Adding Lime to Soil

What are the functions of lime in soil improvement? Lime furnishes calcium which is needed for root development, strengthening of cell walls, and for formation of protoplasm and proteins; counteracts acidity; hastens decomposition of organic matter; aids in development of nitrogen fixing bacteria; reduces toxicity of certain compounds.

What type of lime should be used in the garden? Agricultural lime is the slowest but the most lasting. Several weeks may pass before its effect on soil is noticed. Hydrated and burned lime are much quicker in action, but tend to destroy humus. One hundred lbs. of ground limestone is equivalent in action to 74 lbs. of hydrated lime, of 56 lbs. of burned lime. The amounts to use will vary with the acidity of the soil. Usually 2 lbs. of agricultural limestone per 100 sq. ft. is sufficient, unless soils are extremely acid.

What is raw ground limestone? Raw ground limestone is calcium carbonate, and is the material most commonly used for counteracting acidity. In urban areas, use fine crushed limestone for drives. Agricultural lime is identical.

What is hydrated lime? Hydrated or slaked lime is formed from burned or quicklime (calcium oxide) and water. Hydrated and burned or quicklime are quicker acting than ground limestone (calcium carbonate). It is sometimes called slaked lime or quicklime.

Is lime the only material with which to sweeten an acid soil? Some form of lime is usually used to correct soil acidity. The most commonly used forms are ground limestone, dolomitic limestone, and hydrated lime. Other materials that may be used are calcium cyanamide and wood ashes.

Can dry lime, left over from plastering a room, be used in any way as a fertilizer? It may be used to alkalize acid soil, but is apt to be too coarse and lumpy. If lime is needed, apply it in the fall.

Would lime, such as I can purchase at the hardware store, be good for acid soil? If it is hydrated lime, it can injure roots.

Can marl be used in the place of lime, with the same, or as good, results? Marl (a natural deposit of calcium-bearing clay) is coarse, and its effect is very gradual and slow. Ordinarily, ground limestone is both less expensive and much more satisfactory.

What is "overliming" injury? Too much calcium (lime) in the soil causes the soil to become alkaline. Some elements such as boron, manganese, iron, zinc, etc., are not soluble in an alkaline solution, and because they are needed in small amounts by plants, poor growth develops. Usually the growth is chlorotic (yellow). Overliming can be corrected by applying sulfur to the soil at 1 lb. per 100 sq. ft. More than one application may be necessary to bring about the desired acidity. Pin oaks are especially sensitive to overliming.

When and under what conditions should lime be added to the soil? Only when the soil is too acid for plants, and when calcium is low.

When, and when not, should lime be used around flowers and shrubs? Use lime only if the soil is so acid as to require correction. Use lime if calcium is lacking and the soil is acid. Use gypsum (calcium sulfate) when calcium is lacking and the soil is alkaline.

What is gypsum? A mineral composed of calcium sulfate which contains 2 molecules of water. Used in horticulture to add needed calcium to the soil when it is not necessary to decrease acidity. It is also used to improve the physical condition of soils and, under some conditions, to improve drainage and soil aeration.

Is gypsum (plaster of Paris) a useful soil amendment? Gypsum is valuable as a source of calcium where the soil is already alkaline and a change in the pH of the soil is not desirable. Called land plaster in England, it has been used for over a century. It is not as effective in breaking up clay soils as ground limestone, however.

Is lime needed to improve a gravelly soil? Have soil tested; it may not need it.

How can lime benefit clay soil, if the soil is originally composed of disintegrated limestone? As stated by some authorities, benefit is obtained by cementing finer particles into larger ones. The flocculation (cementing of particles) of clay soils as a result of liming has been questioned. For cementing soils particles, humus is better than lime.

Should a garden be treated with lime in the fall or spring? If ground limestone is used, it is best applied in the fall, but may be applied in spring.

Is it necessary to put lime on the garden every year? Lime should be used only on acid soils. If needed, apply agricultural lime in the fall. Usually 2 lbs. per 100 sq. ft. is sufficient.

Can lime be strewn over the ground in winter with the snow? Yes, although it is better to apply early in the fall.

Why is it harmful to put commercial fertilizer and lime into the soil at the same time? What chemical reaction takes place? If lime is allowed to come into contact with superphosphate or fertilizer, the solubility, and hence the availability, of the latter may be reduced, especially in a non-acid or slightly acid soil. In soils that are acid, there is no objection to the application of fertilizer and lime at the same time, providing they are well incorporated into the soil and pH is not lower than 5.5.

When leaves are spaded in, in the fall, should lime be used in the spring? Most leaves do not produce an acid reaction, so that liming is not necessary unless your soil is naturally acid.

What crops need lime in the soil, and which do better without it? Legumes do better in neutral or slightly alkaline soils, hence lime additions are often necessary. Acid tolerant plants like azaleas, rhododendrons, etc., need no lime although they need calcium. For most plants lime should be applied only when the soil is very acid, since they do best in slightly acid soil (6.0 to 6.9 pH).

Instead of sand, I put very fine limestone on my soils, which has a preponderance of gumbo. It has made soil nice to work with. Will this small amount be apt to affect garden annuals and perennials? I have also added a great deal of barnyard fertilizer. Small amounts of lime can do no harm. The change in the soil structure was probably due to the manure rather than to the lime.

In foundation planting, I assume it is possible that lime coming loose from building and washing into soil may have disastrous effect on such acid-loving plants as azaleas and rhododendrons. Is this so? There is rarely much lime in the soil from this source. However, any chunks of plaster should be removed. If soil seems alkaline, apply dusting sulfur at 2 to 4 lbs. per 100 sq. ft. Sulfur is an acidifying agent.

Should I sprinkle my lawn with lime in the fall? If soil needs lime, it will be most effective when applied in the fall. In acid soil areas, periodic applications of limestone are recommended.

Will lime put on lawn on which oak and dogwood trees are growing injuriously affect such trees? Not unless excessive amounts are used. Have the soil tested and apply limestone only when needed.

My soil is covered with white pine needles from adjacent trees. Should this make additional liming or other treatment advisable? Pine needles produce acidity, hence constant use of lime may be required to counteract this condition.

Sewage sludge is very acid from aluminum sulfate. Is lime the proper neutralizer, or does it leave the valuable plant and soil bacterial elements in a non-desirable form? Sewage sludge does not necessarily contain aluminum sulfate. If it does, lime is a good corrective; or superphosphate may be used.

I am planning to plant a small vegetable plot. Can one add too much lime? Lime should not be added, unless a test shows it is needed. Decidedly it can be overdone.