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Title: NUTRIENT RELEASE CHARACTERISTICS FROM FOUR TYPES OF CONTROLLED-RELEASE FERTILIZERS

Author
item MERHAUT, DONALD - UC RIVERSIDE
item Albano, Joseph
item BLYTHE, EUGENE - UC DAVIS
item NEWMAN, JULIE - UC DAVIS

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2004
Publication Date: 7/1/2004
Citation: Merhaut, D., Albano, J.P., Blythe, E., Newman, J. 2004. Nutrient release characteristics from four types of controlled-release fertilizers. HortScience. 39:797

Interpretive Summary: A key to limiting the impact of nutrient contamination of water resources on a container nursery is to supply nutrients at a rate that the plants that closely equal a plants nutrient requirements. The use of controlled-release fertilizers (CRF) are supposed to provide nutrients to the plant slowly over the course of many weeks. In this study we compared the nutrient release patterns over an eleven month period for four types of CRFs: Apex 17-5-11, Multicote 17-5-11, Nutricote 18-6-8, and Osmocote 24-4-9. Rate of fertilizer incorporation was 2.3 kg/cm3 of nitrogen. Media consisted of 50% composted forest products, 35% pine bark, and 15% washed Builder's sand. The media was also amended with 0.60 kg/m3 of dolomite. Fertilizer was incorporated into the media with a cement mixer and placed into 2.6-L black polyethylene containers. Containers were placed on benches outside without plants for the purpose of getting absolute relaese rates without the confounding factor of plants that may differ in growth rates. Air and media temperature were monitored throughout the 11-month period as nutrient release from these CRFs is primarily a function of temperature. Containers were irrigated through a ring-dripper system. Leachate (runoff) was collected twice weekly. Leachate electrical conductivity (EC), pH, and nutrient content were measured weekly. Significant differences in nutrient release patterns were observed between fertilizer types throughout much of the experimental period. Release rates were significantly greater during the first 20 weeks of the study compared to the last 20 weeks of the study, regardless of fertilizer type. The significance of these findings are that eventhough CRF release nutrients over the course of many weeks, depending on the product, there is still the potential an initial surge of nutrients in the weeks after application.

Technical Abstract: Release patterns of ammonium, nitrate, phosphorous, potassium, calcium, magnesium, iron, manganese, and zinc were measured during an eleven month period for four types of Controlled Release Fertilizers (CRF): Apex 17-5-11, Multicote 17-5-11, Nutricote 18-6-8, and Osmocote 24-4-9. Rate of fertilizer incorporation was 2.3 kg/cm3 of nitrogen. Media consisted of 50% composted forest products, 35% pine bark, and 15% washed Builder's sand. The media was also amended with 0.60 kg/m3 of dolomite. Fertilizer was incorporated into the media with a cement mixer and placed into 2.6-L black polyethylene containers. Containers were placed on benches outside. Air and media temperature were monitored throughout the 11-month period. Containers were irrigated through a ring-dripper system. Leachate was collected twice weekly. Leachate electrical conductivity (EC), pH, and nutrient content were measured weekly. Significant differences in nutrient release patterns were observed between fertilizer types throughout much of the experimental period. Release rates were significantly greater during the first 20 weeks of the study compared to the last 20 weeks of the study, regardless of fertilizer type.