Hügelkultur
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Hügelkultur (), literally mound bed or mound culture is a
horticultural Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
technique where a mound constructed from decaying wood debris and other
compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
able
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
plant materials is later (or immediately) planted as a
raised bed Raised-bed gardening is a form of gardening in which the soil is raised above ground level and usually enclosed in some way. Raised bed structures can be made of wood, rock, concrete or other materials, and can be of any size or shape. The soil i ...
. Adopted by
permaculture Permaculture is an approach to land management and settlement design that adopts arrangements observed in flourishing natural ecosystems. It includes a set of design principles derived using whole-systems thinking. It applies these principle ...
advocates, it is suggested the technique helps to improve
soil fertility Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.
, water retention, and soil warming, thus benefitting plants grown on or near such mounds.


History

Hügelkultur is a German word meaning mound culture or hill culture. Though the technique is alleged to have been practiced in German and Eastern European societies for hundreds of years, the term was first published in a 1962 German gardening booklet by Herrman Andrä. Inspired by the diversity of plants growing in a pile of woody debris in his grandmother's garden, Andrä promoted "mound culture" as opposed to "flatland culture". This was also posited as an easy way to utilise woody debris without burning, which was illegal. Andrä appears to have been influenced by Rudolf Steiner's biodynamic agriculture. Steiner explained his biodynamic philosophy as developed through
meditation Meditation is a practice in which an individual uses a technique – such as mindfulness, or focusing the mind on a particular object, thought, or activity – to train attention and awareness, and achieve a mentally clear and emotionally cal ...
and clairvoyance, rejecting scientific inquiry on the grounds that his methods were “true and correct unto themselves.” Andrä quotes a 1924 lecture on biodynamics by Steiner, which describes mixing of soil with composting or decaying material in earthen hillocks. Joined by author Hans Beba, another German gardener, "Hill Culture - the horticultural method of the future" was revised and republished several times in the 1970s and 1980s. The technique was later adopted and developed by
Sepp Holzer Sepp may refer to: * Sepp (given name) *Sepp (surname) *Science & Environmental Policy Project * Sepp (publisher) *Substantially equal periodic payments, US tax-law provision *Single Edge Processor Package * State Enterprise for Pesticide Producti ...
, an Austrian permaculture advocate. More recent permaculture advocates such as
Paul Wheaton Paul Wheaton is an American permaculture author,Stollar, R.L“Paul Wheaton and Permaculture”Eugene Daily News. Retrieved January 4th 2013.Fredrickson, Erika"Grow Wild" Missoula Independent. Retrieved May 26th, 2020. Master gardener program, ma ...
strongly promote Hügelkultur beds as a perfect permaculture design.


Use


Construction

In its basic form, mounds are constructed by piling logs, branches, plant waste, compost and additional soil directly on the ground. The pile has the form of a pyramid. The sides of the two slopes both have a grade of between 65 and 80 degrees. The beds are usually about in area and about high. However, this height reduces as decomposition progresses. When positioned on sloped terrain, the beds need to be placed on contour, or put at an angle to the hillside (rather than having them parallel to it). This makes sure the beds do not receive unequal amounts of water. In most cases, it is useful to have the beds positioned against the prevailing wind direction. The raised bed can form light-duty swales, circles and mazes. Mounds may also be made from alternating layers of wood, sod, compost, straw, and soil. Although their construction is straightforward, planning is necessary to prevent steep slopes that would result in erosion. In his book ''Desert or Paradise: Restoring Endangered Landscapes Using Water Management, Including Lake and Pond Construction'', Holzer describes a method of constructing Hügelkultur which incorporates rubbish such as cardboard, clothes and kitchen waste. He recommends building mounds that are wide and any length. Mounds are built in a trench in sandy soil, and without a trench if the ground is wet.


Planting

The mound is left to rest for several months before planting, although some advise immediate planting. Anything can be grown on the raised beds, but if the bed will decompose/release its nutrients quickly (so long as it is not made of bulky materials like tree trunks), more demanding crops such as pumpkins, zucchini, cucumbers, cabbages, tomatoes, sweet corn, celery, or potatoes are grown in the first year, after which the bed is used for less demanding crops like beans, peas, and strawberries.


Lifespan

The original German publications described the mounds as having a lifespan of 5–6 years, after which they had to be rebuilt from scratch.


Evidence

As of 2017 there are no peer-reviewed scientific studies available regarding the efficacy of the technique. A few university student projects investigate Hügelkultur but have not been published in scientific journals. One small scale and short term student project investigated the Hügelkultur method as a potential use for yard trimmings waste, and also if lima beans, kale and okra planted on a Hügelkultur mound showed any signs of nutrient deficiency compared to a non-raised control bed. It was found that over 11 tons of yard trimmings were used in the mound, and no evidence of macronutrient deficiency could be detected in the crops in the short term. Indeed, despite concerns that incorporation of large quantities of high carbon woody matter would lead to nitrogen immobilization and hence nitrogen deficiency in the crop, a higher level of nitrogen was found in the raised bed. However, the micronutrient iron was lower relative to the control bed. The author speculated that no nitrogen deficiency occurred since the roots of the plants did not penetrate past the superficial layers of the mound into the deeper wood-containing region. A student thesis investigated the water holding capacity of Hügelkultur beds and whether the technique could be useful to prevent
karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
rocky
desertification Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused by ...
in China. Over 3 months of measurements, water concentration in hügel mounds remained high. Samples from hügel sites contained almost twice as much water as those from flat control plots. It was suggested that of hügels has 3-10 times more water than a flat plot affected by karst rocky desertification.


