Month: November 2011

“Stealing an idea from one source is plagiarism; stealing from many sources is research.”  This quote has been attributed to so many people I won’t bother trying to list them here.  But the point is a lot of what we do as professors is spend our time digging into the literature to look for substantiating or conflicting evidence for the ideas were interested in testing.  As a grad student back in the 1980’s, a time-honored tradition was to spend the afternoon at the library combing the stacks for journal articles, loading volume after volume onto a cart and then schlepping off the library copy center.  With the mechanical hum in the background and green glare of the scanner radiating off the walls, we’d wear our toner smudges like a badge of honor as the copy machine counte kept track of our progress.

Today, of course, things have changed dramatically.  The hardcopy CAB abstracts have been replaced by Google Scholar and Web of Science.  For those of us at major universities, hundreds of journals are available at our fingertips through on-line subscriptions through our libraries.  And an electronic interlibrary loan request can usually produce a .pdf of even the most obscure reference with a couple of days.  Unfortunately for those of us working in landscape horticulture some of the hardest to find journals were the ones that we often wanted most.  For example, journals from the American Society for Horticultural Science (ASHS) were only available to members and just recently became open access and indexed through Web of Science and other indexes.  Fortunately the situation is improving for two other sources that contain the type of applied research we are often after.  Arboriculture and Urban Forestry (formerly Journal of Arboriculture) and Journal of Environmental Horticulture are both available on-line (or partly available on-line).  More importantly for GP blog readers, neither requires a subscription or university log-in.  

Arboriculture and Urban Forestry is available at http://auf.isa-arbor.com/ 

Journal of Environmental Horticulture is available at http://www.hriresearch.org/index.cfm?page=Content&categoryID=174

Both journals include a search function to make it easier to find related articles.

Yesterday I happened to see a garden calendar encouraging people to pick up their leaves so that they don’t pollute streams and lakes by encouraging algae to grow.  This was a good idea, I thought, but then I started to wonder whether leaves on the lawn might not be a better idea?  After all, the reason that leaves cause algal growth in water is because of the nutrients they have.  And if they have nutrients couldn’t those be used for fertilizer instead of the regular fertilizers which we use?  What if we raked all of our leaves onto our yards?

There’s no denying that leaves which drop in the fall can make great compost, but how well would they work as a fertilizer? So I did a little bit of preliminary research — reading old papers and such — and here’s what I’ve come up with:

Fallen leaves are very variable in nutrient content.  Some leaves have 1% nitrogen, and some can have almost 3% (these are mostly from leguminous trees).  In terms of phosphorus, fallen leaves tend to have around 0.1%, though once again, it’s very variable.   For the purposes of this post I’m going to stick with nitrogen.

For 1,000 square feet of grass yard it takes about a pound of nitrogen per year to fertilize, even with a low input variety.

In a heavily wooded lot it wouldn’t be odd to have around 100 pounds of leaves fall in a 1,000 square foot area.  At 1% nitrogen, the leaves would provide enough nitrogen for the grass, but that would probably end up being a moot point because the leaves would have a good chance of smothering the grass. 

So what I’m wondering is, if we planted trees which were legumes, and had higher levels of nitrogen, and if we chopped up the leaves so they weren’t as likely to smother the grass (using a lawnmower or whatever) could we provide enough nitrogen per year for a healthy low input lawn?  Personally, I think so.  We would need to keep these leaves off of driveways and sidewalks because this is where they would do their worst in terms of contaminating water, but if they were just in yards — I think it might work.