Impact of the horizontal movements of a sprayer boom on the longitudinal spray distribution in field conditions

The influence of horizontal sprayer boom movements on the longitudinal distribution of the sprayed product was investigated in field and laboratory conditions. The boom movements of a sprayer were measured in the field using a specially designed measurement chain, and the resulting ground distribution was estimated by spraying a dye (Nigrosine) on large sheets of wallpaper and using image analysis to compute the spray coverage. The horizontal movements, identical to those measured in the field, were applied to a laboratory boom part moving on horizontal rails, in the absence of wind. For the three tested situations, the longitudinal coefficients of variation (CV) of the spray coverage were very close in the field (8.81%, 6.9%, 10.9%) and in the laboratory (9.17%, 8.17% 10.96%). This indicates that horizontal movements were the main source of spray deposit variations, even if other factors such as vertical movements or wind may have an influence. The mean ratio RCV between the CV of the horizontal movements and the spray coverage was estimated. In addition, the amplitude of the boom movements was investigated in a large range of situations (five different sprayers, three different crops). On basis of the measured movements and the computed RCV, the variability of the longitudinal spray distribution due to horizontal movements was estimated at between 3.5% and 5.2%. (C) 2003 Elsevier Science Ltd. All rights reserved.