Practical in-field soil assessment methods for farmers, based on the “How to Become a Soil Health Expert” article (Sectormentor/PFLA) and AHDB Soil Assessment Methods sheet from Direct Driller Issue 3.
Approach
Developed through collaboration between the PastureFed Livestock Association (PFLA), soils advisor Niels Corfield, and the Sectormentor team. Principle: farmers should set goals for each field, choose 4–5 tests, and monitor trends over time as management changes.
Best time to test in the UK: September and October.
[Source: dd-issue-03, 2026-04-11]
Three Key In-Field Tests
1. Slake Test (Wet Aggregate Stability)
- Place small pieces of soil in a sieve, submerge in water, shake vigorously
- Well-aggregated soil: pieces survive intact; water remains clear
- Poorly-aggregated soil: pieces break down; water becomes murky
- Score: 0–8 scale (8 = almost exclusively true aggregates, high microbial activity)
- Developed with Jenni Dungait (formerly Rothamsted soil health professor)
- Jenni Dungait’s research (forthcoming at time of writing) shows slake test is an excellent proxy for Soil Organic Carbon
[Source: dd-issue-03, 2026-04-11]
2. Earthworm Counts
- Dig 20cm x 20cm x 20cm pit, hand-sort for 5 minutes
- UK average considered good: 15–20 worms per pit
- Best done: late September to early October
- Identify three types for diagnostic value (see Earthworms Under No-Till and #30MinWorms survey):
- Surface worms (litter-feeders) — break down organic matter
- Topsoil worms — aggregate soil, mobilise nutrients
- Deep burrowers — drainage, aeration, deep rooting
- If any type is absent, indicates potential over-cultivation or under-feeding of soil
[Source: dd-issue-03, 2026-04-11]
3. Infiltration Rate
- Use 150mm diameter pipe (chimney flue section), hammer 75mm into ground
- Pour set amount of water, time how long it takes to infiltrate
- Target: under 5 minutes in most soils
- Smaller diameter cylinders (e.g. baked bean tin) can cause artificial compaction, giving misleading slow results — larger diameter recommended
[Source: dd-issue-03, 2026-04-11]
Sectormentor for Soils App
Digital tool for recording in-field soil observations:
- Record photos and numerical results per field
- Build visual diary showing above and below-ground conditions
- Track trends over time with graphs and searchable records
- Share results with agronomists or other farmers for discussion
- Website: soils.sectormentor.com
[Source: dd-issue-03, 2026-04-11]
AHDB Soil Assessment Methods — Grower Ratings
From AHDB information sheet based on 2015 regional grower consultations:
| Method | Skill (1–5) | Time (1–5) | Cost (1–5) | Grower notes |
|---|---|---|---|---|
| Spade diagnosis (30cm) | 1 | 1 | 1 | Most common; “spade is always with me” |
| Plant health monitoring | 1 | 1 | 1 | Seasonal; needs experience |
| Total SOM (%) | 1 | 1 | 1 | No need to do annually |
| Visual soil assessment (AHDB tools) | 1 | 2 | 1 | Assessment speed comes with experience |
| Standard lab test (P, K, Mg, pH) | 1 | 2 | 2 | Directly informs fertiliser strategy |
| Visual evaluation of soil structure (VESS) | 2 | 2 | 1 | Some specific knowledge required |
| Earthworm counts | 2 | 3 | 1 | Seasonal fluctuations; ID skill needed |
| Micronutrient test | 2 | 2 | 3 | Only if deficiencies suspected |
| Soil pit/profile (30–150cm) | 3 | 3 | 1 | Very useful if done properly |
| Soil health test (pH, P, K, Mg, SOM, respiration) | 3 | 2 | 3 | Skill required for interpretation |
| SOM balance modelling | 5 | 5 | 2 | Not commonly used in UK yet |
| Soil life suites (food web, enzymatic) | 5 | 2 | 5 | No standards yet; high skill for interpretation |
[Source: dd-issue-03, 2026-04-11]
Related Pages
- Earthworms Under No-Till — Earthworm counts and #30MinWorms survey protocol
- Soil Carbon and Organic Matter — SOM measurement and slake test as proxy
- The Albrecht Method — Base Cation Saturation Ratios — Base saturation testing as soil chemistry assessment
- Conservation Agriculture — Core Principles — Building soil health as CA goal