Spatial Variability of Crop Production Variables
C. E. Goering,* J. W. Hummel, M. D. Cahn
University of Illinois

A differential global positioning system (DGPS) was developed using a cellular phone to link two GPS receivers for real-time, differential positionings. A low-cost GPS sensor linked to a PC was used as a reference station; a second low-cost GPS receiver linked to a notebook PC was used as a GPS roving station. A computer modem at the reference station communicated with a roving modem via a cellular phone. Radio interference common to FM radio links was avoided, but operating cost of the phone connection was high. Also, the software corrected longitude and latitude directly. The direct correction proved much less accurate than RTCM correction.

The goal of this project is to develop a precision herbicide application (robotic) system for low-input pest control strategies in soybean and maize production. Specific objectives include (1) evaluating the agronomic and environmental benefits of low-input herbicide applications and the status of current technology in this area, (2) developing practical real-time prototype systems for individual plant sensing and equipment control, (3) conducting on-farm trials to evaluate the prototype under the constraints of normal farm operation. With this precision system, herbicide would be only applied to the target plants in the fields.

Equipment and techniques are being developed to improve the application efficiency of agricultural chemicals. Droplet size spectra from various atomizers are measured to determine target coverage versus spray drift potential. Field studies of spray drift deposits are used to verify the droplet size evaluations. Sensors and automatic control systems are being developed to apply pest control substances as a function of soil organic matter, travel speed, and other input variables. Techniques for incorporation of herbicides in the soil profile of conservation tillage systems are being developed and evaluated.