Precision Agriculture and Drift Management

By definition, spray drift is composed of applied pesticide that has failed to reach the intended target. Most sprayers treat an entire area with little consideration for or ability to adapt to target or environmental conditions. Sensing and control systems for agricultural sprayers can reduce spray drift by adjusting the spray output to focus deposition exclusively on targets, compensate for variable environmental conditions or alter the application rate in accordance with a priori knowledge of the crop or other target. Technology and techniques for such applications is generally referred to as “precision agriculture”. In this paper, the term “precision application ” refers to technologies and strategies where broadcast application of agrochemicals is replaced by targeted application and / or control of the application based on sensing of environmental conditions. Specific examples include target detection systems for field and orchard crops, droplet size and rate control systems and selective application systems that allow reduction or elimination of chemicals with potential drift concerns. Sensing and control systems can significantly reduce the applied rate of pesticide while maintaining target deposition levels necessary for efficacious pest control. Order-of- magnitude reductions can be achieved under some conditions while 25 – 50 % reductions in are present at the time of treatment. Examples include selective control of emerged weeds and foliar applications of insecticides and fungicides when crop plants are sparse or exhibit spatial non-uniformity. The systems require sensors, algorithms and spray system actuators with fast response times and high spatial resolution. “Spot spray ” systems are examples of the sense-and-treat approach. Map-based control is often used for application of pre-emergent herbicides and crop nutrients on spatial scales limited by GPS accuracy or width of individually-controllable spray boom sections. In these systems, sensing and treatment chemical rate can be routinely achieved