Mulch, Compost and Soil Chemistry Questions

Factual Questions
1

I have become the compost Queen, I’m so into it I can’t tell you. So much fun!

Anyway, I know all the “Fresh mix” answers re: carbon/nitrogen. I’ve got that down pretty good, and I’m making some truly awesome (looking, anyway, I haven’trun any soil tests on the actual composition of it) compost.

But here’s the situation: I have a couple of Earth Machine composters, which work extremely well. Get the right mix of goodies in there and you have rich, dark, delicious smelling compost very quickly.

However, it always needs to be sifted, because a fair percentage of the carbon stuff (twigs and leaves) does not finish composting. And that’s fine, I just separate the earth-like fine finished stuff for immediate use, and cycle the semi-composted twigs and leaves back into the next fresh batch, and I also take some of it to use as mulch.

So here are my questions, and forgive me if they seem stupid, but I want to be absolutely certain:

Do the now-softened, damp, half-decomposed leaves and twigs still count against the carbon content of my fresh mix, or do I always have to add more dry, crackly, undecomposed brown stuff in the same ratio to the green, wet stuff? I have been adding relatively small amounts of the unfinished compost (hereinafter referred to as UC) to completely fresh new batches made up of about the right C/N ratio. Could I take a big pile of the UC, and mix it with the green stuff as though it were fresh and get teh same result? Or is the fact that it has already been cooking for awhile change it somehow? I guess my brain is sort of stuck on the whole wet/dry aspect of it.

And along those same lines, if I have green matter that has been sitting in the sun for a week or two and has wilted and turned half brown, but the brown parts are still pliable, is it carbon or nitrogen.

In other words…is it the color that indicates true conversion to carbon, or is it the moisture level, and if moisture is somehow returned to the item in question, as in the UC, does that reverse or otherwise affect the carbon level? And if it does have an affect, does letting the UC dry out again return the carbon-ness of it?

And as you can tell, I have a big hole in my brain where chemistry and biology go. (Or is it biochemistry?)

A few more questions:

If I use the UC as mulch, will it leech nitrogen from the soil because its still in the process of decomposing?

How long does compost have to be part of the soil before it is considered soil itself? What I mean is, no one advises planting anything in pure compost (even though seeds in my compost are sprouting all the time, and the earthworms seem to think its pretty soil-y), but if you keep doing what I’ve been doing over time, which is removing some of the existing soil I have and replacing it with compost (I can’t just add, it won’t all fit!), wouldn’t my soil eventually become pure compost? But since it would be years of doing this, isn’t the compost that was added the first year different 5 years later?

And finally, regarding my stupid soil…I live in the San Fernando Valley, which is mostply heavy clay. So when I bought my house in North Hollywood, I just assumed that my soil was naturally clay, even though it was extremely friable and drained so fast it was kinda weird. I attributed the texture to my awesome gardner, who regularly breaks up my soil and weeds thoroughly, and also to his adding a good few inches of compost as mulch every year.

Well, that’s what you get for assuming. I actually live in a part of the valley that is near some former body of water, and my horticulturist friend pointed out the obvious: my soil is actually very sandy. Hrmph. Which explains a great deal. Duh.

Now, I know that the cure for both clay and sand is to do exactly what I’m doing: compost compost compost. BUT… since clay is the mineral-carrying part of the soil, wouldn’t it be a little helpful for me to add a little bit? Not much, because I know how evil it is, but a little, just for the mineral properties? Or am I really better off just adding compost? And it just seems that compost and sand both drain a little TOO well, we could do with a little of the water-holding ability of clay.

And finally: why do all the compost articles automatically tell you to sterilize compost that is going to be used in pots? Why is it great to be full of life in teh ground, but evil in a pot? Don’t you suck all the goodness out of it by cooking it?

Thank you, my Doper chemists and horticulturists.

Oh, one last thing: is it good or bad to spray compost tea directly on the surface of plants? I have an organic fertilizer that is sprayed directly on plants and I was thinking that my compost tea might be used just the same.

2

I can answer this

Yes it will, though if it is still in big chunks it will do it slowly–while interfering in any digging or cultivating you do. Some stuff seems to take forever to decompose–when you recognize that, you can just throw it away.
The rest is WAGs: I believe the UC browns, twigs and dry leaves, count as carbon, tho a little other nutrients may have washed into them with the moisture.

I don’t know about green-turning-brown.

Oh, another one I know: Over time, compost added to soil or used to replace it decomposes, leaving the mineral soil. This does take (a couple of?) years. Natural healthy soils stay crumbly because the plants grow in the good soil, and drop their leaves to contribute to the soil again, with the soil critters (worms, etc) coming up to eat and pull down the leaf matter into the soil.

I believe the carbon stuff doesn’t decompose or dissolve away as easily as the nitrate stuff does.

Before adding clay, you can check out your soil for content. Get a large testtube or tall drinking glass, or equivalent. Grab a representative sample of your soil, a fistful or two. Put it in the glass with water & shake it up plenty. Put it down and wait. The organics (compost) will tend to float, esp. if you started with dry soil. The pebbles will be at the bottom, the sand will settle down right away on top, the silt-sized stuff next, the clay will stay in the water making it look muddy until tomorrow. Then by looking, or carefully draining the water and spreading out the tube contents, you will see how much of each component is in there.

I’d agree with having some clay in there to provide minerals and hold moisture. Another test is to take a fistful of your soil and briefly squeeze it and release. Sand will fall apart, clay will make a casting of the inside of your fist and will squish if you push it with your finger, and the best soil will make a casting, but when you nudge it, it will tend to break apart.

You can try this with different soils, or dig a comparison sample from down under your amended soil, just to familiarize yourself all this.

And I tried baking compost in my oven to sterilize it, and boy did it stink up the house! So I’ve never tried it a second time.

3

Thanks for the tips. And my soil will make a casting, but it will fall apart completely and instantly if you look at it funny. I think it could definitely use some clay or more time.

I have to say that there is something insanely satisfying about making compost. I don’t know why it is, but it is. I am dumpster-diving on trash day in hegreen cans just to get enough stuff to make compost. I’m going to have so much I’m going to have to start selling it!

I would also like a way to check the chemical composition of my compost. I’ve read about commercially available composts being pretty crappy nutritionally because they tend to be made from things like wood chips exclusively. My composts has everything under the sun in it, including large amounts of goodies from my fridge and and cupboard, since I always buy too much food (terrible American habit…abundance breeds waste). I’m assuming that means my compost is fabulous, but I’m not sure.

I’ve also decided to invest in cheap electric chipper/shredder, which I’m going to post about for opinions. I’ve been hacking my compost matericals into bits manually and it’s killing me already. the exercise is fine, it’s the time I just can’t spare anymore.

I’m still wonding, if anyone has the answers to my questions…