Impact of Phosphorus Legislation on Soil Phosphorus Content of Homeowner Lawns.

In the decade since Minnesota’s first statute restricting phosphorus use on turf went into effect, lawns in the St. Cloud metro area have shown a substantial reduction in soil phosphorus (Bray P1). In 2004, 110 homeowners participated in a study of lawn care attitudes and maintenance practices. Of those, 77 submitted soil for analysis. The study was repeated again in 2014, with 92 homeowners participating in the study, and 65 submitting soil for analysis. In 2004, the average Bray P1 phosphorus level was 80 mg P kg^-1. This average dropped to 43 mg P kg^-1 in 2014. Using the University of Minnesota Extension Service guidelines, which state established lawns with a Bray P1 level greater than 25 mg P kg^-1 should not receive additional inputs of phosphorus, only 4% of the lawns of the participating homeowners needed phosphorus fertilization in 2004. In 2014, this percentage of lawns that needed phosphorus fertilization grew to 23%. While phosphorus based fertilizers are available for purchase, and while the overall level of phosphorus in lawn soil is still rather high, it seems legislation and education have made an impact to lower soil phosphorus in lawns.