Summary Table

IAMP-Cover Crop Practice
(NRCS Code 340)

Description

A seasonal/annual vegetative cover that is not harvested, baled, or sold as a specific commodity other than grazing. See NRCS Cover Crop (340) guide as a reference. Cover crops may be established between successive production crops or companion-planted or relay-planted into production crops. Select species and planting dates that will not compete with the production purpose(s).

Benefits

Reduce erosion, improve soil health, increase soil organic matter, reduce off-site losses and availability of easily transported nutrients, suppress excessive weed pressures and break pest cycles, improve infiltration, soil moisture efficiency, minimize soil compaction.

Soil Carbon Impacts

Depending upon the overall growth, type of vegetation, and management will result in increased soil carbon. The permanence of the increased soil carbon depends on the frequency of cover crops in a particular crop rotation.

Greenhouse Gas (GHG) Impacts

Increased conversion of inorganic forms of nitrogen can lead to increased nitrogen use efficiency resulting in decreased N2O emissions. Depending upon type and amount of carbon, CO2 production could increase as microbial driven decomposition of labile forms of carbon leads to increased respiration.

Considerations for Success

  • In arid regions cover crops may reduce soil moisture, affecting subsequent cash crops. Growers are encouraged to use the timing of cover crop termination to minimize this risk.
  • The additional costs to the growers include:
    • Seed costs,
    • Fuel costs,
    • Labor,
    • Possible fertilizer and irrigation costs, and
    • If replacing a cash crop, then loss of revenue.
  • Possible disease carry over.
  • Cover crop production and impact sensitive to weather.
  • Regrowth or volunteers in following cash crop, particularly if using no-till practice.
  • Potential risk to following crop quality (higher blemish rates in potatoes).
  • Constraints on herbicide selection through the rotation.

IAMP Preferences/Considerations

The IAMP project incentivizes practices that result in a net reduction in GHG and increase in soil carbon. Ideal cover crops have a high C/N ratio, maximize total biomass, are planted early/harvested late (e.g. winter cover crops preferable), have high nitrate uptake/conversion to biomass, are included in the rotation 1 out of three years. Avoid fertilizing cover crop unless the increase in biomass justifies the risk of increased N2O emissions.

Specific Details

IAMP has several requirements for cover cropping to document the practice was implemented correctly and to document the effectiveness of the practice from the current cropping strategies employed in the field. The cost of analysis of any required soil, crop, or biomass sampling and analysis will be covered by the IAMP project. For an overview of all required sampling for each IAMP practice, see IAMP required sampling. Implementing partners will be assisting with the collection of any sampling related to the practice. Each of these requirements is described below.

  1. Baseline strip: Producers will maintain a minimum strip of 80 ft in length and a minimum width of 20 ft where the full baseline synthetic fertilizer rate will be applied as a comparison to the rest of the field. The actual dimensions of the strip can vary to be compatible with the width of implements used to manage the field.
  2. Soil Carbon sampling: Paired soil sampling points in the baseline strip and in the treated field at the start of the project and at the end of the project is required to track the changes in soil carbon over the duration of the project, see the IAMP Soil Sampling Protocol.
  3. Soil Nutrient sampling: Paired soil sampling points in the baseline strip and in the treated field prior to planting and after harvest is required every ft down to 2 ft to assess the impacts of the practice on available soil nitrogen, and identify any nutrient deficiencies/benefits from the implemented practice, see the IAMP Soil Sampling Protocol.
  4. Crop Biomass sampling: Paired above ground crop biomass measurements at the paired soil sampling locations will be required prior to harvest and will be evaluated for total dry biomass weight as well as the percent carbon and nitrogen, see the IAMP Crop Biomass Sampling Protocol.
  5. Grower supplied field management information:
    • Type of species mix: Single or multi-species mixes may be used including grasses, legumes, brassicas, or other broadleaves. Cover crops may be planted as winter or summer cover.
    • Seeding rate. Field coverage should be above 30%.
    • Seeding date of cover crop.
    • Depth of seeding.
    • Type of termination (tillage, crimping, grazing, mowing). Note: Plant as early as possible and terminate as late as practical to maximize plant biomass production.
    • Date of termination and/or criteria used to determine the termination date.
    • Fertilizer and pesticide application information (type, timing, rates, methods of application).
    • Irrigation strategy: Irrigation may be necessary to initiate cover crop growth if planted during summer months. Applications of additional irrigation should be kept to a minimum.

Criteria/Verification

  • Certificate from seed suppliers.
  • Evidence (e.g. as-applied seed map, photographs) that the cover crop was planted following the agreed plan in the contract.
  • Evidence that the cover crop was not burned or baled.
  • Evidence or statement that the cover crop was not harvested for seed.
  • Confirmation that the cover crop was terminated consistent with NRCS guidelines.
  • Confirmation that, if grazed, the cover crop mix complies with pesticide label rotational crop restrictions.
  • Confirmation that cover crop management is consistent with applicable local criteria and soil/site conditions.

Incentive Payments

$74/acre/year, for the years that the cover crop is planted.

Stacking or Companion Practices

The cover crop practice is compatible with Biochar, Conservation crop rotation (>2 crops), Intercropping, No tillage from conventional, Reduced tillage from conventional, Nutrient Management (Basic, Enhanced and Precision), Prescribed grazing, Soil Carbon amendment. We encourage growers to explore grazing of cover crops as a stacked practice. Growers could also convert a cereal crop to a legume or inter-seeded cropping practice in alternative years. Nutrient management practices which replace synthetic fertilizers with compost or manure is another option. Reduced tillage and biochar practices would also be good options. It is recommended to account for soil nitrogen gains resulting from cover crops when calculating next year's fertilizer needs.

Sources

Additional Resources