How much lime do I need to raise my pH?

From the buffer capacity of your soil. As a planning figure: 100 to 150 g per square metre lifts a sand by half a unit, 200 to 250 g lifts a loam by half a unit, and 300 to 400 g lifts a clay by half a unit. A soil test gives you the exact number.

Can I lime and fertilise at the same time?

Separate them by at least three weeks. Lime raises surface pH and can convert ammonium nitrogen to ammonia gas, which is lost to the air rather than taken up by the lawn.

Not reliably. Removing moss needs better drainage, aeration, more light or a higher cutting height. Lime changes pH, and on most mossy lawns the pH is not the limiting factor.

Why is my centipedegrass yellow after liming?

Because you pushed the pH above 6.0, where iron becomes insoluble and this species cannot take it up. Apply 2 g per square metre of ferrous sulphate for the colour and stop liming. The soil will drift back down on its own over two to three years.

operation2026-10-29By The Turf Deskliming

Lime and pH: rate per 0.5 unit, and the species that must not be limed

Parameter sheet

Operation

liming

Implement

Drop spreader or rotary broadcast spreader for granular lime. A soil auger or trowel for sampling to 100 mm. A pH meter or a laboratory soil test; the cheap probe meters sold for garden use are not accurate enough to base a rate on.

Season window

Early autumn, so the lime has a full winter of freeze-thaw and moisture to react before the spring growth period. On warm-season turf, apply in late autumn after growth has slowed. Lime moves only 25 to 50 mm a year through the soil, so the reaction is measured in seasons, not weeks.

Frequency

Only when a soil test says so. On a loam that was limed three years ago the pH may have moved by 0.2 units and no further application is needed. A soil test every third year, plus a rate calculated from the buffer capacity of the soil, is the whole programme.

Target pH, most cool-season turf

Target pH, centipedegrass

Target pH, buffalograss

Lime to raise loam by 0.5 pH units

Lime to raise clay by 0.5 pH units

Lime to raise sand by 0.5 pH units

Maximum per application

Sampling depth

Lime movement through soil per year

6.0 to 7.0pH

5.0 to 6.0pH

6.5 to 8.0pH

200 to 250g per square metre

300 to 400g per square metre

100 to 150g per square metre

250g per square metre

100mm

25 to 50mm

Prerequisites

Take a soil test first. Sample 10 to 15 cores at 100 mm depth from across the lawn, mix them in a clean bucket, and send 250 g of the mixture. Sampling only the surface 50 mm will read artificially high.
Ask for the buffer pH or lime index, not just the pH. The pH tells you where you are; the buffer capacity tells you how much lime it takes to move.
Apply lime at least three weeks apart from any nitrogen or phosphorus fertiliser application.
Mow first and do not water for 48 hours after application, so the granules sit on the soil surface and react there.

Do not run it when

Do not lime centipedegrass, camellia beds or any acid-loving planting above pH 6.0. On centipedegrass lime above that figure locks up iron and the lawn yellows within a month.
Do not apply more than 250 g per square metre in a single application. Split it across two or three seasons; a single heavy application can push the pH past the target and is very hard to reverse.
Do not apply lime and a pre-emergent herbicide in the same week; lime raises the surface pH and can break down the herbicide barrier faster.
Do not use lime to fix a moss problem without addressing drainage and shade. Lime changes pH; it does not drain water or remove shade.

Calibration

Check the spreader drop rate on a 1 square metre sheet over a hard surface before the first pass; lime is bulky and 250 g per square metre is a visible quantity.
Walk at a steady pace in two passes at right angles at half rate each. Streaking with lime produces pH bands that are visible for years.
Retest 12 months after application, not six weeks. The reaction takes a season to show in the reading.
Record the date, product and rate. The next rate calculation depends entirely on knowing what the last one was.

