Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2009
Publication Date: 9/1/2009
Citation: Grey, T.L., Czarnota, M., Potter, T.L., Bunnell, B.T. 2009. Timed Release of Flurprimidol From a Granular Formulation With Mulches and Sand Soil. HortScience. 44:512-151. Interpretive Summary: Production of ornamental plants in containers is a rapidly growing industry throughout the southeastern USA. To produce plants of suitable size for transportation and transplantation, plant growth regulators are often used. A favored active ingredient is flurprimidol. It is highly effective at slowing the growth of numerous plants at relatively low doses. The compound has relatively high water solubility thus leaching from potting media and mulches may be rapid. To slow leaching and prolong retention in plant growth media use of a granular formulation is recommended. We conducted an investigation of the rate of release of flurprimidol from a commercially available product and assessed leaching rate through columns of pine and hardwood bark mulch. Both materials are commonly used for potting media for container plant production. Results showed that about ¾ of the flurprimidol applied would be released following daily irrigation for 22 consecutive days and that the bark mulches substantially slowed leaching. Only 5 to 20 % of the flurprimidol was lost from columns packed with these materials to depth of 5 to 10 cm. These results indicate that flurprimidol will leach from granules over time and that it will move through sand and mulches used in container media and reach the roots of growing plants for extended periods. Data describing release and leaching of the compound can be used to estimate an optimal treatment regime with this formulation for container plant production and will aid growers in the effective use of this product.
Technical Abstract: Flurprimidol is a Type II plant growth regulator widely used in the landscape industry. Leaching of the compound from a commercially available granular formulation and movement through 30-cm diameter columns of bark mulch covered to a depth of 1.5 cm with sand was evaluated in a greenhouse and laboratory experiment. The study was conducted to evaluate flurprimidol release characteristics, and movement with respect to soil and organic media commonly used in landscape bedding and ornamental plant production. Two bark mulches, pine and hardwood, and two mulch depths, 5 and 10 cm, were used. After applying the formulation to column surfaces at the label recommended rate, 2.54 cm of irrigation was applied daily for 22 consecutive days. Leachate was collected and analyzed directly by HPLC-APCI-MS. Cumulative loss from the control column (sand only) was 71% of applied. For hardwood and pine bark packed at 5 and 10 cm depths, values were 20.7 and 14%, and 25.3 and 13%, respectively. These results indicate that flurprimidol will leach from granules over time and that it will move through sand and mulches used in container media and reach the roots of growing plants. Data describing release and leaching of the compound can be used to estimate an optimal treatment regime with this formulation for container plant production and other applications.