Garden compost is a crumbly, dark, organic material, processed from
waste materials from the kitchen and garden. It is made by soil bacteria
and other microorganisms, which break down and rot the raw materials. Grass clippings can be used “raw” as a mulch, but are much more
effective once composted.
Building the pile
Your role in making compost is to provide soil organisms with warmth,
moisture, and a good mix of materials. Placing bins on bare soil allows
these organisms to get inside. Alternatively, add a spadeful of compost
from an old pile, or soil, for every 12 inches (30 cm) of material.
Shredded materials will rot down faster than unshredded ones. You can
chop most stems and leaves up with a spade, but it may be worth renting a
shredder in fall to break down heavier woody material and leaves. It is
best to store your compost in a bin; either buy one, or make your own
using mesh or wood. A pit is another possibility, but it will be hard to
empty and may become waterlogged in the winter. Whichever type of bin
or pile you use, it will need a lid to keep out rain.
In theory, you should fill your compost bin with a good blend of
materials in as short a period as possible. In practice, it is likely
that the bin will take time to fill up. Therefore it probably won’t
generate enough warmth for thorough composting; weed seeds and roots may
survive, as may organisms in diseased material. Large-scale municipal
composting reaches temperatures that eliminate these problems, but small
volumes of homemade compost cannot match this, so be careful what you
add to your heap.
If you cannot achieve the ideal blend of ingredients, you could try using “activators.” These nitrogen-rich materials help to break down woody materials, and can be useful when you have too little soft green material. Alternatively, add a thin layer of manure, mushroom compost, or a sprinkling of nitrogen-rich fertilizer to every 6 inches (15 cm) of woody material. Adding lime is sometimes recommended, but is usually unnecessary, unless you are composting lots of shredded conifer prunings or waste fruit, which can be very acidic.
Ready to Use?
Turning the compost can speed up the process. Empty the bin and mix the contents, adding water to dry material before returning it to the bin. To check the progress of your pile, pull back the upper layers to see if the fibrous material is breaking down. If not, it may be too dry, or it may need more soft, green material, such as lawn clippings, to add nitrogen. If you have a small household or modest garden, your compost may not turn out to be the ideal uniformly crumbly, brown material you had hoped for. Instead, it will probably have twiggy and semi-rotted parts mixed in with a dark brown mass that smells like damp woodland. Pick or sift out the unrotted components, and add them to your next compost batch; they will rot down eventually. Bad smells indicate compost is too wet—turn it and add fibrous material. A layer of well-rotted compost from another bin or a layer of spent potting mix will also help seal in odors.