Conventionally, herbicides are applied uniformly in the fields, while there is strong evidence that weeds are not distributed uniformly within crop fields and they tend to occur in clumps or patches. This manuscript presents the development of a prototype patch sprayer for target oriented weed control system by integration of differential global positioning system (DGPS), Geographical Information System (GIS), and solenoid-activated spray nozzles in response to signals generated by a displacement sensor. A set of Ashteck Promark2 DGPS receivers (fixed and rover) was used to collect weed position data in the test plots. A micro-controller was designed, fabricated and used to retrieve weed patch locations on the electronic map and simultaneously receiving grid signals from an infra-red displacement sensor mounted on the sprayer front wheel to generate and send activating signals to the sprayer nozzle solenoids. A randomized complete block experiment was conducted with three herbicide spraying treatments consisting of targeted patch spraying, conventional (uniform) spraying, and nospraying (control) in three replications to assess the field performance. In the patch spraying treatment, spray mixture (Gramoxin, 10%) was sprayed only over the target (weed-infested) grids as controlled by a displacement sensor, an electronic weed map, and a microprocessor, while the conventional treatment plots received uniform and continuous application of the spray mixture. Patch spraying application was as effective as the conventional (uniform) application method in controlling weed infestation. The two spraying methods were significantly different at 99% confidence level with mean values of herbicide consumption rates of 40 and 12.21/ha for the conventional and patch spraying methods, respectively This indicates that targeted weed patch herbicide application resulted in 69.5% saving compared to the conventional application. (C) 2008 Elsevier B.V. All rights reserved.
