Lime and Gypsum Fertilizers
Although lime and gypsum are both used to improve the soil in your lawn and garden, they serve very different purposes. Adding lime to soil raises the pH so it becomes less acidic. This can help increase vegetable production in the garden and enhance the appearance of your lawn. Gypsum is often used as part of a strategy to correct compacted soil or soil with large amounts of clay. It can also be used to counteract excessive saline levels in soil and has the added benefit of not affecting the pH of soil. Before you prep your soil with lime or gypsum, consider the following questions:
• Have you tested the pH level of your soil?
• Should you apply lime and fertilizer at the same time?
• Is there clay or a hard layer of topsoil in your garden?
• Do you live in an arid or maritime climate?
Lime, Gypsum and Application Tips
The best way to determine whether or not your soil needs liming is to test its pH. Since the most fertile gardens and lawns are those with a proper pH balance, having your soil tested every few years is highly beneficial. The target pH level of turf grass, for example, is between 6.2 and 6.5, so if your soil has a lower pH it will likely benefit from the addition of lime. Remember, though, too much lime can be as harmful to your lawn as too little, so always test the soil and read the instructions on the lime package before application. To determine if a soil can benefit from gypsum, you can test saline amounts or simply observe if you are working with soil that is heavy with clay or hard to break up. Although it may be tempting to apply your lime, gypsum and fertilizer at the same time, it's not a good idea to introduce too many chemicals at once.
Lime: Lime is a compound made up of calcium or calcium and magnesium and is used to reduce the damaging effects of acidic soil on lawns and gardens. Lime also reduces the toxicity of elements in the soil, such as aluminum, manganese and iron, which can adversely affect plant growth. Lime also adds desirable nutrients, such as calcium and phosphorus. In addition, lime increases bacterial activity, which helps improve soil structure. The two most common types of lime used in gardening are calcitic lime and dolomitic lime.
• Soil in the eastern U.S. often requires the addition of lime to reduce acidity
• Calcitic lime is pure calcium carbonate and is the cheapest form of lime
• Dolomitic calcium contains calcium carbonate and equal parts of magnesium carbonate
• Vegetables thrive best in a slightly acidic soil, with a pH between 5.8 and 6.3
• Adding too much lime to soil can damage it as much as having high acid levels
Gypsum: Gypsum is actually an element called calcium sulfate that is used to loosen up stubborn, compacted or clay soils. Gypsum works by pulling together clay particles in the soil to make bigger particles, creating porous spaces for air, water and plant roots. For saline-infused soil, gypsum removes sodium and replaces it with calcium. For all soil types, gypsum adds calcium and sulphur, which are necessary elements for plant growth. Gypsum also helps soil retain water and helps decrease soil erosion.
• Gypsum will not alter pH levels and is relatively inexpensive and easy to use
• Soil in the southeast U.S. often contains clay and may benefit from gypsum
• Arid and coastal regions that feature high soil salts can benefit from gypsum
• Gypsum prevents surface crust deposits on soil that adversely affect seed emergence
• Gypsum can correct lawn damage from salt and other winter ice-melting chemicals
Application Tips: It is easy to apply lime and gypsum using a drop spreader or broadcast spreader. Since lime is insoluble, it tends to stay exactly where it is spread, so these devices ensure uniform coverage. Gypsum is neutral and does not change the pH of your soil so you can use it around acid-loving plants, such as rhododendrons and azaleas, to provide extra calcium. As with all fertilizers, apply lime and gypsum as directed on the label. Both substances are safe to use and are nontoxic to humans and plants.
• Although best applied in the fall, lime can be applied at any time
• For even coverage, apply half the lime in one direction and the rest in a crisscross pattern
• Apply lime and fertilizer at least two weeks apart to avoid damaging plants
• Both lime and gypsum can be easily applied using lawn spreaders
• Lime can burn a lawn if misapplied, but gypsum will not
Consult the chart below to learn more about how to apply these useful substances to your lawn and garden.
|Gypsum||Any time of year||• Established lawns: 40
to 50 lbs. per 1,000
• New lawns w/ heavy
clay: 300 lbs. per
1,000 sq. ft.
• Gardens: 20 to 30 lbs.
per 100 sq. ft.
• Roses: 1 lb. per
bushShrubs: 2 lbs.
• Evergreens: 2 to 3 lbs.
|Twice per year||• You do not have to
work gypsum into
the soil -- simplyuse a
spreader to distribute it
over the surface of
your lawn or garden
• For garden application,
also mix in compost or
• Water immediately after
|Lime||Fall, winter or early spring||20 to 30 lbs dolomitic lime per 1,000 sq. ft.||Every 3 to 5 years||• For new lawns, mix lime
deeply into soil a day
or two before planting
• Use a spade to work
the lime 6" into the oil
• For existing lawns,
distribute evenly over
lawn or garden with a
• Water soil to
Calcitic Lime: Mined from natural limestone, calcitic lime is then crushed up into finely ground powder granules. Pelletized lime is created from finely ground lime plus a cementing agent that is added to form pellets. Pellets are more expensive but easier to use and eliminate the dust problem of granular lime. Pellets dissolve in water so it's important to water thoroughly after application. Calcitic lime also contains calcium, a necessary element to encourage healthy plant growth. Calcitic lime is most often applied to lawns but may also benefit garden plants, shrubs and flowers.
Dolomitic Lime: Dolomitic lime is mined in the same manner as calcitic lime and is also crushed and sold in either finely ground powder form or pellets. Dolomitic lime provides both calcium and magnesium. Dolomitic lime is most often applied to lawns but may also benefit garden plants, shrubs and flowers.
Granular Gypsum: Gypsum is ground up into a fine, white powder and sold in the form of granular gypsum, which is applied using a lawn spreader. Granular gypsum may be applied to turf grasses, garden plants, shrubs and flowers. Finely ground formulas are rapidly available to plants and soils.