Case study: Peter Bartlett, Cleeves Farm Estate, Oxfordshire

Peter Bartlett – photo supplied by Peter Bartlett

A key priority for Oxfordshire grower Peter Bartlett is to move towards a more sustainable farming system on his 160ha arable farm by using less artificial nitrogen fertiliser.

He has spent three years looking at alternatives to synthetic nitrogen. which he hopes will enable soils to regenerate and become more productive.

Overall farm fertiliser use has been cut by about 30%, with certain crops being reduced by up to 50%.

This has been achieved through several changes at Cleeves Farm Estate, a key one being the introduction of fertility-building clover leys to fix nitrogen in the soil.

He has also tweaked the rotation, growing fewer crops that require higher nitrogen rates.

Another change is the use of a microbial seed treatment to replace some of the synthetic nitrogen. Peter first tried it in a crop of January 2022-sown Skyfall second winter wheat.

In a field-scale trial, he compared his usual farm practice with a reduced level of nitrogen plus GramaxNP and a seaweed product sprayed in early spring.

Both parts of the field had a starter fertiliser of 50kg/ha of N. The farm standard then had an additional 55kg/ha of nitrogen applied during spring.

The Biolevel part had no other additional applications.

While it wasn’t a high-yielding site on Cotswold brash soil, the final yield from both treatments was similar, according to Peter.

“The Biolevel treatment yielded about 95% of the normal farm standard.”

The trial was repeated the following year with similar results. It is currently used on about 50% of the farm and he is hoping to increase this next year. 

However, he admits that he won’t know if his approach is enabling soils to regenerate for at least five years or more.

“The benefits are long term”, so time is needed before assessing the full effects, he says.

Microbial biofertiliser: What is Gramax NP?

The microbial seed treatment contains a diverse mix of bacteria which have been selected to improve the efficiency of N, P and K use by crops.

Developed by Biolevel in partnership with CertisBelchim, what makes the product unique is that it mixes eight different strains, while most other biological products contain a single strain, explains co-founder Laurence Berman.

This, combined with being in a stable form, is the reason behind its consistent results, he says.

Different strains shine in different conditions (soils and climate), and that’s why you need different strains, he says.

“Soil is a complex environment, and we have seen many times soils saturated with water and no one strain would deliver nitrogen fixing in soil with no oxygen.”

The mix also contains microbes that solubilise the unavailable P and K in soil, and these nutrients help plants respond to the extra nitrogen, says Lutz Glandorf, co-founder of Biolevel.

For example, P helps root development of the plant, and better roots mean better N uptake, water uptake and drought tolerance.

Effectively mobilising the P and K can help shift the nitrogen response curve upwards, resulting in either more yield or maintained yield with less N, he explains.

Stable form

In the past, microbial products have not been stable and have had a narrow use window after being mixed.

So the company has developed a liquid seed treatment that can be used straight from the container and does not need to be refrigerated.

“Farmers can also treat seed well in advance of drilling and use existing seed dressing equipment,” says Laurence.

Historically, biologicals have contained live bacteria in a powder form and, once mixed, they have to be used within 6-12 hours – and in a precise way.

“Just get one thing wrong and farmers end up with dead microbes,” he says.

The product is stabilised with the bacteria in a dormant state. Consequently, the treatment can stay on seed for months and remain viable.

This results in greater consistency and he believes this will make it more attractive to mainstream growers.