Mulch vs compost

Differences. Pros cons of each.


Forgive me if this has already been asked….

To me, mulch is something that a person puts on top of the ground for several reasons, especially to help hold in moisture.  Over time this will help build soil.

Compost is browns and greens material that has turned into the next best thing to the soil.  It is actually better than soil as it has lots of nutrients.

I have pondered this question for almost 30 years.

There is no ultimate answer to it. It all depends on your local conditions.

Whatever makes best use of your organic material is best.

When you use your organic material for mulching, some of it will integrate with the soil while some of it will be emitted into the atmosphere. Dry and hot weather will cause more carbon to be emitted into the atmosphere, while wet and cool weather will cause more carbon to integrate with your soil.

By composting your organic matter, you reduce the surface area from which carbon can be lost to the atmosphere; however, during high-temperature composting, a lot of carbon goes up into the air.  With low temperature composting, you lose less to the air; however, since it takes longer, the end result is similar.

Moreover, if you use all your organic material for composting, you won't have anything to cover your soil, which again results in a loss of soil organic matter (SOM) into the atmosphere.

The way I ended up doing it after 30 years of trial and error is that I cover all my soil with mulch during the hot and dry season and only use whatever surplus I have for composting. During the cold and wet season, I don't have to cover my soil with mulch to conserve humidity.

When I have different materials for mulching, I use green mulch (grass, weeds, etc.) for a lower mulch, which I cover with a 2nd layer of brown mulch of shredded branches, etc. Thus, I can protect the green mulch from gassing off into the air by a brown upper mulch layer, which will take longer to disintegrate.

The third way, which makes even better use of your organic matter, is by passing your organic matter through the digestive track of farm animals and by using manure to feed your soil. However, if you use all your organic matter for feeding your animals, you may end up leaving your soil bare, which isn't ideal either.

So when I take the goat, pig, and chicken manure and pile it up with browns and greens, keeping moist and flipping it now and again =compost.

Taking the goat beans and piggy booms and mixing it with browns and greens and using as a top dressing= mulch

You kinda lost me with the “losing to atmosphere”. You mean like the wind blows my pile or If chickens scratch my compost down to scattered, dried weeds and leaves. Spread over an area of the yard it wasn’t intended for?

My yard is too steep for a mower(I’ve started building terraces) and covered with dandelion and plantains. I’ve been “hand mowing” and just putting the greens around my pumpkins and tomatoes. Then I add a layer of woodchips. That’s mulching then, correct?

You kinda lost me with the “losing to atmosphere”. You mean like the wind blows my pile or If chickens scratch my compost down to scattered, dried weeds and leaves. Spread over an area of the yard it wasn’t intended for?

No, organic matter consists mostly of carbon. When organic matter disintegrates, some of that carbon is emitted into the atmosphere as CO2 and some of it is integrated with the soil as humus. Humus consists mostly of carbon. The surplus carbon in the atmosphere that causes climate change is missing in the soil in the form of humus.  Non-organic industrial farming has resulted in the loss of humus (carbon) in the soil and an excess of carbon (CO2) in the atmosphere.

You can make the test yourself. Pile up a heap of grass in one corner of your land. After 5 years, there is almost nothing left of the heap. Most of it has gassed off into the air.

I guess I never thought about the where’s, why’s, and how’s, of smaller piles after time.
Thanks!

Maybe it's a matter of terminology. I'm in a relatively dry location, and this year it's a drought. In my system, much of my compostable material is too fibrous to be added "as is." So it goes in a composter and by next year, it will be partially composted, and a happy addition to the top of the soil. I consider "mulch" a protective layer (usually straw, sometimes wood chips) that I use as a top-dressing to keep the semi-composted material from drying out. The excess, dry protective mulch may be raked off prior to panting and reused; eventually it ends up on the soil too.

Or then there's the Charles Dowding style of gardening, where you use fully finished compost, and only compost, as your mulch. Apparently in the UK slugs are a huge problem, and it turns out that slugs don't find much to eat in finished compost so they won't proliferate in the garden if the whole surface is finished compost. And supposedly if you use uncomposted materials as mulch, you get much more slugs and they hide under it during the day, too.

On the other hand there are also slugs in North America, and Ruth Stout, speaking of mulching in Connecticut, said she really didn't see any direct relationship between mulching and slug problems.

Where I garden in the high desert there are no slugs and I use everything I can find as mulch, but I usually dig the compost in rather that leaving on the surface where it tends to go hydrophobic and look diminished and windblown and sad.

