Potato Review

www.potatoreview.com POTATO REVIEW NOVEMBER/DECEMBER 2022 23 COVER CROPS P OTATO growers could get some welcome help from cover crops in building soil fertility in the battle to keep inputs to a minimum without compromising quality or yield. Cover crops take up residual N left behind in the soil or released from crop residues after harvesting the preceding cereal crop. When the cover crop is destroyed in the spring, the N is returned to the soil and some of it becomes available to the next crop, and although the amount of N released depends on a range of factors, such as soil, rainfall and species of cover crop used, it still provides a useful input. “Cover crops are an integral part of good soil management, and the aim should be for no bare stubble elds over winter,” said Andrew, but said they are not “a silver bullet”. “Cover crops should provide around 20t/ha of biomass above ground with a healthy root biomass, thereby reducing the impact of the rain on the bare soil. e weight of winter rainfall is often referred to as having the same weight as eight bags of potatoes on top of each other, pushing the soil down. Having the ground covered helps reduce the impact of this weight,” he said. By having roots in the soil, cover crops help to reduce soil erosion and the consequent loss of nutrients such as phosphates. Other bene ts include reducing run-o and leaching of all important nutrients, including potash, magnesium and sulphur, which is particularly important when elds are close to river courses. “By taking up N, there is less risk of nitrate leaching in winter months after rainfall,” said Andrew. “Moreover, cover crops help improve soil structure and therefore improve organic matter content and water holding capacity. is can improve soil resilience and also cash crops become more resilient to adverse conditions.” Nonetheless, cover crops have to be cost- e ective, he said, noting that planting a radish cover crop with the aim of avoiding the need to subsoil, needs to cost the same, or less, than the cost of cultivation. A cover crop costs around £40/ha to grow, and it’s about another £30/ha spend on cultivations to get planted. However, a cover crop can supply 35-40kg/N and 15kg/K, which suggests a gross margin of around £50/ha. ➜ Agronomist and Potato Specialist Andrew Goodinson discusses how to get best results from haulm destruction strategies. ANDREW GOODINSON Based in Herefordshire, Andrew has been working for Hutchinsons for 16 years and looks after nearly 8000 ha of farmland, ranging from Cirencester, to the Welsh borders, south Shropshire and Worcester. Cover crops – lots of advantages but no silver bullet