Urban Lawn Infiltration Rates and Fertilizer Runoff Losses under Simulated Rainfall

Abstract Infiltration runoff measurements were made on nine urban lawns using a sprinkling infiltrometer in conjunction with the application of a complete fertilizer at three rates. The amounts of inorganic N, P, and K removed with the runoff water were determined. Results of the infiltration measurements show that the presence of textural and compaction discontinuities within the soil profile, formed during building and lawn construction, was probably the greatest factor affecting infiltration. Where these discontinuities were distinct, water intake was reduced to about 35% of that for a lawn with an undisturbed profile. For lawns with similar infiltration characteristics, a first order relationship appeared to exist between amounts of fertilizer applied and amounts lost. A second order equation, however, best described the relationship between percent of applied fertilizer in the runoff and 90‐min cumulative infiltration. When the simulated storm was applied immediately after fertilizer application, fertilizer losses averaged 10.6%; however, when fertilizer application was followed by recommended watering before the intense storm, average losses were reduced to 1.7% of the amount applied.