Recycling Clippings and Tree Leaves in Home Lawns

Recycling Clippings and Tree Leaves in Home Lawns Dr. Matt Fagerness KSU Turfgrass Extension

Outline • Environmental challenges in lawn care • Turfgrass ecology basics • Clipping recycling: fact and fiction • Tree leaves: the fallen frontier • Tips for dealing with clippings and leaves

Lawns are Vulnerable to: • Soil erosion (especially during establishment) • Surface runoff (rain, uneven irrigation) • Movement of fertilizer and pesticides offsite • Improper use of fertilizers and pesticides • Wasted nutrients and organic matter • free resources!!

Resource Recycling in Turfgrass • Free resources in turfgrass include : • contents of harvested clippings (are they really free?) • fallen tree leaves • Best Management Practices (BMPs) address the other four listed vulnerabilities in turf. Resource recycling and composting addresses the fifth.

Goals of BMPs • 1)Reduce or eliminate offsite transport of sediment, nutrient, and pesticides • 2) Reduce total chemical use through an IPM approach • 3) Control the rate, method, and types of chemicals used • 4) Use biological and mechanical soil and water conservation practices • **5) Educate the public on the relationship between environmental issues and turf management

Turfgrass is a “Limited” Perennial • Most turfgrasses are intended perennial “crops” but plants undergo constant recycling • Phytomer: individual shoot unit, produced periodically by a turfgrass plant every 2-4 weeks. • When we mow, leaves don’t regrow the cut portion; rather, it is replaced by new phytomer(s)

Phytomer Pros and Cons • Pros: • allow turfgrasses to withstand mowing and other mechanical injury • allow for recovery from disease and insect injury • Cons: • plants act as moving conveyor belts for water and nutrients • we have the option to loop this belt or leave it going in one direction

Turfgrass Community Dynamics • Turfgrass plants compete for light, water, nutrients, and available space. Their competitors include: • other turfgrass plants (planting density is critical) • weeds • other plants (shrubs, trees, etc.) • debris (leaves, piles of clippings)

How Biological Debris Stacks Up Against Other Competitors • Clippings and leaves: • not as competitive with turf for water and soil nutrients (no longer active) • can be very competitive (indirectly) for light and physical space • can also compete for the “attention” of beneficial microbes, especially if debris is not partially decomposed (mulched) • All these factors must be valued, especially in fall

Grass Clippings • Do: • contain 80% or more water so they break down easily • procure most N taken up from the soil for new growth • contain N in a more readily usable form (ammonium) • comprise an important part of nutrient recycling in turf • Don’t: • contribute to thatch because of their rapid break down

Soil Nutrient Cycling We return valuable nutrients to the soil when clippings are recycled. NH4 NO3 NO3 NO3 Fertilizer NO3 NH4 NH4 NO3 NO3 Soil microbial pool of N

Fate of Clippings • When recycled, clippings: • optimize turfgrass use of applied fertilizer (we must apply up to 25% more if clippings are removed). • eliminate the need for waste disposal. • When removed, clippings: • must be composted or taken to disposal sites. • Pile composted clippings may yield less N than when directly recycled because of volatilization.

Tree Leaves • Much like turfgrasses, tree leaves contain more N when they’re actively growing • This trend changes when leaves begin to turn color and fall off (increased C:N ratio) • Fallen leaves, as a result, are a better source of organic matter than nutrients • Different species have different chemical compositions but compounds toxic to turf are rare

Management of Fallen Leaves • Because leaves aren’t themselves toxic, they don’t directly inhibit turfgrass growth. • However, they can appreciably shade turf and act detrimentally in this way • Most deciduous tree leaves have thick cuticle/ waxy layers so composting is a slow process

Strategic Challenges of Fallen Leaves • Different trees drop leaves at different times • How to deal with leaf removal and newly seeded turfgrasses • How may leaves can be mulched into turf before turf becomes choked?

Different Trees Drop Leaves at Different Times

Tips for Recycling Clippings • Keep mower blades sharp: remaining surface heals slower and clippings will decompose more uniformly • Follow the 1/3 rule: hay rows are indicative of too long a time between mowings and will choke out turf beneath them (act as small compost piles) • Maintain moisture: clippings recycled/ mulched and left on dry ground will lose their value

Mowing Issues

Tips for Composting Tree Leaves • Mulch leaves, either into the lawn or in compost piles, to speed their decomposition. • Up to 4” of leaves can be mulched into a lawn without hurting quality the next year • incremental mulching may allow for more • Be careful with mulching or raking leaves in new turf as young plants can easily be uprooted or damaged.

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Recycling Clippings and Tree Leaves in Home Lawns