Author: jeffgillman003

If you’re getting sick of the compost tea debate then you can skip this post.  If not, then read on! 

This past week I received my copy of Arboriculture and Urban Forestry 37(6).  And in it, page 269, I discovered an article titled “Laboratory Assays on the Effects of Aerated Compost Tea and Fertilization on Biochemical Properties and Denitrification in a Silt Loam and Bt Clay Loam Soils” by Bryant Scharenbroch, William Treaurer, Michelle Catania and Vincent Brand.  Basically what the authors did was to add dilute compost tea, concentrated compost tea, and a fertilizer to a couple of different types of soil in a laboratory setting to establish how they changed the soil.  To be honest the article was a little tough to read for a non-soil scientist and I found myself looking up terms quite often.  Still, I found their conclusions fascinating.  There were actually a number of conclusions, I’m just going to cover what I think are the most interesting:

1. “Aerated Compost tea appears INFERIOR  [you read that right – inferior] compared to fertilizer in its ability to increase microbial biomass, microbial activity” and a few other things.   Hmmm…I’d been told that microbes hated synthetic fertilizer.  I guess not all microbes agree.  In terms of the fertilizer used, it was a 30-10-7.  I didn’t see it explicitly stated in the article, but I’d bet it was a synthetic fertilizer called Arbor Green Pro.  It was applied at what I would consider a heavy dose.
2. Aerated compost tea, or at least the compost tea tested in this article, did contain a significant amount of nutrients.
3. On the up side for compost tea it was pointed out that compost tea treatments might help a poor soil retain more nitrogen.  Maybe…but the authors also pointed out that “only the fertilizer treatment appeared to deliver enough available nitrogen to potentially meet tree needs in the Bt horizon soils” (in other words poorer soils).  Interesting – but if we just added compost we’d have a better soil anyway, which brings us to the next point….
4. The compost tea tested contained only a small portion of the microorganisms that compost does.

So what’s the take home message from this article?  This wasn’t explicitly stated in the article — in fact I’m not even sure the authors would agree with me — but to me the important message is 1) ADD COMPOST and 2) IF YOU NEED TO ADD NUTRIENTS ADD FERTILIZER NOT COMPOST TEA (though I’d go with a nice renewable organic rather than a synthetic).   

Over the years I’ve gotten a lot of questions about how to compost.  I’m not a composting expert, and don’t want to pass myself off as one, but I do understand the basics and I like to think of myself as a proponent of composting.  Having said that, there is a composting practice which I’m asked about frequently that I never know quite how to answer.  Should you put meat into your compost?

The easy answer to the question of whether meat belongs in compost is that it is an organic material which will break down just fine along with all of the vegetable matter in your compost.  But there’s more to it than that.  I’ve been to some areas that specifically forbid meat in compost because of the vermin that it will attract.  And it’s true, at least to some extent, that meat attracts vermin.  Rats, raccoons, and other mammals will go after meats.  It’s the high protein content.  How can they resist?  While leaves and grass can have as much as 4% nitrogen, meats will typically have between 5 and even as high as 16% nitrogen.  Of course they go for it! 

Besides the vermin issue, if raw meat is placed in a compost pile it tends to stink, especially if it isn’t mixed into the pile.  Cooked meat (table scraps) breaks down a little bit more slowly than raw meat and doesn’t stink as much.  Because of the high nitrogen content of meat it will get a compost pile to compost a little bit faster.  Personally, I’m in favor of using meat in compost piles as long as you’re careful to turn the pile frequently to keep it inside the pile where it can’t do as much harm.  If you’re a casual composter then you might want to avoid using meat because of the potential problems.  So there it is – in my mind the answer to whether you should put meat in compost or not comes down to how closely you like to monitor your pile, whether there are laws against it in your area, and also the likelihood of mammals getting into it where you live.  Also, at most meat should be a small component of a compost pile — not the main component.

Back in 2006, when I first started garden writing, I was invited to give a talk in Michigan.  It was really exciting to get this kind of invitation so early in my writing career and I was thrilled to have the opportunity to talk to an audience that wasn’t composed primarily of students or academics. 

Looking back at those talks…well…they weren’t particularly good.  Sure, there was good information, but I wasn’t particularly comfortable giving talks at that stage and so I’m not sure I got my information across nearly as well as I should have. 

After my talks there really wasn’t much to do besides listening to other speakers, and so that’s what I did.  That’s where I got to listen to Jeff Ball, a garden writer and self-proclaimed yardener.  I was amazed at how this guy filled the room with people who wanted to hear him speak and further amazed at how well he spoke.   Being in academia I’m always surprised when someone speaks without visual aids – I had always idolized Michael Dirr, my former advisor and one of the greatest speakers I know, who always played off of his magnificent slides of plants.  I really had never seen anyone give a talk without slides, or overheads, or powerpoint, or a chalkboard, before.  But Jeff Ball did a talk right off the top of his head with nothing else, and he was magnificent.  I remember not agreeing with everything he said (can’t remember what specifically), but more importantly, I remember how the tone of his voice and his wonderful sense of timing and rhythm kept the audience interested and engaged.   After that day there were two speakers who I idolized, Mike Dirr and Jeff Ball. 

Jeff Ball passed away this past week.  It’s always sad when someone who you know and admire passes, but their passing also provides a time for you to think back on the good things which they did.  I didn’t know Jeff well at all.  Indeed, I never saw him speak again after that day.  But his talk was inspirational and led me to really think about how I give a presentation, and for that I can’t thank Jeff enough.

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.