The results were vastly reduced losses of nitrogen. Dr Silgram explained: ‘The plants took up much of the nitrogen that would otherwise have leached away or run off. This method saved around 70kg per hectare of nitrogen.’
Using this kind of green manure also helped put more organic matter back into the soil. It also helped retain water in the light soils, which are normally used for potatoes. The plants could also prevent soil erosion.
Several plants were trialled. These included mustard, oil raddish, winter rye, barley and oil seed rape. They offered a range of different benefits. Mustard was one of the more expensive plants, but was best at retaining nitrogen and helped build up organic content. Oil raddish had the advantage that it helped reduce compaction, because of its large roots.
Dr Silgram reckoned that growers could save up to £20 per hectare in lost nitrogen. He further calculated that the additional organic matter was worth a further £40 per hectare in profits. Growers using these techniques might also be eligible for Environmental Stewardship grants.
Dr Silgram, who will be presenting his findings at the ADAS Syngenta 2012 Potato conference in Nottinghamshire on 22 November, said: ‘These techniques will help growers conserve nutrients and cope with the extremes of weather. They offer great opportunities to reduce losses.’