Development and performance of electro-hydraulic proportion control system of variable rate fertilizer

For raising the utilization rate of fertilizer, decreasing fertilizer waste and its environmental pollution, electro-hydraulic proportion control system was developed for variable rate fertilizer applicator by using MC68HC908GP32 MCU as the core control unit. The upper computer acquires GIS information from GPS-based service to generate the position nutrient recommendation and then transmits the data to variable rate fertilization embeded?system through RS485 bus. The embeded?system controls hydraulic actuator and realizes variable flow rate fertilization at different position in real-time. Through static test in laboratory and dynamic practical application in field, the system was proved to be reliable for variable control with good effect. The control precision was less than 4%.