Azospirillum and Vesicular-Arbuscular Mycorrhizae Use In Ornamental Crop Production

Sustainable horticulture is an issue of increasing importance in response to a growth of environmental consciousness and conservation. A particular area of sustainable horticulture that has not been widely explored in the United States is the reduction of chemical fertilizers through the use of beneficial microorganisms for the enhancement of ornamental plant performance.  A two-part study took place at the University of Maryland Eastern Shore Agricultural Experiment Station.  A survey was constructed and distributed amongst target horticultural professionals, exploring their perceptions of microorganism applications. Key areas emphasized in the survey were fertilizers and irrigation practices (i.e. type of fertilizer/s used; interest in reducing fertilizer input; interest in reducing water usage). Keeping in mind that 35% of survey responders used multiple types of fertilizer, inorganic was most commonly used, utilized by 91%; organic was used by 43%. Ninety-four percent stated their interest in reducing fertilizer input, while 100% were interested in reducing water usage. When asked about employment of microbial inoculants, 79% confirmed their interest. Geared by the survey results, a preliminary study was then conducted in which Azospirillum (nitrogen-fixing bacteria) and vesicular-arbuscular mycorrhizae (VAM) fungus (improves the uptake of nutrients, confer drought and disease resistance, and reduce pest infection and damage) were applied to marigolds. Marigold treatment-free seeds were germinated in a growth chamber, transplanted into six-inch pots containing treatment-applied promix, then placed in a greenhouse in a randomized complete design from January to March 2011. Four repetitions of four treatments were applied as follows: 1) Control; 2) 2ml/pot Azospirillum; 3) 1 teaspoon/pot VAM; 4) 2ml/pot Azospirillum plus 1 teaspoon/pot VAM. Liquid fertilizer (20-20-20) was added to all treatments at a rate of 238 ppm nitrogen every two weeks after transplanting. Every week following transplanting, the marigolds were evaluated by taking measurements of plant height, number of flower buds present, bud size, and number of flowers present. In March, the roots and shoots were separated, measured, and oven dried at 70^o C for 72 h. The results indicate that there was a significant difference between flower numbers (p<0.01) and shoot dry weights (p<0.04). VAM had a significant effect on flower numbers and shoot dry weights.