Controlled-release Fertilizers Affect Nitrate Nitrogen Runoff from Container Plants

Container plant runoff NO 3 -N levels varied with sampling time and were periodically higher than the 10-ppm federal drinking water standard during 4.5 months following fertilizer application, even though controlled-release fertilizers Nutricote 18N-2.6P-6.6K Osmocote 18N-2.6P-10K, Prokote 20N-1.3P-8.3K, and Woodace 19N-2.6P-10K were used. Leachate collected from containers had a higher NO 3 -N level than runoff regardless of sampling time. Leachate NO 3 -N ranged from 278 ppm for Nutricote 3.5 months after application to 6 ppm for Prokote 1 week after application.