Peter Ako Larbi 2015-06-23 01:02:29
Agricultural application equipment—such as grain planters, boom sprayers, and fertilizer spreaders— applies production inputs continuously to a limited area while in motion. This instantaneous rectangular coverage area that sweeps along with the equipment is known as the swath. Generally, the swath width is determined by the number of discharge points and the distance between any two adjacent discharge points. The number of discharge points usually corresponds to the number of crop rows that the equipment can span while traveling across the field. In most conventional equipment, the swath width is fixed for a given application, and a constant application rate is set for the input being applied. However, constant application rates are not efficient due to variations in the soil and crop conditions within the field. Variable-rate application Naturally, most agricultural fields are characterized by significant variability in soil conditions and crop characteristics. With conventional application, this variability can lead to excess inputs applied at some locations and insufficient amounts at other locations. In addition, agricultural inputs are expensive, and inefficient application increases the farmer’s production costs, impacts the environment, and poses possible health risks even beyond the application site. These concerns have influenced the development of precision technology that allows a more responsible way of applying agricultural inputs. By using less input, due to more efficient application and more precise distribution, farmers can realize financial benefits with less impact on the environment and human health. Precision agriculture acknowledges the variability in the field and uses that information to the farmer’s advantage by varying the application based on site-specific need, a practice known as variable- rate application. Automated variable-rate application is made possible by a decision support system (a computer program) that performs highly computational decisions based on information about the current location, and then passes commands to the delivery components in order to implement the treatment. The information about the current location may come from on-the-go crop and soil sensors or from previously created GIS (geographic information system) or GPS (global positioning system) maps. Variable-rate application of production inputs, such as water, nutrients, and pesticides, minimizes waste, increases productivity, and promotes environmental sustainability. Thus, precision agriculture aims to optimize returns on inputs while preserving resources. Swath control technology New technologies are being developed to achieve variable- rate application, and they are available on new equipment and can be installed on older equipment. One such technology is swath control technology, which controls individual output components, such as nozzles, or groups of outputs, such as sprayer boom sections, based on real-time sensor data or GPS maps. One example is the GPS-based Section Control (formerly Swath Control) developed by John Deere for field sprayers. With this technology, individual boom sections and nozzles are controlled by turning them on and off automatically based on a GPS coverage map. By delivering the input only when and where needed, the application is highly efficient. An updated GPS map is created as the sprayer travels through the field. Section Control can also be used with John Deere’s AutoTrac hands-free assisted steering to reduce overlap and eliminate skips in the field, thus achieving even greater efficiency. Another example is Raven’s OmniRow planter control system. This system features a fully integrated design with real-time kinematic (RTK) sub-inch positioning accuracy. With this technology, precise seeding rates can be maintained for individual rows or sections. For best performance, the OmniRow works in tandem with Raven’s Envizio Pro II field computer and Slingshot RTK online service. This configuration provides variable-rate seeding, automatic on-off planter control, and real-time seed monitoring while eliminating skips, doubles, and overplants. Looking ahead While swath control technology automatically turns inputs on and off to avoid application to unwanted locations, the best efficiencies are achieved by adjusting the inputs within a range of values. For example, in variable-rate application based on a GPS map, individual nozzles can be adjusted to deliver different flow rates to different zones, in addition to observing no-spray zones. Using highly reliable sensors to obtain real-time data in place of GPS maps may further increase the flexibility of this technology. Some of these advances are already featured on newer larger equipment. Technological improvements are continually needed to perfect each generation of agricultural equipment. Just as important, though, is the need to scale down this sophisticated technology, so that it can be accessible and affordable not only for farmers in advanced countries but also for farmers in developing countries. ASABE member Peter Ako Larbi, Assistant Professor of Agricultural Systems Technology, College of Agriculture and Technology, Arkansas State University, Jonesboro, USA, and Division of Agriculture, University of Arkansas, Fayetteville, USA, firstname.lastname@example.org.
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