Hugelkultur: Using Woody Waste in Composting
Hugelkultur is an ancient form of sheet composting developed in Eastern Europe. It uses woody waste such as fallen logs and pruned branches to build soil fertility and improve drainage and moisture retention.
If you walk through natural woodland, you will see many fallen logs and branches on the ground. The older these logs are, the more life they sustain. A log that has rested on the ground for a few years will be covered in moss, fungi, wildflowers and even new saplings. If you disturb it you will notice that the decaying wood is damp in all but the most severe droughts.
Hugelkultur is the practice of making raised beds filled with rotten wood. This produces raised beds loaded with organic material, nutrients, and air pockets. As time passes, the deep soil of the bed becomes richer with life. As the wood shrinks, it makes more tiny air pockets - so the hugelkultur bed becomes self-tilling. During the first few years, the composting process will slightly warm the soil giving you a slightly longer growing season. The woody matter helps to keep nutrient excess from passing into the ground water - and so re-feeds it to your garden plants.
Hugelkultur is designed to take advantage of the natural fertility and moisture-conserving qualities of rotting wood, while speeding up the process of decomposition. The heat produced by decomposition also helps protect cold-sensitive plants.
How to Build a Hugelkultur Bed
Gather woody waste materials such as dead logs, extra firewood, pruned or clipped branches etc. The wood can be either rotting or fresh, although already rotting wood is preferable because it decomposes faster.
Lay the wood in a mound about 1-2 feet high and stamp on it to break it up. Or dig a trench to lay the wood in.
Cover the wood with other compost materials such as autumn leaves, grass clippings, garden wastes, and manure. This stage is optional if you aren't planning to plant the bed immediately, but bear in mind that wood is high in carbon and will consume nitrogen to do the composting. This could lock up the nitrogen and take it away from your plants (nitrogen robbery). But well-rotted wood doesn't do this so much. If the wood is far enough gone, it may have already taken in so much nitrogen that it is now releasing it. Adding a nitrogen-rich component is therefore a good plan if you want to start growing right away. The waste from end of season peas and beans would be good for this – in fact anything you might grow for green manure could be used. Rotted manure or your own compost made from household waste will also do the job.
Cover the wood and compostibles with a few more inches of soil and/or prepared compost, and you are ready to begin using the bed.
Among the plants known to do well in hugelkultur beds are potatoes, squash, and a number of different species of berries. Some gardeners plant the bed with cover crops for the first year to improve fertility even more before adding vegetables or other plants. These could be alfalfa, Hungarian grazing rye, red clover, buckwheat, field beans, white mustard etc, all of which are good nitrogen fixers.
The bed will initially be quite deep, but will settle out considerably. It will probably be about 1/3 the original depth a year from making. Then you can place rocks or wooden edging around it and rework it a little into a slightly more elegant raised bed. In the meantime it will work really well for a goodly crop of potatoes, which, if you are starting the process at the end of summer, could be a late variety suitable for harvesting in December.
Growing potatoes as a first salvo is a really good idea. They seem to improve soil structure, and the earthing-up and harvesting processes add even more benefits. Earthing-up can even be done with straw, which is a popular method of growing them in Scandinavia. It makes it easy to harvest small early crops of mew potatoes without disturbing the plants too much, and the straw acts as an insulator, adding even more warmth, and also stops weeds getting a hold in the top layer of soil.
You can achieve similar results, though much more slowly, by simply burying logs and other wood waste in trenches around your garden in areas where you want to improve fertility and moisture control.
In swampy areas, buried logs will suck up significant quantities of water quickly and release them slowly, reducing the chance of flooding.
In drier areas, the logs will act in the same way, releasing stored water slowly into the surrounding soil and reducing the need to water.
In preparing this guide, we acknowledge with thanks the ideas and inspiration on http://hubpages.com/hub/Hugelkultur-Using-Woody-Waste-in-Composting and http://www.richsoil.com/hugelkultur/