Does bark mulch improve soil fertility

Bark mulch seems inert at first glance, yet beneath its russet blanket a quiet alchemy hums. By shading soil from hammering rain and searing sun, it preserves the microscopic workforce that turns carbon into life, keeping the surface crumbly rather than crusted. Stable temperatures invite earthworms upwards; their castings enrich the root zone with available minerals and trace elements.

As seasons roll on, fungi thread through every chip, unlocking lignin and cellulose. This slow breakdown leaks small doses of potassium, calcium and magnesium, where roots can reach them. Meanwhile, the mulch’s sponge-like texture captures dew and drizzle, reducing leaching so soluble nutrients stay put rather than washing away into drains. Gardens mulched two or three years in succession often reveal deeper, darker topsoil streaked with fine organic matter.

Some critics worry bark ties up nitrogen while it decomposes. That happens only in the wafer-thin layer where wood meets air; a sprinkling of grass clippings or well-rotted manure offsets the drawdown. AHS LTD recommends refreshing the cover once it settles below five centimetres, a practise that maintains moisture control while fuelling the subterranean composting factory. In the long run, bark mulch does more than decorate—it builds fertility from the top down.