Last month we looked at the limitations of poor quality compost, but don’t think for a minute that compost is something to be avoided. Composting is a natural process that happens all by itself without our intervention. But, like many other things in nature, we can manage the process for our benefit.
Although composting happens on its own, not every living thing that dies gets composted. One of the reasons we make compost is that, without our intervention, much valuable plant material is lost through oxidation. When plants grow up and are left to stand after they die, a great deal of nitrogen and carbon evaporates directly into the atmosphere. The nutrient value of the dry stalks of annual crops standing in the spring is a good bit less than the same mature plants the fall before.
This is one of the reasons why well-managed grazing by livestock builds soil a lot faster than land left fallow for numerous years. The manure left behind is only one reason. An equal or greater factor is the trampling of livestock pushing plant residues down against the soil where they can be microbially digested instead of oxidizing back into the atmosphere.
Furthermore, composting helps us to concentrate plant nutrition. When organic waste is accumulated in an area, such as when cattle are fed all winter in a barnyard, composting will reduce the volume of material to be handled. We can then spread the compost in our gardens.
When compost systems are designed to reach a sufficient temperature, above 140° F (60° C), weed seeds and plant diseases are destroyed. Another reason to compost is that the very best composts, such as commercially made humus compost or the end product of a Johnson-Su bioreactor, are very helpful biological inoculants for dysfunctional soil.
Composting can be very simple or very complicated. There are good reasons for some of the more complicated processes, but if simple is all you have time for, that is still very good.
The simplest method of composting is known as the static pile. This method relies on time rather than work. To build
a static pile, simply pile up raw material in a place where it won’t need to be disturbed for two or three years.
To get the best results from a static pile, try to mix coarse and fine material as well as high-carbon and lower-carbon material in equal proportions. The idea is to have some airflow. You don’t want to use all fine material that packs together and becomes anaerobic. Using only coarse material will leave too much airflow and won’t hold enough moisture to facilitate composting.
Also if the nitrogen-carbon ratio is too high, such as in a pile of lush green material, there is a lot of nutrient loss to the atmosphere. If the nitrogen-carbon ratio is too low, such as all wood chips or straw-like material, there is not enough nitrogen to support the bacteria and fungi needed to compost. It will take a very long time to break down.
By paying a little more attention to detail, you can incorporate some features that will speed up the composting process. If you have access to corn or sunflower stalks, you can use biodegradable twine to tie them together in bunches approximately 6 inches (15 cm) in diameter. Place bunches vertically in the midst of your pile, 12-16 inches apart, to facilitate better airflow to the bottom of the pile.
Using wire mesh to create a circle at the edge of your pile creates more consistent composting and, especially at a smaller scale, allows you to hold more material in a smaller area. Wood pallets tied together can also be used for this purpose. The downside to using pallets is that the bottom edge often rots away by the time the compost is ready for use, leaving loose nails in the residue.
Any edge to a static compost pile should be permeable. Plywood, solid metal panels, or concrete blocks stacked with open cores up restrict air flow, making them poor options. Concrete blocks with open cores horizontal to the ground can make excellent walls.
To do this, use blocks for three sides, with an easy-to-remove front side. This could be as simple as branches reaching from a block core on the left to the block core on the right. Or, you might use chicken wire between two tomato stakes. The point is, you want easy access.
While static-pile composting is simple, it will most likely not generate the level of heat necessary to kill weed seeds. In fact, static compost piles will likely need to be weeded multiple times between beginning and finish to avoid generating more weed seed.
To take composting to the next level and kill off all viable seeds and disease organisms, compost will need to be turned multiple times. On a commercial scale, compost turners are large machines, either pulled by a tractor or self-propelled. These are used to turn compost windrows every couple days at the beginning of the process and usually less frequently as the compost finishes.
When compost is created by these commercial machines or by a shovel and sweat from a smaller-scale gardener, we can turn raw material into a nice compost in a matter of a few weeks instead of a few years. Done properly, the process creates enough heat to kill off pathogens.
The classic method of turning compost by hand is to use some form of wire mesh tied together at the ends to create a boundary for the initial pile. A couple days after the initial creation, the wire mesh is removed and the circle fence is recreated right next to the original pile. Then everything is forked or shoveled into the new circle, and the process is repeated every few days.
If you are using an open core concrete block bin, a second bin constructed beside the first one is ideal. Remove the front wall and just flip the compost into the neighboring bin.
A long-stem compost thermometer is used to monitor the temperature. A day after being turned, the temperature should be above 140° F. When the temperature drops below 120° F (49° C) it’s time to turn it again. After several cycles, the temperature will cease to rise into that target range. At that point, the turning frequency can be diminished to about once a week until the compost appears soil-like and ready to use.
In a static pile that you intend to keep for years, it is fine to add ingredients to the compost pile as they come to hand. If you want to do rapid composting, it works best to build the pile all in one day. Also if you are turning by hand, you will want to avoid very coarse material. Corn and sunflower stalks, pea and bean vines, and similar materials need to be shredded before use. These can be useful for airflow in static piles, but long stalks and stems in a turned compost pile make the turning process very difficult.
Making Good Compost
