Tactic TR-8: Fertilization for Vegetation Recovery
Fertilizer is applied to ensure an abundant supply of the three main nutrients needed by plants for growth and reproduction: nitrogen (N), phosphorus (P), and potassium (K). 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. Fertilizer can also be applied to enhance microbial degradation of hydrocarbons (Tactic TR-3).
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. 92–93) or carry (Fig. 94). Larger sites can be treated with a spreader pulled by a 4-wheeler (Fig. 95). 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. Fertilizer may also be applied beyond the boundaries of the spill, to enhance seed production in the surrounding tundra and increase seed rain onto the affected area.
When and How Often to Apply
Fertilizer should be applied before 15 July or after 1 September. Elevated nutrient levels are not desirable late in the growing season, as they can delay normal plant senescence and result in winter mortality. One application of fertilizer often is enough to enhance plant growth for several years, but multiple fertilizer applications over one or more growing seasons may be required to meet vegetation performance standards.
What Type to Apply
The type of fertilizer to apply will depend on the treatment goals for the site. Use 20-20-10 if vegetation recovery is the primary goal. Other types and rates of fertilizer may be needed if fertilizer is also being applied to enhance microbial degradation of residual hydrocarbons (Tactic TR-3).
How Much to Apply
Tundra soils are typically deficient in all three major nutrients, so soil testing to determine nutrient requirements is usually not needed. The total amount of fertilizer for most sites should not exceed 200 lbs/acre during a single application and 400 lbs/acre during a single growing season. Rates can be higher for sites where microbial degradation of hydrocarbons is the primary goal (Tactic TR-3).
Table 3 provides ranges for rates of fertilizer application to enhance vegetation recovery. See Tactic TR-3 for fertilizer application rates to enhance microbial degradation of residual hydrocarbons.
Table 3. Recommended fertilizer application rate
Considerations and Limitations
- It is easy to apply too much fertilizer, which can cause plant stress, or even kill plants. Weigh fertilizer needed for a given area to prevent the application of too much fertilizer.
- Fertilizer will have little effect if contaminants 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 can move off-site in surface water; therefore it is not recommended for aquatic tundra.
- Fertilizer application rates are not the same as nutrient application rates, although both calculations are based on the relative percentages of the nutrients on the bag label. Nutrient application rates are commonly used in agricultural practice, but are not included in this manual.
- Spread fertilizer, seed (Tactic TR-11), and soil amendments (Tactic TR-13) separately. Apply fertilizer or soil amendments, and then apply seed. Do not mix fertilizer with seed or soil amendments for application because the differences in density make proper mixing and spreading with a cyclone spreader difficult.
- Applying fertilizer without a spreader (i.e., scattering by hand) is not recommended, even for small areas, because the spread will be uneven, resulting in patchy growth of plants.
- 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. The fertilizer will become essentially unusable after these clumps form.
- Spreaders that can be pulled by a vehicle may be needed for large sites.
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) for workers (e.g., rubber gloves, dust respirator).
* For historical reasons, the percentage of nitrogen (N) is reported directly, but P is reported as the fraction of phosphorus oxide (P2O5), and K as the fraction of potassium oxide (K2O). This is a standard method used in all fertilizer labeling.