Abstract: A supply tank for the individual openers of an air seeder includes two separate tank elements each formed from two separate tanks. Each opener has two supply ducts, one from each tank element. Each tank has a dispensing roller across its bottom metering material into the separate supply ducts. The two tanks of each element feed into a common tube within a closed enclosure dispensing into a feed end of a respective pipe for a respective one of the openers. The pipes within the enclosure are monitored by a camera system so that the operator can see the dispensing of the material on a monitor screen. The tanks are covered by a sealed lid which pivots about a vertical post at one edge. An air supply pressurizes the tanks and a heater selectively heats the air to one of the tanks selected for supplying fertilizer.