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Title: NUTRIENT RELEASE FROM CONTROLLED-RELEASE FERTILIZERS IN NEUTRAL-PH SUBSTRATE IN AN OUTDOOR ENVIRONMENT: I. LEACHATE ELECTRICAL CONDUCTIVITY, PH, AND NITROGEN, PHOSPHOROUS, AND POTASSIUM CONCENTRATIONS

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

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2006
Publication Date: 12/1/2006
Citation: Newman, J., Albano, J.P., Merhaut, D., Blythe, E. 2006. Nutrient release from controlled-release fertilizers in neutral-ph substrate in an outdoor environment: i. leachate electrical conductivity, ph, and nitrogen, phosphorous, and potassium concentrations. HortScience. 41(7):1674-1682.

Interpretive Summary: Controlled release fertilizers (CRF) are polymer-coated prills containing nutrients that are leached over the course of weeks based on temperature. In this study, the release characteristics of four different polymer-coated fertilizers (Multicote, Nutricote, Osmocote, and Polyon) were studied over a 47-week period under commercial nursery production conditions. Plants were grown in 2.4 L containers, filled with high-fertility, neutral-pH growing media. Container leachates (runoff) were collected weekly and monitored for electrical conductivity (EC), pH, and concentrations of ammonium, nitrate, phosphorous and potassium. Concentrations of most nutrients in leachates were relatively high but fluctuated frequently during the first third of the study period, and then gradually decreased and stabilized during the last 27 weeks. Osmocote often resulted in greater ammonium and total inorganic N concentrations in leachates than other fertilizers during weeks one through five and Multicote produced higher ammonium in leachates than most of the other fertilizer types during weeks nine through 12. Total phosphorous concentrations were greater with Multicote during a third of the experimental period treatment, especially when compared with Osmocote and Polyon. Differences were also observed among treatments for leachate concentrations of potassium with Polyon and Multicote fertilizers producing greater potassium concentrations in leachates compared with Osmocote during several weeks throughout the experimental period. Leachate concentrations of nitrate and phosphorous from all fertilizer types were usually high, especially from week five through week 30.

Technical Abstract: Release characteristics of four different polymer-coated fertilizers (Multicote, Nutricote, Osmocote, and Polyon) were studied over a 47-week period in a simulated outdoor containerized-plant production system. The 2.4 L containers, filled with high-fertility, neutral-pH substrate, were placed on benches outdoors to simulate the environmental conditions often used for sun-tolerant, woody perennials grown in the southwestern United States. Container leachates were collected weekly and monitored for electrical conductivity, pH, and concentrations of NH4+-N, NO3 -N, total P and total K. Concentrations of most nutrients in leachates were relatively high but fluctuated frequently during the first third of the study period, and then gradually decreased and stabilized during the last 27 weeks. Osmocote often resulted in greater ammonium and total inorganic N concentrations in leachates than other fertilizers during weeks one through five and Multicote produced higher NH4+ in leachates than most of the other fertilizer types during weeks nine through 12. Total P concentrations were greater with Multicote during a third of the experimental period treatment, especially when compared with Osmocote and Polyon. Differences were also observed among treatments for leachate concentrations of K, with Polyon and Multicote fertilizers producing greater K concentrations in leachates compared with Osmocote during several weeks throughout the experimental period. Leachate concentrations of NO3 and P from all fertilizer types were usually high, especially from week five through week 30.