Potato growers carrying out inappropriate or poorly timed soil cultivations are endangering their profitability by impeding rooting, and consequently yields and quality, says Cambridge University Farms’ researcher Mark Stalham.

Growers must be more patient and modify practices to alleviate the threat of soil compaction, he warned at the British Potato 2005 fresh convention.

“Two-thirds of UK fields have a serious impediment to rooting within the potential profile, which has severe consequences on potato yield and quality.”

It would not become easier in the future as financial margins and land availability tightened, he said.

With rented land production expected to rise, Dr Stalham said growers might have less control over cultivations.

“Time pressures may mean soils are cultivated when wet causing compaction.”

Losses caused by poor soil conditions would be exaggerated by any future restrictions on irrigation and if the forecast drier summers from global warming became a reality, unless the problem was addressed now.

“Rising fuel costs will also exaggerate the energy wastage of unnecessary cultivations.”

Growers could produce seed-beds without compaction within existing GAEC guidelines, he believed.

“But we have to be patient.”

That meant waiting for the soil to be in the right condition to be worked without compaction.

“Many growers are creating thin compacted layers during planting and others are failing to remove deep compaction below the plough layer,” he said.

The latter was partly because sub-soiling was carried out while soils were too wet.

“Sub-soiling is frequently done when the soil is not dry enough to result in extensive cracking.

Growers should look to subsoil in late summer/early autumn when the soil is at its driest.”

But it was shallow compaction to about 30cm which was most damaging because it reduced root growth rates when they were at their most rapid.

That was caused by cultivations before planting, he said.

He advised measures such as ploughing immediately before bed-forming rather than ploughing, leaving and risking slumping before bed-forming, and again making sure soils were dry when forming beds to avoid the risk of smearing.

Dr Stalham’s recommendations were workable, Frontier’s Paul Overton told Farmers Weekly.

“But the whole industry won’t get there tomorrow,” he said.

The constraints include growers not getting fields sorted out early enough after the autumn harvest on rented land and limitations on time and machinery available.

fwarable@rbi.co.uk