A pneumatic seed planter utilizing air pressure to dispense the seeds in a central hopper to a plurality of laterally spaced seed planting assemblies. Mounted on the planter is a system for dispensing granular chemicals such as fertilizers, herbicides and insecticides from a separate hopper to the rows planted by the planting assemblies. The system uses air pressure from the planter (rather than a mechanical drive) to convey the granular material out of the separate hopper to the planting assemblies. Air is directed upwardly through an opening in the bottom of the chemical hopper and into a material conveyor tube spaced from the opening. The granular chemical is drawn through the space and into the conveyor tube by the air stream. A plurality of delivery tubes is connected to the conveyor tube for directing the chemical to the respective plurality of planting assemblies. The rate of delivery into the conveyor tube is controlled by adjusting the position of the tube relative to the inlet opening--the rate increasing with an increase in the space between the opening and the tube. Means are included for directing an auxiliary flow of air into the space to assist movement of material into the conveyor tube. Control means are provided for varying the auxiliary flow in response to varying the space between the opening and tube. Further control means are provided for starting and stopping the dispensing of chemicals automatically in response to movement of the planting assemblies between operative and nonoperative modes.