Water Quality as a Result of Lawn Cover and Management Intensity.

The application of fertilizers and pesticides can improve turf density, root structure, and increase water infiltration rate and uptake, potentially reducing nutrient loss through leaching and runoff compared to a landscape that receives no inputs.  Thirty two plots having 6 to 8% slopes were constructed in 2007 under highly compacted conditions to study runoff and leaching dynamics of eight different lawn types and management programs.  Treatments ranged from 100% Poa pratensis (Kentucky bluegrass) treated with fertilizer, herbicides, and irrigation, to plots containing 80-90% broadleaf weeds or 80-90% annual grassy weeds that are only mowed weekly in order to simulate a wide range of possible lawn types.  Polyvinyl chloride (PVC) pipe (61 cm diameter by 91.4 cm in length) was placed at the top of each plot to create a free draining lysimeters.  A channel drain gutter was placed with a 0.5% slope at the base of each plot to collect runoff. Water samples from all plots were analyzed for NH₄⁺-N, NO₃^--N, total N, orthophosphate and total P using colorimetric methods.   Variations in seasonal precipitation influenced the amount of nutrients lost in runoff and leachate.  The highest runoff volumes occurred within the first several months of establishment when infiltration rates were low due to compacted conditions and lawns were not thoroughly established.  This contributed to large mass loss of nutrients in plots containing less dense canopies (i.e. annual grasses) or in fertilized plots that had higher concentrations of nutrients in runoff.  Phosphorous was the predominate nutrient lost from plots in runoff while there were some losses of ammonium nitrogen following fertilization.  Nitrate nitrogen loss predominated in leachate, and losses were predominately driven by winter precipitation.  Plots which receive no fertilization had similar mass losses to fertilized plots due to larger volumes of water lost to runoff and leachate.