Ground limestone, commonly known as garden lime, is sometimes added to garden soils that are acidic, or low in lime. The active ingredient of garden lime is calcium carbonate. Do not confuse garden lime (calcium carbonate) with the industrial product quicklime (calcium oxide). Quicklime is not suitable for adding to garden soil because it’s stronger and quicker-acting than garden lime, and can cause eye, skin and respiratory injury if not handled properly.
Improving Clay Soil With Lime – The Complete Guide
If you’ve tried growing plants in dense, compacted clay soil, you know how challenging it can be. Clay soils are sticky when wet, rock hard when dry, and contain very little air space for roots to spread. However, there are ways to transform stubborn clay into a fertile planting medium. One of the most effective methods is adding lime to clay soil. In this complete guide, we’ll discuss how and why lime improves heavy clay ground.
What is Lime?
Lime, also called agricultural lime or dolomitic limestone, is a soil amendment made by crushing pulverized limestone. It’s composed mostly of calcium carbonate and magnesium carbonate. Gardeners have used lime for centuries to increase soil pH and encourage aggregation in heavy soils. The effects of adding lime include
-
Increasing pH – Clay soils tend to be acidic. Lime raises pH, making nutrients more plant-available.
-
Improving soil structure – The calcium in lime helps clay particles stick together in aggregates, creating better crumb structure
-
Reducing compaction – Lime promotes drainage and aeration, making clay less prone to compaction.
-
Adding calcium – An essential plant nutrient, calcium is required by many crops.
-
Enabling nutrient exchange – At higher pH, clay particles hold positively charged nutrients like potassium and ammonium.
-
Boosting microbial life – Lime creates a better environment for beneficial soil bacteria and fungi.
When to Apply Lime to Clay Soil
Lime can be added to clay soil any time of year, but early fall is ideal. This gives the lime several months over winter to begin reacting with the soil before spring planting. Allow 2-3 months minimum for the lime to start working. Test soil pH first to see how much you need to raise it.
How Much Lime to Use
Soil texture and pH determine lime amounts. Clay needs more lime than sand to change pH. A general guideline is 50 lbs of lime per 1000 sq ft to increase pH by 1 point. Specifically:
-
For mildly acidic clay, apply 50-75 lbs/1000 sq ft
-
For moderately acidic clay, apply 75-100 lbs/1000 sq ft
-
For highly acidic clay, apply 100-150 lbs/1000 sq ft
Apply half the lime first, then the remainder 2-3 months later to prevent drastic pH swings. It’s better to start with smaller amounts of lime and retest pH after a few months.
Application Methods
There are several effective ways to spread lime over your lawn or garden:
-
Use a hand-cranked drop spreader for precise application rates. Walk at steady pace.
-
Use a rotary broadcast spreader on the proper setting for your desired application rate.
-
Apply by hand for small areas like garden beds. Wear gloves and a mask.
-
Use a tractor-pulled lime spreader for large acreages. Make several passes.
After spreading, water lightly to wash lime into the soil surface. Allow a few months for full incorporation before planting.
Tips for Using Lime on Clay Soil
-
Till lime into the top 6 inches of soil to speed up reactions.
-
Add compost too – it will also improve clay’s texture.
-
Use dolomitic lime to add magnesium. Calcitic lime is pure calcium carbonate.
-
Don’t overdo it. Excess lime can damage plant roots.
-
Reapply lime annually or biannually as it washes out over time.
-
Consider sulfur to lower pH if it becomes too alkaline.
With proper liming, even the most compacted clay soils can be transformed into lush, fertile planting media. Take the time to test, amend, and condition your native clay appropriately. With wise management, you can successfully grow vegetables, flowers, trees, shrubs, and more in improved clay soils.
Which crop plants need limy soil
Brassicas such as cabbage, Brussels sprouts, swede, kale and broccoli grow best on slightly alkaline soil and can be more susceptible to the disease clubroot in neutral to acidic soils.
