The Earthway Seeder is a common sight in home gardens, small scale commercial farms and in research plots. These lightweight, inexpensive planters are sold with six different vertical metering plates that allow the unit to be used to seed a range of vegetable crops. A lack of precision is a major concern with all vegetable seeders. Inaccurate seed spacings can arise due to problems with both the seed singulation and metering system and the distribution and coverage system. When Parish and Bracy evaluated the performance of commercial vegetable planters (Stanhay and Gasparo) they found that even the best units were less precise than desired, particularly with irregularly shaped seed like carrot and spinach. In a similar series of tests using the Earthway planter, they found that its precision was far inferior to the commercial units. However, they felt that the Earthway still did an acceptable job and at 1/10 the price of the commercial planters. They noted that for many crops, the recommended seeding plates for the Earthway dropped more seed than was required. They recommended that for beets, broccoli, carrot and corn a portion of the holes in the seeding disks should be blocked with tape. We however found that taping the holes shut tended to allow small seeds like broccoli to slip between the plate and the body of the planter – at which point the seed was often crushed. An alternative solution to the problem of over-seeding is to dilute the seed of the vegetable crop with dead seed from a low cost, comparable-sized alternative crop. We use heat-killed canola seed to dilute seed of cabbage and broccoli, while spice crops like dill or caraway can be used to dilute carrot and beet seed.
Source : Parish and Bracy (2004). HortTechnology 14: 257-261.