Variable-rate application of herbicides based on soil properties and crop yield potential may be a viable approach to reducing the quantities of herbicides used in crop production. Application accuracy of direct injection equipment is an important issue for variable-rate application. A simulation model was developed using SIAM II to assess the performance of a direct injection sprayer used for site-specific application of preemergence herbicides in corn. Field data from a university research farmwere used as input to the model (i.e., soil texture, organic matter content, and yield potential). Several factors such as in-line mixing location, hose diameter, nozzle spacing and size, and ground speed were investigated for their effects on systemperformance. A complement of system parameters was identified to reduce application errors. Multiple system errors were combined using the mean square error approach. Results of the simulation were input to a GIS software to generate herbicide application rate maps and the corresponding error rate maps. Application errors for direct injection systems were as high as 40 for mistreated areas of the field, with changes in chemical concentration at the remote nozzles occurring after as much as 80 m of travelpast the point of a step change of the input command to the controller Recommendations for reducing delay times at the nozzle include moving the in-line mixing location close to the boom and using smaller line sizes to reduce line volume, withoutappreciably increasing pressure drop.
展开▼
