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Glomalin, Holding it All Together
by LuAnn Rolling, District Conservationist, Allamakee County
We’ve been talking about healthy soil and soil microorganisms. One of these is mycorrhizal fungi and how important it is for healthy plant function. This fungi attaches to the plant roots and can grow out from the roots to assist in obtaining nutrients and water. What we haven’t discussed is that this fungi is covered with a special coating called glomalin. This is a sticky compound that keeps water and nutrients from getting lost on the way to and from the plant.
Glomalin is extremely “tough”. It is resistant to microbial decay and can last at least 10 and up to 50 years in the soil if not disturbed. The fungi growing in the soil acts like a frame upon which soil particles collect. The fungi produces glomalin which glues the soil particles together. Once the soil is covered with glomalin glue it is hard to break apart. These are called soil aggregates.
Once aggregates are present the soil can form spaces for air to be in the soil and for water to infiltrate into the soil. These spaces also allow for plant roots to grow freely because they are not restricted by a compacted layer or lack of air and oxygen.
If the soil is not aggregated, it is unstable, and water can easily detach and move it. This type of erosion is visible as dirty water after a rainstorm and rills and gullies in fields. Poorly aggregated soil quickly forms surface crusts. Once the crust is present rainfall quickly runs off and does not infiltrate for future plant use. Research has shown that 1/32” of crust will restrict so much water and air from entering the soil that plants can starve due to lack of oxygen.
Some farming practices that lead to poor soil aggregation include tillage, chopping or grazing to the point of bare soil, removing organic matter by baling crop residue and using pesticides that are harmful to the beneficial microorganisms like fungi.
There are farming practices that can improve soil stability. Obviously no-till since tillage breaks the strands of glomalin forming fungi and disrupts any channels or pore spaces present in the soil. Planting cover crops as all soil microorganisms need for a growing plant to survive.
In addition, aggregates form readily in soil receiving manure, as it is high in carbon and nutrients and stimulates microbial growth. The opposite is true of synthetic or commercial fertilizer as it has the nutrient but not the energy source.
Well managed pasture and planting forage plants with fibrous root systems that contribute organic matter will encourage microbial activity and the production of soil aggregation.
