Injecting beneficial bacteria into the furrow when planting potatoes could help increase marketable yields and decrease skin blemishes, according to trials.

The microbes in Omex‘s Biomex Starter – a liquid formulation of the naturally-occurring plant-friendly bacteria Bacillus amyloliquefaciens – improve the release of nutrients from fertilisers, while at the same time help develop rooting and provide the plant with a defence against infection, according to Neil Fuller of Soil Solutions, who has been developing the concept for a number of years.

Biomex can be applied either with placement fertiliser in two rows either side of the seed tuber at planting, as a seed treatment, or sprayed directly into the furrow.

“The idea is that the live bacteria added to the starter fertiliser colonise the plant roots, which feed the bacteria with carbon-rich root exudates,” he explains.

“In return, the microbes increase nutrient uptake, making fertilisers more efficient, and as a side effect, produce metabolites that stimulate healthy growth and suppress disease.

“As the plant grows, so the microbes get stronger and more active. This is the exact opposite of most chemicals and biostimulants, which lose efficacy as the plant develops.”

The result is a plant that has better access to water and nutrition. “Potentially these microbes could get 30% more phosphorus out of applied fertiliser, so replacing about80kg/ha of P,” he claims.

Results from trials suggest varieties differ in the way they respond to Biomex. In a trial last season on Maris Piper aimed for the chipping market, the variety producing fewer tubers, but 18% more marketable yields.

In the previous year a similar 16% increase in marketable yield of Fianna grown for packing was seen. But in this case more tubers were produced, with them finishing around the desired 100mm size with less over- or under-sized tubers, he says.

There have also been significant decreases in common scab and black scurf blemishes on tubers, particularly where higher doses of the microbial treatment were used.

At the highest dose of 2litres/ha tubers from Maris Piper plots treated with bacillus had only 6% infection with common scab compared with 36% in the untreated controls and 3% black scurf compared with 15%.

The effects from the microbes are enhanced when phosphite is also applied, he adds.

“Foliar phosphites help promote root development, and are also linked with suppressing disease. We’ve found some good synergy between the two.”

The combination of microbes and conventional agronomy is an exciting development, he claims. “Integrating microbes with conventional fertilisers and agchem is setting new horizons for our crop production.”

Omex sold about 1000ha of Biomex last year, Gidon Bahiri, the firm’s product development manager, says. “We hope to double, maybe even treble that this year.”

The firm obtains the product from the German manufacturer ABiTEP.

A dry formulation is also available to be used as a seed treatment (see panel). “It doesn’t appear to be more effective one way or the other, but it does need to go on at planting.”

Biomex costs £78/ha for a 0.5 litres/ha liquid application and about £25/ha for a 1kg/t seed treatment.

Branston experience

Potato packers Branston interest in exploring biocontrol options in potatoes has led them to trial the seed treatment version of Bacillus amyloliquefaciens, confirms Andy Barker.

“These products have often been given the muck and mystery label, but this doesn’t fall into that category.”

He is confident enough in the results to recommend pre-pack growers test the product, which Branston is selling as Branston Fence, on half field comparisons, particularly on old potato ground where they are aiming for Class one product.

“In trials we’ve seen anything up to a 15% increase in top marketable yields and improvements in skin finish. It seems to discourage tuber-harmful pathogens, such as rhizoctonia, in the first four to six weeks.”

The product shouldn’t be seen as a replacement for pesticides, but it does negate the need for higher rates in some cases, Dr Barker suggests.

“We recommend using it in combination with half rate Monceren as a seed treatment.”