Hugelkultur: Irrigating with old wood
Hugelkultur is a German word (pronounced hoogle culture: it should have some umlauts over the first ‘u’ but I have no idea how to do that) which translates as hill culture. It is a process of building raised beds with a core of old wood. The benefits are that as the wood decomposes it not only releases nutrients into the soil, but it holds water like a sponge. Rain water is collected inside the bed, then as the warmer weather sets in and heat dries out the outer shell, it will wick that moisture back out. Presto! Irrigation in the dry season. As the wood decomposes it creates air holes into which deeper roots may penetrate and absorb nutrients that aren’t being washed into the ground water. Also, growing on a tall hugelkultur bed makes harvesting easier because vegetables are often located higher off the ground. The process was popularized by Sepp Holzer, although he didn’t actually call it that.
Hugelkultur may be started flat on the ground, by hand or by machine, dug into the ground, stacked very tall or short, or even level to the ground. The best way to build a bed is to place it on contour where rainwater will collect, preferably facing North and South so that both sides receive equal sun.
I have areas of ground that are either very heavy clay, or are decomposed granite with stones left over from the building of the house. Some trees don’t receive the drainage they need from irrigation because of the clay, which causes the roots to suffocate, or else plants dry up because water perculates too swiftly through the soil.
I also have stacks of brush that were left when the garden was created as hiding places for animals while the garden grew. I don’t need that many brush piles anymore now that the garden is large. I have three wire cages filled with woodier weeds and prunings that are in ‘slow compost’ mode, and leftover trimmings from bamboo used in bridge construction. Perfect hugelkultur components!
I targeted an area between the pathway and a plant guild with two apricots and vegetables in it. When it rains that area has standing water on it because of the clay content. The area should become part of the guild, but the soil needs mucho amending. I have areas like this all around the property. How to amend two acres of soil? How to get rid of the ever-rising mountains of prunings? How to make the rain water permiate the soil and perculate down rather than sheet across? One guess. Yep, hugelkultur. I bury that wood!
I had made a small hugelkultur experiment a year ago with a raised strawberry bed. There was old lime firewood rotting on the property, so I placed several of these logs along the side of the bed, then covered them with soil and planted strawberries. It worked very well. The strawberries loved the acid, even growing into the decomposing logs, and the logs held the moisture. Some wonderful showy fungus came up, too. I will be reworking that bed and this time I will cover the ground with logs, throw on some llama or horse manure, cover with compost and replant the strawberries. I shouldn’t have to fertilize that bed or add soil for a long time.
For the big hugelkultur bed I wanted a deep hole that would capture rain and allow the wood to absorb it. My faithful assistants Lori and Steve and Jacob work on this project with me. Steve and Lori dug this ginormous serpentine pit about 2 1/2 feet deep and the same wide.
Since the paths had just been covered with mulch, the dirt was piled on top of plywood layed over the mulch for protection.
Then we began filling the bed with the largest wood first.
We didn’t have large logs which would have worked well, but we had lots of thick branches. This hole took a lot of prunings and we jumped on them to compact them down.
The hugelkultur bed was left for a few days to settle (and we had run out of time and energy that first day!), and then we worked on it again. Extra dirt from the rain catchment basins that the men were enlarging was hauled down and thrown into and around the wood.
The mound was watered well. In dry areas it is important to water the wood and the soil well as you are building or else the bed will want to draw water from the area around it, drying up any seeds or plants planted on it.
Of course if this is a temporarily boggy area, the hugel bed would help dry it out. There were subterranean irrigation lines across the area already, and since we have a dry climate and the wood I used wasn’t old spongy logs and would take some time to become absorbant, we reestablished the drip system across the top of the hugel bed.
Because there weren’t large logs, there were a lot of spaces to fill with dirt. Gradually the mound grew and was sloped down to the pathway. Finally a couple of inches of dirt was packed on top. Unfortunately this was mostly clay from the excavation site, but if it had been good soil to begin with, I wouldn’t have needed the hugel bed now, would I? Yes, I did give it a sprinkling of sugar just to get the microbes feeding.
The next day I dug up soil from the bottom of the wire cages that were now empty of branches, vines, and sticks. In less than a year since making the wire beds they’d begun to decompose and there was several inches of nice soil at the bottom. I hauled it over to the new bed and topped the clay with the compost.
I want to break up the clay soil so I threw around a cover crop mixture of peas and wheat. The peas will fix nitrogen in the soil, the wheat roots will stabilize and break up clay, I can harvest food from both and then slash and drop the plants to bring nutrition to the soil surface. I also had a bag of mixed old veggie seeds. Last year or so ago I pulled out all my little envelopes of veggie seeds that were very old and mixed them all up. I planted batches around the property and had many things germinate. I still had about 2 cups of the seed left so I threw it around the new hugelbed along with the cover crop. Why not? If the seed isn’t viable, no loss. If it is, terrific! I can always transplant the sprouts if there are too many of any one thing.
I watered the seed down, and then raked out the old straw from the Fowl Fortress. Here is a warning about straw: it will germinate. People say straw doesn’t have seeds in it because the seeds are all in the tops which is cut as hay, but they lie. They live in a dream. Straw still has seeds in it and I had a nightmare of a time weeding pathways the first year of the garden because they were all strewn with straw mulch. However if you put straw down for your hens first, they will eat all the seeds, poo on it, kick it around in the dirt, and then you will have a much better quality straw to use. Straw is difficult to get wet, and it needs to be wet when placed on the bed unless you live in a wet climate or have timed the planting to be just before a long soaking rain.
Even then it is good to soak the straw first and then apply it to the bed. Some people soak the straw in an enriched liquid, using manure tea, kelp, microbial brews, organic molassas, etc. The mulch acts as an insulator for moisture and warmth (the decaying wood will eventually produce some heat to warm the little plant feet), and a suffocator for weeds. It can also be a home for sow bugs if too thin. In wetter climates the straw layer can be an inch or so thick. In drier climates the straw or whatever you use as a top mulch should be several inches thick or else it will just wick moisture out of the bed. The same rule applys when using newspapers as a mulch. TIP: don’t let your chickens near the new bed! They will ‘rediscover’ their old mulch and start kicking all your work apart!
If I had wanted to plant established plants on the hugelkultur bed rather than seeds, I would have forgone spreading compost and just covered the poor soil on the mound in wet newspaper or cardboard, and then piled on the straw mulch. To plant I would have cut a hole through the paper, added a handful of good compost and planted in the hole.
So the bed was done, and just before a predicted rain event, too. As it rains the water will roll into the bed, be absorbed and held by the soil around the branches which will eventually begin to absorb the moisture as they decay. The seeds will sprout through the mulch and their roots will hold and amend the clay on the mound. Eventually the roots of the apricot trees will reach over towards the hugel bed, and that patch of icky clay soil will become beautiful. All the while I can still grow crops on the raised bed. My three wire bins are empty, an enormous brush pile is reduced to a small mound, and extra dirt found a new home. Plus we all had some fantastic upper body workouts. A winning situation all around.
More hugel beds will be created in troubled spots; some may only be a couple of feet long below a tree’s root line to help with soil drainage while amending the planting bed.
If you are in an area where the top mulch might wash away in heavy rains, make a latticework of sticks held down with landscape pins or more sticks over the top of the straw. Or cover with wire until the plants begin to sprout; you don’t want the wire to remain on the bed.
So try a hugelkultur bed, big or small. You’ll wonder why you never tried it before.