A fixed-amount and variable-rate fertilizer applicator based on pulse width modulation.

•A fixed-amount and variable-rate fertiliser applicator with vertical a spiral conveyor is proposed.•The rate changes with the travel speed but keeps the amount of fertiliser constant.•The fertilization uniformity relies on the changes of duty of the PWM pulse.•The accuracy relies on the linearity between duty and consumption per unit distance.•Regression statistics was used to research the degree of the linearity between duty and consumption.