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Composting for Beginners: Part II

How To Build a Compost Pile

If you haven’t read our first post on “How to Compost”, Part I of this composting series will give you insights into the basics of composting and what you can add to your pile.

Building a compost heap

Place your compost heap in a convenient but unobtrusive location. Choose a nearby location if the compost will be used primarily in the garden. A convenient source of water is beneficial because the compost pile must be kept moist. Compost should never become soggy or wet, as this will halt the decomposition process. As a result, avoid locating a compost heap in areas where drainage is poor and water can stand, even for short periods of time. A shaded area is also ideal for composting to prevent overheating. However, compost heaps should not be located near trees. Tree roots are drawn to the loose, moist, organic material that is forming at the bottom of the pile. During the summer, the roots of some trees may spread rapidly throughout the lower areas of the heap, making it difficult to dig and use the compost.

Compost pile size

The size of the pile required can vary greatly depending on the amount of material available. A pile should be at least 3 feet wide and 3 feet tall. Anything smaller than this cannot decompose properly. A typical gardener might prefer a pile that is 5 feet wide, 5 feet long, and 5 feet deep. Where there is more compost available, the heap should still be about 5 feet wide (for easy working) and any length that is convenient.
If enough compost is available, the average gardener may discover that two or three small piles provide more flexibility than a single large one. In this manner, a pile can be constructed and allowed to begin undisturbed, while a second pile serves as a repository for organic materials as they accumulate. Three piles are even better: one that is finished, one that is decomposing, and one that is being replenished with new materials. This ensures a nearly continuous supply of compost.
The urban gardener may not have enough materials or space to construct several piles. In such cases, a single, tall pile might suffice. Although not ideal, fresh materials can be added to the top and decomposed material can be extracted from the bottom. This prevents turning, which aids in complete decomposition and heating. Nonetheless, with limited space and material, a pile like this serves a specific and useful purpose.

Keeping the pile in check

Although it is possible to stack the compost in a loose pile, decomposition is improved and space is saved if it is made in a bin or enclosure. Many different materials can be used. The sides should be loose enough to allow for some air movement. One side should be open to allow for easy compost turning and removal. The heap can be round, square, rectangular, or any other shape that is convenient.

Compost Enclosure varieties

A compost heap can be surrounded by woven wire fencing (hog wire, chicken wire, chain link), wood slat fencing (snow fence), cement blocks, bricks, or scrap lumber. Corner supports are required for fencing materials, but a small round heap made of slatted fencing requires little or no support. If the woven wire fencing is too loose to contain fine materials, line the enclosure with plastic (aeration holes included) to keep the pile neat and speed decomposition. Bricks or concrete blocks can be stacked without mortar, but some space should be left between them to allow adequate air flow through the sides. Scrap boards work well as sides because there is usually enough space between them for air movement. Exposure to damp compost gradually deteriorates lumber, and boards must occasionally be replaced as they decay.

Building the compost pile

Layers are commonly used to describe compost pile construction. Such layers are less well defined in practice. Layering is not required, but it provides the quickest and most complete decomposition.
In most cases, the pile can be started directly on the ground. However, to provide aeration to the pile’s bottom and improve drainage, a trench across the base of the area may be dug and covered with stiff wire mesh (hardware cloth) before the layers are started. Begin the pile by spreading a layer of organic matter 6 to 8 inches thick over the area. If you have a choice of materials, put the coarsest on the bottom. Shredded or chopped materials decompose the fastest, so coarse organic matter should be run through a shredder if one is available. Matting materials, such as grass clippings, should be placed in layers no more than 2 to 3 inches thick. Moisten, but do not soak, the organic material layer.
Sprinkle a complete garden fertilizer, such as a 12-12-12, over the layer of plant material. 1 cup for every 25 square feet of top surface area should suffice. If the finished compost is to be used for acid-loving plants, an equal amount of ground limestone should be added. If fresh animal or poultry manure is available, a 1 to 2-inch layer can replace the commercial fertilizer. Then, add a 1 to 2 inch layer of soil or sod. Microorganisms in the soil help to initiate the decomposition process. If topsoil is unavailable, a layer of finished compost can be used as a substitute for the soil.
Special compost activators or starters are not required when layering with soil or old compost and fertilizer. Continue to alternate the layers of organic materials, fertilizer or manure, and soil until the height reaches about 5 feet. Firm each layer as it is added, but not so much that air cannot freely pass through it. Each layer should be watered as it is added.

Take care of the pile.

For proper heating and decomposition, the compost pile must be kept moist (but not soggy). Microbial activity is reduced when there is insufficient moisture. Excess moisture can lead to unwanted decomposition and offensive odors. Adding supplemental water with weekly soaking may be necessary during dry weather. During extremely dry periods, covering with plastic can reduce moisture loss and aid decomposition. During periods of heavy rain, a plastic covering also keeps the pile from becoming too wet.

Periodically “turn” or mix the pile to speed up decomposition. This will help to aerate the pile and reverse any negative reactions. During warm weather, the pile should be rotated once a month. Decomposition is slower in cool weather, and frequent turning is not required. Except in very large piles, little decomposition occurs during the winter. If a strong ammonia or other offensive odor is detected, the pile should be turned immediately.
Turning can be accomplished by slicing the pile and inverting each slice. Where space is available, it may be possible to shift the entire pile into another bin, which will then be moved back. The primary goal of turning is to move materials from the pile’s edges closer to the center, where they can better heat and decompose.
It should be hot in the center about a month after you start the pile. This indicates that the pile is properly decomposing. Failure to heat could be caused by too much water, insufficient aeration, insufficient nitrogen, or a pile that is too small.
The pile should shrink to about half its original height as the materials decompose. The time required will vary depending on the size of the pile and the time of year. If the heap does not decompose, it may be necessary to rebuild it with new materials.

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