Can a Variable-Rate Sprayer Be Efficient and Economic? Testing and Economic Analysis in Viticulture

The European Union has set ambitious goals in terms of reducing pesticides in agriculture. These goals could be achieved in different ways e.g. by Variable-Rate Application (VRA) technologies. This work aims to assess the spraying performance of a VRA sprayer and its economic sustainability. To evaluate operational performance, three trials (BBCH 65, BBCH 73, BBCH 83) were performed in a vineyard following a profile sampling strategy (BS ISO 22522:2007). A randomized complete block design was performed with three replications for each application mode (Uniform and Variable - UA and VRA). Variables (normalized deposition and spray coverage) were extracted from artificial targets using spectrophotometry and image analysis techniques, respectively. Moreover, the economic performance of the VRA sprayer compared to the UA sprayer was performed for an entire vegetative season in two plots. Normalized deposit results showed differences between detection heights (H1, H2, H3, H4) rather than between modes (VRA vs UA). Therefore, VRA and UA efficacy was confirmed, given the similar values of deposit. The same trend was evident in the spray coverage results, even though the UA spray coverages were higher than VRA, usually exceeding the overspray threshold. The economic performance highlighted an average volume saving of 35% for VRA, ranging from 76% in the first session to 10% in the last. The resulting economic saving was €2,599.50, consisting of: €2,502.5 in pesticides, €52.14 in water and €44.86 in fuel. Overall, the VRA system showed good spray performances reducing the spray volume significantly and enhancing economic sustainability.