I do not see mulch and compost as mutually exclusive, as I often  use them in conjunction. Compost might be the ideal mulch if it is infinitely available, but I’ve never seen that situation. I generally use compost on top of the topsoil of a hugel, covered by a coarse carbon rich mulch. A benefit of mulch I haven’t seen mentioned is in protecting soil tilts, humus, nutrient, and organic matter levels from rain compaction, erosion, leaching, as well
as wind/hsun. Active decomposition from animals and microbes integrated into the process  can help make the mulch or leaf litter accumulated turn into excellent humus. In areas with high winds, I would use the coarsest woody debris I could find, as long as it is short enough that it can maintain soil contact. If that were not available, I’d use rocks as mulch for condensation.

On the other hand there are also slugs in North America, and Ruth Stout, speaking of mulching in Connecticut, said she really didn't see any direct relationship between mulching and slug problems.

There definitely is a relationship between mulching and slugs. Mulch provides both habitat and food for slugs, which makes it harder to contain slugs.  Still, bare-soil cultivation without mulching isn't an option for me. That means one has to find out strategies for containing slugs. That starts by observation. Go out at night with a torch and see where the slugs are. Then figure out what to do about it.

I live in an arid hot climate with mild winters. People think that slugs are only a problem in cold climates. That's not true because in an arid climate you have to irrigate if you want to grow food. That means the slugs too get food even during the dry season. That also means that slugs can be worse in an hot arid climate than in a wet cold climate because the slugs can proliferate 12 months a year on irrigated land in a dry climate while they are killed off during the winter months in a cold climate.

When I started growing in an arid hot climate, I had a slug problem worse than what I had known from cold climates. As I kept on, I found that the slugs almost disappeared from land I had cultivated for more than 10 years because the yellow clay soil had turned into a humus-rich black soil due to enriching the soil with compost, mulch and manure year after year. One other thing I noticed is that the slug infestation was particularly bad near some perennials like horse radish and sugar cane, which provided both food and habitat for the slugs all year round. I will never plant horse radish and sugar cane anywhere near my vegetable plots again.  

As for other vegetables, salads or fruits, they need to be removed as soon as it's harvesting time or the slugs will proliferate. It's also a good idea to move a chicken tractor onto the harvested plot. The chickens will reduce the slug population.

Erin Conte wrote:Differences. Pros cons of each.


Forgive me if this has already been asked….

------------------	COMPOST	MULCH
MATERIAL	Always made from decomposed organic residues; usually diverse/mixed origin of materials	Not necessarily organic, could be rocks, or plastic even
CONSISTENCY	Usually smaller, somewhat fine material, gummier, and it more rapidly integrates into soil	Homogenous material; usually larger or chunkier, and slower to break down;  inorganics will not break down
PRIMARY FUNCTION	Provides well-rounded soil nutrition for plant health	Provides a covering for top layer of soil
OTHER FUNCTIONS	Increases soil food web diversity, soil structure, water retention; and all sorts of other good soil health benefits	Inhibits weeds; may prevent compaction; temperature moderation; aesthetics; may prevent runoff; if woody: increases fungal dominance of soil, can grow mushrooms; if organic, it will eventually become compost
APPLICATION	As top or side dressing, or mixed into planting medium	Always on top, not mixed in
AVAILABILITY	Usually more time/labor/cost intensive to obtain fine material (e.g. Thermo-composting of food waste and carbonaceous materials in a month; or slow compost in a year);  Lesser supply, higher demand	Usually less expensive by volume due to less material processing and homogenous nature (e.g. Fresh wood chips, cut straw, paper)
CONS	Expense, time, or expertise to obtain enough of it; pile can go anaerobic or attract nibblers if not taken care of properly; weeds easily grow in compost	Can over-apply mulch which deprives soil of oxygen; can kill trees or plants if applied too closely to trunk/stem; pretty Big Box store mulch is costly; Chipdrop free arborist chips may have urban gunk; takes lots of energy to evenly spread (petrol tractor, human shovel and wheelbarrow or bucket, or chicken scratching/spreading)

George,
That's a pretty nice summary of mulch and compost. I'm not sure where it leaves "chop and drop", which I consider a form of mulching. I do quite a bit of messy gardening: composting in situ, letting the slugs and other digesters do the work for me. I don't grow many annuals at present, soa healthy slug population isn't too much of an issue.  Hopefully I am building up the slug predfator population too!

