Potato Review

28 POTATO REVIEW MAY/JUNE 2022 SUSTAINABLE FARMING contact-based rather than systemic material, so coverage is really important,” Jim explained. Modern nozzle designs can deliver a spray quality that minimises spray drift without compromising either spray coverage or product efficacy. “At the end of the day you only have 13 perfect spraying days in any given year, so on those other days, farmers have to be using the right nozzle to ensure they have good coverage,” continued Jim. “Nozzle selection in the potato crop should be made on a case-by-case basis; taking account of each operational parameter to ensure optimal product delivery and performance. A complex range of factors that influence sprayer output, and thus product delivery, must be considered. Water volume, operating pressure, boom height, product formulation and concentration may all adversely affect spray quality and product efficacy. However, a better level of canopy coverage is achieved by 90% drift reduction nozzles with a coarser spray quality being less prone to off-target spray drift.” Elsewhere he has been looking at the difference between sulphate of potash and muriate of potash – the latter being a more expensive fertiliser but better source of potassium for seed crops. “The difference in our canopy throughout the season has been quite striking,” reflected Jim. “SOP has kept the canopy more upright which has made for easier roguing and it is a better target for spraying.” A range of integrated pest management techniques are being trialled, including wildflower corridors stretching from headlands to the middle of the field to entice natural aphid predators into the potato field. He explained that for too many years the sector has been so reliant on pyrethroid insecticides. Over reliance on a single class of frequently used insecticide has resulted in selection for pyrethroid resistance in some aphid species. Another form of natural defence he has been assessing is that of straw mulching, spreading chopped wheat straw before emergence of potatoes. A range of integrated pest management techniques are being trialled, including wildflower corridors. Potato flowers.