2017 ASHS Annual Conference

The drawbacks of traditional sources of fertilizer provided to horticultural crops grown in containers led us to explore alternatives. Our objective was to compare two microalgae-based materials (pelletized microalgae biomass and a paste suspension of microalgae in wastewater) with commercially available fertilizers for effects on growth, nutrient content, and salability ratings of three crops (‘Honeycomb’ marigolds [Tagetes patula L.], ‘Beefsteak’ tomato [Lycopersicon esculentum Mill.], and ‘Ambrosia’ sweet corn [Zea mays L.]). The experiment comprised a two-way factorial of treatments. Four sources of fertility (microalgae pellets, microalgae paste, the organic fertilizer Milorganite, and the controlled-release fertilizer Florikan CORE 16-5-11) were one factor, and two media types (sphagnum peat moss plus perlite and a commercial soilless medium with a starter charge of fertilizer) were the other factor. Treatments of 763 g N·m^–3 were applied in containers with top diameters of 11.4 cm. Fertility source, medium, and their interactions affected growth, nutrient content, and salability ratings. Responses were similar among crops, so results for only marigolds will be presented for simplicity. The microalgae pellets and paste promoted shoot height, width, and weight of marigolds in the medium without nutrient charge; the gains were similar to those that resulted from the Florikan CORE, and the microalgae was more effective than Milorganite. Marigolds in the medium without nutrient charge and provided microalgae in paste form were rated as most salable. Although growth of plants was somewhat less responsive to treatments when the medium with nutrient charge was used, salability ratings were highest for plants provided Florikan CORE or microalgae in either form. These results provide proof of concept of the effectiveness of wastewater-grown microalgae fertilizers for use with crops produced in containers.