| [Image: bulk metering planter] |
| [Image: garden seeder] |
| [Image: precision belt seeder] |
Many seeder types and models are available for direct seeding vegetable crops. Smaller growers typically use the less expensive seeders, but larger growers can justify more expensive precision seeders. This list gives a range of vegetable seeders in order of increasing precision (uniformity of seed spacing):
Bulk Metering
Some relatively inexpensive vegetable seeders use the bulk metering principle (Figure 1). These seeders have interchangeable metering orifices through which the seeds flow. There is no attempt to singulate the seeds; they just stream through the orifice. These seeders can do a satisfactory job of planting seeds that don’t require singulation such as mustard or turnip, but often cannot deliver the low seeding rates needed for other crops and will not deposit the seeds uniformly.
Grain Drill
Some vegetable growers have access to a grain drill used for other farming operations. A grain drill can be used to plant the same crops that can be planted with a bulk metering seeder such as mustard and turnip. A grain drill will not singulate seeds, but it can accurately meter out the correct seeding rate. The unneeded metering ports can be temporarily blocked to allow seeding in the desired row pattern. A grain drill can be used to plant on the tops of beds as well as on flat ground. Many grain drills have two metering hoppers: one for small seeds and one for large seeds.
Garden Seeders
Some small, inexpensive walk-behind garden seeders (Figure 2) actually do a pretty good job of metering and singulating vegetable seeds. These seeders can be used for a wide range of vegetable seeds. Testing at the LSU AgCenter Hammond Research Station has shown that performance of these seeders can be improved by using optional plates and/or modifying plates by closing off some of the cells with masking tape. These seeders are less expensive than the bulk metering seeders and work much better.
Plate
Traditional agronomic (corn and cotton) planters used horizontal plates to meter and singulate seeds. This concept still works well with many types of vegetable seeds. Horizontal, inclined and vertical plate designs are available. Selection of plate/cell size is critical to correct metering and singulation. Plate seeders work best with spherical (round) seeds.
Finger
Seeders using a finger metering system have become popular for corn and some other agronomic crops. These seeders can do an acceptable job with large seeds such as sweet corn, peas and beans but do not work with small vegetable seeds.
Vacuum
Several European manufacturers export vacuum seeders to the United States. Although they are often considered to be the ultimate in precision seeding, testing at the LSU AgCenter over many years has shown that vacuum seeders outperform belt seeders only with oddly shaped seeds. Although vacuum seeders typically singulate seeds effectively, they don’t maintain the uniform seed spacing by the time the seeds reach the furrow in the soil. Vacuum seeders do excel in handling oddly shaped vegetable seeds like cantaloupe, squash, cucumber and watermelon.
Belt
Seeders using a metering belt (Figure 3) offer the ultimate for uniform spacing of spherical or nearly spherical seeds. Belt seeders can also meter odd-shaped seeds, but they will deliver multiple seed drops and/or skips. It is essential that the belt hole size as well as the choke and base be properly sized to the specific seed size to be metered.
Other articles on this site address specific details of some of the above seeders.