9The changes in the shape and size of vines during the growing season, requires a 10 continuous adjustment of the applied dose to optimize spray application efficiency. 11Target detection with ultrasonic sensors can be used to adapt the applied dose following 12 the principles of the variable rate technology. A multi-nozzle air blast sprayer was fitted 13 with three ultrasonic sensors and three electro-valves, to modify the flow rate from the 14 nozzles in real time, in relation to the variability of crop width. A constant application 15 rate of 300 l·ha -1 was compared with a variable rate application using the tree row 16 volume principle at a 0.095 l·m -3 canopy. The total flow rate sprayed by the nozzles was 17 modified according to the variations of crop width measured by the ultrasonic sensors. 18On average 58% less liquid was applied compared to the constant rate application, with 19 similar deposition on leaves with both treatments. A detailed analysis of savings 20 indicates differences between the lower, middle and top part of the crop, in accordance 21 with the leaf area distribution with crop height. No significant differences between 22
The use of a low-cost tractor-mounted scanning Light Detection and Ranging (LIDAR) system for capable of making non-destructive recordings of tree-row structure in orchards and vineyards is described. Field tests consisted of several LIDAR measurements on both sides of the crop row, before and after defoliation of selected trees. Summary parameters describing the tree-row volume and the total crop surface area viewed by the LIDAR (expressed as a ratio with ground surface area) were derived using a suitable numerical algorithm. The results for apple and pear orchards and a wine producing vineyard were shown to be in reasonable agreement with the results derived from a destructive leaf sampling method. Also, good correlation was found between manual and sensor-based measurements of the vegetative volume of tree-row plantations. The Tree Area Index parameter, TAI, gave the best correlation between destructive and non-destructive (i.e.LIDAR-based) determinants of crop leaf area. The LIDAR system proved to be a powerful technique for low cost, prompt and non-destructive estimates of the volume and leaf-area characteristics of plants.
A prototype of an electronic control system based on ultrasonic sensors and proportional solenoid valves for a proportional application to the canopy width of tree crops was mounted on an air-assisted sprayer. The sprayer flow rate adjustment was based on the relationship between the actual tree width measured by the ultrasonic sensors and the maximum tree width of the orchard. The prototype was tested in olive, pear and apple orchards to assess the system performance in different crop geometries. The spray deposit distribution was measured in comparison with conventional air-assisted applications. Metal tracers were used so that spray deposits for each treatment could be measured on the same samples, reducing sampling variability. Liquid savings of 70%, 28% and 39% in comparison to a conventional application were recorded in the olive, pear and apple orchard respectively, which resulted in lower spray deposits on the canopy but a higher ratio between the total spray deposit and the liquid sprayer output (i.e. better application efficiency). A reduction of the maximum tree width parameter in the control algorithm in the apple orchard reduced spray savings but increased spray deposition, with spray savings mainly in the middle level of the outside canopy, compared to conventional air-assisted applications.
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