The straw bale compost system
compost seive
compost seive

For many years I have used straw bales to contain my compost. Gardening books often recommend wire or wooden enclosures, but straw bales have many advantages, especially if you need to turn the compost.

If the moisture and carbon to nitrogen ratios are good, turning the compost at least four to five times will produce the high temperatures necessary to kill weeds and diseases. It also ensures that all the contents of the pile go through the hot interior section of the heap. Turning also allows you to view the heap to check that moisture and other factors are OK, and reduces the time needed to finish the compost.

I find that straw bales do not tangle the compost fork. They are easily moved out of the way to allow access to the heap for turning or removing finished compost, and they can be made to any shape. The compost can also be moved to another site easier than with wooden structures.

Straw bales fit almost any size area, except the smallest gardens. They can be made to conform to slopes, which can help reduce labour by starting the heap on high ground and turning downhill.

Straw bales also insulate the heap, to retain the high temperatures longer, and conserve moisture better than wood or wire.

Best of all, straw bales provide refuge for worms when the compost is too hot or wet. Eventually the bales become matted with worm castings. When they finally start to fall apart they can be added to a new compost or broken into "biscuits" which are ideal for mulching.

Wheat straw lasts longer in the bale, but pea straw does add some nitrogen. Lucerne provides the best nutrition if you can afford it. I avoid meadow hay because it is more likely to be contaminated with weed seeds. Some grasses sprout in the wheat straw, so I simply turn the bales over occasionally.

When the bales get really old it is best not to move them much, as they fall apart. They can usually be hauled around for six months or so, and last around twelve to eighteen months in my conditions, if I am careful. They also grow fantastic fungi the size of a dinner plate on the decomposing straw during winter.

I arrange the bales into walls to create bays, and turn compost between the bays, using gravity as an aid where ever possible.

To cover the compost in summer, I use biscuits of straw from the bales. Covering the heap slows water loss. In winter, to stop excessive wetting, I place boards across the bales (the heaps have usually sunk below the top by then) and spread tarps over the boards. This leaves an air space between the cover and the heap, so the compost can continue maturing during the winter months, without becoming water-logged.

When the compost is ready, I sometimes sieve it, to get a cleaner product for potting soils and using around the roots of young vegetable seedlings. An old wire bed frame makes an ideal sieve, which removes the occasional bone buried by the dog and tough items such as corn cobs or brassica stalks which don't always compost the first time around. These items disappear completely in the next compost. I don't bother to sieve compost for rougher uses, such as spreading under trees in the orchard.

If you have big dogs and collect lots of bones, try layering them in a wooden box with lime or wood ash. The alkalinity causes bones to soften. When soft, they can be composted or placed on a concrete path and rolled with a heavy roller to form 'bone meal' dust.

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