Digital map-based site-specific granular fertilizer application system

Variable rate application is the process of applying different rates of crop inputs according to the variability within an agricultural field. Variable rate fertilizer application is a technology that regulates the fertilizer application rate based on site-specific needs within a field. A GPS-based variable rate fertilizer application (VRFA) system was developed, which consisted of a differential global positioning system (DGPS), micro-processor, micro-controller, DC motor actuator, power supply, threaded screw arrangement and fluted roller metering mechanism. The digital soil nutrient availability and application maps for targeted yield were also developed. DGPS was used for real-time identification of grids. Based on the micro-controller algorithm, application rates were varied by changing the feed roller exposure length. The observed fertilizer application rate was 5 and 300 kg/ha for exposure length of 0 and 44 mm respectively. The results indicate that the fertilizer application rate changes according to the prescribed application rate at the identified grid with coefficient of variation of 11.7-15%. The values of root mean square error and relative difference of the system for different levels of application rates were 2.62 and 3.71 respectively. It can be concluded that the developed VRFA system closely meets the target fertilizer application rate at the selected grid point.