What is a Johnson-Su bioreactor and why do they create compost that benefits our soils?

The Johnson-Su Bioreactor is a method of composting designed specifically to foster an abundance of fungal and microbial life in compost, ultimately yielding a highly biologically active humus. Developed by Dr. David Johnson and his team, this composting process is part of a broader regenerative agricultural approach that promotes soil health through rich, diverse microbial ecosystems. This feeding of the soil complements the action of our grass fed beef cattle and lambs on the pasture. Below, we explore the steps involved in creating a Johnson-Su Bioreactor and the unique benefits it brings to the soil biome.

The Johnson-Su Bioreactor Process

The Johnson-Su Bioreactor process is designed to produce a high-quality compost with minimal intervention and no need for turning. It supports an optimal environment for microbial and fungal growth, using a slow, aerobic decomposition process that differs significantly from traditional composting. Here are the main steps:

1. The Structure:

   • The bioreactor typically consists of a large, cylindrical frame made from materials like wire mesh or perforated plastic tubing. The structure is placed on a breathable base (often made from pallets or perforated mats) to allow air circulation from the bottom.
   • Vertical perforated pipes are inserted evenly around the cylinder's circumference, reaching from the bottom to the top. These pipes are left in place throughout the composting process and serve as aeration channels that supply oxygen to the compost pile, reducing the need for turning.

2. Composting Materials:

   • The bioreactor is filled with a balanced mix of green (nitrogen-rich) and brown (carbon-rich) materials, such as plant trimmings, straw, manure, and other organic matter. A Johnson-Su Bioreactor typically avoids heavy doses of high-nitrogen materials like food waste, focusing instead on plant-based materials that encourage fungal growth.
   • Unlike hot composting methods, the Johnson-Su method works at ambient temperatures, allowing for a gradual buildup of microbial populations.

3. Moisture Management:

   • The compost moisture is critical, especially at the beginning. The ideal moisture level is around 60-70%, which feels like a damp sponge. Periodic watering is essential to maintain this level throughout the composting period, which typically lasts 9-12 months.

4. Compost Maturation:

   • The Johnson-Su compost matures over a period of one year, a slow, aerobic process that supports the establishment of fungi and beneficial bacteria. By the end, the compost resembles a dark, crumbly humus rich in microbial life and stable organic matter.

Benefits of the Johnson-Su Bioreactor

The Johnson-Su Bioreactor produces a compost that is uniquely beneficial for the soil biome due to its high fungal content and microbial diversity. Here are the specific benefits:

1. Enhanced Fungal Dominance:

   • Traditional composting methods often produce bacterial-dominant composts. However, fungal populations are critical in ecosystems like grasslands and forests, where they play key roles in nutrient cycling and plant health. The slow decomposition process in the Johnson-Su Bioreactor fosters a balanced environment that supports a greater fungal presence, essential for restoring degraded soils and promoting root-plant symbiosis.

2. Increased Microbial Diversity and Activity:

   • The passive aeration and moisture-controlled environment create a habitat for a wide variety of beneficial microbes, including bacteria, fungi, actinomycetes, and protozoa. These organisms contribute to organic matter breakdown and release nutrients in a form readily available to plants.
   • Microbial diversity is central to soil resilience. By introducing a wide array of microorganisms into the soil, Johnson-Su compost helps build a robust soil ecosystem that can better withstand pests, diseases, and environmental stresses.

3. Improved Soil Structure and Water Retention:

   • The fungal networks established in Johnson-Su compost contribute significantly to soil aggregation, which enhances soil structure and water infiltration. Improved soil structure helps soil retain moisture and supports root growth, reducing the need for irrigation and increasing drought resilience.

4. Carbon Sequestration Potential:

   • A Johnson-Su Bioreactor compost is particularly valuable in carbon sequestration. Fungi play a central role in stabilizing carbon in the soil, converting organic material into stable humus. The high fungal content in Johnson-Su compost enables soils to sequester more carbon, making it an environmentally beneficial practice in combating climate change.

5. Reduced Labor and Maintenance:

   • Unlike traditional composting, which requires frequent turning to maintain aeration, the Johnson-Su Bioreactor is virtually maintenance-free once it is set up. This passive system reduces labor costs and energy expenditure, making it a more sustainable option for larger operations and individuals with limited time.

Application of Johnson-Su Compost

Johnson-Su compost can be applied directly to soil or used in compost teas to distribute its microbial and fungal benefits across fields or garden beds. For best results, apply Johnson-Su compost as a top dressing around plants or work it lightly into the top few inches of soil. Compost tea can also be brewed from Johnson-Su compost, enhancing microbial activity and diversity in the soil in a targeted way.

Incorporating Johnson-Su compost into a soil management plan aligns closely with regenerative principles​​. It enhances soil health and productivity in the long term without relying on synthetic inputs, supporting a more self-sustaining soil ecosystem while addressing soil degradation and carbon sequestration. The Johnson-Su Bioreactor is thus an invaluable tool for anyone committed to sustainable and regenerative farming practices.