Theory

Many publications and websites advocate the technique based on personal experience of the authors. Some have criticised the technique as lacking genuine scientific principles, and running counter to the ecological principles of soil building with
litterfall Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constitue ...
. Hügelkultur is said to replicate the natural process of decomposition that occurs on forest floors, however in natural ecosystems wood would be present at the soil surface. Trees that fall in a forest often become nurse logs decaying and providing ecological facilitation to seedlings. As the wood decays, its porosity increases, allowing it to store water like a sponge. The water is slowly released back into the environment, benefiting nearby plants. These beds are also considered beneficial because of the airpockets created by the settling caused by the wood's decomposition. This gives the benefits of tilling, without the destruction of soil microorganisms that come with tilling ("every time you till the soil, you lose 30% of the organic material (microbial soil life is killed, and plants feast on their bodies)"). And, the organic material of the rotting wood also houses beneficial soil microorganisms. Hügelkultur beds are said to be ideal for areas where the underlying soil is of poor quality or compacted. They tend to be easier to maintain due to their relative height above the ground. The decomposition speed of organic material depends on the
carbon to nitrogen ratio A carbon-to-nitrogen ratio (C/N ratio or C:N ratio) is a ratio of the mass of carbon to the mass of nitrogen in organic residues. It can, amongst other things, be used in analysing sediments and soil including soil organic matter and soil amendme ...
of the material, among other factors. Wood breaks down relatively slowly because it has one of the highest carbon to nitrogen ratios of all organic matter that is used in composting. If the wood is not processed into smaller pieces with larger surface area to speed up chemical reactions, breakdown is even slower. The decomposition process may, in the short term, take more nitrogen from the soil through microbial activity (
nitrogen immobilization The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biolo ...
), if not enough nitrogen is available. Thus, in the short term, the fertility of the soil may be decreased before, eventually, perhaps after one to two years, the nitrogen level is increased past the original level. Traditionally, therefore, it is said to be advantageous to balance "browns" (e.g. woodchippings) with "greens" (e.g. grass clippings) for efficient composting, and to allow compost to become well-rotted before applying it to a bed, to prevent competition between soil bacteria and plants for nitrogen, which reduces yield.


Criticisms and controversy


Hügelkultur mounds as solid earthworks

Although Hügelkultur beds can safely retain water in light-duty applications (for example, conserving the moisture of rain that falls on the bed), creating heavy-duty rainwater retention areas behind Hügelkultur beds on contour, to catch
surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when th ...
from surrounding areas, can be dangerous. Some designers conflate the Hügelkultur bed's appearance with that of solid
earthworks Earthworks may refer to: Construction *Earthworks (archaeology), human-made constructions that modify the land contour * Earthworks (engineering), civil engineering works created by moving or processing quantities of soil *Earthworks (military), m ...
, but Hügelkultur beds cannot predictably control large amounts of
stormwater Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
in the way that solid earthworks can. Whereas
embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...
s or the hillsides of swales can be relied on to hold back many thousands of gallons of water for weeks to allow it to seep into the ground, and berms can slow runoff, Hügelkultur beds are different in two ways: earthworks have no buoyant core (whereas Hügelkultur mounds contain logs), and the soil that they are made of is compacted. If fresh or dried timber is used in the bed, it may become buoyant in the water-saturated substrate, bursting from the soil covering and releasing all the sitting water through a breach. This can be an issue for years, until the wood is sufficiently rotten and infused with water. Another consideration is that Hügelkultur beds will degrade, shrinking over time into much lower mounds of soft, rich soil. This means that the retention area will have less depth as time goes on, but it also means that the uncompacted soil will remain a threat to breaching even if the logs become saturated. Some permaculturists have taken mild positions against the "hügel swales" still being promoted by other permaculturists, citing the danger and cross-purposes of Hügelkultur beds and swales. Swales are for long-term installations where perennials - like fruit trees - are grown. Hügelkultur is used for shorter term, more annual crops, as the soil settling that occurs with hugel decomposition is bad for the root system of fruit trees. There is a recorded instance of a breach occurring in a new project. Upon the first rainstorm, the retention areas behind the Hügelkultur beds filled with water and broke through. The released water carried the freshly-buried logs and dirt downhill, smashing a hole in a building being used as a church and filling the space with mud. No injuries were reported.


Overfertilization, contamination of soil and water habitats

Over-fertilized plants are said to have less flavor, and too much nitrogen can be consumed by eating certain plants which have been over-fertilised (e.g., spinach). Advocates state that overfertilization is a risk in the first year if woodchips are used, which will break down too fast. Instead raised beds made with whole logs release nutrients slowly over a period of years. It has been suggested that excessive use of decomposing organic matter in Hügelkultur could leach out and contaminate and disrupt soil and water habitats.


See also

*
Hotbed A hotbed is a biological term for an area of decaying organic matter that is warmer than its surroundings. The heat gradient is generated by the decomposition of organic substituents within the pile by microorganism metabolization. A hotbed cove ...
*
Hot container composting Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
*
Vertical farming Vertical farming is the practice of growing crops in vertically stacked layers. It often incorporates controlled-environment agriculture, which aims to optimize plant growth, and soilless farming techniques such as hydroponics, aquaponics, and ae ...


References


External links

* *Practica
step by step guide to implement hügelkultur raised bedshugelkultur: the ultimate raised garden beds7 Things to Know About Hugelkultur GardeningHugelkultur: Composting Whole Trees With Ease
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