Abstract

Abstract: A variable rate fertilizer system was developed for control of fertilizer amount by optical sensor measured NDVI of crop. The paper analyzes the input and output conditions of control system, and designed hardware, algorithm and control of fertilizer, mainly software flow and a feedback control way. In the paper, the variable-rate control system consisted of 6 optical sensors mounted on a boom in front of the tractor, interface module, micro controller, speed sensor, rotation sensor, PWM valve, and hydraulic motor. This type of VRT system does not use prescription maps, but relies on sensors to provide real-time crop detection information which is used to dispense fertilizer amount for the crop need. According to the amount of fertilizer information, fertilizer controller can automatically control flow amount by adjusting hydraulic valve based on working speed, which changes the hydraulic motor rotation to achieve the variable work. Experiments of fertilizer by pre-setting different dosage, the results shown that the errors of fertilizer amount are well in fact, and the errors are less than 5.17 %, and it shown CV is from 0.35 % to 2.67 %. The fertilizer response time of controller system is less than 0.875 s, it can meet the need of practical production. The system is well resolves to achieve variable rate fertilizer based on optical sensor.