NEW technology is being put to full use to show that reduced use of fertiliser and fine-tuning seed spacings can save money while increasing potato yields, in trials at the AHDB’s SPot Farm, at Meigle.

Working with hi-tech specialists, Soil Essentials, a range of measures – including satellite imaging and radar technology – have been used to evaluate how crops have been growing and how they respond to different regimes on the SPot farm.

Claire Hodge, AHDB’s potato specialist and a Nuffield scholar who majored in the seed potato supply chain, said there was a ready access now to equipment and data, but that it wasn’t always clear about what to do with the results.

“So we’ve been looking at what technology can be used to zone in on what’s the crop’s doing, using technology to help make management decisions to help manipulate the ultimate aim of yield and quality,” she said at a recent open day.

“In our nitrogen application trials, we really thought at the start that we could get the same yield by reducing nitrogen in some fields – but we have actually shown that reducing N can also lead to better yields in some areas which have inherent high organic matter in the soil.”

At Bruce Farms, four treatments were trialled in 2018 – 1, placement at planting of 179kg/ha of N, followed by 185kg/ha of calcium nitrate as a top dress; 2, reduced amount at planting of 147kg/ha and no top dressing; 3, further reduced N at planting of 90kg/ha and no top dressing; and 4, control of 179kg/ha at planting and standard top dressing.

Method No 2 came out best both in terms of actual and dressed out yield at packout, of 29.7 tonnes/ha and 44%, respectively. The worst yield and lowest packout came for method 4.

One startling result was that for the ultra-reduction trial (No 3) which produced 28.7 tonnes/ha and a packout of 41%.

These stats are also quite universal throughout the AHDB’s SPot farms across the UK, pointed out Mark Stalham, a senior research associate at NIAB CUF. “Essentially, all SPot farms have been confirming these results. In some cases, we have substantially reduced N and yet yields have at least been maintained or increased in some trials.”

This year’s trials will be evaluating what other added benefits reduced N might have, like encouraging early crop senescence, thus making burn down costs lower and the influence that it will have on skin set, which will allow quicker harvesting after haulm kill/removal.

Mr Stalham added: “The one thing we all have to remember is that we’re growing tubers, not leaf. If we want the crop to start dying on its own, then reducing N can really help that.”

He said that the next stage in such work might be to trial zero N on fields which carried a high organic matter in the soil – the rule of thumb is not to try this on soil with anything less than 10% organic matter.

Seed spacing manipulation to hit spec’

Seed spacing trials at Bruce Farms have also shown that high value crops, such as salad potatoes, can be greatly influenced by tweaking rates.

At the site, salad potatoes are an important crop for the business and increasingly variable seed spacing is being used to manipulate the percentage of crop which will hit the right spec’. (See Table, above right).

However, it is a delicate balancing act between total field yield and getting the packout percentages right for the eventual customer, admitted Bruce Farms' manager, Kerr Howatson. “Hitting the spec’ has a massive effect on the crop’s profitability,” he said. “So we’re working at using different seed rates to hit different specifications. Getting it right or wrong can really make or break a crop.”

Basically, wider seed spacing produces greater yield, but not necessarily the best packout yields for certain spec's. The theme at Bruce Farms is to use new technology to fine-tune variable rates across different parts of each field to level out production of in-spec’ tubers.

Soil mapping, using satellite images from the past five years, is used to assess productivity across fields and then a template can be made to calculate variable seed rates to level out tuber size and production across different areas.

Using technology supplied by Soil Essentials, Mr Kerr said: “The soil scan is about £20 per ha – and for improving packout in a salad crop, that expense is a no-brainer.”

Further work will assess if new technology can also be used to fine-tune irrigation, which would also be a way of saving money while maintaining or improving yield in certain field areas.

Seed spacing table

Seed spacing 33cm 38cm 47cm Variable

Boxes per ha 55 62 54 53

Graded t/ha 51 57 51 47

Packout % 51 43 42 42

Yield t/ha 27.9 26.7 22.9 22.1