For ornamental plants, it’s far better to select plants that thrive in your natural soil conditions, rather than trying to alter it.
Why apply garden lime?
Garden lime improves growth and productivity of lime-loving vegetable crops if the soil is naturally acidic. Garden lime can also be applied to improve the structure of clay and compacted soils, encouraging the tiny particles to combine in larger crumbs.
Why Use Lime to Stabilize Clay Soils
FAQ
What happens when you put lime on clay soil?
-
Raising pH:Lime is a base, so it raises the soil pH, which can be beneficial for acid clay soils.
-
Flocculation and Aggregation:Lime encourages clay particles to clump together, forming larger aggregates or “flocs”.
-
Improved Structure:These larger aggregates lead to a more friable and easier-to-work soil.
-
Construction Applications:Lime stabilization is used in road construction to improve the engineering properties of clay soils, making them more suitable for construction.
-
Pozzolanic Reaction:Lime can react with silica and alumina in clay soils, forming calcium silicate and alumina hydrates, which can increase soil compaction and stability, particularly under freezing conditions.
-
Potential Issues:Over-liming can lead to nutrient deficiencies, especially for micronutrients, so it’s important to test your soil pH and cation levels before applying large amounts of lime.
-
Lime Fixation:Lime fixation is the process by which lime is held by the soil and is not available for pozzolanic reactions.
-
Different types of Lime:Quicklime (CaO) and slaked lime (Ca(OH)2) are both effective in drying wet clay and silt soils.
-
Structure Liming:Structure liming, which involves applying a mixture of ground limestone and slaked lime, can improve the agronomic properties of clay soils.
How much lime do I add to clay soil?
most soil drying applications, approximately 3 to 5% lime (based on dry weight of soil) is required, depending on degree of wetness.
What is the best soil improver for clay soil?
Adding materials such as organic compost, pine bark, composted leaves and gypsum to heavy clay can improve its structure and help eliminate drainage and compaction problems. Avoid adding sand or peat moss to clay; they can make those problems worse.
Does lime dissolve clay?
In addition to cationic exchange, the high pH environment induced by lime enables the dissolution of the alumino-silicate constituents of clay minerals, promoting the development of the pozzolanic reactions [15].
How much limestone do you add to clay soil?
In general, you want to add 20-50 pounds of ground limestone (lime) per 1,000 square feet of clay soil. Doing this should correct a mildly acidic garden and help to increase its pH level. However, if your clay is super thick or heavily acidic, you may need to increase that 20-50 pounds closer to 100.
How much lime should I shuld in clay soil?
The amount of lime you shuld add to your clay soil will depend on a few factors, including the soil’s current pH level and the type of lime you’re using. In general, you’ll want to use no more than 8 pounds of dolomite lime per 100 square feet of acidic clay soil with a pH level between 5.0 and 6.0.
Does lime help clay soil?
Lime does not help clay soil in any other way. Adding compost (organic material) is also a benefit to clay soil, as is sand. But sand does not have the nutrients that compost does. Aeration and adding nitrogen and organic material to your soil are the best options for making clay soil better for planting gardens as well as for a healthy lawn.
How much lime should I add to my soil?
For clay soils, aim for a pH between 6.2 and 7.0 after adding lime. The amount of lime needed depends on your soil’s pH and texture. Clay soils usually require more lime than sandy soils to raise the pH. A general guideline is to add 50 pounds of lime per 1000 square feet to increase pH by one point. Here are some more specific recommendations:
How do you make a clay soil look better?
Till lime into the top 6 inches of soil – Incorporating lime helps it work more quickly. Add organic matter too – Compost, manure and peat moss will also improve the texture of clay. Use dolomite lime for magnesium – Dolomitic lime contains magnesium, unlike calcitic lime which is pure calcium carbonate.
What happens if you mix lime and clay?
Mixing lime with clay results in a chemical reaction that improves the soil’s properties, making it easier to work with and more stable. If you are looking to break up clay soil, there are several organic amendments that can be added to improve its structure.