Replacement of a Peat-Lite Medium with Compost For Cauliflower Transplant Production

Seedlings of ‘Candid Charm’ cauliflower (Brassica oleracea L. Botrytis group) were grown in six different media comprised of varying proportions of a commercial peat-lite mix (PL) and a 50% yard trimmings 50% biosolids compost. A control of 100% PL was compared to treatments of PL:compost at 80%:20%, 60%:40%, 40%:60%, and 20%:80% respectively by volume, and 100% compost. The experiment was performed twice. Electrical conductivity of the medium increased with increasing compost additions, while the carbon:nitrogen ratio was greatly decreased. Increasing proportions of compost blended with PL inconsistently affected medium pH. Seedling emergence was delayed when compost comprised the majority of the medium, but stands were not reduced except with 100% compost. Decreases in seedling height and dry weight began to occur in the 60% PL, 40% compost treatment and were more pronounced with higher amounts of compost. Seedlings grown in 80% PL, 20% compost were similar to those grown in 100% PL with one exception: the compost blend resulted in an increased seedling N concentration. While we cannot conclude that a 20% replacement rate is ideal, the 80% PL, 20% compost medium was horticulturally acceptable as an alternative to 100% PL for cauliflower transplant production.