Schematic for the operation Adjusting soil pH with lime — Operation section and season window, generated from this page

Lime is the cheapest long-term improvement you can make to a lawn, and the most commonly misapplied. The rate depends on the soil texture and the buffer capacity, not on the pH alone, and there is a whole group of species that should never be limed at all.

Why pH matters more than any fertiliser

Soil pH controls whether nutrients are available to the root, regardless of how much of them you apply. Below pH 5.5, phosphorus locks up with aluminium and iron and nitrogen cycling slows sharply. Above pH 7.5, iron, manganese and zinc become insoluble and the lawn shows interveinal chlorosis, yellow leaf with green veins.

The pH also controls the microbial population that decomposes thatch. Below pH 5.5 the bacterial population collapses and fungi take over; on a lawn with a thatch tendency of 4 or 5 that is the difference between a 10 mm layer and a 25 mm layer.

The target band for most cool-season turf is 6.0 to 7.0. Tall fescue and fine fescues tolerate 5.5 to 6.5. Kentucky bluegrass, ryegrass, bermudagrass, zoysia and St. Augustinegrass are all comfortable in 6.0 to 7.0. Centipedegrass wants 5.0 to 6.0, and buffalograss tolerates 6.5 to 8.0.

Target pH band by species, and what happens outside it

Species	Target pH	Below the band	Above the band
Buffalograss	6.5 to 8.0	Weak growth, iron available but P locked	Tolerated
Kentucky bluegrass, ryegrass	6.0 to 7.0	Phosphorus locked, thatch builds	Iron chlorosis
Tall fescue, fine fescues	5.5 to 6.5	Thin stand, red thread	Iron chlorosis
Centipedegrass	5.0 to 6.0	Tolerated	Iron locked, yellowing within a month
Bermudagrass, zoysia	6.0 to 7.0	Slow establishment	Iron chlorosis

Working out the rate from the buffer capacity

The rate depends on how much the soil resists a change in pH. A sandy soil with a low buffer capacity needs 100 to 150 g of lime per square metre to move half a pH unit. A loam needs 200 to 250 g. A clay needs 300 to 400 g, and the same 250 g that fixes a sand lawn will move a clay lawn by only 0.3 units.

A soil test report will normally give a lime index or buffer pH and a recommended rate in grams per square metre or in kilograms per 100 square metres. Use that number rather than a rule of thumb; the whole point of paying for the test is to get it.

Never exceed 250 g per square metre in a single application. Where the requirement is larger, split it across two or three autumns. An over-limed lawn takes years to correct, and correcting it means applying elemental sulphur at 100 g per square metre to drop the pH by 0.5 units on a loam.

Which soils and which lawns should not be limed

Calcitic lime raises pH and adds calcium. Dolomitic lime raises pH and adds both calcium and magnesium; use it only where the soil test shows magnesium is low, because in a soil with adequate magnesium it creates an imbalance that reduces potassium uptake.

There is also a group of lawns where liming is actively harmful. Centipedegrass is the clearest case and the target band is 5.0 to 6.0. A pH of 6.5 causes interveinal chlorosis and thinning within one season. Where the same soil also grows acid-loving shrubs, the lawn and the beds need different treatments, and the bed edge is the boundary.

Moss on a lawn is only sometimes a pH problem. Moss establishes where the surface stays wet, the soil is compacted and the light is low. Raising the pH in those conditions does not remove the moss; improving drainage, aerating and raising the mowing height does.

Application, timing and the pieces people get wrong

Apply in early autumn. Lime is not water-soluble and moves through the profile at 25 to 50 mm a year, so it reacts in the top 50 mm of soil first and takes several seasons to influence the root zone at 100 mm. Applying it in spring means the reaction coincides with the stress period rather than preceding it.

Apply in two passes at right angles at half rate. Lime is a bulky material and a single pass streaks badly, leaving pH bands that are visible in the growth for several seasons. Wear a dust mask; lime dust is alkaline and unpleasant rather than toxic, but there is no reason to breathe it.

