A Formula for Compost

There are many ways to compost in the garden.  From elaborately engineered manufactured bins to a pile of garden waste heaped in the corner, there are no excuses for not composting.   Even apartment gardeners can compost in a red wiggler vermicomposting box.   The options are as numerous as gardener imagination.  At one extreme is the Cadillac of compost bins that is built as an elaborate series of large cedar boxes with hinged lids to keep out the rain.  Usually these large “toy boxes” are built in threes, but there really is no limit to how many boxes can be strung together.  The “low maintenance” method is to compost in a pile (the garbage bag is optional) at the edge of the garden without any cost or construction.   This throw and dash method can even take place underground in a trench.  All of these methods will produce compost – the difference is the time it takes to create “black gold” for the garden.  Most gardeners opt for a simple structure purchased from their municipality or a “do-it-yourself” frame made from snow fence or wood pallets. 

Before beginning to shovel materials into a raw compost pile, it is important to think about what makes a good recipe for compost.  Composting is the decomposition of organic material where a plant product (fleshy leaves and stems) is turned into a valuable soil amendment.  The idea is to mimic nature in this plant recycling process.  To be successful, composting requires three ingredients: organic plant material, moisture, and air.  A fourth component, soil, will speed up the composting process by seeding your pile with plant-digesting microorganisms.  These microscopic decomposers are the living bacteria, fungi and protozoa that transform a compost heap into great soil. Bacteria are the ones that do most of the work, particularly at the beginning when compost piles get quite warm.  In some situations compost piles may be so warm they start to steam.  At lower temperatures, physical decomposers are at work.  These are creatures such as mites, millipedes, sow bugs, snails, spiders, beetles, ants, flies, and most importantly the earthworms that are the champions of composting.  All of these creatures feed on decaying plant material (and sometimes each other) as they aid in the process of decomposition. 

 Moisture is essential for the decomposition process to work and not having enough is the most common reason that composts fail.  Moisture levels should be the same as a wrung out sponge.  The ideal compost is slightly damp but not wet or too dry.  If composts are too dry they will take forever to decompose (if they do at all).  Alternatively, if composts are too wet they will start to decompose anaerobically (without air) and will have a very foul smell.

 Having the right moisture level will allow for air to be present in the pile.  Air is critical to the health of organisms at work in your compost pile.  Keep them happy by turning your pile periodically to bring a fresh supply of air throughout the pile.  Wet, whole leaves can mat together and form a barrier for good air exchange.  Most gardeners turn the pile by moving it from one location to another or by using a compost aeration tool. 

Another factor in achieving successful compost is to consider the size of the raw compost pieces. The smaller the pieces, the faster they will decompose.  Think of this as cutting up food so that even the smallest bacteria can digest materials fast.  Finely ground leaves will also be easier to turn. Many gardeners don’t have easy access to leaf shredders to do this job, but there are several alternatives to renting equipment.  Line/string trimmers can be used to easily shred leaves.  Fill a large plastic garbage can half full with leaves, put on safety glasses and start shredding.   Another method to reduce the size of leaves is to use your rotary lawn mower to repeatedly mow them into smaller pieces.  Several passes over the leaves are necessary to achieve this. 

 Gardeners may want to consider oak leaves for an extra special compost pile.  Oak leaves are one of the slowest leaves to break down because of their acidic properties and high tannin levels.  Eventually these leaves will decompose and produce an excellent acidic soil amendment.  It just takes considerably longer.  Keeping them separate will speed up the composting process for the rest of the leaves and will allow the oak leaf compost to be used on rhododendrons or other plants that prefer an acidic soil. Pine needles can be combined with the oak leaves for this purpose.

 Compost piles work best with a mix of “brown” (carbons) and “green” (nitrogen) ingredients.  Fall compost piles that are just leaves do not have the ideal ratio of carbon to nitrogen.  The ideal ratio is 30:1 (carbon to nitrogen).  Fallen leaves fit into the brown category because they don’t have much nitrogen left in them at the end of the season.  If a pile was made just of leaves they may take years to break down.  To speed up the process add nitrogen (a green) that will be a good food for the hard working bacteria.  Manure is the best green source to add to leaves.  Manure is high in nitrogen and works well if 1 part is added to every 6 parts of leaves.  If manure is not available, consider using blood meal or bone meal instead.  Lightly sprinkle this powdered supplement at 30 cm intervals at the pile is being built.  Raking leaves and getting them to the compost pile fast is a good practice.  Whatever nitrogen they might still have will be valuable to the composting process. 

 Just about all the materials from the garden and kitchen are great for the compost.  Avoid diseased and insect ridden plants, weed seeds, pet wastes, salad dressings, coloured inks, poisonous plants, and vegetable seeds to name a few.  These products a) could be hazardous if the compost is used near edible crops, b) do not become totally inert during the composting process and can reappear at a later date, and c) destroy soil organisms.

 One of the best outcomes of a fall compost pile is leaf mould.  If just leaves are used, the result is a dark product similar to what is on the forest floor.  Leaf mould can be made in a black plastic garbage bag, a plastic garbage can or a circle of snow fence.  The method is very simple.  Gather your leaves, contain them, moisten if needed and wait.  Leaf mould can be used as mulch in the garden to conserve moisture or to mixed with garden soil as an amendment. 

 Which compost system is the best?  Gardeners faced with this decision should consider that the system must enclose the materials, provide an opportunity for air exchange, possibly give access for turning, and allow for finished compost removal.  Consider the sheer volume of leaves produced by trees and shrubs in the fall.  Will the system be large enough to handle this volume?  How fast should the finished product be ready?  Can the compost structure be built or is a prefabricated model better suited?  Will an on-the-spot pile or trench be sufficient?  The answers to these questions will determine if a plastic garbage can, black garbage bag, “wandering” pile, one bin, three bin or homemade enclosure should be used.  Most importantly of all is to compost!

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