Submitted to: Ohio State University Extension Publication
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2007
Publication Date: 1/11/2007
Citation: Frantz, J., Pasian, C. 2007. Controlled Release Fertilizers: An Environmentally Sound and Efficient Method for Greenhouse Crop Fertilization. Ohio State University Extension Publication. 3:1. p. 5-7. Interpretive Summary:
Technical Abstract: Lake Erie is the most polluted of all the Great Lakes. In fact, the Maumee River Watershed alone contributes most of Lake Erie’s phosphorus and sediment load but only 3% of its water, due to the large concentration of agriculture in this portion of the state. The use of controlled release fertilizers (CRF) is common among nursery growers, but not among greenhouse growers who currently rely primarily on applying fertilizer solutions directly to plants. A study was done with vinca grown with five different levels of nutrition and supplied as 100% CRF, 50% CRF and 50% liquid feed, and 100% liquid feed. At each irrigation, all the leachates were collected, measured, and sub-sampled for complete elemental analysis. Periodic measurements of pH, EC, plant size, and chlorophyll content were taken throughout the growth period. A combination of CRF and liquid feed fertilizer produced high quality plants that contained many flowers. Leaves were greener (more chlorophyll) with more fertilizer, but could only be measured with the meter – our eye could not detect any differences in leaf “greenness”. In the liquid feed rate of 100 ppm N, plant height and flower number reached the upper limit with no additional benefit obtained with more fertilizer up to 400 ppm N. Initially, there was no difference in the amount of runoff from individual pots. By the end of the production cycle, there were huge differences in the amount of fertilizer contained in the leachate between the liquid feed only and CRF/liquid mix. Even at the lowest fertilizer supply tested (13 ppm N), fertilizer runoff was reduced by between 20% and 40% for different nutrients. At 100 ppm N, fertilizer runoff was reduced by 50% to 80%, depending on the nutrient. The combination of CRF and liquid feed allowed for adequate growth of vinca plants at a feed rate of 150 ppm, but reduced runoff by half or more, depending on the nutrient. We believe that changing fertilizer supply from an entirely liquid feed to a combination of CRF/liquid mix provides excellent control of nutrient supply, can produce high quality plants, and reduce the environmental impact of bedding plant production.