Air suction from the holes of the seed plate
caused the seed to stick to holes 4 mm in diameter. Seed was
released from the rotating plate by blocking air suction over the
opener, which had no seed tube. Each sowing unit was
independently mounted on a four-bar parallel linkage equipped
with joint springs to apply downward force on the sowing unit and
was composed of a furrow opener followed by a press wheel,which
closed and compacted the seed furrow. The seed metering system
was adjusted for a nominal seed spacing of 204 mm for maize and
102 mm for soybean in the row and a nominal depth of 50 mm for
both types of seeds. The seeder was calibrated in the laboratory
before field operation.