Lime is a useful tool for earthwork contractors struggling with wet soils. When other drying methods have been exhausted (e.g. using an agricultural disc to turn the soil) and the schedule must be met, a common solution is to bring in lime.
As an avid gardener, I’m always looking for ways to improve my soil and help my plants thrive. Recently, I’ve been exploring the use of hydrated lime as a soil amendment and wanted to share what I’ve learned.
What is Hydrated Lime?
Hydrated lime also known as calcium hydroxide or slaked lime is a powdery substance produced by mixing quicklime (calcium oxide) with water. It has a high pH and calcium content which provides benefits for soil and plants.
Some key facts about hydrated lime
- White powdery appearance, feels chalky
- Produced by adding water to quicklime
- Highly alkaline with a pH of 12-13
- Provides calcium and adjusts soil pH
- Can be caustic and requires safe handling
Benefits of Using Hydrated Lime
When used properly, hydrated lime can provide the following advantages:
Increases Soil pH
Many plants prefer a soil pH between 6.0-7.0. Hydrated lime raises pH in acidic soils, making nutrients more available.
Supplies Calcium
Calcium improves soil structure, plant cell walls, and prevents issues like blossom end rot.
Improves Soil Structure
Hydrated lime can minimize compaction and improve drainage and aeration.
Deters Pests
By raising soil pH, hydrated lime creates an environment less hospitable to certain insects and diseases.
How to Apply Hydrated Lime
To safely use hydrated lime as a garden amendment, follow these steps:
Test Your Soil
Use a soil test kit to determine your garden’s current pH. This will indicate if lime is needed and how much to apply.
Calculate Application Rate
A typical application is 1-2 lbs per 100 sq ft. For each pH point you want to raise, apply 2 tons of lime per acre.
Spread Evenly
Using gloves and a mask, spread hydrated lime evenly over soil using a spreader.
Incorporate into Soil
Lightly rake lime into the top 2-3 inches of soil to fully integrate.
Time Application
Apply lime in fall or early spring so it can react with soil before growing season.
Using Lime Safely
Because hydrated lime is caustic, take precautions when handling:
- Wear gloves, long sleeves, and a dust mask
- Avoid skin and eye contact
- Store away from children and pets
- Apply on calm, dry days to prevent irritation
- Wash exposed skin immediately after application
Quicklime and hydrated lime can cause severe injury if used improperly, so make sure you understand how to apply them safely before using them in your garden.
Alternatives to Hydrated Lime
If you want to avoid working with caustic lime products, some alternatives can also adjust soil pH and provide calcium:
- Agricultural lime (calcium carbonate)
- Wood ash
- Bone meal
- Crushed eggshells
While these options work more slowly, they are safer to handle.
Which Plants Benefit from Lime?
Many vegetables, fruits, and ornamentals prefer the neutralized soil provided by lime:
Vegetables that benefit: broccoli, cabbage, beets, carrots, legumes
Fruit trees/bushes: apple, peach, blueberry
Ornamentals: lilac, daffodil, poppy, iris, daylily
However, some acid-loving plants may be harmed by raising soil pH too much:
Avoid liming around: azaleas, rhododendrons, camellias, gardenias, heathers
Using Lime Correctly
To avoid issues, keep these tips in mind:
- Test soil first to see if lime is needed
- Follow recommended application rates
- Thoroughly incorporate lime into soil
- Wait 2-4 weeks before planting in limed soil
- Re-test soil every few years to monitor pH changes
When used properly, hydrated lime can be a useful soil amendment to create ideal growing conditions for many plants. Pay close attention to application rate and safety precautions. Alternatively, consider gentler options like agricultural lime if you want to avoid working with caustic materials. Testing your soil first and selecting appropriate plants is key to successfully using lime in your garden.
What Does Lime Do to Soil?
Chemically drying soils is accomplished by integrating lime in the wet soil to reduce the free (non-chemically bonded) water in the soil to achieve the optimal moisture content as determined by the soil’s moisture-density relationship. Approximately 1% to 2% of granular quicklime by dry weight of soil is normally applied, an amount not generally sufficient to achieve chemical modification or stabilization.
