Applying a nitrogen-fixing endophyte bacterial spray in potatoes can boost leaf chlorophyll content, tuber numbers and tuber yields, replicated trial plots in Yorkshire have shown.

Conducted by agronomy company ProCam at the Stockbridge Technology Centre near Cawood last season, the trial tested the endophyte bacterial spray Encera, applied with an adjuvant at the tuber initiation stage in mid-June to maincrop potatoes planted on 2 May.

The work followed other successful results seen with the treatment in other crops, says ProCam trials manager, Rebecca Tunnicliffe. After application, Encera bacteria enter the plant where they fix nitrogen (N) and supply it directly inside the plant’s cells, Ms Tunnicliffe explains.

“Consistent with this nitrogen-fixing ability, results showed the Encera treatment boosted leaf chlorophyll levels by more than 5% compared with untreated plants in the trial by mid-July,” Ms Tunnicliffe says. “All other inputs of herbicides, fungicides and conventional fertiliser were kept the same on treated and untreated plots throughout the trial.

“By 23 July, tuber digs revealed that Encera-treated plants had gone on to produce an average of 10% more tubers, at 15.4 tubers per plant. But more importantly, the benefits continued through to harvest.

“Compared with untreated plots, Encera treatment resulted in an average 8.4% uplift in yield of tubers in the 45-65mm marketable size fraction, from 57.3 to 62.1t/ha.

“There was also a substantial 24.4% increase in the number of tubers in this marketable grade. And total tuber numbers at harvest were similarly increased by a massive 25.9%. Maximising marketable yields is clearly central to potato profitability,” Ms Tunnicliffe adds.

Following this early stage work, Ms Tunnicliffe says ProCam will be adding to its knowledge about Encera in potatoes this season by testing it at a range of application timings, from in-furrow to late tuber bulking, to see whether this affects tuber numbers and yields. The effects of applying it more than once in the season are also being explored, she notes.

Meanwhile in Scotland, ProCam regional technical manager, Alistair Gordon, who advises on potato crops in Easter Ross and the Black Isle, has practical experience of using Encera on potato seed crops on-farm.

“With seed potato production, we’re not looking at total yield; we’re looking to burn the crop down early to produce smaller tubers,” says Mr Gordon. “So I was very interested in a product to increase tuber numbers in the seed sized fraction.

“As per the Yorkshire trial, Encera was applied once at tuber initiation to the seed crop potatoes. It was tank-mixed with the third blight spray. The grower was pleased with the results, and we’re repeating it again this season.

“Based on the results of the Yorkshire trial, I can see how Encera can also benefit ware crops. Another important reason for using an endophyte treatment is that it diversifies the N sources available to the crop, so that plants still have a level of N being provided even if soil conditions are too dry for traditional granular N uptake. We’re using Encera with the normal N fertiliser dose,” Mr Gordon concludes.