Controlled-release fertilizer application rates
The experiment was repeated for the 2013 growing season with rates of CRF incorporated at 0.05, 0.35, 0.65, 0.95, and 1.25 kg·m−3 N. Plant performance (i.e., growth index) and leachate electrical conductivity (EC) and pH were evaluated once every 3 to 4 weeks during the respective growing seasons. The amount of N and P lost to the environment was determined for the 2012 growing season. The interaction between nutrient supply rate and target species affected most response variables. Although higher levels of fertilization produced larger plants and had the potential to decrease production time, increased losses of N and P and higher EC leachate values occurred.
Results of this study indicate that an acceptable range of CRF application rates can be used for each species depending on the production goals, i.e., decreased production time, maximum growth, or decreased nutrient leachate. Overall, the highest acceptable CRF rates within the optimal range were: 1.25 kg·m−3 N for Spiraea; 1.7 kg·m−3 N for Hydrangea; 2.1 kg·m−3 N for Cornus; and 2.5 kg·m−3 N for Weigela, Salix, and Hibiscus. The lowest acceptable rates within the optimal range were: 0.35 kg·m−3 N for Hibiscus; 0.65 kg·m−3 N for Cornus, Weigela, Salix, and Spiraea; and 0.80 kg·m−3 N for Hydrangea.
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