How Do You Measure 40% Humus in Soil?

#permaculture #soilhealth #humus
Permaculture often recommends building soil with up to 40% humus — but what does that actually mean in practice?

In this Q&A, Geoff explains how to recognize humus-rich soil, how deep to measure it in a garden, and why root depth matters more than exact percentages. Filmed in a productive kitchen garden, Geoff shows how sandy soil can be transformed into rich, living soil through compost, mulch, worm castings, and biology.

This video is taken from Geoff’s 2019 Online Permaculture Design Course, which includes weekly Q&A sessions where he answers student questions. Learn more about Geoff’s courses at: https://www.discoverpermaculture.com

Key Takeaways:

00:00:04 – 00:00:13: The question: When we say garden soil should be about 40% humus, how do we actually measure that?
00:00:13 – 00:00:30: The challenge: In raised beds volume is clear, but how do we measure humus when working directly in the ground?
00:00:30 – 00:00:55: Building humus in the garden through organic inputs like mulch, compost, worm castings, compost tea, and cover crops.
00:00:55 – 00:01:22: Visual clues of humus-rich soil: dark color, crumb structure, moisture retention, and abundant earthworms.
00:01:22 – 00:01:46: In this garden, the rich topsoil layer is about two feet deep and continues improving as organic matter is added.
00:01:46 – 00:02:03: A practical way to gauge soil depth is simply using a spade to see how deep loose, healthy soil extends.
00:02:03 – 00:02:29: Root depth is the most useful measurement. Humus tends to be richest near the surface and gradually decreases deeper down.
00:02:29 – 00:03:08: When averaged through the root zone, a well-built garden soil can reach around 40% humus — even if it started as poor sandy soil.