Glomalin is a glycoprotein found abundantly in soil, often described as “soil glue” due to its sticky properties. Identified in 1996 by Dr. Sara F. Wright of the USDA, glomalin plays a significant role in soil health. Its presence helps create a more stable and fertile ground for plant life.
The Source of Glomalin
Glomalin originates from arbuscular mycorrhizal fungi (AMF), microorganisms that form beneficial relationships with most plants. These fungi extend thread-like structures, called hyphae, into the soil, creating an extensive network beyond plant roots. In this symbiotic partnership, fungi gather water and nutrients, like phosphorus and nitrogen, for the plant. In return, the plant provides the fungi with carbon compounds from photosynthesis.
Glomalin is produced on the surface of these fungal hyphae and spores. This coating helps seal the hyphae, allowing them to efficiently transport water and nutrients to host plants. As fungal hyphae naturally decompose, glomalin is released into the soil, where it begins to affect soil structure.
The Function of Glomalin in Soil
Glomalin acts as an adhesive, binding soil components like sand, silt, clay, and organic matter into larger, stable units called soil aggregates. This “gluing” action forms a protective coating around particles, creating a more organized soil structure. Aggregate formation is an important process for healthy soil, influencing its physical properties.
The creation of stable aggregates significantly improves soil quality by establishing a network of pore spaces. These spaces allow for better water infiltration, reducing surface runoff and enhancing the soil’s capacity to hold moisture for plants. Improved aeration also results from these pore spaces, providing oxygen to plant roots and beneficial soil microorganisms. Glomalin-mediated aggregation increases the soil’s resistance to erosion from wind and water, protecting valuable topsoil.
The Role of Glomalin in Carbon Sequestration
Glomalin is a carbon-rich compound, containing between 30 to 40 percent carbon. Its chemical makeup, including proteins and carbohydrates, contributes to its stability in the soil. This glycoprotein resists decomposition by microbes, allowing it to persist for extended periods, from 7 to 42 years, and up to 100 years when bound with iron or other heavy metals.
This resistance to breakdown means that glomalin effectively “locks away” atmospheric carbon within the soil, preventing its release back into the atmosphere as carbon dioxide. By physically protecting organic matter within soil aggregates and resisting microbial degradation, glomalin contributes significantly to long-term soil carbon storage. This process, known as carbon sequestration, makes glomalin a meaningful component in the broader effort to manage atmospheric carbon levels.
Agricultural Practices to Increase Glomalin
Farmers and gardeners can adopt several practices to encourage glomalin production and improve soil health. Minimizing soil disturbance through no-till or reduced-tillage farming preserves the hyphal networks of arbuscular mycorrhizal fungi. Conventional tillage disrupts these fungal structures, leading to lower glomalin levels and reduced soil aggregation.
Planting diverse cover crops supports healthy AMF populations by providing continuous living roots, necessary for fungal growth and carbon supply. Mixtures of legumes and grasses, for example, positively impact AMF diversity and soil fertility.
Reducing reliance on synthetic fertilizers, particularly those high in nitrogen and phosphorus, encourages AMF activity, as fungi thrive when plants need their nutrient uptake assistance. Avoiding broad-spectrum fungicides is also beneficial, as these chemicals can harm AMF populations. Implementing these practices fosters a soil environment that naturally increases glomalin levels, leading to more resilient and productive land.