Hydraulic Properties of Sands Treated with Fungal Mycelium of Trichoderma virens

Filamentous fungi grow by extending and branching hyphae through soil pores, which creates an interconnected fibrous network known as mycelium. Fungal mycelium can cross-link and entangle soil particles, which reduces pore size and alters pore structures. Fungal mycelium also can secrete hydrophobic compounds, increasing the water repellency of soils. This study investigated the effect of fungal mycelium on the hydraulic properties of sands, including the soil-water retention curve (SWRC), soil water repellency, and hydraulic conductivity. Ottawa 20/30, 50/70, and 100/200 sands were treated with a filamentous, nonpathogenic, and saprotrophic fungus, Trichoderma virens (ATCC 9645). The results showed that fungal mycelia increased air entry suction by as much as 11.8 times, and increased water repellency at the sand surface from hydrophilic to extreme water repellency after 10 days of fungal growth. Hydraulic conductivities of fungal-treated sands decreased (by as much as 21 times at 20 days of fungal growth) with increasing fungal contents. The reduced hydraulic conductivities of fungal-treated sands can be maintained even under starvation condition (i.e., absence of nutrients). Scanning electron microscopy (SEM) images showed that fungal mycelia modified pore structures by cross-linking and entangling sand particles.