Development and implementation of a laboratory spray device and rainfall simulator for retention research using small amounts of agroformulations

BACKGROUND: Rainfall greatly affects the retention of foliar-applied agro-formulations. Improving their resistance to wash-off is therefore of great importance in spray applications. While developing such formulations, small-scale laboratory assays are generally required. A set-up for retention studies using only small amounts of agro-formulations (< 0.5 L) was developed. The set-up consists of a spray device and a rainfall simulator. The effect of rain quantity (1, 3, 6 mm) on the spray retention of agro-formulations was evaluated using this set-up. RESULTS: The data showed that uniform and repeatable spraying was achieved with the small-scale spray device (CV = 23.4%) on potato pot plants (Solanum tuberosum L.). Rain quantity significantly affected the spray retention. Approximately 40% of the initial deposition was lost after 1 mm of rain at an intensity of 25 mm h-1. Additional losses decreased with increasing volumes of rain (65% and 80% loss after respectively 3 mm and 6 mm of rain). CONCLUSION: Future studies could implement the set-up to evaluate the effect of different rainfall characteristics and formulations on spray retention in order to improve the rainfastness of agro-formulations.