Do not water it in. Unlike urea, lime needs surface contact with moist soil and reacts over months; irrigation immediately after application moves fines into the thatch where they do less good.

Record what you applied. A lawn that received 250 g per square metre in 2024 needs the 2027 test result before another application, not a second application on a fixed annual schedule.

Questions that come up on this page

How much lime do I need to raise my pH?: From the buffer capacity of your soil. As a planning figure: 100 to 150 g per square metre lifts a sand by half a unit, 200 to 250 g lifts a loam by half a unit, and 300 to 400 g lifts a clay by half a unit. A soil test gives you the exact number.
Can I lime and fertilise at the same time?: Separate them by at least three weeks. Lime raises surface pH and can convert ammonium nitrogen to ammonia gas, which is lost to the air rather than taken up by the lawn.
Will lime kill moss?: Not reliably. Removing moss needs better drainage, aeration, more light or a higher cutting height. Lime changes pH, and on most mossy lawns the pH is not the limiting factor.
Why is my centipedegrass yellow after liming?: Because you pushed the pH above 6.0, where iron becomes insoluble and this species cannot take it up. Apply 2 g per square metre of ferrous sulphate for the colour and stop liming. The soil will drift back down on its own over two to three years.

Sources

The public reference material the figures on this page were checked against:

Annual nitrogen budget15 g·m⁻²

Irrigation per week20 mm

recomputed on these two numbers · species profiles inside ±15%: 8/12 · operation cards touched: 6/7

Kentucky bluegrass, Turf-type tall fescue, Hybrid bermudagrass (Tifway 419), Perennial ryegrass, Zoysiagrass (Empire), St. Augustinegrass (Floratam), Common bermudagrass (seeded), Centipedegrass

Mowing to a set height, Hollow-tine core aeration, Nitrogen programme with split applications, Overseeding and slit-seeding, Irrigation to a deficit or ET replacement schedule, Scarifying and thatch removal

bench heat, dim to bright: 0 / 4 / 4 / 4 / 0

Adjacent entries

Symptom reading table

Four field symptoms, each read back to the parameter that produced it rather than to a product. The last column is the one number that row turns on, with the threshold drawn on it.

