Summary Table

IAMP-Interseeding
(implied within NRCS Code 328)

Description

Interseeding is the practice of planting a second crop with a primary cash crop. The practice increases plant diversity and creates beneficial interactions or services such as nutrients for the primary cash crops. The following practices fall within Conservation Cropping Systems Code 328. Within Code 328, E328N applies. Only Code 328 is authorized under the IAMP project, allowing any of these specific intercropping practices.

  • Interseeding legumes: direct seeding legumes into a primary cash crop, either at the planting of the 1st crop or later (after establishment). Legumes are specified for their ability to fix nitrogen, potentially reducing need for applied inorganic nitrogen.
  • Relay cropping: a mix cropping or interseeding practice in which the second-planted crop (“relay crop”) is planted into an established primary cash crop in a manner that allows separate agronomic maintenance and harvest of each of the crops unless otherwise defined in the Crop Provisions (e.g., planting legumes/cover crops into a small grain field before harvesting small grains).
  • Companion planting: planting different crops in proximity to provide ground cover and weed control for the slow-growing crop (e.g., oat-alfalfa).
  • Other approaches to intercropping can be considered if they have the potential to reduce GHG emissions based on COMET-farm.

Benefits

Interseeded legumes provide a source of N that may allow reductions in applied N fertilizer during the cropping year or the subsequent year; improves cropping system diversity; uses resources (e.g., light, water, and nutrients) more efficiently than monocropping; potentially results in overyielding; may have lower insect pressure. Potentially harvestable with the main crop for unique marketing opportunities (e.g., mixed grain for animal feed and soups and potentially high-protein pasta) or for separation and marketing as single commodities.

Soil Carbon Impacts

Potentially increases crop residue that can be incorporated or increased root activity.

Greenhouse Gas (GHG) Impacts

Reduced applied N associated with N-fixing legume in the cropping year or in the subsequent year could reduce N2O emissions.

Considerations for Success

  • Seeding modifications are likely to require additional or modified equipment. Talk to your Soil and Water Conservation district about the potential for rental equipment.
  • Consult with your implementing partner and/or crop advisor to select plant species that will be compatible and not over-compete cash crops.
  • Potential yield loss in the main crop due to competition between crop species.
  • Mid-season plant tissue and/or soil samples are recommended to understand nutrient interactions and make adjustments to nutrient management applications as necessary.
  • May harvest small grains and legumes separately if the harvestable parts (e.g., spikes and pods) are of different heights.
  • Extra costs for sorting/cleaning mixed seeds.

IAMP Preferences/Considerations

The IAMP project incentivizes practices that result in a net reduction in GHG and increase in soil carbon. Interseeding legumes provides an alternative source of N that can enable reduced N application rates. Interseeding can also result in increased crop biomass particularly with companion planting in row crops where rows may be typically fallow. Other diversified cropping plans may or may not provide the intended GHG and soil carbon benefits. This practice will likely be implemented and incentivized coupled with reduced applied N either in the implementation year or in the following year in the rotation.

Specific Details

IAMP has several requirements for inter-seeding 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 primary cash crop will be grown without any companion crop 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 at termination of the crop 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:
    • Crop yield maps (if available for both the baseline strip and the remaining field).

Criteria/Verification

  • Certificate from seed suppliers.
  • Crops grown in a planned sequence as outlined in the IAMP contract with a GHG Reduction Plan.
  • Photos of intercropped species establishment 4-6 weeks after planting.
  • Soil and Crop biomass sampling to track carbon and nitrogen impacts.

Incentive Payments

$60/acre in the year of implementation.

Stacking or Companion Practices

Fall compost addition, biochar, reduced or no-till, N management, cover crops (in rotation), conservation cropping. As part of a rotation, the additional N from an interseeded legume could support the Nutrient management practice (reduced N by 15%) in the following year.

Sources