Strangely enough, the most common and costly mistake in lime application is inadequate moisture. When lime touches the moisture in the soil, a chemical reaction begins that causes heat, steam, and a rapid expansion of the lime to several hundred times its original volume. Sometimes additional water must be added to initiate the required chemical reaction. When too little water is available to completely hydrate the quicklime, water entering the soil after compaction causes expansive pressures to develop, resulting in the ground heaving; or even worse a pavement constructed on top. Proper incorporation of the lime into the soil is also necessary. It requires thorough mixing, and adequate time (approximately 24 to 48 hours) for the lime mixture to mellow (react with the soils). The final step requires remixing of the soil. Mixing and mellowing the soil should continue until there are no visible lime particles.
Types of Lime for Drying: Quicklime vs. Hydrated Lime
Although the term ‘lime’ is used loosely, it’s important to know that hardening or drying soils requires either quicklime or hydrated lime. More than one inexperienced contractor has assumed he could cut costs by running down to the local lawn and garden store and purchasing agricultural lime (calcitic or dolomitic lime) for this purpose. Since these types of lime don’t react to moisture in soil, the result is wet soils, wet agricultural lime, and a waste of money.
- Quicklime is manufactured by heating limestone (calcium carbonate) to approximately 900°C and grinding it into gravel, sand-sized particles, or a powder.
- Hydrated lime (calcium hydroxide) is produced by adding a controlled amount of water to quicklime, a process commonly referred to as “slaking.”
Because hydrated lime contains chemically-bonded water, approximately one-third more hydrated lime is typically required to dry the soil.
How to use LIME in your LAWN for GREAT RESULTS
FAQ
Can I use hydrated lime on the garden?
Hydrated Lime is designed for use on lawns, gardens, & potted plants. For gardens, work in Hydrated Lime around each plant & water normally. For potted plants, mix one tablespoon of Hydrated Lime in one gallon of water & apply as you would normally water.
What are the disadvantages of hydrated lime?
Ammonia can be very dangerous to the health of both animals and people. Studies have concluded that even low levels of ammonia can cause stress to an animal’s respiratory system. It is therefore extremely important to control ammonia within confined spaces.
What plants like hydrated lime?
Hydrated lime, which raises soil pH, is beneficial for plants that prefer alkaline conditions. Specifically, plants like asparagus, onions, garlic, and spinach thrive in slightly alkaline soil, as do certain flowers like gypsophila, delphiniums, and buddleia, according to Green Matters.
Is hydrated lime good for tomato plants?
Benefits of Using Lime in Tomato Gardening
Calcium increase: Absorbing calcium helps tomatoes grow vital, healthy cells and roots to stave off blossom end rot. Permeability increase: Lime makes it easier for water to drip through the solid and reach the roots, providing an overall health boost.
Is hydrated lime good for garden soil?
Hydrated lime, also known as calcium hydroxide, is a fine white powder created by adding water to quicklime (calcium oxide). This process results in a product that is effective in managing soil acidity, making it beneficial for gardening. How does hydrated lime benefit garden soil?
What is hydrated lime?
Hydrated lime, also known as agricultural lime or calcium carbonate, is a readily available and affordable soil amendment. When applied to the soil, it gradually releases calcium and magnesium ions, which play vital roles in plant growth and soil fertility. – Improves soil pH, creating an optimal balance for most plants.
How do I use hydrated lime in my garden?
Using hydrated lime in your garden can improve soil conditions effectively. Here’s how to get started. Soil Testing: Test your soil to determine its pH level. This step ensures you apply the right amount of hydrated lime. Dry Application: Spread hydrated lime evenly over the soil surface.
What plants need hydrated lime?
Potatoes – Scab disease is reduced in acidic soils, so hydrated lime helps create suitable growing conditions. Legumes – Beans, peas, clover, and alfalfa need extra calcium that hydrated lime provides. For these crops, the fast pH change from hydrated lime lets plants access soil nutrients right away for best growth.
Is hydrated lime safe?
It can be used to raise soil pH in acidic soils and provide calcium. However, hydrated lime is caustic and requires safe handling. This article covers the differences between hydrated lime and agricultural lime, how to use hydrated lime properly, and safety precautions when using it.
Is hydrated lime better than agricultural lime?
Dehydration of hydrated lime, on the other hand, is twice as effective at raising pH levels as agricultural limes. Because it does not provide magnesium, gardeners with a high nutritional load in their garden soils may prefer hydrated lime, which is often more desirable than limes commonly used in gardens.