Potato producers often rely on the biggest, most expensive machinery coupled with high inputs to boost production, however evidence suggests that smaller tractors and lower rates particularly of nitrogen, will not only improve the quantity but also the quality of crops produced.

These were just a couple of the revelations highlighted at the AHDB Potatoes farm demonstration day at Bruce Farms, near, Meigle, on Tuesday, where yield benefits of up to 3t per ha are expected by reducing nitrogen applications by 25-30kg per ha.

Furthermore, Dr Mark Stalham, who did a PHD on the subject some 28 years ago, said reducing nitrogen fertiliser by 10-15% not only increases the amount of potatoes produced but also the quality in terms of dry matter and skin finish.

“The data is all there – it’s just up to farmers to take it on board,” said Dr Stalham.

“Potato crops are largely over fertilised and top dressing generally produces canopies that are too green, when ultimately less fertiliser would allow it to die off naturally.

“If you produce a canopy that is too big, it can’t intercept the light and you are taking away from the bulking rate of the tubers,” he said pointing out he expects the same could hold true with potassium and phosphate.

And, contrary to popular belief, Dr Stalham said there were yield benefits to be had from ploughing and planting at shallower depths, which depending on the type of soil used would see crop improvements of 2t/ha plus.

“Our soils are becoming increasingly difficult to cultivate because of bigger, heavier types of machinery used which have damaged our soils.”

He said that the deeper and more intensively soils are worked, the more they break down leading to very porous seed beds that lose air space which in turn make for denser soils and increased clod formation.

“There is no benefit to deeper ploughing, but there is a gain to working at shallower depths of around 2cm both in terms of yield and costs of production.

“Planting at shallower depths also does less damage to soils especially in wetter areas.”

He said that trials had shown that reducing the depth of destoning had no effect on total yield, but that reducing the bedtilling depth from 12” to 6” increased work rates by 50%, which coupled with other reductions in cultivation depths could produce fuel and labour costs by almost £30 per ha.

Comparing cultivation depths was just one of the objectives of last year’s trials on the farm, which revealed some unbelievable differences in overall yields at harvest and packout. (See table below).

The project demonstrated that soil should not be cultivated deeper than 27-28cm (23-25cm for clay soils) in depth prior to planting.

It also highlighted that deeper cultivation, reduced yield, increased fuel, labour, repair and depreciation costs, however there were no negative affects on tuber quality.

Shallow destoning resulted in 20-40% faster work rates, giving greater opportunity for soils to be cultivated closer to their optimum soil water content, thereby reducing compaction and improving yield.

Additionally, shallower destoning and bedforming on heavier soils resulted in fewer clods than deep destoning and can reduce the reliance on bedtilling.

Dr Stalham concluded: “The best packout came from Bedform 12”, no bedtilling and destoning took place at 10” – which is very close to what I would call best practice.