Phosphorus Availability In Turfgrass Root ZonesAfter Applications of Organic and SyntheticNitrogen Fertilizers

摘要

Organic fertilizers have increased in popularity over the past ten years due to thebelief they are more environmentally sound to use than synthetic fertilizers. Mostfertilizers derived from organic materials contain phosphorus as well as nitrogen,so use may be affected in states that legislate the application of P to lawns. Statesare considering exempting organic fertilizers from their zero-P legislation, asWisconsin did, because it is thought that P from organic sources is less likely to belost in leachate or runoff. Fertilizers are applied on turfgrasses as needed based onN form and content. Many organic fertilizers contain as much P as N in theirformulations, and therefore similar amounts of P and N are applied with eachapplication. Soil tests in native soil and a fairway sand and peat mix used in thePacific Northwest showed that organic fertilizers applied at rates to provideadequate N for acceptable turf increased soil Bray-1 P levels from 16 to 18 mg/kgto 23 to 66 mg/kg within 3 years. Oxalate extractable Fe, Al, and P wasdetermined for all treatments in both soils and used to calculate phosphorussaturation (PSI ). PSI values from sand treated with one organic fertilizersource were significantly higher than measured in other treatments, indicatingfuture risk of P loss with repeated applications of this organic fertilizer.