Organic Compostfrom THE GARDEN SPOT
by Mort Mather

Simply put, compost is the best soil amendment there is. It adds nutrients, improves soil texture, improves the soil’s ability to hold moisture and at the same time improves the soil’s ability to dry when it is too wet. Compost widens the acidity/alkalinity (pH) range within which plants will thrive. Properly done it will kill pathogens and weed seeds. It will turn smelly materials like fish scraps and manure into clean-smelling humus.

Composting is taking place in nature all the time. It is how the rich soils of our Great Plains were built. It takes place in our lawns if we leave the grass clippings and on forest floors. It is part of the cycle of life turning dead things into nutrients to feed the living. It is the process whereby organic materials are turned into humus.

You may have noticed a pile of leaves that seems to stay pretty much the same for years. Composting is going on here but only at the bottom of the pile where the leaves come in contact with the soil. Composting needs a combination of materials. The leaf pile also sheds water when it rains so that you may find the pile to be pretty dry. Composting needs to be moist but not soggy.

Most organic gardeners separate their kitchen scraps from other waste and add it to the compost pile. It cuts down on the waste stream and puts the valuable nutrients back in the soil where they belong. This practice causes some others to say, "How do you keep it from smelling?” The smell associated with garbage is due to anaerobic bacteria. Sometimes we will let our compost bucket hang around too long and we will get a little smell. That is due to the materials on the bottom ending up under too much compacted material so they get no air.

Meat will also get smelly. We put meat scraps in a plastic bag in the freezer. Sometimes I compost these as well. Sometimes they go to the dump. In the winter we don’t have a lot of vegetative material to add to the pile which means that birds and animals can pick through it. We don’t want to attract meat-eating animals. Sometimes in the summer I’m too busy to make sure meat scraps are well covered by other materials, so to the dump. Meat scraps also take longer to be decomposed, usually surviving several compost piles.

So, compost needs organic materials (more than one kind), water and air. There are a lot of ways to do it. Sheet composting is the easiest. You just throw whatever you have on the garden and turn it in. I have done this many times with manure mixed with sawdust, shavings or straw and sometimes straight manure. I spread it in the spring and turned it into the soil. Certified organic growers have to compost manure, by the way, or spread it 120 days before harvest.

Sheet composting is fine as long as there is a good supply of nitrogen. Manure is the usual supplier of nitrogen. If you spread just sawdust which is a material high in carbon, The soil microorganisms will be overworked for a while breaking down the material and crops may suffer from a lack of fertility. Some say the organic material has robed the soil nitrogen. It is more accurate to say “borrowed” as once the soil is back in balance it will benefit from the additional organic material that, for a time, caused an imbalance. Thus we have another consideration in making compost, the carbon nitrogen ration C:N.

The C:N ratio of sawdust is 400 to 1 while for rotted manure it is 20 to 1 and young sweet clover is 12 to 1. All of these materials once composted are pretty close to 50 to 1. I’m not going to go any further into C:N here other than to say you will have a better compost pile if your mix of materials includes some high nitrogen materials and some carbonaceous materials.

That’s all you really need to know. If you shred the materials, they will compost much faster. No surprise as you are exposing much more surface for the microorganisms to work on. The better you mix them, the faster they will work. If you put them in a bin with vertical sides through which air can flow, the pile will compost faster and be neater. If you are going to leave the pile through a rainy season, it is best to cover it so nutrients won’t leach away.

Here is an example. I have a bin I made nearly 30 years ago out of wire mesh and 1 by 3 redwood. It is 4 sides about 3.5 feet to the side and the same height. I screw the sides together with 2 screws to each corner. I can remove the screws and take the sides away to relocate the bin next to the pile and turn the pile back into the bin or start a new pile.

I generally start a pile with weeds or garden refuse, fairly coarse stuff. Then some leaves or grass clippings being mindful that if I make too thick a layer of these they may pack down and stop the flow or air. Then some more weeds, then an inch of soil, then some leaves or grass, some garbage collected from somewhere, some more topsoil, some fish scraps from the fish market, more weeds, etc. I may have been collecting materials for weeks or months. I’ve always got my eye out for some organic matter that I can pick up free and store easily. I mentioned fish scraps. Great fertilizer. Remember the Native Americans used to put a fish in each hill of corn? It can get pretty smelly and attract insects and animals if not incorporated into the pile. I collect these goodies when I have other materials handy and am otherwise ready to build the pile.

Dampen the materials as you build the pile. If there is a good C:N ration, the pile will get quite warm in a few days. When it cools turn it trying to get the outside closer to the inside of the pile. If you shredded the materials you will have finished compost in a couple of weeks, so they tell me. I’m pretty casual about the whole thing so I usually start a pile in the fall and finish it in the spring. Spread it and start another which usually just get incorporated into the fall pile.

Remember, this process is going to take place with or without you. To the extent you control it you will capture more nutrients for your garden and let less good stuff end up in a landfill or incinerated. Can there be a much more foolish waste of energy than to cart organic materials that are mostly water many miles to an incinerator to burn them?

© 2001, Mort Mather

Mort is a husband and father. He authored a book, Gardening For Independence and was named Environmentalist of the Year by Down East Magazine in 1987. He is a consultant for organizations. You can eat his organic produce at his son's southern Maine restaurant. His address is 802 Bald Hill Road, Wells, ME 04090.