Video: How cutting nitrogen may improve potato yields

Potato growers could achieve higher crop yields while slashing their nitrogen fertiliser inputs, according to the latest findings from independent farm-scale trials.

Work at the AHDB Potatoes strategic potato – or “Spot farm” – in Staffordshire has built on a decade’s worth of trials comparing farm standard nitrogen rates to the lower rates that the AHDB deems to be best practice.

Marc Allison, senior researcher with Niab’s Cambridge University Farm, says these comparison trials showed that it is possible to grow the same crop specification with less nitrogen input.

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The comparison trial work took place on 22 different farms in the past nine years and is now being fed into research at the Staffordshire Spot farm, working with grower James Daw.

“What we have shown is that often the grower is applying too much nitrogen and by reducing the nitrogen application rate by 28kg/ha we can actually increase the yield of the potato crops.

“Farmers will often apply more nitrogen than they think they need as an insurance amount and it is really important in our work to help farmers hit the top of the nitrogen response curve to avoid losing yield,” he explains.

Spot farm crop nutrition findings

The same method was applied at the AHDB’s Staffordshire Spot farm trial last season, with the best practice nitrogen rates adjusted based on the variety, soil type, season length and previous cropping of the trial field.

Mr Daw had also applied 40t/ha of pig manure mixed with straw, giving a low supply of nitrogen to the potato crop of about 22kg/ha.

“We worked out a nitrogen application rate for that crop and then subtracted the 22kg/ha of N to account for the nitrogen already supplied by the pig manure,” says Dr Allison.

Yields of the strips with and without pig manure applications were compared and the findings showed that there was no yield benefit gained from adding an extra 22kg/ha of N in excess of the pig manure.

The top potato crop yield was hit when 210-220kg/ha of nitrogen was available to the crop over the growing season.