CWMI Leaf Mulching Study

Improving Turf and Soil Health, Reducing Energy Use, Conserving Water, and Assessing Pathogen and Tick Populations when Mulching Leaves in Place

- Westchester County, NY multi-year study (begun 2015)

In the Northeast, including NYS, municipalities banned leaves from being placed in landfills. Instead, they collect leaves and compost them locally or ship them long distances. Fall leaf management is a challenge for communities, especially in densely populated areas with high tree densities. Roadside leaf piles clog storm drains, cause flooding and pose other hazards. Leaf pick-up and transport is costly and increases fuel use and emissions.

Mulch mowing leaves requires one to pay close attention to size and amount of leaves left on the turf or leaf litter build up which can potentially kill the underlying turf or provide a suitable habitat for insect pests to proliferate. Gaining better understanding of how leaf and grass mulching will affect insect and pathogen populations, soil and turf quality will allow homeowners landscapers and property managers to make better yard waste management decisions.

Mulching leaves in place may help to decrease community labor and collection costs, lower carbon footprint with decreased fuel use, improve soil health and water infiltration, decrease runoff and reduce irrigation needs, increasing community sustainability. The project team will assess the potential effects of this practice on soil and turf quality, soil nutrient supply for spring regrowth and monitor effects on tick and other insect pest populations, while educating the public about the importance of healthy soils, water conservation, and reduced greenhouse gas emissions.

Research Objectives
Research goals are to assess the effects of mulch mowing leaves in place on turf and soil health, soil nutrient concentrations, and insect/tick population dynamics. We will (i) Measure the effects of mulching leaves in place annually over many years on chemical, biological and physical soil health, including nitrogen (N) mineralization potential, phosphorus (P), potassium (K), micronutrients, pH, microbial activity, aggregate stability, available water holding capacity, and compaction. (ii) Measure changes in turf quality over time. (iii) Measure changes in tick population dynamics over time. (iv)Estimate changes in greenhouse gas emissions associated with clearing leaves versus mulching them in place per season.

Categories of Properties
A Steering committee comprised of representatives from NYSDEC, NYS Turf and Landscape Association, Westchester Department of Solid Waste, Cooperative Extension, environmental groups and homeowners will help guide the research. Twelve sites will be selected with the help of the leaf mulching initiative, Four sites will have been mulch-mowed for 1-3 years, 4 will have been mulch-mowed for 4-7 years, and 4 sites will have had leaves removed. In order to evaluate the challenges and costs of mulch mowing leaves in place versus collection, transportation and municipal management of leaves, interviews will be conducted with property managers, municipal solid waste and department of public works personnel documenting practices, challenges and costs. Information on fuel use for transport and handling of leaves by the municipality versus on-site fuel use many gas-powered mulch mowers will be analyzed to assess the effect on GHG emissions differences.

Read more about the project protocol - research program checklist for participating sites.

Mary Schwarz
Jean Bonhotal
Cornell Waste Management Institute
Dept. of Crop and Soil Sciences
813 Bradfield Hall
Ithaca, NY 14853