A comparison of biological effect and spray liquid distribution and deposition for different spray application techniques in different crops

The objective of this study was to compare a selection of spray application techniques with different application volumes, with respect to the spray liquid distribution on flat surfaces, the deposition in fully developed crops and the biological effect. The spray application techniques in this study were conventional spray technique with three different nozzles: Teelet XR, Lechler ID and Lurmark DriftBeta, and also AirTec, Danfoil, Hardi Twin, Kyndestoit and Släpduk. The dynamic spray liquid distribution was measured on a flat surface, spraying a water and black dye solution on pre-glued wallpaper lengths. Spraying the same dye-water solution in established crops, the spray deposition on plant and on the ground was studied by measuring the absorbance of sampled leafs' and collectors' rinsing water. Spray deposition studies were made in winter wheat and potato. The biological effect was studied in field experiments with plots with linearly increased dose. The field trials in this study were weed control in spring barley, fungi control in winter wheat and potato late blight control. The weed weight was sampled and visual assessments were made of the infection of fungi. Grain yield and 1000-kernel-weight were sampled in the wheat trial. The dynamic spray liquid distribution resulted in coefficients of variation, for all spray techniques, between 5% and 16%, which were considered to be at acceptable levels. Relatively large significant differences were found in the spray deposition measurements in potato canopies. For conventional spray technique, 90% spray deposition was recovered in the top of the canopy. Higher deposition was recovered in the lower part of the canopy and on the ground for Danfoil, Hardi Twin and Släpduk than the other techniques. In the wheat crop, the differences in spray deposition between spray techniques were smaller. Släpduk had the greatest increase in liquid deposition on the head and the flag leaf. The techniques with external air assistance, Hardi Twin and Kyndestoft, had the lowest deposition on the ground. Analysing the effect of weed control in spring barley, fungi control in wheat and potato late blight control, no significant differences were found. This might be seemed remarkable when large differences in spray liquid deposition were found in the potato canopy. One conclusion could be that the penetration ability in dense potato canopies is not of equal importance as to protect the upper parts of the canopy. It is indicated that it could be important to consider other factors, not included in this study, such as the ability to reduce drift and increase capacity, when selecting spray application techniqu

Fördelning av sprutvätska i spannmåls- och potatisbestånd med fyra olika appliceringstekniker

The aim of this study was to compare spray deposition in field crops using different application methods. Field trials were carried out in potato and winter wheat crops. A tracer dye (Nigrosin WLF, Bayer) was added to the spray liquid, and deposition was measured on leaves at three different levels in the crop and plastic objects placed on the ground. The leaves/objects were rinsed in water and deposition was quantified with spectrophotometer measurements. Four different application methods were compared: a conventional sprayer, air-assistance (Hardi Twin), in-built spray with crop opener (Lehner-boom) and last a nozzle-sledge developed at the Swedish University of Agricultural Science, Department of Agricultural Engineering. The last three methods all improved canopy penetration. In some cases the ground deposition increased as a consequence of improved penetration. At 100 l/ha application rate in winter wheat the nozzle-sledge improved the deposition on the ear-leaf compared to the other application methods, and at 200 l/ha air-assistance improved deposition on the ear-leaf compared to conventional application. On the second and third leaves there were no significant differences between the application methods. The nozzle-sledge decreased ground deposition compared to the other methods in all cases but one. At 200 l/ha application rate the nozzle-sledge and air-assistance gave equal ground deposition. The measurements in potatoes showed that air-assistance, Lehner-boom and nozzle-sledge all improved canopy penetration compared to conventional application, The nozzle-sledge yielded highest penetration. Using conventional and nozzle-sledge application resulted in ground depositions between 15% and 20% of applied spray. The sprayers equipped with air-assistance and Lehner-boom increased ground deposition to between 25% and 35% of applied spray liquid. The investigation has shown that there is a potential to more effective and hence reduced doses of agrochemicals by using modern application technology. Still though, there is a lack of important knowledge in this area and further research is needed