Compost vs Mulch

I have mentioned compost in several articles in this the North Columbia Monthly over the past couple of years, notably Composing Compost in June 2019, and Laws of Nature, September 2020.  So it is gratifying to get some positive feedback from readers about their experiences.  Recently, J. Foster Fanning, another regular NC Monthly author, sent a picture and a story about raking up the leaves and needles on his Riverhome lawn and leaving them as compost piles rather than burning them. 

He wrote: “At some point in the spring I found a big onion and a few potatoes in my basement cold storage spoiling and sprouting. “Well, what the heck,” I thought and hauled them out to the newly piled compost area. I tucked those remnants of non-eaten veggies under the bottom edge of the pile and soon they were covered over by more material being added. I thought nothing of it until a month or so later I noted the slender rich green of onion shoots poking up out of the litter. “Cool!”… today, after a morning of 19*F I found myself working near that compost pile and, well I dug into it and discovered what I sent along to you as an image with this note. Ha! I’m a gardener once again.”

Note that Foster kept the pile wet while watering his lawn.  Also note that although onions and potatoes are root crops, he did not actually bury them in dirt, just compost.  Years ago I did something similar. I had a bag of sprouting potatoes and a truckload of rotten hay.  I spread the potatoes in rows on my uncut field and covered them with hay.  They sprouted and grew right through the hay.  In the Fall I lifted off the hay and had hundreds of pounds of potatoes to harvest without any digging!  I just lifted the rotten hay.  I thought this was very clever but heard in a podcast recently that a farmer’s family had been doing that for generations. (A word of caution: on a couple days while I was laying down the rotten hay I got sick and had to stay in bed.  It finally dawned on me that the white clouds of mold coming off the hay were making me sick.  Use wet hay.)

In my September article I mentioned the recommended temperatures for compost, 130° to kill bugs and 160° to kill weed seeds.  I want to back off from those temperature recommendations.  Truthfully, microorganisms like pretty much the same temperatures we do, between 70° and 80° F.  So you get them in compost no matter what.  Sure there are a lot of bugs in compost.  I consider that a good thing, not something to be reduced.  And yes the seeds that survive can sprout in unexpected places but encouraging temperatures up to 160° to kill them along with the worms and bugs is not a good idea in my opinion. Those “bugs” in the compost do a lot of the work.  My compost pile has legions of sow bugs, more officially known as woodlice, and unofficially known as roll-up bugs and many other names.  “Woodlice, like earthworms, are generally considered beneficial in gardens for their role in controlling pests, producing compost and overturning the soil” (Wikipedia) My compost also has lots of red earthworms.  Those tell me that it is really alive.

As for the seeds; I prepared a soil mix that included compost for a new garden bed this summer.  A lot of squash plants sprang up in it.  We let one grow and it eventually covered about 100 square feet of garden and produced 6 huge green squash shaped like pumpkins.  They taste great and keep well.  We are still not sure what to call them. 

My garden soil mix is not much different from the mulch mix I use around the vineyard.  There is probably more bark and shredded prunings in the mulch, but it still has compost, biochar, spent grape pressings and aged manure.  There are reasons for each of these components and a reason to put them down as mulch rather than waiting until the compost pile is through working and digging the compost into the garden bed.  Let me explain.

The biggest component of good soil and good compost is cellulose; we are talking shredded prunings, straw, leaves etc.  It contains a lot of carbon, hydrogen and oxygen, and not much else.  Most microbes will not digest it but mycelia (fungi) love it.  Other microbes in turn eat the fungi and the whole cycle of soil renewal begins.

But it is just a beginning.  If you look carefully at the structure of chlorophyll, the stuff that lets green plants convert sunlight to sugar and other useful things, you will find a lot of nitrogen.  When I was a kid you could buy a couple pounds of ammonium nitrate at the local feed store.  We used it for making our own gun powder.  Those days are gone but commercial farmers still use it extensively to add nitrogen.  Unfortunately the straight chemical kills microbes and pollutes the water. For really active compost, you need to add nitrogen that comes naturally from urine and manure.  Some of it can be “green manure” like lawn clippings, grape must and dying tomato plants.  They have chlorophyll and therefore, nitrogen.

I add 10% biochar. It absorbs a lot of moisture which provides a shelter for microbes since the water does not leach away.  If you have ever gotten a batch of biochar wet, you can attest that the water makes it really heavy and that letting it sit around does not really dry it. Biochar also is valuable because, as pure carbon it, does not get digested by microbes and can sequester carbon out of the atmosphere for hundreds of years. 

So am I leaving out important stuff?  Definitely! Soil is not a Petri dish. Knowing the chemicals is a way to understand some of the elements, but all living matter contains the magnesium, phosphorus, calcium and other things important to growth.  The more variety you can throw into a compost pile, the better off it is.  Rudolf Steiner, a compost pioneer and father of Biodynamic Farming, advised layers of leaves, wood, green manure and many special inoculants to get compost going.  Good compost is aerobic.  You want it to be both moist and have air circulating. You can mix in a portion of any finished compost to provide a start for the microbes, insects and millions of other tiny life forms that do the real composting work.

To my way of thinking, compost is just a component of mulch.  Fungi are composed of thousands of strands of mycelium, the vegetative part of a fungus.  When you move compost, you break these filaments and set back its development.  By letting these mycelia develop in place as mulch you let them continue to break down cellulose and feed the whole soil biome, but they also link to plant roots and supply nutrients in exchange for sugar.  You want them to grow once and keep growing.  When I see mushrooms in my vineyard, I know it is fertile.  You may think that is mulching is a rotten way to finish the year, but you will love it in the Spring.