Compost as Mulch

http://www.bearpathfarm.com/compost-as-mulch.html


I'd be worried that the compost would just dry in my southern Californian heat and would turn into dust.

Currently I lay down compost and then cover it with tree trimming mulch.

Would love to figure out how to mulch and compost on the ground where I am planning to plant.

Ideas and opinions about the article (and anything else) would be cool!

Nolan Robert wrote:I'd be worried that the compost would just dry in my southern Californian heat and would turn into dust

Me too. I see my compost as being alive, and needing a bit of protection from sun, rain etc.
I also want the worms to pull it into the soil, and the microbes to do their thing with it.
If I had it as a mulch, the worms would only be able to get at the bottom layer since the top would be too hot/dry/light for them.
I don't know about the microbes, but I suspect they'd feel the same

I use massive amounts of tree mulch in the perennial areas,
and while the fruit trees get a bit of compost if they're lucky, most of it goes on the vegetable garden.
The annual garden gets lower carbon mulches like pea straw and dried weeds so I don't get into nitrogen tie-up issues by digging in tree mulch.

Nolan Robert wrote:Ideas and opinions about the article

It may well be true that mulching with compost is awesomer nutritionally-but I can't imagine many people have enough compost to use it like that!

Well, bear path farm has a reason to encourage us to mulch with compost, they sell compost.

I once worked at a farm that was located at a compost-making facility. We had access to all the compost we wanted to use and we used it! We mulched with it, top dressed with it, layered new beds with it. In the long run I wouldn't recommend it. Once or twice, sure, but compost is not soil. Eventually the organic matter is too much and it needs to be mixed with soil. I've noticed the same thing in the lovely garden of some friends who have been mulching with composted animal bedding for many years. It's lovely to have the nutrients and organic material in there but after a while there's not enough clay and silt in there.

My knee-jerk reaction is "Go for it!".

My second thought is "Hmm, it depends."

If you have a healthy microherd (bacteria, fungi, insects, worms, etc.) in your soil, they should gobble up all of that organic material and incorporate it into the soil.

How fast they gobble would depend on lots of factors. For instance:

1) Available moisture: The herd likes a drink with whatever it's eating. If you have to inject a lot of water (and labor) into the system to keep it moving in the desired direction, that's not good.
2) Food balance: All the microcritters don't eat the same thing. Supplementing the compost layers with other stuff to keep the whole herd happy could tip the cost-benefit ratio too far into the 'cost' side.
3) Plantings: The plants among the mulch will have an influence as well. Shade will help with keeping the moisture around. Accumulators will help keep the herd fed. Cover cropping and chop-n-drop on top of the compost would combine both functions.

Is there a reason that you don't want to continue as you have been with the tree trimmings on top of the compost?

Have you had a soil test done? What's the worm population like? Depending on your percentage of organic matter, dumping a few inches of compost on your soil could have a big impact on the health of the soil food web and whatever you are growing.

As for not having enough clay/silt, I think you would have to put down several hundred tons per acre for a number of years to have any detrimental effect.

Thank you guys for the good and timely thread. Ive been layering and mulching with compost for several years without incorporating it into the soil and am starting to wonder if my results couldnt be improved by mixing in more of the native clay/loam soil. Iam on a good slope with no drainage problems.

Leaves + coffee grounds are my compost ingredients and create enough to make it the easiest source of mulch. I do notice the active and alive compost gets instantly dried unless its piled several inches thick and then its just the bottom inches that stays moist. Getting some wood chips/tree mulch is on the to do list..

Perhaps you could expand or point me in the direction of discussions on growing in pure organic soils and/or possible benefits of mixing in the native soils?

Frank Brentwood wrote:My knee-jerk reaction is "Go for it!".

My second thought is "Hmm, it depends."

If you have a healthy microherd (bacteria, fungi, insects, worms, etc.) in your soil, they should gobble up all of that organic material and incorporate it into the soil.

How fast they gobble would depend on lots of factors. For instance:

1) Available moisture: The herd likes a drink with whatever it's eating. If you have to inject a lot of water (and labor) into the system to keep it moving in the desired direction, that's not good.
2) Food balance: All the microcritters don't eat the same thing. Supplementing the compost layers with other stuff to keep the whole herd happy could tip the cost-benefit ratio too far into the 'cost' side.
3) Plantings: The plants among the mulch will have an influence as well. Shade will help with keeping the moisture around. Accumulators will help keep the herd fed. Cover cropping and chop-n-drop on top of the compost would combine both functions.

Is there a reason that you don't want to continue as you have been with the tree trimmings on top of the compost?

Have you had a soil test done? What's the worm population like? Depending on your percentage of organic matter, dumping a few inches of compost on your soil could have a big impact on the health of the soil food web and whatever you are growing.

As for not having enough clay/silt, I think you would have to put down several hundred tons per acre for a number of years to have any detrimental effect.

I haven't had a test done yet, and I have absolutely zero worms. I have very dry, non absorbent sandy soil.

Maybe I could compost over a garden area by laying nitrogen down and covering it with carbon, lay down chop and drop, cover it with nitrogenous material, and cover that up again with carbon material to keep in the moisture? It would be mulch and also be decomposing and when it eventually becomes compost than I can start over again in the same area?

