In a recent column about the benefits of organically farmed soil I mentioned that soils with higher carbon stored more moisture.

The mechanism for this interaction is glomalin, a sugar protein that was only identified and named in 1996.

Studies by US researcher Kristine Nicols have found that glomalin levels were higher in soils under native grasses than soils under introduced species, and that shifting cattle before they over-grazed an area helped to raise soil glomalin levels.

Her cropping study found that cultivation and fallowing lowered glomalin levels because cultivation destroyed the hyphae, and fallowing starved them.

Glomalin is produced by mycorrhizal fungi that live inside plant roots and extend hairlike filaments or hyphae into the surrounding soil to obtain more nutrients.

The sticky glomalin proteins sit on the hyphae like small gobs of chewing gum.

Together, the hyphae and glomalin form a sticky net that traps particles of sand, silt, clay and organic matter and holds them together to form lumps or aggregates of soil.

On the surface of these lumps or aggregates, the glomalin forms a waxy coating to stop water pouring into the aggregate and breaking it up.

Aggregates are important in soils because they allow water infiltration, hold water for plant use, and provide organic carbon for soil organisms to feed on.

At the same time, the aggregates also store carbon deep inside the aggregate that microbes cannot access.

Glomalin has other benefits as well.

It coats the fungal hyphae to protect them from decomposition and microbial attack and to ensure that water and nutrients reach the plant.

Scientists are now thinking that glomalin also helps hyphae stay rigid enough to extend into the soil and span the air spaces between soil particles.

So how do you know how much glomalin is in your soil?

Basically, the more you have, the better your soil texture and structure.

If you’d like to read more about glomalin and Kristine Nichols’ work go to www.ars.usda.gov/Research/docs.htm?docid=15971