Abstract
Controlled-release fertilizers (CRFs) are commonly used in the production of ornamental plants. They are often used to reduce labor costs, provide consistent nutrient availability over time, and potentially reduce nutrient losses due to leaching. Studies were initiated in Apopka, FL, in May 2007 to compare two 16–8–12 experimental CRFs, one with a 6-month (ECRF6) and one with a 9-month release term (ECRF9), to a commonly used commercial CRF with a similar release term (Osmocote® Plus 15–9–12 or Nutricote® Total 17–7–8 type 270/70, respectively). Tissue-cultured liners of interiorscape cultivars Dieffenbachia ‘Camille’ and Spathiphyllum ‘Ty’s Pride’ were potted into a sphagnum peat-based container medium and grown in a shaded greenhouse using one of the two 6-month release materials. Cutting-derived liners of landscape shrubs Loropetalum chinense ‘Burgundy’ and Viburnum odoratissimum were transplanted into containers filled with a pine bark-based mix and grown in full sun using one of the two 9-month release products. The interiorscape plants grew equally well using ECRF6 as with the Osmocote® Plus. Loropetalum growth and grades were similar using both 9-month release fertilizers; however, growth of viburnums fertilized with ECRF9 was somewhat greater after four months than those fertilized with Nutricote®. Initially, nitrate-nitrogen (NO3-N) leaching, determined using the pour-through method, was greater for ECRF9 than for Nutricote®. Subsequent leachate concentrations from containers with plants were mostly similar for the two products and ranged from 4 to 21 ppm [mg·L–1].
