A discharge apparatus for discharging materials from a container onto a field, the apparatus comprising a power discharge device disposed adjacent to a discharge outlet defined by the container, the arrangement being such that when the apparatus is being used to spread the materials onto the field, the materials move from the container through the outlet towards the discharge device. A motor is drivingly connected to the discharge device for rotating the discharge device. A power sensor senses the power used by the motor and a control controls the rate at which the materials are spread. A data storage device associated with the power sensor and the control regulates the control. The arrangement is such that the data storage device dependent on the power sensor regulates the control for controlling the rate at which the materials are discharged so that when the container is moved across the field, the materials are discharged onto the field at a varying rate in order to optimize usage of the materials.