Spraying Technique in Potatoes
Conclusion and summary
Potatoes are sprayed intensively to keep them free of blight. Only limited knowledge has been accumulated as to how the various spraying techniques affect the deposition in the potato plant. This study includes various sprayer types and nozzle types. Three sprayer types were included in this study: A traditional field sprayer, a field sprayer with Hardi TWIN air assistance, and a Danfoil air sprayer. These sprayers were tested with various nozzles, as well as with varying water volumes and at varying running speeds.
These sprayer techniques were evaluated based on
- Washing off and measuring of trace element.
- Registration of drop placing with water sensitive paper.
- Visual evaluation of spray liquid placing with fluorescent liquid and ultraviolet light.
Uniform coverage of all leaves is essential for protection against potato blight since agents with contact action are generally used. Using ultraviolet light and optical white, the distribution of spray liquid in the crop may be viewed visually. We have not managed to photograph this or otherwise document the uniformity of the various treatments. This will require further studies, either by way of improved photo technique or by spraying with trace elements with subsequent analysis of leaf areas smaller than those used during this test.
Measurements performed show a high degree of variation. Separating the various techniques is thus not possible with statistical certainty. The results would, however, seem to indicate what is outlined below:
- Spraying using the air assisted Hardi TWIN sprayer and the Danfoil air sprayer showed higher deposition of spray liquid in the upper part of the potato crop.
- The Danfoil sprayer provided the highest deposition in the middle of the potato plant.
- Using a traditional sprayer produced the highest deposition in the upper part of the potato top with compact air injection nozzles. This applies under favourable as well as unfavourable weather conditions. Under unfavourable weather conditions, 40 % higher deposition was measured on the upper leaves than after ordinary flat spread nozzles.
- Under unfavourable wind conditions, significantly better deposition was achieved using Hardi TWIN air assistance as compared to spraying using ordinary flat spread nozzles without air assistance. The Danfoil sprayer was not tested under unfavourable wind conditions.
- Since the wind conditions varied at the three speeds, it cannot be concluded whether the speed affects the deposition.