Alkaline lawn soil encourages some weeds, restricts the lawn grasses ability to absorb certain nutrients and can negatively affect your lawn's overall health.
Identify the problem
Alkalinity is measured by pH. pH above 7 is alkaline and below 7 is acid. While fine fescue grasses prefer pH of low acidity down to 5.5 most lawn grasses prefer neutral pH between 6.5 and 7.0. Alkaline soil may cause deficiency of iron, zinc, copper and manganese in lawn grass. Iron chlorosis (loss of green colour) in grass, caused by inadequate iron, is a common problem in alkaline soils.
Soil test kits and meters are available for checking the soil pH. See McGregor's Moisture, Light and pH Meter.
- Plain elemental sulphur (or sulfur) is probably the easiest and most common way to lower the pH of soil. It can be spread on top of the soil. Sulphur is slow-acting, you should not apply more than 1 kg per 10 m2 at any time.
- Lime and Sulphur for Soil pH Adjustment.
- Fertilizers that contain ammonia (such as ammonium nitrate), urea, or amino acids will have an acidifying effect on the soil in your lawn. LawnPro All-in-1 can be used to reduce soil pH.
Mulches and Compost
- When organic matter breaks down, it tends to make soil more acidic. Regular use of organic compost and mulches will bring the soil pH closer to the neutral to slightly acidic level levels suitable for lawn grasses.
After the pH has been corrected you should repair any bare patches of lawn by applying:
Lime should not be added to lawns unless the soil pH is below 6.0. Liming neutral to high pH lawns can lead to chlorosis, general weakening of grass plants, and eventual death.