Development of Sensor Technologies for Site-Specific Crop Management.

Various information from an agricultural field allows producers to site-specifically apply appropriate amounts of production inputs throughout a field. This practice in crop management can maximize farm profit and minimize environmental impact. Sensor technologies were developed for crop production, including a mass-flow sensor and a cotton yield monitor (CYM), a plant health sensing system, and a wireless sensor network (WSN). These sensing systems have been used to collect different types of information for crop management research and crop production. The mass-flow sensor measured the mass flow of conveyed reflective materials, such as cotton, in a stream of air or non-opaque fluid. A CYM was developed using the mass-flow sensor. The CYM was mounted on a cotton harvester to measure cotton yield. Cotton yield maps were generated using the CYM data. During a 4-year study, eighteen prototypes of the yield monitors including 36 mass-flow sensors in three versions were designed, fabricated, and field tested for mapping cotton yield across the U.S. cotton belt. Results indicated the sensor and the CYM performed well. The plant health sensing system included an optical sensor, an ultrasonic sensor, a GPS receiver, and a data acquisition unit (DAQ). The optical sensor measured crop canopy reflectance in four wavebands. The ultrasonic sensor measured plant height. The DAQ is an intelligent device for recording the data from the optical sensor and ultrasonic sensor, and the spatial information from the GPS receiver. The system was installed on a tractor. In field operation, as the tractor travelled across the field, the sensors automatically and continuously scanned the plant canopy. One measurement of canopy spectral reflectance at the four bands and the plant height was taken in each second and the data along with the spatial coordinates of each measurement point were stored into a memory card in the DAQ. Using the data, crop spectral indices and plant growth rates were calculated, and plant height maps and spectral reflectance maps were generated. The WSN included soil moisture sensors, weather sensors, wireless data loggers, and a wireless modem. Soil moisture sensors were installed at various depths in soils across fields. Weather sensors were mounted on a tower. Using the WSN, soil moisture and weather conditions including precipitation, solar radiation, wind speed, and humidity were measured every minute and the hourly averages were collected. The soil moisture data and weather data were automatically and wirelessly transmitted to the internet making the data available online. Data collected by the WSN have been used in irrigation scheduling research in various crops.