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Inici > English version > GRAP research > GRAP works > Variable dose rate in plant protection products

Variable dose rate in plant protection products


The GRAP basically started his research in the field of spray application techniques. One of the first research lines was the variable rate application of plant protection products developing a sprayer prototype able to modify the sprayed flow rate in a way proportional to the size of the target trees. The aim of the prototype is to achieve an approximately constant deposition of product on the leaf surface independently of the size the canopy all around the orchard, vineyard or citrus grove.


In the conventional applications, the sprayers apply a constant flow rate regardless the size of the trees and foliage contained (A). Step by step, the implementation of electronics in agriculture has generalized the use of sensors boarded on agricultural machinery. A specific successful application is the possibility to interrupt the spraying when there is no vegetation facing the spray nozzles. This achievement allows costs and environmental impact to be lowered due to the reduction of plant protection products sprayed and to the location of the product only where necessary (B). The developed prototype goes a step further since it is measuring the canopy size and estimating the amount of product to be sprayed along the rows (aprox. every 10 cm). Finally, the prototype adjusts the sprayed flow rate by means of electromagnetic valves actuated by specific control signals (C).




Canopy volume estimation

The first version of the prototype measured the canopy width with 1 or 2 ultrasonic sensors (An Electronic Control System for Pesticide Application Proportional to the Canopy Width of Tree Crops and Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies). Un a second stage, the sprayer prototype was fitted up with 3 ultrasonic sensors (D) or with 1 lidar sensor (E).


The paper explaining the second prototype is tittled Variable rate sprayer. Part 1 – Orchard prototype: Design, implementation and validation. Parallely, a variable rate sprayer prototype to apply plant protection products in vineyard was also developed. It is explained in the paper Variable rate sprayer. Part 2 – Vineyard prototype: Design, implementation, and validation. Both papers were published in 2013 at the journal Computers and electronics in agriculture.


Sprayer_1 Sprayer_2




The results show that the prototype perfectly matches the sprayed volume (blue line) with the canopy volume (green line) while and conventional application (orange line) is always applying the same mixture volume across the orchard.


In conclusion, the variable rate application sprayer prototype is able to keep the mixture per unit canopy volume ratio closer to the objective than a conventional treatment. The latter is only getting close to the objective when the canopy is big enough.


Source: Computers and Electronics in Agriculture, 95: 122–135; DOI: 10.1016/j.compag.2013.02.004



Last modified: 13/05/2015
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