Applying lime to raise soil pH

Confirm first

Only lime if a soil test shows pH below about 6.0. Moss and thin grass can have other causes, and over-liming pushes the soil too far the other way, where trace nutrients get locked up and some lawn weeds thrive.

Which lime

• Ground limestone (calcium carbonate): slow and gentle, the usual choice.
• Dolomitic lime: also supplies magnesium, useful if a test shows it is low.
• Avoid quicklime and hydrated lime on lawns; they act fast and can burn grass.

How much and when

The amount depends on how far off the pH is and on soil type; clay needs more than sand. Use the rate your test or soil lab recommends, and on an established lawn split large amounts into doses of no more than about 100–150 g/m² (2–3 lb per 100 sq ft) per application. Autumn or early spring is best; rain works it in.

How

• Spread evenly with a spreader on dry grass, then water in.
• Do not apply at the same time as a nitrogen fertilizer; leave a couple of weeks between them.
• Retest after six to twelve months before adding more.