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Getting compost and soil preparation right in spring sets up everything that follows. The window between the last frosts and the first sowings is the best time to work organic matter into the beds and check what your soil actually needs. For what to sow once your beds are ready, see our March sowing guide. The RHS guide to soil improvement covers the science in detail.
Part of our Composting Hub — the complete UK guide to bins, tumblers, leaf mould, the seasonal jobs, and what to add and what to leave out.
Spring soil preparation is one of the most satisfying jobs of the gardening year — and one of the highest-return investments of time on any plot. This guide covers what to add, how much, and when.
My allotment is on chalk with thin topsoil near the East Sussex coast — some of the most free-draining, low-organic-matter soil you’ll find in a UK kitchen garden. On chalk, an annual spring compost top-dressing is the single most important job on the plot. Beds that get it consistently, year after year, grow crops that the original chalk soil simply wouldn’t support. The improvement is gradual but it’s real and it accumulates.
Understanding your soil
Do a field test before you start. Take a handful of damp soil and squeeze it: clay holds tightly in a ball that doesn’t crumble; sandy soil falls apart into individual grains immediately; loamy soil (the ideal) holds loosely and crumbles easily; chalky soil is pale, often with visible chalk fragments, and drains almost immediately.
pH matters for some crops — most vegetables prefer slightly acid soil (pH 6–7). A basic pH test kit from any garden centre is worth doing once on a new plot. On chalk the pH is high (alkaline), which can lock out certain nutrients. Annual compost additions gradually buffer the pH over time.
When to start preparing in spring
The signal that soil is workable: it crumbles rather than smears. If you squeeze damp soil and it sticks together in a smooth ball, wait — working wet soil damages structure and creates hardpans that roots can’t penetrate. In the south of England, soil is often workable from late February. In most of the UK, early to mid-March is ideal. In the north and Scotland, wait until April.
What to add in spring
Garden compost: The best option if you make your own. Well-rotted compost — dark, crumbly, earthy smell, no recognisable original material — is ready to use immediately. Add 5–10cm to bed surfaces. On chalk, I go heavier: 8–10cm every spring, because the organic matter breaks down faster than on heavier soils.
Well-rotted manure: Horse or cattle manure aged for at least a year is excellent. Fresh manure burns plants — it must be rotted first. Local stables and farms sometimes offer it free or cheaply. It transforms chalky and sandy soils over several seasons of consistent use.
Peat-free bought compost: For top-dressing beds, peat-free multipurpose compost works well. More expensive than homemade but effective and now comparable in quality to peat-based alternatives.
What NOT to add in spring: Fresh grass clippings (they heat up and can scorch plants); unrotted plant material; anything from diseased plants (spreads disease into the bed). Partially rotted compost can be used as a mulch under established plants, but keep it away from direct seedbed use.
No-dig method in spring
Lay 5–10cm of compost on top of beds without digging it in. Worms and soil organisms incorporate it naturally over weeks. This approach preserves soil structure, doesn’t disturb beneficial organisms, improves water retention, and is much easier on the back than annual digging. It also builds soil quality year on year in a way that repeated digging doesn’t.
Making your compost heap work better in spring
In spring you’re adding a lot — kitchen scraps, old plant material from winter clearing, first grass cuts. Keep it working efficiently with a roughly 60:40 ratio of brown (cardboard, leaves, straw) to green (grass, scraps, young weeds). Too much green and it becomes anaerobic and slimy; too much brown and it barely decomposes. Layering comfrey or nettles between additions speeds things up — both are high in nitrogen which feeds the decomposition process.
How much compost to add per bed
5–10cm as a top-dressing is the standard guidance, and it’s correct for most established beds. For new beds built from scratch, a deeper layer (15–20cm) is worthwhile. For chalk or sandy soil, go to the upper end — 8–10cm. Repeat every spring and the improvement compounds over time.
Can I use homemade compost directly in spring?
Yes, if it’s fully rotted — dark, crumbly, earthy smell with no recognisable original material. If it’s still fibrous or smells strongly, let it mature longer or use it as a mulch under established plants rather than in active seedbeds.
How much compost should I add per bed?
Around 5–10cm as an annual top-dressing. On chalk or sandy soil, go to 8–10cm. For new beds being built from scratch, 15–20cm gives the best start.
What chalky soil teaches you
The annual compost top-dressing is the single most productive job on the plot. Nothing else — no fertiliser, no special treatment — has made as consistent and visible a difference to crop quality as steady, generous, annual compost additions over many seasons. Start now, do it every spring, and the soil five years from now will be dramatically different from what you’re working with today.
If you’re gardening on alkaline ground, our guide to gardening on chalky soil covers which plants thrive and how to improve your soil over time.
If you’re gardening on alkaline ground, our guide to gardening on chalky soil covers which plants thrive and how to improve your soil over time.
If you’re gardening on alkaline ground, our guide to gardening on chalky soil covers which plants thrive and how to improve your soil over time.
Related Buying Guides
- Best Compost Bins UK — Hotbin, tumblers, traditional bins: our picks
- Best Garden Tools UK
- Garden & Outdoor
- December on the Allotment: Gentle Winter Jobs for Real UK Plots
Where to Buy Compost and Soil Improvers
For quality compost, soil conditioners, and growing media, Thompson & Morgan stock a reliable range — particularly useful if you’re ordering seeds at the same time. Dobies also carry seed composts and growing media alongside their seed range.
Last reviewed: April 2026
📋 From the D&L Shop: Planning your growing year? Our Your First Year on the Allotment guide covers every month from clearing the plot to your first proper harvest — written from 15+ years of UK growing experience. £9.99, instant PDF download. Also useful: the Allotment Plot Planner (£4.99) for mapping beds and planning crop rotation. Browse the full shop →
Incredipeatfree Premium Peat Free Multi-Purpose Compost for Beds Baskets & Containers For Strong Root Growth & Healthy Flowers & Foliage 1 x 70 Litre Pack by Thompson and Morgan
🛡 Our standards: How we research · Editorial policy · Affiliate disclosure · Corrections · Last reviewed: April 2026
About Gareth
Gareth Isherwood is the editor of Danbury & Lovejoy. He has baked bread at home for 25+ years and has 15 years of growing experience across gardens, containers and other growing spaces, including an East Sussex allotment for the past three years. Read his full story →
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