Long periods of hot, dry weather and spells of excessive rainfall place considerable pressure on lawns. How we manage the grass and the soil beneath it can influence how well a lawn survives these conditions and recovers afterwards.

Nitrogen, acidity and soil life

Nitrogen fertilisers do not simply kill soil life. However, continued use of acidifying nitrogen fertilisers can gradually lower soil pH, particularly where the soil has little capacity to buffer that change.

If the soil becomes excessively acid, conditions become less favourable for some beneficial organisms, including those responsible for breaking down organic material. Excessive nitrogen feeding can also increase the production of grass stems and roots. Together, increased growth and slower decomposition can encourage thatch to accumulate.

This does not mean that an acidified lawn contains no soil life. Rather, its biological community and activity may change, reducing some of the natural processes on which healthy turf depends.

Checking soil pH is essential

Fine lawn grasses, including many fescues, can grow successfully in slightly acid soil. A pH around 6.25 can be suitable, but there is no single ideal figure for every fine lawn: the grass mixture, soil and management all matter.

Neutral pH is 7; a reading of 6.5 is already slightly acid. Soil testing should therefore come before any attempt to raise or lower the pH.

Acidity can influence which weeds thrive, but it is not a reliable general weed-control method. Daisies favour neutral or chalky conditions, yet can occur in soils above pH 5.5, so a lawn at pH 6.25 may still contain them.

Understanding thatch

Thatch forms when resistant grass material accumulates faster than it decomposes. It contains mainly stems, roots and crowns, with both living and dead material present.

Short grass clippings normally break down readily and recycle nutrients. They should not be confused with the more persistent material that forms most thatch. A thin thatch layer can be useful, while excessive build-up can create problems for roots and water movement.

What pastures and verges can show us

Comparing lawns with pastures, verges and other grassed areas illustrates how different management regimes can affect recovery after drought or waterlogging.

These comparisons are useful observations, although differences in grass species, mowing height, soil structure, drainage and compaction also need considering. They cannot establish soil acidity as the sole cause.

One possible solution – Overseeding with microclover

Overseeding an existing lawn with microclover creates a mixture of grass and clover. Clover is a legume: bacteria living in nodules on its roots convert nitrogen gas from the atmosphere into forms the plant can use.

Some of that nitrogen subsequently becomes available to the surrounding grass through the breakdown of clover material, roots and returned clippings. Where sufficient clover establishes, this can remove the need for routine nitrogen fertiliser in a modestly managed lawn. Simply scattering a small amount of seed does not guarantee that result.

Microclover is nevertheless a living plant with its own limitations. It can suffer during severe heat and drought, so it should be regarded as one part of a more varied lawn rather than a guarantee of year-round green cover.

The practical aim is to support healthy soil, appropriate nutrition and a suitable mixture of plants, giving the lawn a better chance of coping with changing conditions.

Notes on the Cuffley lawn recovery plan

The aim is to loosen the compacted soil and thicken the grass cover. Start when the soil is moist and workable. Leave feeding and overseeding until spring if the grass has stopped growing or the ground is cold and wet.

1. Test the soil. Check the pH before applying anything. Add garden lime only if the test shows the soil is too acidic for the grass mix. Apply lime and chicken manure on separate visits if both are needed.
2. Spike the compacted areas. Push a garden fork into the soil and gently rock it back to open up the ground. Work across the affected areas when the soil is moist. Wait if it’s waterlogged, frozen or too hard to fork.
3. Feed once the grass is growing. RocketGro lists its chicken manure for beds, borders and vegetable plots. Ask RocketGro to confirm whether it suits an established lawn and what rate to use before applying it. RocketGro Organic Chicken Manure RocketGro
4. Overseed the thin patches. Lightly rake the surface so the seed touches the soil. Sow when the soil is warm enough for the chosen mix. Keep the surface moist for the first three weeks and continue if the seedlings are still establishing. Tim will add the grass mix and sowing rate separately.
5. Review the lawn in spring. Check whether water drains more freely and where the grass is still thin. If using MycoForce Inoculant, follow Symbio’s turf instructions so it reaches the root zone. Symbio MycoForce turf inoculants symbio.co.uk
6. Trial the water-retaining polymer separately. The Accepta link currently lists 4302S. Confirm the grade, application rate and method for an established lawn with Accepta. If suitable, try it on a small patch and compare it with a nearby patch that gets the same aeration and seed. Keep the polymer and MycoForce applications separate unless the suppliers confirm they can be used together. Accepta Super Absorbent Polymer