All vegetable seeders require openers, coverers and presswheels to provide a furrow for the seeds and to then cover the seeds and assure proper soil contact. These devices must be matched to the soil type and condition for optimum germination and seedling vigor.
OpenersEither disk or shoe openers can be used, although shoe openers are more common on precision vegetable seeders and tend to provide better depth control – especially for shallow planting of small seeds. Disk openers are more commonly used on agronomic planters designed for larger seeds (deeper planting depth) and operation under conservation tillage conditions. Shoe openers generally require a clean soil surface with little or no plant residue. Shoe openers are available in many configurations (Figure 1) for planting single lines as well as two or three lines per row in narrow or wider configurations.
CoverersSeeder coverers are available in several styles and degrees of aggressiveness to accommodate different seed depths and soil conditions (Figure 2). Shallow-planted seeds and light soil will require a coverer that moves minimal soil over the seed; larger seeds planted in a deeper furrow and/or heavier soil will require a more aggressive coverer to move more soil. Drag bars and drag chains tend to be less aggressive, with heavier drags being more aggressive than lighter drags. Knife coverers can be very aggressive and are good for cutting into crusted or compacted soils.
PresswheelsPresswheels of different configurations are available for different soil types and seed planting depths (Figure 3). A smooth, flat presswheel is adequate for many conditions. If the soil has a tendency to crust, a presswheel made of expanded metal may help but may result in less soil to seed contact. Separated presswheels can be either concave or flat. They allow pressing and firming the soil beside the furrow without packing the soil right over the seed furrow. This can be an advantage in soils prone to crusting.
In summary, there are many options in seeder openers, coverers and presswheels. You need to select the combination appropriate for your seed size/seed depth and soil conditions. Don’t be afraid to change from crop to crop or field to field.
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