Sheet mulching

Technique

A model for sheet mulching consists of the following steps:

1. The area of interest is flattened by trimming down existing plant species such as grasses.
2. The soil is analyzed and its pH is adjusted (if needed).
3. The soil is moisturized (if needed) to facilitate the activity of decomposers.
4. The soil is then covered with a thin layer of slowly decomposing material (known as the weed barrier), typically cardboard. 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.
5. 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.
6. A layer (at most 15 cm thick) of weed-free, woody and leafy matter is added in an attempt to mimic the forest floor, or O horizon. Theoretically, the soil is now ready to receive the desirable plant seeds or transplants.

Variations and considerations

• 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, list of beneficial weeds.
• Very thick barriers can create anaerobic conditions.
• Often the barrier is applied a few months before planting to ensure the penetration of roots of newly planted seeds.
• Sheets of newspaper and clothing can be used instead of cardboard.
• Fibrous mulch from redwood bark, sometimes called "gorilla hair", can be advantageous in windy areas, due to its ability to weave together in a continuous mat.
• One variation of mulching, called Hügelkultur, involves using buried logs and branches as the first layer of the bed.
• 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 permaculturists incorporate composting in step 5, step 6, or both.

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 life, and prevention of soil erosion.
• 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 and species of bindweed) may persist under the barrier and within the soil seed bank.
• Termites 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

References

1. (1998). "Sheet Mulching: Greater Plant and Soil Health for Less Work". Agroforestry.net.
2. Mason, John. (2003). "Sustainable Agriculture". CSIRO.
3. Hemenway, Toby. (2009). "Gaia's Garden: A Guide to Home-Scale Permaculture". Chelsea Green Pub..
4. (March 2023). "Transformation of Organic Soils Due to Artificial Drainage and Agricultural Use in Poland". Agriculture.
5. Stout, Ruth. (February–March 2004). "Ruth Stout's System". Mother Earth News.
6. Parker, Henry. (2024-07-30). "Gorilla Hair Mulch 101".
7. Nicole Faires. (4 May 2012). "The Ultimate Guide to Permaculture". Skyhorse Publishing Inc..
8. "Sheet Mulching". StopWaste.Org.
9. Phelps, Dave R.. (2013). "Use of Less-Toxic Herbicides and Sheet Mulching in Landscapes". California Weed Science Society.
10. . (March 11, 2014). ["Sheet Mulching from the Ground Up"](https://www.santabarbaraca.gov/civicax/filebank/blobdload.aspx?BlobID=34092). *[[Santa Barbara, California*.
11. (2012-06-20). "Why I don't like cardboard mulch".