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21 April 2011

How Mulch Is Too Mulch?

A fresh load of compost/mulch was delivered at The Learning Garden and I got to run my fingers through this stuff right off the truck!  Gardeners love the way this stuff smells.  Mere humans often dislike it. Compost can be a mulch - it is not necessarily 'mulch' but can be used as one. 

Jeanne Kuntz is preparing a post for over at Mar Vista Patch using a clever play on the word 'mulch' (Mulch to be Grateful For) so, I couldn't resist getting a little punny here.

A bit of Q & A between myself and Jeanne follows:  

JK:  How does mulch condition the soil?

When mulch is laid on soil, it stops sun rays from hitting the soil and baking the top layer.  The mulch also prevents water evaporation by breaking the water column in the soil.  (Water molecules stick together and 'pull' water through the soil.  In evaporation, one molecule evaporating causes the next molecule to move towards the surface to evaporated.  When the soil medium is no longer homogeneous, i.e. mulch on top has a different consistency than the soil, the water column is broken and evaporation of below- surface water is stopped.) 

But mulch's big contribution to the soil is that it provides food for a whole host of critters in the soil that break the mulch down.  Mulch feeds the micro and macro life of the soil and THAT increases soil's fertility.  One of the main critters chowing down on the mulch is the earthworm.  The earthworm makes a tunnel from below to the surface to chow at the mulch banquet, grabbing a plateful, which the earthworm carries below the surface, creating yet another tunnel.  Many earthworms = many tunnels - painlessly, effortlessly creating the same delicious soil tilth we used to double dig, breaking out back, to achieve.  I've got garden beds that have never been dug and you can easily put your hand into them as though I had spent days out there sweating by double digging.  

What is the main difference between the various types of mulch?

Well, 'mulch' is technically anything you put on the surface of the soil to protect it.  That includes rocks and plastic and other materials.  We are, I think, talking about 'organic mulches' - the ones that used to be plant material (leaves, wood chips, compost or even bagged materials like 'organic compost' or 'planters mix') and they have differing effects on the soil.  If it is broken down to the point of being more black than not, it does what I was saying above.  The differing mulches will contribute slightly different nutrients to the soil, but, in the main, there isn't much difference in their action - some will break down more slowly and some more quickly, but they will all break down and feed your soil biota.

JK:  Is there are difference between how one uses mulch for edibles vs ornamental plantings?

I wouldn't think so.  I think mulch in flower borders is much more attractive than dirt - it saves water and cuts down on the need of fertilizers.  I add mulch about three inches deep in spring and in fall and that's all I add to my garden, ornamental or veggie. 

JK:  Is the mulch you have at The Learning Garden at Venice High School available to the public?
The Learning Garden's mulch is from Los Angeles Bureau of Sanitation and is delivered to us because we make it available to the community at large.We are open Wednesday through Sunday, from about 10 to about 5:00 - I say 'about' because I'm there alone and if I have to pick something up from the hardware store or go to lunch, that means we're closed for that amount of time.   

And by the way The Beautiful Food Garden Blog turns three today!  Thank all of you for your support!


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