Intelligent VRT controller for variable rate liquid fertilizer applicator- mature oil palm plantation & other tree crops.This invention is about Intelligent VRT controller works to monitor NPK status of soil and make the decisions itself to control the fertilizer application at variable rates for the operation of variable rate liquid fertilizer applicator. It can handle NPK straight fertilizers (urea-46 % N, triple super phosphate-46 % P2O5 , murate of potash-60 % K2O) in water soluble form and can vary the application rate of these fertilizers individually according to the respective nutrient’s requirement of plant.Intelligent VRT controller is installed with variable rate liquid fertilizer applicator for mature oil palm plantation to make its operation automatic.With programs modification, this intelligent VRT controller has potential to operate with VRT liquid fertilizer applicators for other tree and cereal crops.