It's so dry here year round that I don't think the microbial populations are high enough to decompose chop and drop/mulch on their own, so I feel like it might be more useful to apply the mulch when it has already been broken down and composted. Otherwise the mulch just oxidizes when it's left alone on the soil surface. Just turns grey.

I don't have any reason really for changing the way I do it, just exploring different possibilities. It's hard to haul in all the tree trimmings and also I'm not getting the mulch from what I grow, so I'm trying to "close the circle" if you get my meaning. I'd like to find the most efficient way of feeding the micro organisms in the soil and increasing the soil health. I know that covering the surface is an extremely important part of this.

Nolan Robert wrote:I haven't had a test done yet, and I have absolutely zero worms. I have very dry, non absorbent sandy soil.

DIY Soil Tests

Go to this link and scroll down. Look for the descriptions of how to do a "Soil Structure Test" and a "Soil Percolation Test". These are two free tests you can do yourself and can give you a good amount of information on your soil. (Yes, it is a lawn care forum. Good advice is good advice, whatever the source.) Zero worms indicates a pretty poor herd health. Unless it is terribly compacted, sandy soil generally wouldn't be "non absorbent". Water tends to flow through sandy soil quickly, too quickly to do the soil or the plants much good. The Soil Structure Test will give you a better picture of what's going on. If you have a sand/clay mix, it could be hardened to the point that water runs off. In either case, more organic matter in the soil will help.

As for more formal testing through a lab or county extension office, those cost money and their recommendations (at least in my limited experience) are hit-and-miss. Perhaps someone with more experience or knowledge could recommend something?

Nolan Robert wrote:Maybe I could compost over a garden area by laying nitrogen down and covering it with carbon, lay down chop and drop, cover it with nitrogenous material, and cover that up again with carbon material to keep in the moisture? It would be mulch and also be decomposing and when it eventually becomes compost than I can start over again in the same area?

It's so dry here year round that I don't think the microbial populations are high enough to decompose chop and drop/mulch on their own, so I feel like it might be more useful to apply the mulch when it has already been broken down and composted. Otherwise the mulch just oxidizes when it's left alone on the soil surface. Just turns grey.

I don't have any reason really for changing the way I do it, just exploring different possibilities. It's hard to haul in all the tree trimmings and also I'm not getting the mulch from what I grow, so I'm trying to "close the circle" if you get my meaning. I'd like to find the most efficient way of feeding the micro organisms in the soil and increasing the soil health. I know that covering the surface is an extremely important part of this.

Anything you lay down will help with the moisture levels by reducing water lost to evaporation, but the more I think about it the more I think that applying finished compost may not give you the best results. If your soil food web is lacking in "critters", putting down compost may not feed them as well as putting down something a bit less "digested". Of course, my philosophy is that unless you are putting down something toxic, it is all good in the end. Your thoughts on putting down layers sound reasonable enough to me, but I'm really just starting my own journey through the soil improvement jungle.

One thing that has been suggested to me several times that might help you is to use compost tea. If your soil food web is lacking, go ahead with your plans to put down whatever kind of covering you can on the ground. Spraying with actively aerated compost tea should give your soil biology a big shot in the arm. If you do it after each layer of covering, the layers should hold some of the moisture for a longer time and give the herd a chance to build up and digest whatever you are putting down.

Another thing that pops into my head: Several people on these forums have mentioned digging holes or pits that they then fill with leaves, manure, wood chips, twigs & branches, etc.. Being deeper and composed of more organic matter, they act like a mini-hugel and hold water for extended periods of time. I even think I remember someone in Southern California mentioning that his were still moist after two months without rain or watering. It seems like that might be an idea worth trying if the digging is within your abilities.

Hope this helps and doesn't just muddy the picture.

How odd you should post this.... I made compost using 3 year old tree trimmings, and the trimmings are still pretty evident. I thought they'd break down quicker. I call it mulchpost. Seems to work!

The most interesting part of my garden right now, in my opinion, is the small plot where I have laid down a bunch of dead cuttings and trimmings from comfrey and various other plants. Occasionally, I will also throw in some finished compost on top.

I keep adding nitrogenous material like kitchen waste and plant trimmings, adding more when the previous layer oxidizes. The ground underneath this "mulch" is very dark and now appears to have a higher organic matter content. It also retains moisture much much better than other parts of the yard.

It's like a constantly decomposing (I think/hope) mulch. I recently planted clover seeds in the soil before covering them up with the "mulch" again.

Main problem will, once again, be the brittleness of my area and thus the lack of microorganisms feeding on the plant litter and decomposing it. Maybe compost tea is the answer, or urine, or continual toppings of finished compost.

Haven't figured that one out yet...

I know that in healthy grasslands, ruminant manure is "placed" on top of plant litter on the soil, and microbes live in the guts of the herbivores. This ends up composting, so I guess the floor of grasslands and forests are big, slowly decomposing compost piles.

(sort of like the back to eden garden, how it performs better when it has chicken manure placed on top of it. When it's just the wood chips/mulch some people have trouble with it breaking down and I think it might be because there is a lack of... nitrogen? Microbe food? Microbes themselves?

I'm not quite sure, but Joel Salatin's composting system comes to mind, except out in a garden plot acting as a mulch while it decomposes, as opposed to being in a barn and then spread out on pastures)