Farm Composting Guide: Turn Waste into Black Gold

Updated 2026-07-10 · Soil & fertility

Compost is the cheapest, most reliable way to build soil fertility and structure from materials you already have — crop residue, animal manure, kitchen and market waste. The whole craft comes down to four things microbes need: the right carbon-to-nitrogen balance, moisture, air, and a bit of time.

Get the carbon-to-nitrogen balance right

Think of two families of material:

• "Browns" (carbon) — dry straw, dead leaves, wood chips, husks, cardboard. Bulky, slow, energy for microbes.
• "Greens" (nitrogen) — fresh manure, green weeds, kitchen/market scraps, gram/legume trash. Wet, fast, protein for microbes.

Aim for roughly 2–3 parts browns to 1 part greens by volume (about a 25–30:1 C:N ratio). Too much green goes slimy and smells of ammonia; too much brown just sits there.

Build the pile

Make a heap at least 1 metre wide and high — smaller piles do not hold heat. Layer browns and greens like a lasagne, adding a few shovels of old compost or garden soil as a microbe starter and a sprinkle of water on each layer. A handful of rock dust or wood ash is optional. Chop coarse material so it breaks down faster.

Moisture, air and heat

• Moisture: as damp as a wrung-out sponge — a squeezed handful should feel wet but not drip.
• Air: microbes need oxygen. Turn the pile every 1–2 weeks (or insert vent sticks) to keep it aerobic and avoid smell.
• Heat: a working hot pile reaches 55–65°C in the centre within days — hot enough to kill most weed seeds and pathogens. When it stops reheating after turning, it is maturing.

Know when it is ready

Finished compost is dark, crumbly and smells of forest earth — you cannot recognise the original materials, and it no longer heats up. This usually takes 2–4 months hot, or 6–12 months cold. Using unfinished compost can rob soil nitrogen and burn roots, so cure it fully. Screen out lumps, keep it covered from heavy rain, and apply it to your beds — or brew a small batch into compost tea for a biology boost.