Distribution of spray applied to a cereal crop and the effect of application parameters on penetration

Abstract

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, 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, 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 influence 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 80° 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.