who provided technical support for the trial, says many soils in Wales are known to be deficient in selenium – a mineral that plays an important role in livestock performance.

“Raising the selenium status of forage through the use of fertilisers containing selenium has the potential to improve productivity, and can be a useful addition, or an alternative, to mineral supplementation and bolusing,’’ he says.

Sulphur deficiency in grassland is also now more commonplace; this can impact on grass yields and protein and sugar levels and impede nitrogen uptake, resulting in residual nitrogen in soil, which can leach over winter.

Farming Connect partnered with Yara for the project, supplying its Silage Booster and Nutri Booster fertilisers for application, to trial against control fields spread with standard fertiliser blends.

The trial was run during the 2021 growing season at Rhiwaedog, a beef and sheep farm at Bala, Mountjoy Farm, a dairy farm near Haverfordwest, and Bodwi, a beef and sheep farm on the Lleyn.

Rhiwaedog ran the trial in two of its first cut silage fields and Mountjoy Farm in a second cut silage field, while Bodwi monitored a field’s performance at both first and second cut.

Rhiwaedog applied Silage Booster at 375kg/ha with 21:8:11 as the control, Mountjoy applied Nutri Booster at 375kgN/ha with ammonium nitrate as a control, and Bodwi applied Silage Booster at 375kg/ha on the first cut and at 310kg/ha on the second, using 21:8:11 as the control.

Mr Duller sampled the grass, and analysis showed that across all sites, in both fresh herbage and silage, the Booster fertiliser increased the selenium content – by typically five times in fresh grass and by two or three times in silage.

Yield benefits of up to 11% were recorded on all three farms.

With the typical cost of adding sulphur to each silage cut at around £7/ha, the extra grass grown in this trial – 300kgDM/ha – is worth nearly £50 in terms of energy and protein.

“That’s a healthy 7:1 return on investment,’’ says Mr Duller.

He reports that crude protein and energy levels were very variable in the fresh herbage, with no clear trends, but sugar levels were higher in the grass where the Booster fertiliser had been applied on five of the six sample runs.

“Silage analyses recorded an increase in ME at all sites/silage cuts and an increase in crude protein in three of the four samples,’’ says Mr Duller.

Historically, sulphur fertilisers have been recommended for multi-cut silage systems and high nitrogen users.

“This trial confirms that even at lower nitrogen levels, sulphur is an important and economically valuable input,’’ says Mr Duller.

Farming Connect is delivered by Menter a Busnes and Lantra Wales, and funded by the Welsh Government and the European Agricultural Fund for Rural Development.