Evaluation of the OSU Ndvi Pocket Sensor

Abstract

There are methods to increase nitrogen use efficiency through optical sensor based nitrogen application; however, the sensors are expensive and cost prohibitive to farmers in the developing world. This study evaluated a reduced cost prototype Normalized Difference Vegetative Index (NDVI) sensor to determine if it could be used with the same level of accuracy as a commercial sensor. The stability of the prototype sensor (Pocket Sensor) to maintain an accurate calibration over time, the effect of operator on sensor readings, and sensor performance in maize and wheat were assessed. Sensor stability was evaluated using turf grass canopies over a 6 month period, and the effect of operator was tested using wheat canopies in existing field experiments. Sensor performance in wheat and maize was also tested in existing field experiments at the International Maize and Wheat Improvement Center (CIMMYT), Ciudad Obregon, Mexico. The prototype sensors were highly correlated to the commercial GreenseekerTM sensor in turf grass, wheat, and maize canopies (r2>0.97, r2>0.95, and r2>0.91 , respectively). With adequate training there was no significant operator effect on sensor readings. The Pocket Sensors lacked some precision in comparison to the commercial sensor (NDVI of the commercial sensor 0.02, 0.05, 0.06 in turf grass, maize, and wheat); however, even with the reduced precision the cost of the sensor and robustness of N fertilizer algorithms compensate for this apparent weakness. The Pocket Sensor is a viable tool to determine NDVI in wheat and maize and make nitrogen recommendations based upon the data collected with this sensor.