Composting Masterclass: Black Gold for Your Allotment

Composting is one of the most valuable skills for allotment gardeners. Done well, it improves soil structure, feeds crops, reduces waste, and cuts watering needs. Done badly, it can become slow, smelly, or full of pests.

This guide explains how composting works, what to add (and avoid), how to fix common problems, and how to compost successfully on a typical allotment site.

🌱 1. What Composting Actually Is (and Why It Matters)

Composting is a controlled natural process where microorganisms break down organic material into a dark, crumbly soil improver.

Good compost:

• improves soil structure

• increases water retention

• feeds soil life (not just plants)

• reduces need for bought compost and fertilisers

On allotments, composting is especially important because:

• soil is often poor or compacted

• large volumes of plant waste are produced

• importing compost is expensive and labour-intensive

🧺 2. Composting Systems on Allotments

Compost Heaps (Open or Binned)

The most common allotment method.

Typical setups:

• Wooden pallet bays (often 2–3 bays)

• Plastic compost bins

• Open heaps (less tidy, slower)

Best practice:
At least two bays:

• one “active” (being filled)

• one “resting” (finishing compost)

🍃 3. What to Compost: Greens & Browns Explained

Successful compost relies on balance, not precision.

“Greens” (Nitrogen-rich)

These speed decomposition.

• vegetable peelings

• fresh weeds (no seeds)

• grass clippings

• green plant waste

“Browns” (Carbon-rich)

These provide structure and air.

• cardboard (plain, torn up)

• paper

• straw

• dry leaves

• wood chips (small amounts)

👉 Aim for roughly 50:50 by volume, but don’t overthink it.

🚫 4. What NOT to Compost (or Use with Care)

Avoid:

• cooked food

• meat, fish, dairy

• dog or cat waste

• diseased plants (unless hot composting)

• perennial weeds with roots (bindweed, couch grass)

These attract pests or survive the composting process.

🔥 5. Hot vs Cold Composting (Allotment Reality)

Cold Composting (Most Common)

• Add material gradually

• Takes 6–18 months

• Kills fewer weed seeds

• Low effort

Hot Composting

• Large volumes added at once

• Needs turning

• Reaches high temperatures

• Faster (2–4 months)

👉 Most allotment composting is cold composting — and that’s fine.

🔄 6. How to Build a Compost Heap (Step-by-Step)

1. Start with a coarse base (twigs, straw)

2. Add alternating layers of greens and browns

3. Water lightly if dry

4. Keep heap damp, not wet

5. Cover if possible (retains heat and moisture)

Turning:

• Speeds decomposition

• Adds air

• Optional but helpful

🐀 7. Preventing Smells & Pests

To avoid smells:

• Add browns if compost is wet or slimy

• Turn heap to introduce air

To deter rats:

• Avoid food waste

• Bury fresh material

• Use wire mesh base if needed

A healthy heap smells earthy, not rotten.

🌾 8. When Is Compost Ready to Use?

Finished compost is:

• dark brown to black

• crumbly

• smells like soil

• no recognisable food waste

Uses on the allotment:

• mulch beds

• improve soil before planting

• potting mixes (screened)