art and science of hugelkulture
There have not been many true scientific papers published on hugelkulture in the USA, the above is however one of the best.
Most published information on the ancient method would be found in the 19th century and perhaps one or two from the 18th century.
The method was used by many cultures, Gauls, Celts, The east coast Nations of Turtle Island and Vikings.
The Native Americans built many growing mounds along the East Coast of Turtle Island (North America) most started their life as leftover depositories as evidenced by excavations where fragments of pottery, processed bones and
wood fire ashes have been documented.
The usual method of building a mound is to start with a shallow hole in the ground, this is filled in layers with dirt put on as a cover between layers. Over time this "trash pit" becomes full of left over material, the dirt was used to contain odors as the pit filled up.
Once the pit was full, the site was continued to be used for depositing the refuse and the "mound" began to take shape. When it became necessary to start another pit, it was noticed that plants grew very well and with out the need of watering the mound.
This
led to the use of the no longer used trash mound as a garden space. This was a common practice as far back as the 1400's and perhaps even further back in time. My elders tell several different versions of how we came to use mounds in the eastern nations.
The premise and practice of hugelkulture, as currently used, is an invention from the Franks and Gauls (now Germany/ Austria/ Poland) who used trenches filled with wood and covered with dirt as a way to hold
water deep for plant
roots to tap into.
The height of these mounds makes harvesting easier as well as increasing the quantity of food that can grow in a space. Decaying wood acts as a sponge, soaking up water and holding it until the roots of the plants draw the water from the wood.
This is not a method that works very well in extremely dry climates, nor does it work very well in extremely wet climates. It performs best in areas where there is at least 10" of rain fall or more.
A mound will change over the years, as the wood decays the mound will settle and different organisms will be present in the soil covering the decaying wood. Small mounds do not work as well as larger mounds, mostly because there is not
enough material present to decay.
One of the ways I build my mounds to get them to work very well is to include bones, meat scraps, freshly cut grasses and other greens in the lower layers of the mound build.
I also do not leave air pockets as I layer up a mound. I do not start a build at ground level, I start with a trench, this trench determines the finished size of the mound since it is actually the base of the mound.
I use the largest wood at the bottom, fill in the cavities with smaller sticks then add a layer of green materials, any kitchen bones and scraps that will not be fed to our animals, then cover with a layer of the soil that was removed to create the trench.
I then build up, in thin layers, using what materials I've gathered or just add to the mound as I create new materials from the work on the farm.
Once I have decided the mound is high enough, I mix
straw and dirt to use as the final cover, this goes on the top and as it dribbles down it forms the shape of the finished mound.
I don't try to make tall and narrow mounds, mine are more rounded with less steep sides at the start.
The steepness gets built as crops are grown and harvested, the mound settles and I add more dirt and straw/grass/etc. This allows the mound to be very stable, with little erosion since there are many roots holding the soil in place.
Cover crops and winter crops add to the
root structures that hold the soil where it is and cover crops are chopped and left in place as mulch.
The real science of a mound is more hydrological than most people would think, it is more about building ground water than piling dirt.