The 2011 ASHS Annual Conference

Studies were conducted to evaluate the effects of pre-plant compost and subsequent fertigation on landscape performance of organically-grown marigold. A locally produced composted broiler litter was used for initial soil amendment in the field at three rates: 0, 3 tons/acre (low rate), and 6 tons/acre (high rate). A liquid catfish processing byproduct MultiBloom (2-2-2 or 2N-0.8P-1.6K) was chosen as organic fertilizer for fertigation after transplanting at three rates: 0, 100 ppm N (low rate), and 200 ppm N (high rate). Results showed that incorporating composted broiler litter into the soil before transplanting significantly increased plant growth index [PGI = (height + widest width + perpendicular width) ÷ 3] on both 20 and 40 days after transplanting (DAP). Plants receiving the high compost rate had similar PGI as plants receiving the low rate. Regardless of the compost treatment, plants receiving the low fertigation rate had significantly higher PGI than plants receiving the high fertigation rate on 40 DAP, and plants that did not receive any fertigation had similar PGI as plants receiving the high fertigation rate. On 52 DAP, plants that received the high compost rate had significantly more flowers than plants receiving the low compost rate. Plants that did not receive any compost had the lowest number of flowers. Regardless of compost treatment, plants receiving the high fertigation rate had similar number of flowers as plants receiving the low fertigation rate, and plants that did not receive any fertigation had the lowest number of flowers. These results indicate that appropriate rates of pre-plant compost applications and subsequent fertigation can lead to good performance of marigolds in an organic landscape setting. However, just as with synthetic fertilizer sources, higher rates of organic fertilizers may not be needed and can actually reduce plant quality. We recommend users of these materials test them thoroughly before incorporating them into their practices.