Agricultural methods to reduce the risk to birds from cereal seed treatments on fenlands in eastern England. II. Rolling and harrowing as post-sowingcultivations

The objective of this study was to assess the usefulness of two common agri cultural cultivations to cover exposed seeds after sowing, with the purpose of reducing the risk to birds from pesticide-treated grain. In three exper imental trials, both rolling and harrowing buried a large proportion of exp osed seeds after drilling or broadcasting, but their relative efficacy was affected by seedbed condition. In a fine seedbed, the proportion of seeds c overed by harrowing (84-86%) was substantially higher than that for rolling (53-58%). In a rough seedbed, rolling gave slightly better results (76-84% ) than harrowing (73-77%). In trials simulating seed spills, harrowing prov ed very effective irrespective of seedbed condition, as it dispersed most s pills and buried most of the exposed seeds (85-92%). Rolling was of much le ss value for spills because seed coverage was lower (25-60%) and most spill s remained as clumps of seeds. Estimates are presented of how reductions in surface grain by cultivations would affect an index of risk to two granivo rous species of birds from fonofos, a common insecticide seed treatment. Th e potential of these cultivations for reducing the risk of acute bird poiso ning is discussed. A decision scheme summarises recommendations on how to u tilize these cultivations in different parts of the field in relation to so wing depth and seedbed condition for agronomic and environmental benefits. Crown copyright (C) 1999 Published by Elsevier Science B.V. All rights rese rved.