Hugelkultur, which is a German term meaning “bury tons of crap in the ground,” is a soil-preparation technique that has attained almost mythical status among permaculture enthusiasts. (I’m lying about the English translation, by the way.) Basically, to commit the act of hugelkultur is to bury carbon-rich logs under nitrogen rich compost and the two elements interact with one another over a period of years producing allgedly phenomenal benefits for the plants that grow above them. Although there are variations on the theme, fundamentally hugelkultur involves layering different elements into a growing area so that the interaction between the layers creates a supercharged growing medium for plants. Typically, hardwood logs are the bottom layer of a hugelkultur bed, and high-nitrogen compost is placed on top of the logs. As a third layer you can crown the assemblage with topsoil or seasoned compost. Seedlings are planted in the top layer and as they grow send roots deep into the lower layers.
The logs undergo accelerated decomposition because of the nitrogen. (Along a similar vein, an ancient method farmers used to remove tree stumps was to place manure over the stumps, quickly rotting them away into insignificance.) As the logs decompose they release carbon and other nutrients, and their structure softens and becomes spongy. The logs are then able to hold water, and they become a reservoir for plants that send roots deep into the hugelkultur bed. The rotting logs also give off heat allowing gardeners to stretch the growing season for cold sensitive plants. So, the rotting wood provides any number of important benefits to plants: nutrients, water, and heat among them.
We use hugelkultur in One Acre Eden. We build our raised beds out of urbanite and then fill the base with logs (usually chunks of sweet gum trees). Hugelkulterists are generally advised to avoid coniferous woods and instead focus on broad-leafed hardwoods. Over the sweet gum logs we dump chicken manure compost. We may cap the mix with a little topsoil. Then, we sit back and reap the benefits for years to come. That’s pretty simple.
Here’s a pic of the first phase of constructing a hugelkultur bed.