Spray Behaviour Field Conditions
The project studying Distribution of spray applied to a cereal crop and the effect of application parameters on penetration was funded by the HGCA.
A series of trials were carried out, both in the field and in a wind tunnel, to investigate the distribution in a winter wheat canopy of a spray application, to identify the factors which influence the distribution, and in particular the quantity of spray depositing on the lower stem. Increasing application volume was shown to have no influence on the quantity of active ingredient reaching the lower part of the canopy. Recommendations to increase volumes to improve penetration of a dense canopy cannot, therefore be justified.
The best application system, out of those tested in this study, to achieve high penetration into a canopy, as well as good overall plant deposits, was a small droplet air-induction nozzle operating at 100 L ha-1. Other factors that influenced deposition of spray in the lower part of the canopy are wind speed and potentially boom height. Use of an air-induction nozzle effectively eliminated the effect of wind speed and so would be likely to deliver a more uniform distribution over the canopy. An 80o nozzle also increased penetration, but its effect might be reduced by the need to increase boom height with narrower angle nozzles in order to maintain a uniform distribution.