Currently, in the Malaysian tree crop plantation, fertilizer is applied manually or mechanically at uniform rate without due consideration to nutrient variability. Potential wastage and excessive application of this fertilizer contaminates ground water and raises its mineral contents above the World Health Organization (WHO) limit for safe drinking water. However, Variable Rate Technology (VRT) fertilizer application promotes Green Engineering practice by reducing excessive fertilizer application, land degradation and pollution through leaching and volitization. It could also increase yield and profit.
A VRT fertilizer applicator for band application of granular fertilizer on tree crop was designed, developed and tested. The applicator is equipped with a long-range Radio Frequency Identification (RFID) reader to detect the stored tag ID on the available passive RFID tags attached on the trees.  The Tag ID is used by the control program of the VRT system in triggering the rotary valves which are the metering units for the system. A database containing the GPS coordinates, the RFID tag ID and the amount of fertilizer to be applied on specified area has to be earlier developed and stored in the memory of computer system of the VRT applicator. When the control program receives the RFID tag ID on the tree, it relates the tag ID to the information in the database and triggers the VRT fertilizer applicator system to apply precise amount of fertilizer to that particular area. Based on the experimental evaluation of the response time of the VRT applicator, it was found to take 2 – 3 seconds to changes in application rate depending on the magnitude of the change. The VRT applicator has a field capacity of 7.60 ha/h and 8.10 ha/h with field efficiencies of 0.55 and 0.57 at the travelling speed of 4.43 km/h and 4.92 km/h, respectively. The machine performance could be enhanced if the task of filling the fertilizer into the bin is automated.  The use of RFID technology has proven to be able to serve as alternative solution for position determinations for the fertilizer applicator in the plantations where the presence of tree canopies hinders the use of available GPS technology.