This custom made seeder does not just plant arugula seeds, it just just about all of our salad and greens crops plus wheat and alfalfa. It was made for us by John Bauer at Snow Seeds in Salinas. We now buy so much more seed from them but our yield has dramatically increased also.
There are six seeder units, each sowing two rows. So we can and have sown six different varieties of lettuce on one bed at a time. It is each to remove the seed from each unit and set it just right for that particular seed in the hopper. See picture below.