A mobile injection device including a peristaltic pump assembly configured to be installed in a device for placing material on or beneath the soil surface. The device delivers material into the soil subsurface as a fluid or a suspension. The peristaltic pump has a rotor assembly that urges a fluid additive in precision amounts through flexible tubes into a manifold. A pressurized fluid is introduced to the manifold to mix the additive in the pressurized fluid and inject the mixture into the ground through an injection nozzle. A computer control system monitors the ground speed of the device and determines the amount of additive to be pumped into the manifold to provide a uniform distribution of the additive to the soil.
