Similar targets for spuds and soil

What’s best for potatoes in terms of soil condition is also best when it comes to fulfilling environmental obligations, growers to last week’s BPC open day on Farmers Weekly’s western Barometer farm heard.

But allowing for the vagaries of the weather looks set to remain a challenge in achieving that goal.

SAC agronomist Eric Anderson pointed out that under the EC’s Soil Framework Directive adopted in September 2006, which recognised that soil was an irreplaceable natural resource, growers had a “duty of care” to look after their land.

And since January 2007 growers had been obliged to put into practice the measures pinpointed in their obligatory Soil Protection Reviews.

A key aim was to avoid soil erosion, which carried away fertile topsoil and nutrients, especially phosphorus, reduced productivity and risked polluting watercourses, explained Mr Anderson.

SAC Recommendations
  • Subsoil in late summer/early autumn or possibly at planting on sands which re-compact easily
  • Bed-form when soils are dry and more resistant to slumping. On heavy land this may mean late summer/early autumn
  • Plough immediately ahead of bed-forming – less chance of slumping and slow dryingOver-wintered beds in high rainfall areas are “generally disasters”
  • Avoid destoning too deeply and over-vigorous bed-tilling

One in 10 potato fields was at risk of erosion, he warned. And because the crop tended to be grown on light soils sediment run-off could soon occur –even on gentle slopes of only 2-3°.

Standing in a pit excavated to show the impact of below–ground conditions and discussing ways to avoid such erosion and maximise crops’ use of rainfall and irrigation water, he stressed the need to avoid compaction.

“In many respects the Environment Agency’s aims are really the same as what we want for getting the best from the crop.”

That meant ensuring that the soil structure was open enough to allow good water penetration and deep rooting.

Compacted areas restricted rooting, which led to smaller canopies and less sunlight being absorbed by the crop. They could also encourage erosion.

The big danger lay in trying to get on the land too early, he explained. Although the surface might seem dry enough, tractor wheels and ridger tines could cause compaction and smearing on the damper hidden soil.

“Just because you can move on the land with high horse-power doesn’t mean it is right to be there.”

Host farmer Richard Solari acknowledged he might have been more patient on the evidence of some slightly compacted areas.

“We had a very wet February. The beginning of March was drier, but it was cold and we were still getting 1-2mm of rain a day, so we didn’t get any proper drying.”

But there was a dilemma in deciding whether to wait for ideal conditions and so risk delayed planting if further rain occurred, he pointed out.

“The question is do we go when conditions are 80% right or what?

“In the previous year we might not have started planting until May.”