Q: I want to do the right thing but I am concerned about not using any phosphorus on the lawn. How do I know if the lawn is deficient?
A: Nutrient deficiencies seldom occur alone and these deficiencies in plant material often look similar. It is therefore difficult to determine exactly which nutrient is lacking simply by looking at the grass blades or plant leaf. Some studies on forage (lawn grass cousins) grasses and agriculture crops have indicated the blades may lose their green color because of the breakdown of chlorophyll in the blades. The other color pigments such as anthocyanins (red, purple, or blue) will no longer be masked and the leaves may develop purple edging or streaks. However, this same coloration may occur when the grass blades are exposed to cooler temperatures. Phosphorus is important in cell division and elongation of cells, therefore the blades may be somewhat stunted but not many people complain about not having to mow as often. So, how do we know if a phosphorus deficiency has occurred? A soil test would help you determine if the soil is lacking in phosphorus which would enable you to add phosphorus (according to the fertilizer label) to the lawn. You would need to send the soil to a reputable laboratory for analysis. The University of Florida Soils Lab will charge only $7 for such a test. It will take about ten to fourteen days to receive the report back, which would be a worthwhile investment for you. Contact your local County Extension Office for information of obtaining a soil test kit. Refer to the FDACS publication on urban turf fertilizers: http://www.flaes.org/pdf/Urban_turf_fact_sheet.pdf