The 2011 ASHS Annual Conference

Urban lawns and gardens are cited as major contributors to non-point source pollution. In many cases, potential pollution results from routine application of fertilizers containing phosphorus and potassium to soils already containing excessive levels of these minerals. If homeowners can be convinced to apply fertilizer based on soil test results, this would significantly reduce potential pollution from home lawns and gardens.  The University of Missouri Soil Testing Labs received 2312 samples from the Extension Centers from urban lawns and gardens in Greater St. Louis, Kansas City and Springfield in 2008. A soil test summary indicated that 55 to 75% of the lawn and garden soils tested high (67 to 135 kg^-1ha^-1) or very high (greater than 135 to kg^-1ha^-1) in soil test phosphorus (P) levels and 65 to 80% of the samples tested high (291 to 336 kg^-1ha^-1) or very high (greater than 336 kg^-1ha^-1) in soil test potassium (K) levels. Some home garden soil samples tested high as 1008 kg^-1ha^-1 of P and 1120 kg^-1ha^-1 of K which is considered extremely high. The majority of homeowners who submitted soil for testing had built their soil test P and K levels high and should not apply additional fertilizer containing P and K. Over-building certain nutrients can result in imbalance of nutrients in soils causing reduced mineral uptake and poor plant growth. It may also lead to degradation of water quality as P and K move offsite with runoff and soil erosion resulting in eutrophication of lakes and rivers. The information derived from this soil test summary is used widely in extension education programs throughout the state to emphasize the importance of soil testing as a tool in promoting proper and efficient use of fertilizers and amendments in urban lawns and gardens.