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morpheuspa

The Last Mow, Now With More Leaves

I blew out the gardens and dead air spaces today, sending lovely plumes of leaves across the lawn.

The mower is out there now, chopping it in for me. So far, it's already nearly invisible with an hour and a half to run yet.

I attached the Grounds Maintenance Magazine study using "excessive" leaf litter up to 450 pounds per thousand square feet (for me, that would mean hauling close to 4,500 pounds of leaves and ain't nobody got no time for that).

Here is a link that might be useful: Leaves on Grass--Study

Comments (12)

  • danielj_2009
    9 years ago

    Great article! I'm so glad to see that article (not that I didn't believe you!). It appears there are virtually no negatives to mulching. It was interesting that the C/N ratio was nearly unchanged even after adding an excess of leaves.

    Thanks.

  • dchall_san_antonio
    9 years ago

    That is the reason we always mulch mow and do not collect grass clippings.

    Back in the late 1800s there was a Russian researcher working on this field of study (can't remember his name but it started with an O). He used different terminology for what we now call mulch and dew, but his observations were very interesting. He was interested in how the mulch layer collected dew. He observed that when mulch was present the soil seemed to be more fertile even when no fertilizer had been added. My interpretation of that is that he had discovered several things that have only recently been reported in the West. One is that dried leaves can absorb ammonia gas. This is well known in composting circles. When you have a stinky compost pile, the solution is to cover it with dry leaves. The other scientific fact that the Russian did not know about was that ammonia gas is very readily absorbed into water. He may have known about that but did not discuss it in his article. Ammonia is a reasonably good source of nitrogen for plants, so when the ammonia laden mulch became moist with dew, what resulted was a liquid fertilizer that dripped back into the soil. Oh, I left out the part about where ammonia comes from in the soil. Any time protein decomposes, ammonia gas is released. Everyone has smelled sour milk, rotting meat/fish/chicken, or some stinky mess. The basis of the stink is ammonia. It might be mixed with other stinky stuff like methane, but that's the idea. When dead insects or microbes in the soil decompose, ammonia is released. If you have mulch, the mulch catches the gas. If you have bare soil, the ammonia dissipates into the air.

  • maplerbirch
    9 years ago

    I don't know if anyone here has the answer to this, but the C/N ratio in this article raised questions in this sense:
    When the leaves are partially digested in the Spring they said the c/n ratio was higher but under the 30/1 mark.
    My thought is that the level of N goes up as further decomposition occurs and the grass clippings mulched in over the Summer would also be high in N.
    Am I off on this?

  • tibbrix
    9 years ago

    I'm also mulching my leaves this year (see the thread, 'Mulching leaves into grass"). Still waiting for all the leaves to come down. I'm also going to blow the leaves out of the garden areas so that I can mulch them with my mower, but I'm going to toss a bunch of the mulch back onto the gardens when I'm done.

  • morpheuspa (6B/7A, E. PA)
    Original Author
    9 years ago

    >>My thought is that the level of N goes up as further decomposition occurs and the grass clippings mulched in over the Summer would also be high in N.
    Am I off on this?

    That's correct. In the article, they were discussing (in part) digging in to agricultural sites. We don't do that, we top dress.

    Most of our top dressing is things like bark mulch, which is high in C and very low in N. We want it to rot slowly and not to stink.

    With the leaves, we want them to hang around for at least some of winter and very slowly work into the soil to improve our organic matter levels.

    They'll do that. And up top they aren't robbing the soil around the roots of any nitrogen. They gather most of it from ammonia and from growing plaques of nitrogen-fixing bacteria.

  • sc77 (6b MA)
    9 years ago

    I wish this worked for me. I tried mulch mowing the leaves into the lawn 3 years ago. I used a combination of my lawn mower, plus a leaf vacuum/shredder with the bag removed to evenly scatter the confetti of leaves that I generated. So, they were shredded very well. Maybe I went to heavy on the leaf shredding, even without collecting other yard's leaves I had a ton... either way, the following spring I found myself just cleaning up the majority of the leaves I worked so hard to shred. Seem like during the cold months my lawn just couldn't process the leaves, even with respectable 8-10% organic matter, microbial life, worms, ect...

    I'm not sure if I did something wrong, or what, but my yard just didn't seem to consume much of the leaf matter. The last 3 years I have been collecting the leaves, shredding, then active composting for 1 year until they are ready, and I put down the "black gold" the next fall. I add coffee grinds, fruit/vegetable scraps and turn the pile until mid-December or so when it gets too cold for it to stay hot, even at the core. The next spring, It wakes up and goes back to work and by fall it's pretty well cooked.

  • danielj_2009
    9 years ago

    Dchall said:
    Everyone has smelled sour milk, rotting meat/fish/chicken, or some stinky mess. The basis of the stink is ammonia. It might be mixed with other stinky stuff like methane, but that's the idea.

    Just a minor point but methane has no odor.

  • morpheuspa (6B/7A, E. PA)
    Original Author
    9 years ago

    >>I'm not sure if I did something wrong, or what, but my yard just didn't seem to consume much of the leaf matter.

    Probably low levels of lignin and cellulose eating bacteria and fungi. If you'd kept going, the second year would have been better, and so on.

    There are plenty of reports of people mulching feet (literal multiple feet) of leaves into their lawns. After years of doing it, the lawns have no issue sucking up any amount of leaves being thrown at them.

  • BoatDrinksq5
    9 years ago

    Before leaf down next year you might want to add some of that compost over the yard (thinly) along with some cracked corn and/or sawdust type product (pellets or actual dust) to help get the microbes all in line and ready for leaf eating.

    Maybe a compost tea during the mulching period and a little before?

    A dry fall always seems to be killer for the digesting of leaves for me.

  • morpheuspa (6B/7A, E. PA)
    Original Author
    9 years ago

    Well, it's good I got that done yesterday.

    For one, last night's rain rendered the lawn completely leaf-free as it pushed the bits down.

    For two, we're getting six to eight inches of snow (!) on Wednesday into Thursday!!!11!!!1one!!!

  • danielj_2009
    9 years ago

    I'm in exactly the same boat as you, morph, being in northern NJ I guess our weather patterns are similar.

    Oh, dchall, I meant to thank you for the interesting post re the researcher in the 1800's. Neat stuff!

  • morpheuspa (6B/7A, E. PA)
    Original Author
    9 years ago

    Given that I'm in eastern PA, they should be similar! I'm charging everything chargeable just to be sure...