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

Provides a source of N to allow reductions in applied N fertilizer; improves cropping system diversity; uses resources (e.g., light, water, and nutrients) more efficiently than monocropping; 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).

Soil Carbon Impacts

Possibly increasing crop residue that can be incorporated.

Greenhouse Gas (GHG) Impacts

Reduced N applications associated with N-fixing legume 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 SAP 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. 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.

Criteria/Verification

• Certificate from seed suppliers.
• Crops grown in a planned sequence as outlined in IAMP contract with GHG Reduction Plan.
• Total nitrogen fertilizer applied to the crop must be at least 15% less than growing each individual crop under a baseline condition.
• Photos of intercropped species establishment 4-6 weeks after planting.

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.

Sources

• NRCS Conservation Crop Rotation (328)
• USDA - Idaho Supplement To Conservation Enhancement Activity E328N
• WSARE Guidelines for Intercropping
• USDA RMA Managers Bulletin: MGR–22-002