Reading	What you see	Chain of causes	Parameter correction	Field confirmation	Scale
Bare patchesreleasedflag the species on the bench →	Bare patches and thin, worn ground recovery window 3–10 wk	Cutting height has been held below the species floor, thinning the stand from the centre of the lawn outwards until the soil is exposed. Concentrated traffic along a path, at a gate or in front of a goal has worn through the canopy to soil, and the species has no rhizomes to repair it. Drought dormancy has gone past the survival limit, four to six weeks for cool-season turf and six to eight for warm-season, and the crowns have died. A fungal patch disease, large patch on warm-season turf or summer patch on cool-season, has killed the crowns in a ring pattern. Grub or chafer larvae have eaten the roots under the patch, and the turf lifts away from the soil like a carpet when pulled. A spill of fertiliser, petrol, herbicide or a concentrated dog urine patch has killed the leaf and the crown together.	Raise the cutting height to the species band: 25 to 40 mm for Kentucky bluegrass, 30 to 50 for perennial ryegrass, 50 to 70 for tall fescue, 40 to 60 for fine fescue. Scarify or core-aerate the bare area to 75 mm depth so the seed has soil contact rather than a compacted surface. Seed at the species rate: 15 g per square metre of Kentucky bluegrass, 30 of perennial ryegrass, 35 of tall fescue, 20 of fine fescue. Where the area is over 1 square metre, use a blend rather than a single species. Where the species has no rhizomes, which is tall fescue, fine fescue and St. Augustinegrass, the only repair is seed or plugs. There is no parameter change that will fill the patch. For a dog urine patch, water 25 mm immediately and leach the salts below the root zone, then reseed. Do not add nitrogen; the patch is already salt-burned. For grubs, confirm by lifting the turf and finding 10 or more larvae per square metre, then treat; below that threshold the lawn recovers on its own. Replace the traffic. A worn path worn again and again needs a hard surface or a paving strip, not another reseed.	Pull a handful of turf at the edge of the patch. If it lifts like a carpet with no roots attached, the cause is grubs or a root disease; if it resists, the cause is surface wear or drought. Look for a ring pattern. Large patch and summer patch kill in expanding rings with a green centre or a green edge, which wear and drought do not produce. Check the cutting height against the species band; scalping produces a uniform thinning across the whole lawn rather than isolated patches. Dig a 100 mm deep spadeful at the edge of the patch and check for larvae, white fungal mycelium, or a hard compacted layer at 50 mm.	4 wk weeks to close
Mossreleasedflag the species on the bench →	Moss colonising thin or shaded turf recovery window 8–24 wk	The surface stays wet: compacted soil, a thatch layer over 15 mm, or a hollow that collects water keeps the top 20 mm saturated for most of the year. Light has fallen below the compensation point of the grass, usually under four hours of direct sun, so the turf thins and stops competing. Soil pH has fallen below 5.5, which suppresses the grass and the bacteria that decompose thatch while moss tolerates the acidity. The cutting height has been held below the species floor for long enough to thin the stand, opening the surface to colonisation. Nitrogen has been below the species budget for several seasons, or above it, in both cases leaving a stand too weak to close the surface. Soil has been compacted by traffic to the point where infiltration drops below 5 mm an hour and every rain sits on the surface.	Core-aerate to 75 mm depth at 50 to 100 mm spacing, two passes at right angles, to break the compacted layer and restore infiltration. Scarify 5 mm in early autumn where thatch exceeds 15 mm, then overseed at the species rate; a thin stand is what moss is colonising. Raise the cutting height to the top of the species band. In shade that means 60 mm for fine fescue and 70 mm for tall fescue, not 30 mm. Switch the species to creeping red fescue, shade rating 5 of 5, where direct sun is under four hours. Moss tolerates shade; most lawn grasses do not. Apply lime only if a soil test reads below pH 5.5, at 200 to 250 g per square metre on a loam, and retest after 12 months. Do not lime on the assumption that moss means acid. Bring the annual nitrogen to the species budget in a shaded lawn, which is a third less than in full sun: fine fescue 4 to 6 g per square metre, tall fescue 8. Improve drainage where water stands: a French drain, a surface swale, or the removal of a compaction pan at 150 to 200 mm.	Push a screwdriver into the soil. If it takes two hands and stops at 50 mm, compaction is the driver and aeration is the first action. Time how long a 100 mm ring filled with water takes to drain. Under 25 mm an hour is compacted; under 5 mm an hour is severely compacted. Map the sun: note how many hours of direct sun the mossy area receives in midsummer, not in spring. Under four hours, no grass species will win without changing the light. Test the soil pH. Moss tolerates a wide range, so pH is only sometimes the driver and should never be assumed. Read the thatch depth with a knife and ruler; above 15 mm the mat is holding the moisture that moss needs.	pH 5.5 soil pH
