Soil Test 6: Penetration Resistance

Purpose: to identify compacted soil layers that may restrict root growth and water infiltration.

Material needs: metal rod (we used a 4mm rod from Bauhaus cut to 40cm), ruler

Time estimated: 5 minutes

Step-by-step instruction:

1. Use the metal rod to probe vertically into the soil.
2. While pushing the rod down, determine changes or differences in penetration resistance. Use a ruler to measure the depth at which resistance is observed.
3. Record the depth of resistance.

Form

Note penetration resistance score:

0 – No resistance: Rod enters easily and can penetrate fully (no compaction perceived).

1 – Slight resistance: Rod enters with minor effort; continuous penetration.

2 – Moderate resistance: Noticeable effort; may hit a thin compacted layer; penetration often slows/stops around 10–20 cm.

3 – High resistance: Rod enters only with strong effort; penetration limited to ~5–10 cm.

4 – Very high resistance / refusal: Rod will not enter or bends readily at the surface.

Depth of resistances (record several if multiple exist): _______