Division of Spill Prevention and Response

Breadcrumbs

Tactic TR-3: Fertilization for Hydrocarbon Degradation (Bioremediation)

Fertilizer is applied to enhance the ability of soil microbes to metabolize hydrocarbons (i.e., biodegradation). Biodegradation occurs most rapidly when oxygen (O2) is available. Applying nitrate (NO3) fertilizer can enhance biodegradation in the absence of oxygen, because some microbes can use nitrate instead of oxygen. In addition to nitrogen (N), microbes also require phosphorus (P) and potassium (K) for growth and reproduction. Commercially available blended fertilizers supply all three of these essential nutrients. Fertilizer composition varies, and is shown on the bag label as (N-P-K)* followed by the relative percentage of each, e.g., 20-20-10.

Microbes with the ability to degrade hydrocarbons are ubiquitous in the environment, because carbon in organic matter provides the energy that supports many biological processes (Atlas 1985) and because numerous sources of naturally produced hydrocarbons exist (Dragun 1988).

How to Apply

The easiest type of fertilizer to apply is inorganic (mineral) fertilizer, typically packaged in 50–lb. bags of dry pellets. Broadcast fertilizer with a cyclone spreader; these are available in different models that one person on foot can push (Figs. 77–78) or carry (Fig. 79). Larger sites can be treated with a spreader pulled by a 4-wheeler (Fig. 80). Practice and calibration of the spreader are required to distribute fertilizer evenly. A good method is to measure and mark off a small area, fill the spreader with the amount of fertilizer 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 77. Push spreader

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Figure 78. Filling push spreader

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Figure 79. Chest spreader

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Figure 80. Spreader pulled by 4-wheeler

When and How Often to Apply

Fertilizer can be applied at any time if effects on vegetation are not an immediate concern. See Tactic TR-8 for constraints on fertilization if vegetation is present. If possible, apply fertilizer when soil is at least partially thawed and free of snow and water. The rate and frequency of fertilizer application should be based primarily on hydrocarbon concentrations in soil, as well as changes in hydrocarbon concentrations over time. If concentrations of diesel-range organics (DRO) in soil are < 4,000 mg/kg, a single fertilizer application is probably sufficient. If DRO concentrations are > 4,000 mg/kg, fertilizer should be applied in early summer and fall during two or more successive growing seasons.

What Type to Apply

Ammonium-nitrate fertilizer (e.g., 34-0-0) has the highest concentration of nitrate, making it the most efficient type to apply, but is not always available. Alternatively, a blended fertilizer with a high nitrogen percentage (e.g., 22-4-4) can be used, at a correspondingly higher application rate. A second fertilizer with proportionately more phosphorus and potassium (e.g., 8-32-16) may be applied simultaneously to promote vegetation recovery (TR-8).

How Much to Apply

In agricultural practice, laboratory analysis of nutrient levels in soil is recommended to calculate the type and amount of fertilizer needed. Levels of major nutrients, however, are low enough in most tundra soils that preliminary measurement of nutrient levels is generally unnecessary. Table 2 provides guidelines for rates of fertilizer application, depending on whether fertilization is also being used to promote vegetation recovery. Different fertilizers can be applied simultaneously, but the total amount of fertilizer should not exceed 800 lbs/acre during a single growing season.

Table 2. Recommended fertilizer application rates

Purpose

Fertilizer to Purchase
DRO < 4,000 mg/kg

Fertilizer Application Rate (lbs/acre)
DRO > 4,000 mg/kg

Biodegradation

34-0-0

(use 22-4-4 or similar if 34-0-0 unavailable

100 to 400

400 to 800

Biodegradation and plant growth

22-4-4 and 8-32-16 (use equal amounts of each type)

100 to 400

400 to 800

Considerations and Limitations

  • Fertilizer will have little effect if contaminant levels are toxic to microbes and vegetation, or if the spilled substance created unsuitable pH or salinity conditions.
  • Fertilizer is composed of salts and can result in higher electrical conductivity (EC) in soil. Application may not be beneficial at sites where soil EC is elevated (e.g., seawater spills).
  • Fertilizer dissolves in water and nitrogen especially can move off-site in surface water; therefore it is not recommended for aquatic tundra.
  • Applying fertilizer without a spreader (i.e., scattering by hand) is not recommended, even for small areas, because the spread will be uneven.
  • Fertilizer should be stored indoors if possible. Unopened bags can be stored outside for 2-3 weeks in dry weather, but the bags are not air tight and the pellets eventually will absorb water from the atmosphere and stick together in hard clumps, making the fertilizer essentially unusable.

Equipment, Materials, and Personnel

  • Necessary quantity of appropriate fertilizer.
  • Broadcast spreader (1 operator) – to spread fertilizer.
  • Vehicle approved for tundra travel (1 operator) – to pull a broadcast spreader over large sites.
  • Personal protection equipment (PPE) (e.g., rubber gloves, dust respirator).

* For historical reasons, the percentage of nitrogen (N) is reported directly, but phosphorus (P) is reported as the fraction of phosphorus oxide (P2O5), and potassium (K) as the fraction of potassium oxide (K2O). This is a standard method used in all fertilizer labeling.


Updated: 12/20/2010