ENH144 Nitrogen Release From Woodace Briquettes 1 T.H. Yeager and D.L. Ingram2 1. This document is ENH 144, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date reviewed: March 2000. Please visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. T.H. Yeager, Professor, and D.L. Ingram, Former Professor, Environmental Horticulture Department; Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean. NATURE OF WORK Fuller and Meadows (1) and Ingram and Yeager (2) determined that Woodace fertilizer briquettes (manufactured by Mitsubishi Chemical Industries LTD. of Japan and distributed by Estech, Inc., Chicago, IL) released nitrogen in a container medium for about a year. However, data comparing nutrient release at different briquette placements are lacking, so the following study was conducted to evaluate the influence of Woodace briquette placement on nitrogen release. Multiple branched lines of Rhododendron spp. 'Mrs. G.G. Gerbing' were potted April 24, 1984 in a 2 pine bark: 1 Canadian peat: 1 sand (v/v/v) medium amended with 5 lb/yd3 (3 kg/m3 ) of superphosphate (9% P) and 3 lb/yd3 (1.8 kg/m3 ) of Perk (micro-nutrient formulation of Estech Inc.) Three 0.6 oz (16 g) briquettes (14-3-3) were used per gallon (3 liter) container. The briquettes were placed either 1) in a circle 0.5 inch (1.25 cm) below the root ball (middle placement) of 5 plants or 2) protruding 0.5 inch (1.25 cm) from the growth medium surface periphery (surface placement) of 5 other containers. The plants were arranged in a completely randomized design on black polypropylene ground cover under 30% light exclusion polypropylene shade cloth and received 0.5 inch (1.25 cm) of water applied as needed by Dramm drip rings. Thirty, 60, 90, 150, 210, 270, 330 and 360 days after potting, 150 ml of distilled water were poured on the surface of each container and leachate collected. Leachate nitrate (NO3 ) and ammoniacal nitrogen (NH4 ) levels were determined by standard analyses (3). On May 1, 1985, stems were severed above the uppermost roots and shoot dry weights were determined. RESULTS AND DISCUSSION Nitrate and NH3 release rates were each similar for surface and middle placement of Woodace briquettes. Leachate NO3 concentrations ranged from 30 ppm on day 30 for surface placement to 3.0 ppm on day 360. Nitrate concentrations were generally higher than NH4 concentrations regardless of placement and may have been due to nitrification or retention of NH4 by the pine bark. Shoot dry weights averaged 2.5 oz (76 g) and were not different due to briquette placement. In another study conducted by the authors (2), azalea shoot dry weights were slightly larger for surface placement of briquettes, however leachate NO3 and
Nitrogen Release From Woodace Briquettes 2 NH4 levels were similar for surface and middle placements. These data indicate that NO3 and NH4 release rates were each similar for surface and middle placement of Woodace briquettes in a container medium. LITERATURE CITED 1. Fuller, D.L. and W. A. Meadows. 1983. Leachate studies with several IBDU fertilizers. Proc. S. Nurserym. Assoc. Res. Conf. 28:67-70. 2. Ingram, D. L. and T. H. Yeager. 1984. Response of Gerbing azalea to Woodace fertilizer tablet, placement and irrigation regime. Proc. S. Nurserym. Assoc. Res. Conf 29:45-47. 3. Rhue, R. D. and G. Kidder. 1984. Procedures used by the IFAS extension soil testing laboratory and interpretation of results. Univ. of Fla. Ext. Circ. 596.