A Map-Based System for Variable Rate Liquid Nitrogen Fertilizer Application

This research designed, constructed and evaluated a map-based variable rate application system for liquid nitrogen fertilizer. Solenoid valves were used to change nozzle flow using pulse-wide modulation technology. A turbine flow sensor and GPS module were used to measure solenoid valve flow and online system coordination, respectively. The graphical user interface software was designed by Visual Basic 6. This program received online coordination from a GPS module, received fertilizer map data, compared online and map coordinates, specified application order, received sensor output and compared it withoptimum data and then applied proportional closed-loop control. To evaluate the system, accuracy and time-delay experiments were carried out with 3 replications. The results showed that the average difference between map data and system flow for open and close-loop controllers were 10.0 and 3.6%, respectively. The maximum time delay was 0.54 s. Results also showed that, at 1% probability, no significant difference was observed between the system flow and nitrogen fertilizer map data.