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Title: Longevity of controlled release fertilizer influences the growth of bedding Impatiens

Author
item ANDIRU, GLADYS - The Ohio State University
item PASIAN, CLAUDIO - The Ohio State University
item Frantz, Jonathan
item JOURDAN, PABLO - The Ohio State University

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2013
Publication Date: 4/1/2013
Citation: Andiru, G., Pasian, C., Frantz, J., Jourdan, P. 2013. Longevity of controlled release fertilizer influences the growth of bedding Impatiens. HortTechnology. 23(2):157-164.

Interpretive Summary: Controlled-release fertilizers (CRF) are fertilizers that are not immediately available instantly, but instead release into the root zone slowly over time; their release ideally would match the growing needs of the plants. The use of CRF is limited within floriculture production, perhaps due to lack of grower experience and research-based information about their incorporation within floriculture production systems. We sought to increase the applied knowledge of these materials by comparing the growth and quality of bedding impatiens (cultivar ‘XTREME Scarlet’) when grown with typical water-soluble fertilizer (WSF) and with different combinations of longevity and rates of a single formulation of CRF. The formulation of CRF used was 16-3.9-10 (Osmocote Plus 16-9-12; The Scotts Company, Marysville, OH) and it consisted of different longevities (3-4, 5-6, 8-9, and 12-14 months) and application rates (1.4, 3.4, 6.8, 10.2 and 13.6 kg per cubic meter). Plants were grown in the greenhouse and consumer evaluations were performed when deemed of a size suitable for sale in the market. Plant canopy cover, flower cover, and shoot dry weight were also determined at that time. Commercially acceptable plant quality was achieved with CRF application rates between 3.4 - 6.8 kg per cubic meter. At low CRF application rates, the treatments receiving the CRFs of faster release rate, which corresponded to the shorter longevity types of CRFs, produced larger plants as measured by dry weight and leaf canopy cover and also had greater flowering than the treatments receiving the slower release rate CRFs. At higher application rates, slower release rates outperformed the faster release CRFs for the same parameters. The WSF-grown plants were larger than the CRF-grown plants when CRF was applied at the lowest rates. No differences in any of the three growth variables measured were found when plants were grown at a rate of 6.8 kg cubic meter CRF of any longevity or with WSF. This information will assist growers in choosing CRF type and application rate for bedding plant production.

Technical Abstract: Controlled-release fertilizers (CRF) have not been extensively used in floriculture production, perhaps due to lack of grower experience and research-based information with their use in herbaceous plant production. Any information about the correct use of CRF should increase growers’ confidence in using this type of fertilizer. The objective of this research was to compare the growth and quality of bedding impatiens (Impatiens wallerana Hook f. ‘XTREME Scarlet’) when grown with typical water-soluble fertilizer (WSF) and with different combinations of longevity and rates of a single formulation of CRF. The CRF 16-3.9-10 (Osmocote Plus 16-9-12; The Scotts Company, Marysville, OH) consisted of different longevities (3-4, 5-6, 8-9, and 12-14 months) and application rates (1.4, 3.4, 6.8, 10.2 and 13.6 kg per cubic meter). Plants were grown in the greenhouse and consumer evaluations were performed at market maturity. Plant canopy cover, flower cover, and shoot dry weight were also determined. Commercially acceptable plant quality was achieved with CRF application rates between 3.4 - 6.8 kg per cubic meter. At low CRF application rates, the faster release rate (shorter longevities) CRFs produced larger plants (dry weight and leaf canopy cover) with greater flowering potential (flower cover) than slower release rate CRFs. At higher application rates, slower release rates (longer longevities) outperformed the faster release CRFs for the same parameters. CRF-grown plants were smaller that WSF plants when CRF were applied at the lowest rates. No differences in any of the three variables measured were found when plants were grown at a rate of 6.8 kg per cubic meter CRF of any longevity or with WSF. Growers should adjust CRF application rates according to CRF longevity.