Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2005
Publication Date: July 7, 2005
Citation: Fare, D. 2005. Fertilizer source affects nitrogen and phosphorus levels in leachate from container-grown Quercus phellos L. and Magnolia virginiana L. HortScience. 40:1048. Technical Abstract: Environmental concerns with nitrogen and phosphorus use at container nursery facilities and the subsequent effects of nutrient-laden irrigation effluent prompted this study. Bare root liners of willow oak (Quercus phellos L.) and sweet bay magnolia (Magnolia virginiana L.) were grown in #5 containers during year one and repotted into #15 containers during year two using 100% pine bark substrate or pine bark:peat substrate (4:1 by vol). Two controlled release fertilizer sources Osmocote 19N-2.2P-7.5K (19-5-9) or Harrell's 17N-2.2P-10.0K (17-5-12) were included in the container substrate in a fluoropolymer bag with 17 g N in each #5 container and 63 g N in each #15 container. Fertilizer bags were placed in the middle on the container during potting. Using a split plot design with fertilizer and media as subplots, a cyclic irrigation regime consisting of three irrigation applications spaced one hour apart to produce about a 20% leaching fraction was compared to a traditional irrigation regime with one irrigation application which equaled the total volume applied in the cyclic regime. Irrigation was applied with micro spray stakes and amount applied was dependent on maintaining a 20% leaching fraction (based on the cyclic irrigation treatment) as plant use increased. Leachate volumes were 15% greater with a traditional irrigation than a cyclic irrigation regime. The pine bark:peat substrate had 18% less container leachate in year 2 than the 100% pine bark substrate. Fertilizer source influenced cumulative amounts (mg/year) of ammonium-N, nitrate-N and ortho phosphate in the container leachate. Nitrate-N and ammonium-N from Harrell's 17N-2.2P-10.0K fertilizer was each about 20% higher in the container leachate from sweetbay magnolia than Osmocote 19N-2.2P-7.5K fertilizer. In the case of the willow oak, the differences were 32% and 19%, respectively. Ortho phosphate averaged about 65% greater in leachate from both sweetbay magnolia and willow oak containers when grown with Osmocote 19N-2.2P-7.5K compared to Harrell's 17N-2.2P-10.0K fertilizer. At the end of year 2, height and caliper growth were similar among treatments with both species.