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 ...

, sheet mulching is an agricultural

no-dig gardening No-dig gardening is a non-cultivation method used by some organic gardeners. The origins of no-dig gardening are unclear, and may be based on pre-industrial or nineteenth-century farming techniques. Masanobu Fukuoka started his pioneering research ...

technique that attempts to mimic the natural soil-building process in

forests A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

. When deployed properly and in combination with other permaculture principles, it can generate healthy, productive, and low maintenance

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s. Sheet mulching, also known as composting in place, mimics nature by breaking down organic material from the topmost layers down. The simplest form of sheet mulching consists of applying a bottom layer of decomposable material, such as cardboard or newspapers, to the ground to kill existing vegetation and suppress weeds. Then, a top layer of organic mulch is applied. More elaborate sheet mulching involves more layers. Sheet mulching is used to transform a variety of surfaces into a fertile soil that can be planted. Sheet mulching can be applied to a lawn, a dirt lot full of perennial weeds, an area with poor soil, or even pavement or a rooftop.

Technique

A model for sheet mulching consists of the following steps: # The area of interest is flattened by trimming down existing plant species such as

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es. # The soil is analyzed and its pH is adjusted (if needed). # The soil is moisturized (if needed) to facilitate the activity of decomposers. # The soil is then covered with a thin layer of slowly decomposing material (known as the '' weed barrier''), typically

cardboard Cardboard is a generic term for heavy paper-based products. The construction can range from a thick paper known as paperboard to corrugated fiberboard which is made of multiple plies of material. Natural cardboards can range from grey to light ...

. This suppresses the weeds by blocking sunlight, adds nutrients to the soil as weed matter quickly decays beneath the barrier, and increases the mechanical stability of the growing medium. # A layer (around 10 cm thick) of weed-free soil, rich in nutrients is added, in an attempt to mimic the surface soil, or

A horizon A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

. # A layer (at most 15 cm thick) of weed-free, woody and leafy matter is added in an attempt to mimic the

forest floor The forest floor, also called detritus, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shed vegetative parts, such as leaves, branches, bark, and stems, existing in various stages ...

, or O horizon. Theoretically, the soil is now ready to receive the desirable plant seeds or transplants.

Variations and considerations

*Often the barrier is applied a few months before planting to ensure the penetration of roots of newly planted seeds. *Very thick barriers can cause anaerobic conditions. *Some permaculturists incorporate composting in steps 5 and/or 6. *Sheets of newspaper and clothing can be used instead of cardboard. *Before step 4, an initial layer (2–3 kg/m²) of matter rich in nutrients (such as compost or manure) may be added to bolster decomposition. *Some varieties of grasses and weeds may be beneficial in a number of ways. Such plants can be controlled and used rather than eradicated. See also:

mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A mu ...

, list of beneficial weeds. *One variation of mulching, called hugelkultur, involves using buried logs and branches as the first layer of the bed.

Advantages

Sheet mulch has important advantages relative to conventional methods, such as tilling, plowing or applying herbicides: *Improvement of desirable plants' health and productivity. *Retention of water and nutrients and stabilization of biochemical cycles. *Improvement of

soil structure Soil structure describes the arrangement or the way of soil in the solid parts of the soil and of the pore space located between them. It is determined by how individual soil granules clump, bind together, and aggregate, resulting in the arrangem ...

soil life Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ter ...

, and prevention of soil

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

. *Avoidance of potentially dangerous pesticides, especially herbicides. *Reduction of overall maintenance labor and costs. *Most of the materials required to sheet mulch can be collected at no cost, and materials can be substituted for those readily available in certain areas. For instance, suburban areas may have a plentiful supply of leaves, and farming communities may have spoiled hay and manure.

Disadvantages

*Some weed seeds (such as those of

Bermuda grass ''Cynodon dactylon'', commonly known as Bermuda grass, is a grass found worldwide. It is native to Europe, Africa, Australia and much of Asia. It has been introduced to the Americas. Although it is not native to Bermuda, it is an abundant invasiv ...

and species of

bindweed Bindweed may refer to: * Some species of Convolvulaceae (bindweed family or morning glory family): ** '' Calystegia'' (bindweed, false bindweed, morning glory), a genus of about 25 species of flowering plants ** ''Convolvulus'' (bindweed, morning ...

) may persist under the barrier and within the

soil seed bank The soil seed bank is the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lak ...

. *

Termites Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blattod ...

are attracted to the area. While they are a natural part of the ecosystem that transforms the weed barrier into rich soil, they can pose a hazard to nearby wood-framed structures. * Slug populations may increase during the early stages of decomposition. However they can be kept away or harvested. *The system may need a constant supply of organic material, at least during the early stages. *Roaming animals may interrupt the sheet mulching process.

References

{{Permaculture Soil improvers Horticulture Organic gardening Permaculture Sustainable agriculture Habitat management equipment and methods