Calibrating Row Crop Planters

Row crop planters are used to plant crops in wider rows than those planted by grain drills. Row crop planters are commonly used to plant large seeds, such as corn, soybeans, and sunflowers, but are used for small seeded vegetable crops such as radishes. Row crop planters will have a speed hopper, a metering unit, a seed tube, a furrow opener and some type of closing or press wheels. Additional hoppers are sometimes used for fertilizer or insecticides, Figure 8.5. The common metering units for row crop planters are plate, disc, drum, and volume or bulk, but other mechanisms are available. Plates are the traditional method for metering seeds, but for most crops they have been replaced with discs. One style of antique plate planter was designed to plant hills of seeds, but most plate and the modern disc metering units singulate seeds. Singulating means each seed is selected from a small volume of seeds and transferred to the furrow. When plates are used the seeds are deposited in holes (cells) on the rim of a ground driven metering plate, and as the metering plate rotates, the seeds leave the plate and fall into a furrow that has been opened in the soil. The seeding rate is changed by using a plate with a different number of cells, or by changing the drive train speed ratio between the drive wheel and the metering unit.

Disc metering relies on air to hold the seeds in the cells. Two different designs are used, based on air pressure either greater than or less than atmospheric. One type uses pressurized air to hold the seed in a vertical seed plate and when the air is shut off, the seeds drop into the opened furrow or are blown into tubes that deliver them to the opened furrow. The other type of air planter uses a vacuum to hold the seeds in the cells in the seed plate.

The drum type of metering unit works on the same principles as the pressurized air disc planter. The primary difference is that the drum has a ring on holes for each row instead of a separate metering unit for each row. Each drum usually singulates seeds for either 6 or 8 rows. The metering rate can be adjusted by changes drums and varying the speed between the drum and the drive wheel.

Fertilizer or insecticide hopper

Seed hopper

Furrow

Fertilizer or insecticide hopper

Seed hopper

Furrow

FIGURE 8.5. Single unit of row crop planter.

Press wheels

FIGURE 8.5. Single unit of row crop planter.

A few manufacturers produce a volume type metering unit that looks like and operates like a grain drill metering unit. The seeding rate (seeds/acre) for the volume metering unit is determined by the speed at which the metering unit operates in relation to the ground speed of the planter.

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