Yes, Nancy's "messy gardening" describes my process as well. What I call "sheet composting" is really dumping a wheel barrow of fresh horse manure at the tree drip-line then rake it to about 6". When I get time, I dump a brown layer on top then rake that to about 6". Then another green, then another brown. All in situ around the drip-lines of tree clusters. Sometimes the horse manure remains on top for a while: is that mulch? It is certainly not "compost." Sometimes the woody debris, shredded wet paper or cardboard remain on top for a while: maybe that's mulch. Sometimes my neighbor drops off leaves which go on top for a few days. Sometimes animal bedding goes on top for a while. That's the reality and like so much in gardening and life, it doesn't exactly conform to tidy labels. Maybe the verb for what the messy gardener actually does could be called, compulching:
"The intuitive and opportunistic practice of compulching helps build humus, conserve water, and supports plant health"

There is certainly overlap between mulch and compost, and many people have given very good explanations. I will link to a post I made from another question regarding woodchips as mulch.

https://permies.com/t/162215/Wood-chip-mulch-season#1271772

Amy Gardener wrote:Maybe the verb for what the messy gardener actually does could be called, compulching:
"The intuitive and opportunistic practice of compulching helps build humus, conserve water, and supports plant health"

Hahaha LOVE this!

Wonderful thread

I started a new mulch experiment today.  I have a lot of ponderosa pines, mixed with oaks.  The previous owner, (and most of the neighborhood) raked and burned, leaving me a lot of piles of mixed pine cones, needles and oak leaves.

I’ve been gathering pine cones and using them as mulch in areas where there has been planting.  I am hoping I can make perimeters around various areas with rocks, then fill with pine cones to a depth of 8-12 inches.  I hope they make a nice insulating mulch, moderating temperature fluctuations and decreasing moisture loss.

I think in the good old days of the Holocene, they got a nice snow cover that insulated the soil.  Might or might not happen here in the Anthropocene.  I don’t want to burn the pine cones and needles as refuse.  

I’m using the raked up pine needles and oak leaves in with horse manure and urine soaked shavings for compost…. If they’ll “go”.  It seems to be warming up inside, but I can’t find my compost thermometer, and I am getting another load of manure every day.  When the stack gets big enough, I will start a new one.

And, I am using the compost pile itself as mulch…. having chosen a location adjacent to my garden where I will be planting black berries, grapes and apple trees.  Their roots will have access to the soil beneath the compost pile.

Just have to see what happens 😊

Dr. Redhawk, please add your wisdom and experience...I thought I had a grip on the difference but, after reading all of these points of view, I be a wee bit confused. (which is a normal state of being for me)...All I can attest to is the 82647 cherry tomato seeds that TOTALLY scoffed at my "hot composting" attempts last Fall...Those buggers have sprouted happily ALL OVER my yard and every place I used what I thought was "finished" compost...Mother Nature is just screwing with me...Tis good to be humble;...Mother Nature is schooling me for sure.

Ben Zumeta wrote:I do not see mulch and compost as mutually exclusive, as I often  use them in conjunction. Compost might be the ideal mulch if it is infinitely available, but I’ve never seen that situation. I generally use compost on top of the topsoil of a hugel, covered by a coarse carbon rich mulch. A benefit of mulch I haven’t seen mentioned is in protecting soil tilts, humus, nutrient, and organic matter levels from rain compaction, erosion, leaching, as well
as wind/hsun. Active decomposition from animals and microbes integrated into the process  can help make the mulch or leaf litter accumulated turn into excellent humus. In areas with high winds, I would use the coarsest woody debris I could find, as long as it is short enough that it can maintain soil contact. If that were not available, I’d use rocks as mulch for condensation.

I use whatever I can so also not mutually exclusive
I tend to put cardboard over the hills created by winter compost heaps along tree drip lines
That helps stop erosion.
I also plant non invasive weeds on tye sides of the hills until carrots get going
I find carrots are the best for stopping hill erosion plus they are biennial
Carrots get planted in a thin layer of poultry manure and soil / composted compost, and I also use rocks and anything else to hold down cardboard until plants get growing on it

get garbage cans, or plastic ones, drill 3 one inch holes in bottom of trash cans.  Load up with 100% greens, put lid on and park in sun.  Easy composting.

Michael Moreken wrote:get garbage cans, or plastic ones, drill 3 one inch holes in bottom of trash cans.  Load up with 100% greens, put lid on and park in sun.  Easy composting.

I've seen people compost with garbage cans with holes drilled all over the place, but never heard of this method.  What keeps it from going anaerobic?