The 2012 ASHS Annual Conference

Fertility management can be challenging in the production of organic vegetable and herb transplants.  Substrate incorporated fertilizer components may damage sensitive seedlings but also not supply enough nutrients when seedlings are grown for an extended period.  In this project we examined the use of vermicompost (worm processed dairy manure, from Worm Power LLC) as one of the primary fertilizer components in organic production of transplants.  The first trial was conducted determine the suitability of vermicompost and blood meal for supplying the nutrients in an organic substrate for seedling germination.  A blend of 60% peat and 40% perlite (by volume) was supplanted with 0%, 5%, or 10% vermicompost (by volume).  Blood meal was added to the mix at 0 or 7 lbs/yd³.  Seeds of basil ‘Casear’, lettuce ‘Buttercrunch’, Mustard (Brassica juncea) ‘Red Streaked Mizuna’, and tomato ‘Celebrity’, were seeded in 200 cell plug trays and misted as needed.  After four weeks germination and plant size were evaluated.  Basil germinated well regardless of vermicompost and blood meal combination. In the absence of blood meal, tomato germination was reduced slightly with increasing vermicompost. The combination of blood meal incorporation and vermicompost significantly reduced germination of lettuce, mustard, and tomato. Blood meal at the incorporated rate appears harmful. Vermicompost at 5% by volume led to suitable seedling size and good germination. Future work should refine the incorporation rates of vermicompost and blood meal.  A second trial was conducted to determine the need for supplemental liquid fertilizer for growing on transplants for 8 weeks in an organic substrate in 4-inch (500 mL) containers.  Seedlings of basil, lettuce, pepper ‘Lady Bell F1’ and tomato were transplanted in the peat and perlite substrate which contained 10% vermicompost and blood meal at 7 lbs/yd³.  Fertilization began 1, 3, or 5 weeks after transplanting and was provided as a weekly drench (150 mL) of 0, 100, or 200 ppm N from a conventional fertilizer (21–5–20) or an organic fish emulsion based fertilizer (Drammatic One, 4–4–1).  For tomato, weekly liquid fertilizer treatments beginning by week 3 (conventional) and week 1 (organic) were required to obtain the greatest plant size. For pepper supplemental fertilizer was note required.  For lettuce, optimum plant size required liquid fertilization beginning by week 3 at rates of 200 ppm N (conventional or organic).  For basil, liquid fertilization beginning at week 5 may give a slight benefit in transplant size.