a nurse distribution system provides dual capabilities for planting different seed varieties from a single planting mechanism . the air cart carries two tanks in which different seed varieties can be placed . the nurse mechanism selectively distributes seed from one tank to the on - row singulation meters , yet can switch to the seed in the second tank to correspond to different soil conditions encountered by the planting mechanism . the planting mechanism carries a first line from the first tank to the nurse receiver and a parallel second line from the second tank to the same nurse receiver . by keeping the nurse receiver as small as possible , thus having a small seed reservoir , the seed variety selection can be switched from one tank to the other in an effective manner .