Composting and improving your soil: the complete guide
By Hovenier Hoofddorp · Updated July 26, 2026
Compost is the fastest, cheapest way to improve the heavy clay soil common in this region: working 5 to 10 cm of compost into the top 20–30 cm every year makes the soil more open, holds moisture better in summer and drains better in winter. Making your own compost costs almost nothing and yields usable garden soil within 6 to 12 months.
How do you make compost at home?
A good compost heap balances two types of material:
- Green material (nitrogen-rich): vegetable and fruit scraps, grass clippings, fresh plant trimmings. Provides moisture and nutrients.
- Brown material (carbon-rich): dry leaves, cardboard, wood chips, straw. Provides structure and air.
Aim for roughly 1 part green to 2–3 parts brown. Too much green (especially thick layers of fresh grass clippings) creates a wet, smelly, airless mass; too much brown slows decomposition right down. Turn the heap every 4 to 6 weeks to add air and speed up the process — this cuts the timeline from over a year to 6–9 months.
What can and cannot go in the compost?
| Suitable | Not suitable |
|---|---|
| Vegetable and fruit scraps (uncooked) | Meat, fish and dairy (attracts vermin) |
| Coffee grounds and tea bags (plastic-free) | Diseased plant material (spreads fungal disease) |
| Dry leaves, grass, weeds without seed | Weeds with ripe seed or persistent roots (bindweed, couch grass) |
| Eggshells, cardboard, unbleached paper | Treated wood, glossy/coated paper |
| Wood chips and fine twigs | Cat litter and dog waste |
How do you improve clay soil specifically?
Sea clay, such as found across this region, is naturally nutrient-rich, but its fine particles pack tightly — suffocating roots in winter and cracking in dry summers. Compost fixes this structurally:
- Work 5–10 cm of compost into the top 20–30 cm every year, ideally in autumn so winter rain works it in further.
- Mix in coarser material (wood chips, sharp sand) for extra airiness in especially heavy spots.
- Mulch borders year-round with a thin layer of compost — this feeds the soil gradually without digging.
- Avoid working wet clay: walking or digging on wet clay compacts the structure right back down. Wait until the soil feels crumbly.
After two to three seasons of consistent composting, the difference in the top 20 cm is clearly noticeable: lighter, darker and easier to work. See also our climate-proof garden guide.
Frequently Asked Questions
How long does it take for compost to be ready?
With regular turning (every 4 to 6 weeks), compost matures within 6 to 9 months; without turning it takes 12 to 18 months. Finished compost is dark, crumbly, smells like forest soil, and the original materials are no longer recognisable.
Can you use too much compost?
In practice, overdoing compost is rare for an average border — 5 to 10 cm a year is a safe upper limit. In vegetable gardens, too much fresh (not fully matured) compost can push nitrogen levels too high, giving plants lots of leaf and little flower or fruit. Use fully matured compost there.
Should I replace clay soil with topsoil or potting compost?
No, that is rarely necessary and often counterproductive — clay is naturally very fertile. Structural improvement with compost delivers a better, permanently fertile soil over time than digging out and replacing, which is also far more expensive.
Why does my compost heap smell bad?
A rotting smell usually points to too much wet green material (often a thick layer of fresh grass clippings) without enough air. Mix in dry brown material immediately (leaves, cardboard, wood chips) and turn the heap — that restores oxygen and stops the anaerobic process causing the smell.
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