Division of Spill Prevention and Response

Breadcrumbs

Tactic TR-13: Soil Amendments

Soil amendments are used to promote plant growth by improving soil conditions affected by spilled substances. For example, brine spills may create saline conditions, or metabolism of hydrocarbons by soil microbes may acidify soils. If soil testing (Tactics AM-4 and AM-5) or active-layer water monitoring shows that soils are extremely acidic or saline, applying an amendment may be appropriate. Tundra soils can be naturally acidic or saline, amendments should be applied only if levels of acidity or salinity are substantially higher than those in nearby unaffected tundra. Periodic monitoring (bi-weekly) of active-layer water (Tactic AM-4) can track changes in soil properties faster than soil testing. Apply soil amendments during the growing season when soils are free of snow and water, if possible.

Apply lime if soils are too acidic, most plants are not adapted for soils with a pH > 8.

A common technique used to reclaim sodium-affected (sodic) soils is the addition of gypsum or calcium nitrate. These soil amendments displace sodium ions from the soil by replacing them with calcium ions, which adsorb more strongly to soil particles. An adequate water supply is necessary for this chemical exchange to occur, and adequate drainage is necessary to flush the sodium from the affected soil. Chloride ions do not bind strongly to soil, and will be flushed out with the sodium ions. Adding gypsum will not necessarily be effective in all saline soils. Laboratory testing is required to determine if gypsum will improve soil conditions (Table 6).

Table 6. Examples of soil amendments used for North Slope tundra

Amendment

Purpose

Lime

(calcium carbonate CaCO3)

To buffer overly acidic soil caused by a spill of an acidic substance, or by microbial degradation of hydrocarbons

Gypsum

(calcium sulfate and water, Ca•SO4 and H2O)

Calcium source to remove salt (sodium and chloride ions) after a seawater or other type of salt spill

Liquid calcium nitrate

Calcium source to remove salt (sodium and chloride ions) after a seawater or other type of salt spill

How Much to Apply

Application rates of soil amendments are site-specific and should be calculated by a soils laboratory. Provide the laboratory with a target pH range (background concentration), and the laboratory will calculate the application rate of a given soil amendment based on results from soil testing. The manufacturer of liquid calcium nitrate will provide information on how much is needed (based on laboratory data) for a certain area to achieve a certain salinity range.

How to Apply

Lime and gypsum are available in powder or granular form, typically packaged in 50–lb. bags. Broadcast lime or gypsum with a cyclone spreader, which are available in different capacities and models that one person on foot can push (Figs. 119–120) or carry (Fig. 121). Larger sites can be treated with a spreader pulled by a 4-wheeler (Fig. 122). Practice and calibration of the spreader are required to distribute lime or gypsum evenly. A good method is to measure and mark off a small area, fill the spreader with the amount of lime or gypsum appropriate for that area, and move in a grid pattern at a steady pace over the area multiple times until the spreader is empty.

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Figure 119. Push spreader

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Figure 120. Applying lime

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Figure 121. Chest spreader

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Figure 122. Spreader pulled by 4-wheeler

Lime or gypsum may be applied simultaneously with fertilizer (Tactics TR-3 and TR-8).

Liquid calcium nitrate can be applied to small sites using weed sprayers or watering cans, or to larger sites using a hydroseeder or similar piece of equipment. The distribution method is similar to that for powder or granular amendments. A given amount of product is sprayed methodically over a given area to achieve even distribution at the correct application rate. Calibrate the sprayer before use.

Considerations and Limitations

  • To determine the types and amounts of amendments needed, soil samples typically are sent to a soils laboratory that routinely conducts analyses for agricultural purposes, such as the University of Alaska Fairbanks Agricultural and Forestry Experiment Station in Palmer, AK. Some analytical laboratories, where soils are analyzed for contaminants, may also be equipped to calculate the need for soil amendments.
  • Extremely alkaline tundra soils are not readily correctable with amendments.

Equipment, Materials, and Personnel

  • Necessary quantity of appropriate soil amendment.
  • Cyclone spreader (1 operator) – to broadcast powdered soil amendments.
  • Vehicle approved for tundra travel (1 operator) – to pull a cyclone spreader over larger sites (optional).
  • Weed sprayer or watering can (1 operator) – to spray liquid soil amendments on small sites.
  • Hydroseeder or similar equipment (2 operators) – to spray liquid soil amendments on larger sites.
  • Personal protection equipment (PPE) - to keep workers safe (e.g., rubber gloves, dust respirator).


Updated: 12/20/2010