|Sheet mulching is a technique of laying organic material in layers on the ground to build up a raised bed of rich soil for your plants. Hugelkultur is an extension of this technique, where a gardener builds quite tall raised beds using logs and dead branches as the first layer in this bed.|
When you walk out into the forest, one of the first things you will notice is that the ground is soft, loaded with organic material and generally moist even in the driest part of summer. The reason for these conditions is the effect of leaf litter and rotting logs collecting over the years on the surface of the soil.
We replicate these conditions when we make a raised bed with sheet mulching. We put down a layer of cardboard, then cover that with some good garden soil or compost, then a layer of leaves, then perhaps some spoiled hay or straw and finally some wood chips or other mulch. Within a month or two, this bed is ready to be planted and provides many growing seasons of fertility.
Hugelkultur, a German word that means "Hill Culture", expands on this idea by including a mound of wood from fallen trees into the mix. By placing the wood down first and then covering it with sheet mulching, you end up with a very dense pile of organic matter that will continue to break down for years to come. This mimics the natural succession that occurs in a forest, where trees fall and nobody cleans them up. As they begin to rot, they act as a sponge, holding water and releasing nutrients and organic matter to the top layer of the forest.
I started a hugelkultur bed in July of 2010, choosing to build it in the shape of a mandala. The first thing I did was go out into the woods and find as many downed and partially rotted logs as I could and brought them back up. In all, I brought 4 or 5 pickup truck loads.
These I laid straight on the ground and arranged them into the pattern I wanted for my bed.
In making the shape, I left one side open to make a pathway for walking into the bed. This step took a while and I took my time. I kept changing my mind on how large I wanted the bed and how wide the walking paths should be. Re-arranging the logs every time I changed my mind took quite a bit of work, so next time I will mark the bed out entirely before I start laying the material down.
Once I had the bed exactly the way I wanted it, it was time to add in the layers. I went back out into the woods and found areas of rich soil and fully rotted material and brought them back up, packing them between the logs and filling as many crevices as possible. Following that, I harvested out of my pasture several loads of freshly cut grass clippings and covered the bed with a generous layer.
Having finished the bed, it was time to take a break and contemplate what to do with my new hugelkultur bed.
The nice thing about burying logs like this is that they will release fertility over a long span of time. The downside, however, is that during the initial "breaking down" period, the wood gobbles up any available nitrogen around it. The solution to this problem, then, is to spend the first little while growing only plants that have minimal nitrogen requirements, like potatoes, onions, other root crops and legumes.
Legumes in particular are very useful for getting a hugelkultur bed started, as they will take nitrogen from the air and "fix" it into the soil in a form that is available to plants. This will drastically speed up the process of getting the bed ready for your real crops.
While waiting for my bed to get past the initial phase of settling down, I started a tray of cowpeas inoculated with the appropriate rhizobium inoculant. By the time they were up and growing, my bed was ready to receive the transplants. I grew these all over the bed for the remainder of that season.
By fall, I was ready to put some herbs and onions in the bed. In January the bed was laying fairly dormant with perennials that Trish had planted.
Once springtime came, the bed sprang to life with our planted daylilies, garlic, cilantro, spinach, rainlilies and daffodils, basil, comfrey, oregano and many other plants too numerous to list.
We found that as the wood decays, pockets in the bed open up. Continuing to fill these holes with compost and organic matter is a maintenance chore, but I expect that in time the bed will be completely settled and will not need this kind of ongoing work. By reaching in and feeling around, it is very clear that the logs are rotting quite nicely.
For watering, we have an overhead sprinkler that we set in the middle of the bed. Owing to the circular shape of this bed, we can water the entire thing at once.
Our farm in East Texas has mostly acidic sandy soil, devoid of life and organic matter, so building up the soil through sheet mulching is the only way we can effectively garden here. Hugelkultur is a technique that is showing a lot of promise.
My expectation is that with each growing season this bed will continue to improve, sinking down as the logs continue to decay and getting richer and richer with fluffy humus and beneficial soil bacteria.
I have the idea of building a titanic hugelkulture garden, 100 feet wide in a circular shape, for the eventual purpose of growing my vegetables. It will be a garden so impressively massive that it will be seen from space. That may be a project for another year, though. :)
Spring 2012 update: The above described hugelkultur bed continues to increase in productivity. This winter we grew a great variety of lettuces, onions, herbs, carrots, broccoli, and more.
On the west side of our house we built a new hugelkultur system, this time making them long beds laid out following the contours of our hill side. We dug ditches exactly on contour and then laid out wood just downhill of those ditches.
These beds have become our primary vegetable garden, growing both annuals and perennials, and we absolutely adore the area. It's right next to our backporch and we walk through it to get to our barn, where we do our milking chores and more.
Everytime it rains, the ditches fill up with water and hold it so that the water has a chance to slowly penetrate into the ground, rather than running off quickly. This has a huge impact on keeping the soil moist for longer.
Summer of 2012:
You can see the productivity of these so-called "hugelswales", even though they are only 6 months old. Pardon the weeds. :)
Spring 2013 update: Over the past year and a half, we have built too many hugelkultur beds to count. The main mandala bed discussed at the beginning of this article was torn apart earlier this spring and all the material was used to make new beds. We were delighted to see the wood was nearly all gone and the bed was full of fluffy organic matter, rich in microbial life. So, here is another benefit of hugelkultur: it prepares the wood into rich compost that you can later re-use in other beds. Kind of like a compost pile that you can garden in while you wait for it to fully break down.
Pictured to the right are the onions of spring 2013. We have cantaloupes growing along the bottom of this particular bed and as they grow they will spread into the neighboring areas. The onions will be harvested right at the time that the cantaloupes really start taking off.
We are finding hugelkultur beds on contour to be the ultimate vegetable garden innovation. With appropriate mulch (we use spoiled hay) the beds hardly ever need any supplemental irrigation. Herbs, too, love living in the hugelkultur beds.