3.3 Composting and soil building techniques

Composting and soil building are crucial techniques in permaculture. They focus on creating nutrient-rich soil to support healthy plant growth. These methods range from traditional composting to innovative approaches like bokashi and biochar, all aimed at improving soil fertility.

Soil building techniques go beyond composting. They include using cover crops, sheet mulching, and compost tea applications. These practices enhance soil structure, increase organic matter, and boost microbial activity, creating a thriving ecosystem for plants to flourish in.

Composting Methods

Aerobic Composting

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• Aerobic composting requires oxygen to break down organic matter into nutrient-rich compost
• Involves layering brown materials (carbon-rich) and green materials (nitrogen-rich) in a pile or bin
  • Brown materials include dry leaves, straw, and wood chips
  • Green materials include fresh grass clippings, food scraps, and coffee grounds
• Requires regular turning to incorporate oxygen and speed up the decomposition process
• Ideal carbon-to-nitrogen ratio is around 30:1 to promote optimal microbial activity
• Maintains a temperature between 130-150°F (54-66°C) during the active composting phase, which helps eliminate pathogens and weed seeds

Anaerobic Composting and Vermicomposting

• Anaerobic composting occurs in the absence of oxygen, typically in sealed containers or bags
  • Produces compost more slowly than aerobic methods and may emit unpleasant odors due to the lack of oxygen
  • Requires minimal maintenance and can be useful for composting food waste in small spaces (kitchen countertop composters)
• Vermicomposting utilizes worms (red wigglers or European nightcrawlers) to break down organic matter
  • Worms consume food scraps and other organic materials, producing nutrient-rich worm castings
  • Requires a controlled environment with proper moisture, temperature, and ventilation to keep the worms healthy
  • Produces high-quality compost that is rich in beneficial microorganisms and plant growth hormones

Bokashi Composting

• Bokashi is a Japanese term meaning "fermented organic matter" and involves fermenting food waste using a specific group of microorganisms
• Utilizes a special inoculated bran that contains beneficial bacteria and yeasts to ferment the organic material in an anaerobic environment
• Food waste is layered with the inoculated bran in an airtight container, allowing the fermentation process to occur over several weeks
• Fermented waste is then buried in the soil or added to a compost pile, where it breaks down rapidly
• Advantageous for composting meat, dairy, and oily foods that are not suitable for traditional composting methods

Soil Building Techniques

Green Manure and Cover Crops

• Green manure refers to the practice of growing crops specifically to incorporate them back into the soil to improve fertility and structure
  • Leguminous plants (clover, vetch, and alfalfa) fix atmospheric nitrogen in their roots, adding this essential nutrient to the soil
  • Other cover crops (rye, oats, and buckwheat) suppress weeds, prevent erosion, and add organic matter when tilled into the soil
• Cover crops are planted between main crop rotations to protect and enrich the soil
  • Provide a living mulch that reduces soil erosion, retains moisture, and suppresses weed growth
  • Improve soil structure and fertility when incorporated into the soil as green manure

Sheet Mulching and Compost Tea

• Sheet mulching, also known as lasagna gardening, is a layered mulching technique that mimics natural soil-building processes
  • Alternating layers of carbon-rich materials (cardboard, newspaper) and nitrogen-rich materials (compost, manure) are placed directly on the soil surface
  • Suppresses weed growth, retains moisture, and gradually breaks down to improve soil structure and fertility
  • Useful for converting lawns or compacted soils into productive garden beds without the need for tilling
• Compost tea is a liquid extract made by steeping compost in water, which is then applied to plants as a foliar spray or soil drench
  • Contains beneficial microorganisms, nutrients, and plant growth compounds that promote plant health and disease resistance
  • Aerated compost tea (ACT) is made by actively aerating the mixture to encourage the growth of aerobic microorganisms
  • Non-aerated compost tea (NCT) is a simpler method that involves steeping compost in water without active aeration

Biochar Amendment

• Biochar is a carbon-rich material produced by burning organic matter in a low-oxygen environment (pyrolysis)
• Improves soil structure, water retention, and nutrient holding capacity when incorporated into the soil
  • Porous nature of biochar provides habitat for beneficial soil microorganisms and helps retain water and nutrients
  • Stable form of carbon that can persist in the soil for hundreds to thousands of years, contributing to long-term carbon sequestration
• Commonly made from wood chips, agricultural waste, or other biomass materials
• Often "charged" with nutrients by soaking in compost tea or other nutrient-rich solutions before application to the soil