Potato growers, Bruce Farms, took part in a three-year programme of trials as part of the Agriculture and Horticulture Development Board’s (AHDB) Farm Excellence network.

The SPot Farm Scotland project, which was part-funded by the Scottish Government, used on-farm demonstration sites at Bruce Farms in Meigle, Perthshire, to host a series of trials on subjects, including cultivation, spacing and nitrogen nutrition. Now, the initial results are gelling into some significant and surprising pointers for potato growers.

Following a successful final year in 2019, Kerr Howatson, farm manager for Bruce Farms, said: “We became host of SPot farm Scotland in 2016 in a quest for knowledge. We wanted to trial ways to reduce costs and improve yields and then share this valuable information with the wider industry.

“From this, we have identified clear processes to follow that demonstrate cost savings and improved packable yield.

He added: “We have learnt that by reducing our cultivation processes, both the number of passes and cultivation depth, we have saved money and time and become more efficient.

“Plus, our nutrition trials have shown that we can cut our nitrogen use in our Maris Piper crops. By reducing the amount of nitrogen we have produced better crops, maintained yield and pack, and saved money.”

The new targeted approach, moving away from whole field treatments, is now embedded in standard farm practice at the Perthshire farm, saving £31 per ha on fertiliser (nitrogen) use and £36 per ha on fuel and labour.

Dr Mark Stalham, head of the National Institute of Agricultural Botany (NIAB) at Cambridge University Farm, commented: “Cultivation, spacing and nitrogen nutrition were our key themes over the last three years of trials on crops of Maris Piper, including a preliminary ‘year zero’.

“Our findings include the following:

“Cultivation – Overall there is a 2.6 tonne per ha advantage from removing the bed tilling operation, compared with bed tilling at 12 inches depth over the last four years. We included a preliminary cultivation trial to give us ‘year zero’.

“Spacing – the results of our spacing trials were inconclusive, however the AHDB recommended spacing, which was much wider than the commercial rate, showed a pack- out yield that was lower than standard. This probably reflected the requirements for slightly smaller size grades in the Scottish market, compared to the English one.

“Nitrogen – despite much industry scepticism that reducing nitrogen rates would increase yield the results show the opposite albeit on a limited basis. The overall result of 0.5 tonnes per ha increase over three years from reducing the application rate of nitrogen by 32 kg per ha is small but there was a saving in costs of £31 per ha and this was combined with no loss in quality.”

Senior knowledge exchange manager for AHDB, Claire Hodge, added: “Our trials have found that reducing nitrogen inputs doesn’t have a negative impact on yield or profit margins, if anything the opposite may be true.”


The nutrition demonstration was set up to question the levels of N and the timing of application – can the crop cope with fewer inputs and will it impact quality?

In 2017, four treatments were trialled:

1, Planting: Liquid (148 kg/N/ha); top dress, standard (29 kg/N/ha)

2, Planting: Standard (147 kg/N/ha); top dress, ridge inject (28 kg/N/ha)

3, Planting: Standard (147 kg/N/ha); top dress, none

4, Planting: Standard (147 kg/N/ha); top dress, standard (29 kg/N/ha)

Research from AHDB’s Grower Collaboration project showed that higher rates of N did not always increase yield. It is thought that the ‘insurance’ N application above the estimated optimal application rate may be negatively affecting yield.

The AHDB’s Strategic Potato Farms form part of the Farm Excellence programme: a network of over 80-plus farms across the UK. This provides a channel for integrating farmers and their businesses into the wider AHDB research and knowledge exchange programmes.