Lawns on sandy, chalk and clay soil in East Kent

Soil varies from garden to garden

Say this first, because everything else depends on it. Soil changes over short distances, and a garden can be different from the one over the fence, particularly where land has been dug out, filled, built on or levelled. Maps and geology descriptions give a broad picture. They do not tell you what is in your lawn.

The national Soilscapes dataset, produced by Cranfield University and shown through the LandIS Soilscapes Viewer, is a good example of how to read this. It is a 1:250,000 scale, simplified soils dataset for England and Wales, and the viewer's own page says it is not intended as a means for supporting detailed assessments. It conveys a summary of broad regional differences. Use it to get oriented, then check the ground yourself.

Below I describe only what the sources I opened actually say about East Kent. Where they say nothing, I say so.

What the sources say about East Kent

Chalk underneath. A British Geological Survey report on the chalk of East Kent covers the North Downs from the River Great Stour catchment to the coast, including the Isle of Thanet, and says the Thanet Sand Formation lies above the Chalk in the northern and central eastern parts of the area. A magazine article on Thanet's geology describes the local chalk as soft, with the top few metres frost-shattered by Ice Age weathering. Chalk bedrock does not automatically mean a chalky soil: other material can sit between the chalk and your lawn.

Sand and brickearth on Thanet. A Kent Archaeological Society report on pipeline works describes the Thanet hills as upfolds of Tertiary Thanet Beds directly over the Upper Chalk, and records deep Thanet Sands capped with brickearth along the Ramsgate Main. That is a record of one pipeline route, not a soil map, but it shows that sand and brickearth are both part of the picture on Thanet.

Clay and silt in the old Wantsum Channel. The same report describes the Wantsum area as an infilled alluvial plain, with blue-grey clay up to 1.80m thick overlain by grey-brown clay or silty clay up to 2.50m thick at the sites investigated, and silty clays at Stonar. Further north it records slightly clayey sandy silts. This is where excavations happened, not your garden, but it points to heavy, silty ground around the former channel.

Sand near the coast. The Thanet article describes the Margate Sands as fine, rounded quartz grains, with wind-blown sand forming dunes at the cliff base. The Kent report mentions a shingle spit north of Deal with overlying windblown sands. LandIS describes a soil association named Sandwich as mainly deep, well-drained, calcareous and non-calcareous sandy soils on dune sand and marine shingle, with little clay or organic matter, which makes them droughty and easily eroded. The page places the Kent example of these soils near Greatstone, so it does not tell you that a garden in the town of Sandwich sits on one.

What I could not establish from open sources is a parish-by-parish list of which soil sits under which town. If someone offers you one, ask what it was drawn from.

What each soil type does to a lawn

These descriptions are from the RHS soil types page, with the lawn implications following.

• Clay: drains slowly, holds nutrients, bakes hard and cracks in summer, takes longer to warm up in spring than sandy soils, and is easily compacted when trodden on while wet. For a lawn, that means waterlogging, moss and compaction are the likely problems.
• Sandy: drains quickly after rain or watering, dries out quickly, and is low in nutrients because rain washes them out. It warms up quicker in spring than clay. For a lawn, think drought stress and thin grass in summer.
• Chalky: the RHS says many chalky soils are shallow, free-draining and low in fertility, often drought-prone and nutrient poor, and very alkaline: cannot be acidified. Where clay is mixed in, nutrient levels may be higher.
• Silt and loam: silt is fairly well drained, fertile and holds more moisture than sand, but is easily compacted. Loam is well drained and fertile.

What that means for treatment

Clay and silty ground. The main job is relieving compaction and drainage. The RHS recommends a hollow-tined aerator for waterlogged lawns, followed by a free-draining dressing such as horticultural sand, and puts hollow-tine aeration on clay or waterlogged soil at roughly every three to four years. Our guide to hollow-tine or spiking goes through the method. Stay off the lawn when it is wet: the RHS notes that walking on a waterlogged lawn makes the problem worse.

Sandy ground. The main job is holding moisture and nutrients. The RHS drought page recommends adding organic matter to improve soil structure so it retains moisture better, and raising the cutting height in dry weather, since close cutting can weaken the grass. It also advises re-sowing sparse areas in the autumn after a dry summer, ideally with a drought-tolerant mix. The RHS shade page says fescues cope better with drought and low nutrient levels, which is worth knowing when choosing seed; see choosing lawn seed. Light soil is also listed by the RHS as a factor in dry patch, where water stops soaking in. Feeding little and in the right season suits this ground better than heavy feeding once, as general guidance; see when and how to feed your lawn.

Chalky ground. Expect a shallow soil layer that dries out quickly in summer. The same drought advice applies. Because the RHS says chalky soil cannot be acidified, do not chase a lower pH with products. Test before you apply anything that claims to change it.

Mixed ground. Many gardens are a bit of each, with a shallow sandy layer over chalk, or a heavier patch where the garden dips. Treat the lawn by what it does: where water sits, aerate; where it dries first, mulch with organic matter and mow high.

How to test your own soil

Add two checks of your own. These are general guidance rather than RHS tests. First, after heavy rain, note how long puddles stay: more than a day usually means slow drainage or compaction. Second, dig a spade-deep hole in a bed beside the lawn and see how deep the topsoil is before it turns to pale chalk, stones or sand. Do this in more than one spot, because depth can change across a single garden.

• Roll it: clay is sticky when wet and easily rolled into a long, thin sausage. Sandy soil is gritty and cannot be rolled into a sausage shape. Silt has a slightly soapy, slippery feel.
• Vinegar test: if soil froths when placed in a jar of vinegar, it contains free calcium carbonate, which indicates lime-rich soil.
• pH kit: the RHS says you can measure pH with a simple testing kit. Neutral is 7, and it describes a slightly acidic soil of pH 6.5 as the best general-purpose pH for gardens.

Putting it to use

Match the work to what the lawn is telling you. A hard, damp, mossy lawn on heavy ground probably needs aeration before anything else; our guide to moss in lawns covers the connection. A lawn that burns to straw in July on light ground needs a moisture-keeping approach. Our hollow-tine aeration and overseeding services are the usual tools, and the annual plan sets out the order across the year.