Comparison of Organic and Synthetic Fertilizers for Sedum Green Roof Maintenance

Abstract

Fertility is an important aspect of green roof maintenance. Aesthetic quality and growth of two sedum species (Sedum album and Sedum rupestre ‘Angelina’) treated with synthetic granular fertilizer [Green View 10N-4.4P-8.3K (10-10-10)] and two organic fertilizers [Coast of Maine 4N-0.9P-1.7K (4-2-2) and Nature Safe 8N-2.2P-4.5K (8-5-5)] at 10 g N·m−2 applied as a single spring application or a split application (spring and summer) and a controlled-release fertilizer [Nutricote 14N-6.1P-11.6K (14-14-14)] at the same rate and a no fertilizer control were evaluated. The best aesthetic quality and growth was for the single application synthetic granular fertilizer, followed by the split application of synthetic granular fertilizer. Also, single applications were better than split application for the organic fertilizers, indicating that sedums use nutrients the most in spring. The organic fertilizers performed poorly because they failed to provide utilizable nutrients in adequate quantities. A low level of microbial activity in green roof media, may have contributed to the minimal amount of utilizable nutrients released by the organic fertilizers. Plants treated with controlled-release fertilizer performed similarly to the control, however, the following spring they had the best aesthetic quality, indicating the prills contained some residual nutrients.