Thatch over 15 mmreleasedflag the species on the bench →	Thatch layer 15 mm or thicker recovery window 4–12 wk	Nitrogen has been applied above the species budget for several seasons, producing more lignin-rich stem and stolon tissue than the soil can decompose. Clippings have been bagged for years on a lawn that is now below 10 mm of thatch, removing the nitrogen the microbes need to break the mat down. Soil pH has drifted below 5.5, collapsing the bacterial population and shifting decomposition to slower fungal pathways. The lawn is a species with a thatch tendency of 5 out of 5 and has never been scarified. Irrigation is frequent and shallow, keeping the surface constantly moist and the mat compressed rather than allowing it to dry and fracture.	Scarify 5 mm, in early autumn when soil temperature at 50 mm is between 15 and 21 degrees Celsius, with the tines set to just graze the mat. Overseed the same day at the full species rate, 10 to 15 g per square metre for Kentucky bluegrass, 25 to 35 for perennial ryegrass, 30 to 40 for tall fescue. Topdress 1 to 2 mm of sand-loam matched to the root zone, then water 6 to 10 mm a day for ten days. Cut the annual nitrogen to the species budget: 15 g per square metre for Kentucky bluegrass, 10 for zoysia, 6 for centipedegrass and fine fescues. Raise soil pH into the species band with 200 to 250 g per square metre of lime on a loam, applied in the following autumn and retested after 12 months. Switch to mowing at the top of the species band and mulch the clippings, which returns 1 to 2 g of nitrogen per square metre per year.	Cut a 100 mm square flap of turf with a knife, lift it like a hinge and read the brown fibrous layer between the green leaf bases and the dark soil with a ruler. Do it in three places. Push a screwdriver into the profile; if it stops in the mat before reaching soil, the layer is thick and hydrophobic. Watch a hose test: water beading and running off a dry lawn instead of soaking in is the signature of a hydrophobic thatch layer. Check for the crown being lifted above the soil line by parting the grass with both hands; crowns 15 to 20 mm above soil dry out in two days.	15 mm mat depth
Broadleaf weedsreleasedflag the species on the bench →	Broadleaf weed species as indicators of soil and management conditions recovery window 8–30 wk	Compacted soil where the taproots of dandelion and plantain can penetrate but grass roots cannot, so the weeds have an exclusive hold. Cutting height below the species floor, thinning the canopy and letting light reach the soil surface where weed seed germinates. Soil pH outside the species band, which weakens the grass while the weeds in question tolerate the reading. Nitrogen below the species budget for several seasons, producing an open, pale stand that clover and speedwell colonise readily. Surface moisture that stays high, favouring species such as creeping buttercup and moss-adjacent weeds that indicate poor drainage. A thatch layer over 15 mm that keeps seed in contact with moisture at the surface, which is what crabgrass and goosegrass need to germinate.	Core-aerate to 75 mm depth at 50 to 100 mm spacing wherever dandelion, plantain or knotgrass dominate; the taproot species are the compaction indicators. Raise the cutting height to the species band and hold it for a full season. Density, not herbicide, is what keeps weed seed from establishing. Bring the annual nitrogen to the species budget: 15 g per square metre for Kentucky bluegrass, 12 for tall fescue, 6 for fine fescue. Clover and speedwell indicate a lawn that has been underfed. Correct the soil pH to the species band: 200 to 250 g per square metre of lime on a loam to raise half a unit, applied in early autumn. Scarify 5 mm where thatch exceeds 15 mm and remove the mat, which is the germination bed for summer annual grasses. Where drainage is the driver, indicated by creeping buttercup or rushes, add a French drain or a surface swale before any other measure. Overseed at the species rate in early autumn to raise density. A stand at 80 percent cover suppresses new weed germination; a stand at 50 percent does not. Where chemical control is used, treat only the species present, at the label rate, when the weed is actively growing and air temperature is between 15 and 25 degrees Celsius.	Read the indicator species: dandelion, broadleaf plantain and knotgrass indicate compaction; clover and speedwell indicate low nitrogen; creeping buttercup and rushes indicate poor drainage; sorrel and sheep sorrel indicate acidity. Push a screwdriver into the soil where the weeds are densest. Two hands and a stop at 50 mm confirms compaction. Count the stand: lay a 300 mm square frame in three places and count grass tillers per square metre. Below 3,000 tillers per square metre allows weed establishment. Measure the canopy closure by looking straight down in midday sun: if more than 15 percent of the view is soil, the stand is too open. Soil test for pH and phosphorus; weed composition is a hint, not a measurement.	15 g annual N