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Agronomic Services — News Release

TUESDAY, NOV. 22, 2005

Contact: Dr. David H. Hardy, Soil Testing Section chief
NCDA&CS Agronomic Division
(919) 733-2655

Tips about soil pH and liming

RALEIGH — In North Carolina, amending the soil with lime is almost always a sound investment. Most people know this but become confused by the variety of liming products available or the wording of recommendations. Here are a few pointers to make it easier to decide how and when to use lime.

  • Take soil samples on a regular basis to determine if lime is needed. The N.C. Department of Agriculture and Consumer Services advises having sandy-textured soils tested at least once every two to three years and clay soils every three to four years. The soil test report recommends the amount of standard agricultural lime necessary to achieve the optimum pH for the specific crop and soil involved.
  • If the soil report recommends lime, apply it as soon as possible. Crops, lawns and gardens cannot flourish without the proper soil pH. Lime is a major source of calcium and magnesium, which are essential plant nutrients. Adjusting soil pH can also increase the availability of other nutrients and neutralize toxic effects of hydrogen, aluminum and manganese. Because it will take several months for lime to fully react, it should be applied as soon as the need is recognized.
  • Choose a dolomitic lime product. Calcitic lime contains calcium; dolomitic lime contains calcium and at least 6 percent magnesium. Although calcitic lime may be cheaper, dolomitic lime is a better choice, especially on sandy soils, which tend to be low in magnesium.
  • Read the lime product label. NCDA&CS soil test recommendations are for standard agricultural grade lime. By state law, labels for all lime products must list the amount of the material equal to 1 ton of standard lime. This amount may be more than a ton or less than a ton. Convert the soil report recommendation based on the label's instructions. If you purchase lime in bulk, ask the dealer for a copy of the label.
  • Calibrate application equipment. Lime recommendations are given in units of pounds per 1,000 square feet for small lawn and garden areas and in tons per acre for pastures and field areas. Application at the correct rate is extremely important. Some spreaders come with settings for fertilizer and lime materials. Calibration involves estimating the size of the area to be treated and measuring the output of the spreader. Small areas can be stepped off to estimate the square footage. It may help to know that 43,560 square feet equal an acre.
  • If possible, mix lime into the soil at the time of application. Mixing lime with the soil places it directly into contact with soil acidity, thereby hastening the neutralizing effect. This procedure is particularly important when preparing the soil for a new permanent planting, such as a lawn or orchard. Once a permanent planting is established, subsequent lime applications can be spread on the soil surface.
  • Never surface-apply more than 1 ton of lime per acre for large areas or 50 pounds per 1,000 square feet for small areas, such as established lawns. If a soil report recommends more lime than this, limit application the first year to the suggested maximum. Apply the remainder the following year. If lime can be tilled into the soil, higher rates can be applied without causing problems.
  • Try to apply lime uniformly. This is tricky because spread patterns are not uniform and there will always be some gaps or overlap. For maximum uniformity, a crisscross application pattern works best. Spread one half of the lime over the entire area in a parallel, back-and-forth pattern; then moving at right angles to the first pattern, apply the second half of the lime in a similar fashion.
  • Contact your NCDA&CS regional agronomist for advice on collecting samples and applying lime. The sooner samples are submitted, the quicker lime can be applied and plans for nutrient management made. Sampling instructions and supplies are available at all county Cooperative Extension offices.
  • The NCDA&CS Agronomic Division Web site also provides sampling instructions, contact information for regional agronomists (Click on “Field Services”) and laboratory results for your samples (Click on “Find Your Report”).

Last Update August 1, 2007


NCDA&CS Agronomic Services Division, Colleen M. Hudak-Wise, Ph.D., Director
Mailing Address: 1040 Mail Service Center, Raleigh NC 27699-1040
Physical Address: 4300 Reedy Creek Road, Raleigh NC 27607-6465
Phone: (919) 733-2655; FAX: (919) 733-2837

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