Managing cultivations and cover crops for improved profitability and environmental benefit in potatoes
Research on potato systems shows that deep compaction caused during ground preparation before planting and shallow compaction caused by repeated traffic for spraying and irrigation post-planting are two significant problems facing potato growers, with implications for yield, quality, soil structure, efficient use of irrigation, and the risk of diffuse pollution in runoff.
The objectives were to:
- Cover crops recovered 15-80 kg N/ha that would otherwise be lost from light soils over-winter.
- Oil radish, winter rye and mustard all proved suitable cover crops at the English site, but oilseed rape (OSR) proved unsuitable at the Scottish site. Mustard was the most cost-effective in England; oil radish in Scotland.
- Early cover crop establishment was vital to ensure good ground cover and N uptake. Late cover crop destruction reduced recovery of its N by the next potato crop.
- By harvest, potatoes typically recovered 15-50 kg N/ha from cover crop residues.
- Net costs of using cover crops could be as low as +£4/ha (range +£12/ha to -£20/ha), depending on the species, seed cost and seed rate used; the establishment and destruction method; and the timing of such operations which influences C:N ratio at destruction and resulting N recovery by the potato crop.These costs may be offset through the points available for using cover crops under agri-environment schemes.
- Rooting depths available to the potato crop following cultivations differed between the Tillerstar (20cm above stone layer), plough (20-25cm), and DTX (33-40cm), which meant that deep compaction from previous years persisted in the Tillerstar treatment. This resulted in significantly shallower depths to soil compaction (p<0.01) and associated shallower rooting depths 9 weeks after emergence (p<0.01) under the Tillerstar treatment (27cm depth) compared to the plough and DTX treatments (47-53cm depth) in Harvest 2013. Such findings were supported by soil compaction and crop rooting data in Harvest 2014.
- In spite of this evidence of the soil physical effects (penetration resistance, rooting) caused by different cultivation treatments, there was no significant difference (p<0.05) in use of the plough, DTX or Tillerstar cultivation methods on potato ware yield or quality, possibly due to both experimental sites being irrigated.