Nutrient Status of Cosmos (Cosmos bipinnatus) in Response to Mycorrhizal Treatment

Mycorrhizae are beneficial root-associated fungi that occur in the environment. They improve water and nutrient uptake for their host plant. Commercial mycorrhizae products are available as inoculants, and may be added to growing media at the time of planting. Soilless media products are also available with pre-added mycorrhizae for use in bedding plant production. The addition of mycorrhizae to soilless media creates a higher cost for inputs of bedding plant production. However, the benefits of mycorrhizae inoculation may be cost-effective, due to the ability of the beneficial fungi to improve nutrient and water uptake by plant roots. Growers may be able to reduce fertilizer inputs while maintianing optimal plant growth. They may realize further benefits of reducing fertilizer run-off in irrigation water effluent, especially two nutrients of major environmental concern, phosphorus and nitrogen. Increased phosphorus uptake could improve floral development, an important aspect of bedding plant production.  

Two mycorrhizae products, Mighty Myco and Mycormax, were applied according to label directions at the time of planting Cosmos bipinnatus seeds. Plants were evaluated for time to germination, time to first visible flower, time to first open flower, shoot and root fresh and dry weight, and for whole-plant fertility at 63 DAP.