Friday, October 26, 2007

Landscape and Turf - Liming Basics

Many turf and landscape companies will be applying lime this fall. Some reminders on liming basics and “do’s and don’ts” are in order.
  • DE soils naturally become more acid over time. Heavy N fertilization will hasten acidification.
  • Liming is the practice of adding materials soils to reduce this acidity (raise the pH) and as a result make soils more favorable for plant growth.
  • The most common liming material is ground limestone. Calcitic limestone which is mostly calcium carbonate is used for high calcium (HiCal) lime, dolomitic limestone has both calcium and magnesium carbonates and is often called HiMag lime.
  • The finer that the limestone is ground, the more reactive it will be. Pelletized horticultural lime is made from this finely ground limestone that is formed into granules so it spreads easier.
  • Lime should be applied only if called for by soil tests. It should never be applied routinely. Only add the amounts recommended. Over-liming can cause the tie up of certain micronutrients (manganese, zinc, iron).
  • Soil samples (taken as recommended) should be sent to accredited laboratories that run standardized lime requirement tests along with pH (a buffer pH). You cannot determine lime requirements by running your own pH’s, even if you have a good pH meter because you do not know the buffering capacity of the soil (the reserve acidity of the soil).
  • Use high calcium lime where magnesium levels in the soil are adequate. Where magnesium levels are low, use liming products based on dolomitic limestone that have both calcium and magnesium. Your soil test results will tell you which lime to use. Do not routinely use dolomitic lime.
  • Hydrated and quick limes are faster acting but generally are not necessary and should not be used over top of existing turf or landscape plants due to potential phytotoxicity (they can be used in initial soil preparation).
  • Alternative liming materials such as wet lime, industrial by-products, and lime stabilized biosolids need to be compared with standard liming products. Use Calcium Carbonate Equivalents (CCE) from laboratory tests of these materials to compare their neutralizing ability to standard lime. Gypsum is not a liming material.
  • Keep limes away from plants such as azaleas, rhododendrons, and blueberries that flourish in acid soil.
  • Apply lime evenly and avoid over-application in overlaps.
  • Incorporate lime in newly prepared beds or areas to be seeded in turf. Applying lime during aeration is recommended in established turf areas to achieve some incorporation.
    Fall applications are preferred if no incorporation is possible (topdressing).
  • If large amounts of lime are recommended (>100 lbs/1000 sq. ft) then split applications half in fall and half in spring.

By Gordon Johnson, Extension Agent, Commercial Horticulture, Kent County.

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