Short answer:
You can assess compost quality with a few simple at-home checks — no lab required. These tests help you tell if a mix is too wet, too woody, or poorly balanced before planting.

1. The Squeeze Test — structure and moisture

• Take a small handful and squeeze firmly.
• If water drips out: it’s too wet — likely compacted or anaerobic.
• If it stays in a firm lump and breaks apart easily: ideal structure.
• If it falls apart like dust: it’s too dry or overly fibrous — re-wet gently before use.

This simple test gives a quick read on porosity and water-holding capacity — both vital for healthy root systems.

2. Smell Test — signs of biological quality

• Pleasant, earthy aroma: good sign — fully composted and stable.
• Sour, silage, or ammonia smell: indicates incomplete composting or poor aeration. Allow to air for a few days before use or mix with mature compost.

3. Visual Check — texture and contaminants

Spread a handful on a clean tray or sheet of paper:

• Even, crumbly texture: good for pots and containers.
• Large wood pieces or unrotted fibres: poor screening or immature compost.
• Foreign materials (plastic, glass, stones): low-grade recycled content.
• Dark brown/black colour: usually higher organic matter or humus content.

See Compost Quality & Stewardship (WTB-C3) for more detail.

4. Container “stability” test (optional)

• Fill a small pot with MPC.
• Plant a hardy, fast-growing seedling (e.g. lettuce plug or marigold).
• Water normally for 2–3 weeks.

Results:
Healthy growth and good drainage → compost is balanced and stable.
Stunted growth, yellowing, or sour smell → compost may be too rich, saline, or oxygen-poor.

This is not a germination test — most MPCs are unsuitable for seeds. See FAQ: Can I use MPC for seed germination? for details.

5. Optional pH and EC (salinity) checks

• pH 5.5–6.8: typical for most MPCs.
• Above 7.5: excess lime or recycled green waste.
• High EC: excessive fertiliser salts — avoid for young or sensitive plants.

6. Compare with the bag label

• Peat-free / peat-reduced / coir-based?
• Any organic certification?
• Suitable uses listed (containers, shrubs, bulbs)?

If appearance or texture don’t fit the description, that’s a warning sign. See What to Look for in the Bag (WTB-C1) for how to decode compost labels.

Summary

Good compost feels alive: springy yet moist, smells earthy, drains freely, and contains minimal debris. A quick squeeze-and-sniff tells you more about quality than most labels — trust your senses.