EXPERIMENTAL AIR-ASSISTED SPRAYING OF A MATURING CEREAL CROP UNDER CONTROLLED CONDITIONS

Outdoor tray-grown cereal plants at growth stage 39-41 were exposed to very fine/fine and medium-quality sprays from hydraulic flat-fan nozz les fitted to an air duct so that spray and air could be directed eith er 45 degrees forwards or vertically downwards. Spraying was done at 0 .5 and 2.0 m s-1 and fluorescein deposits measured on plants and on th e soil for all combinations of the above factors (24 spray options), e ach replicated three times. Finer sprays angled forwards and the use o f air assistance interacted to increase total spray deposition on plan ts and reduce soil contamination. Fine sprays were better retained in the upper canopy and on stems. Forward angling increased deposits in t he upper canopy but reduced penetration. A slower spray speed increase d plant and soil deposition. Increasing amounts of air assistance impr oved plant deposits, especially in the upper canopy and on stems. Comp ared with 'standard' practice (a medium-quality spray, applied vertica lly downwards at 2 m s-1, without air assistance), forward-angled air- assisted very fine/fine and medium-quality sprays increased plant depo sits on whole tillers by approximately 71 and approximately 66% and re duced soil contamination by approximately 46 and approximately 66%, re spectively.