Leaves raked onto curbs adds to phosphorus loading

Below is some timely information that appeared in a recent enewsletter from the Cornell University turfgrass team. In light of the actions by some communities to ban the use of fertilizers containing phosphorus, regardless of what soil tests reveal, we thought it was interesting. Phosphorus runoff, of course, promotes algae and plant growth in streams, rivers and lakes, and none of us wants to do anything to degrade the environment.

The Cost and Waste of Leaf Collecton

Many communities throughout the Northeast and Midwest spend enormous amounts of tax dollars on the collection of fallen leaves. In fact some communities around New York City such as Scarsdale will spend in excess of $1.25 million dollars annually on leaf collection. In these challenging economic times one might consider better use for this money and the science is there on several fronts to support alternatives.

First and foremost bringing the leaves to the curb increases the risk of phosphorus contamination of surface water bodies. Several monitoring studies have found that P loading of lakes and streams peaks during periods of leaf drop suggesting that the leaves are releasing the P as they degrade. Bringing the leaves to the curb awaiting collection is simply increasing the P pollution problems as much as depositing P fertilizer on paved surface essentially bypassing the natural filtration capacity of turfgrass areas.

Of course the regulating of P-based fertilizer is well known and yet there is little discussion of this existing practices effect on water quality. So, if we do not collect the leaves and bring them to the curb what should we do with them?

More than a decades worth of research consistently shows that mulching the leaves effectively into the turf canopy so that they are not in clumps on the surface has no negative effect on turfgrass performance.

Furthermore there is some evidence that leaf mulching can reduce weed problems such as dandelion (see ShortCUTT Week 29; September 29, 2008). While the mechanism of this is not completely understood I suspect of we continue to study this issue more benefits will come to light. In the end, simply mulching the tree leaves into the turf is the most cost effective and environmentally friendly practice to implement at this time of year.

Source: Cornell Turfgrass Short CUTT, Week 32......click on the headline, which will take you to the Cornell Web site where you can sign up for Short CUTT. It's a great source of information about turfgrass in the Northeast and New England.