Putting lime on your lawn can provide many benefits, including raising the pH of acidic soil, providing calcium for plant growth, and improving drainage. However, it is possible to over-apply lime, which can also create problems. Understanding how much lime to apply and when to apply it is important for a healthy lawn.
What does lime do for your lawn?
Lime, which is usually some form of ground limestone, performs several helpful functions when applied to lawn soil. Some of the benefits of lime include:
- Raises pH of acidic soils – Most plants prefer a soil pH between 6.0-7.0. Lime raises pH levels to help create an ideal growing environment.
- Provides calcium – Calcium is an essential plant nutrient. Lime contains calcium which is released into the soil.
- Improves soil structure – Adding lime can improve soil aggregation, aeration and drainage. This allows better root growth.
- Enables nutrient availability – Many nutrients are more available to plants in higher pH soils. Lime corrects low pH conditions to help plants access nutrients.
- Counters soil acidity – Common causes of soil acidity include use of acid-forming fertilizers, rain and microbial activity. Lime counteracts these acids.
By raising soil pH and adding calcium, lime allows plants to take up the critical nutrients they need from soil. This leads to stronger, healthier turfgrass growth.
How much lime should be applied to lawn?
Determining precisely how much lime to apply depends on:
- Soil pH – A soil test determines existing pH. Lime requirements increase as pH decreases.
- Soil texture – More lime is needed for heavy, clay soils than for sandy or loamy soils.
- Organic matter – Soils higher in organic matter require more lime.
- Type of lime – Different types have different calcium carbonate equivalents (CCE), which impacts application rates.
As a general guideline, lime is usually applied at rates between 25-100 lbs per 1000 sq ft. Some common targets include:
- Sandy soil – 1.5-2 lbs of lime per 100 sq ft
- Loamy soil – 3-4 lbs per 100 sq ft
- Clay soil – 5-6 lbs per 100 sq ft
A more precise lime requirement can be determined through laboratory testing. Soil labs can provide recommendations tailored to your soil’s specific needs.
When should lime be applied to lawn?
Timing of lime application includes:
- Fall – The most popular timing for liming lawns is early fall. This allows lime to fully interact with soil prior to spring growth.
- Early spring – If unable to lime in fall, early spring is the next best time. Apply as soon as soil can be worked.
- Avoid summer – Heat and drought stress make summer liming less effective. However, minor touch ups can remedy low spots.
Fall and spring allow adequate rainfall to move lime into the soil profile. Actively growing grass in spring and fall also enables lime to enter plant tissue as it corrects pH at the roots.
Signs you’ve added too much lime
Adding excessive amounts of lime can lead to problems like:
- Alkaline soil – Too much lime raises pH excessively, creating very alkaline soil. A pH above 7.5 starts to cause nutrient issues.
- Salt buildup – Excess lime can create high salt concentrations which damage roots.
- Iron chlorosis – Overly alkaline soils reduce iron availability, causing yellowing of grass leaves.
- Thatch buildup – Fast growth from over-liming increases thatch. Thick thatch prevents water and nutrient penetration.
- Pest issues – Some insects and diseases proliferate in high pH environments created by heavy liming.
A soil test is the best way to determine if pH has drifted too high from over-application of lime. Adjusting pH back down can be difficult and lengthy process.
Dangers of under-applying lime
Insufficient lime application can also create problems like:
- Low pH – Failing to apply enough lime leads to excess acidity. Soil pH below 5.5 dramatically reduces nutrient availability.
- Aluminum toxicity – Soluble aluminum in very acidic soils damages roots and limits growth.
- Loss of grass vigor – Acidic soils deprive grass plants of essential nutrients, which causes thinning and discoloration.
- Weed, moss and algae growth – Low pH soils favor growth of weeds like knotweed and moss.
- Reduced microbial activity -helpful soil microbes responsible for breaking down organic matter function best at neutral pH levels.
Soil testing determines if pH is too low. Additional lime can then be recommended to bring soil acidity back into the optimal range.
How is lime applied to lawns?
Applying lime as evenly as possible ensures uniform pH correction. Types of lime application include:
- Manual spreader – Walk-behind rotary or drop spreaders allow control over application. Even spreading takes patience and practice.
- Towed spreader – Pull-behind spreaders are efficient for large areas. Allow for overlap to prevent strips of missed coverage.
- Professional service – Lawn care companies use advanced equipment to precisely apply lime over entire yard.
- Spot treatment – Small problem patches can be treated individually using a hand-held spreader.
Two or more perpendicular passes provides the most uniform distribution. Watering after application helps move lime into soil. Periodic soil tests determine if follow-up applications are needed.
Types of lime for lawns
The most common lawn liming materials include:
| Liming Material | Properties |
|---|---|
| Agricultural lime | Most commonly used landscape lime. Affordable and suitable for frequent use. |
| Dolomitic lime | Contains calcium and magnesium. Use if soil tests show magnesium deficiency. |
| Calcitic lime | Provides pure calcium carbonate. Highest solubility for rapid pH change. |
| Pelletized lime | Small pellets spread easily with less dust. Effective at low rates. |
| Liquid lime | Suspended lime concentrates allow foliar feeding to bypass soil issues. Short-term pH change. |
The quantity needed is based on the lime’s purity, or Calcium Carbonate Equivalent (CCE). This represents the actual amount of active ingredient. Agricultural lime has a typical CCE of 50-60%.
Should magnesium be added when liming?
In soils lacking magnesium, dolomitic limestone can be used instead of calcitic lime for lawn liming. Dolomitic lime contains significant magnesium along with calcium carbonate. Typical magnesium content ranges from 6-12%.
Benefits of magnesium for lawns include:
- Chlorophyll production – Magnesium is the central atom in the chlorophyll molecule responsible for photosynthesis.
- Carbohydrate metabolism – Magnesium aids in the movement of carbohydrates, fats and proteins within grass plants.
- Root growth – Adequate magnesium allows for healthy, extensive root systems.
- Drought tolerance – Magnesium improves the plant’s ability to withstand heat and low moisture.
- Winter hardiness – Magnesium boosts the grass’s cold tolerance and recovery from winter damage.
Have soil tested to determine if magnesium levels are sufficient. Target levels should be at least 125 ppm. Dolomitic lime can then be substituted if magnesium is needed.
Can too much magnesium be applied?
Although deficient levels are more common, excess magnesium is possible with overuse of dolomitic lime. Signs of magnesium toxicity include:
- Leaf tips yellow and die – High magnesium causes a potassium deficiency by blocking uptake. Yellow leaf tips progress to browning at the ends of leaves.
- Reduced root growth – Excess magnesium impacts calcium availability, causing stunted root development.
- Soil compaction – High magnesium leads to a breakdown in soil structure and reductions in permeability.
- Less drought tolerance – Poor root growth reduces the turf’s ability to access water under dry conditions.
To correct high magnesium, switch to calcitic lime for future applications. Potassium supplements through fertilizer can counteract induced potassium deficiency. Monitor soil pH yearly and add lime as needed to maintain ideal growing conditions.
Conclusion
Applying lime provides many benefits to lawn soil and grass plants when done properly. Have soil tested first to accurately identify pH and nutrient needs. Select an appropriate liming product and apply at recommended rates when grass is actively growing. Avoid excessive applications that raise pH too high or create magnesium toxicity. With the right amount, applying lime keeps soil pH optimized for lush, green turfgrass.
