From 2020 SEVG Handbook
Treatment of Flats. Flats used in the production of transplants should be new or as clean as new to avoid damping-off and other disease problems. If flats are to be reused, they should be thoroughly cleaned after use and completely submerged in a household bleach solution for at least 5 minutes. Use 5 gallons of 5.25% sodium hypochlorite (such as Clorox) for each 100 gallons of solution required. Permit flats to dry completely prior to use. Page 14.
For tomatoes and peppers, 72-cell packs work well. For larger-seeded vegetables; such as cucumbers, squash, and watermelons, 48-cell packs work better.
Liquid Feeding. The following materials dissolved in 5 gallons of water and used over an area of 20 square feet are recommended for use on the transplants if needed:
20-20-20 1.2-1.6 oz/5 gal water
15-15-15 2 oz/5 gal water
15-30-15 2 oz/5 gal water
Rinse leaves after liquid feeding. Fertilizers used for liquid feeding must be 100% water soluble. When transplanting to the field, use a “starter fertilizer” being sure to follow the manufacture’s recommendations.