Early season, The Bean Report

The Bean Report – April 28, 2021

April 28, 2021

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Field Pea Seeding Recommendations

  • Seed peas from late April to early May when the minimum average soil temperature at seeding depth is 5°C. Peas will begin germinating at 4°C but waiting until the minimum average soil temperature is 5°C will improve vigour and emergence. Delaying seeding until late May means the crop will flower during the heat of July. Hot temperatures during flowering will cause flower blasting, which inhibits pod development.
  • A good rule of thumb is to seed peas into at least ½” of moisture. Pea seed depth may range 1.5 to 3” deep. Peas can tolerate deep seeding, but if moisture is closer to the soil surface, shallower seeding will lead to quicker emergence.
  • Inoculate with Rhizobium leguminosarum bacteria and ensure soil test N levels are low enough to accommodate nodulation (<50 lbs N/ac). Single inoculate on fields with a history of peas. Double inoculate on first-time fields using a peat or liquid on-seed and a granular in-furrow.
  • Seed peas on narrow rows between 6 to 12”.
  • Target 80 to 90 live plants/m2 (350-400,000 live plants/ac).

Faba Bean Seeding Recommendations

  • Seed faba beans from mid-April to early May. The minimum soil temperature for faba bean germination is 3 to 5°C. Like peas, delaying seeding will result in fabas flowering during the heat of July which can lead to flower blasting.
  • Seed depth for faba beans ranges from two to three inches, ensuring adequate seed-to-soil moisture contact.
  • Separate tannin and zero-tannin varieties by 500 m to prevent cross pollination.
  • Inoculate with Rhizobium leguminosarum bacteria and ensure soil test N levels are low enough to accommodate nodulation (<50 lbs N/ac). Single inoculant on fields with a history of peas or faba beans. Double inoculate using a peat or liquid on-seed and a granular in-furrow on fields without pea or faba history.
  • Seed fabas on narrow rows between 6 to 14”.
  • Target 45 live plants/m2 (180,000 live plants/ac).
  • If you are planning to seed with an air seeder, check out PAMI’s tips to avoid faba bean plugging issues.

Calculating Seeding Rates for Peas and Faba Beans

There can be wide variation in seed size among varieties and seed lots. Calculate seeding rates using the thousand seed weight (TSW) of your specific seed lot, target plant population and expected seed survivability based on your farm history.

Field peas range from 200 to 300 grams per 1000 seeds and faba beans range from 300 to 700 grams per 1000 seeds. Use the seeding rate reference charts below (yellow for peas, purple for faba beans) to find your suggested seeding rate using TSW and expected emergence. The field pea chart provides seeding rate suggestions to achieve a target plant population of 80 to 90 plants/m2 (350,000 to 400,000 plants/ac). The faba bean chart provides seeding rate suggestions to achieve a target plant population of 45 plants/m2 (180,000 plants/ac). Or, calculate the seeding rate yourself using the equation above.

Soybean Seeding Dates in Manitoba

The soybean seeding window is flexible in Manitoba. According to research from the pulse and soybean agronomy lab at the University of Manitoba evaluating seeding dates from 2017 to 2019, soybean yields did not differ when planted throughout May 1 to 24. Yield was reduced by 15%, on average, when seeding was delayed until May 31 to June 4.

On the flip side, seeding can be too early in Manitoba. Soybeans are susceptible to damage from frost and delayed emergence from cold soil. Check the average date of the last spring frost in your area, avoid cool soils below 8°C and make sure cold rain is not in the forecast for the first 24-48 hours after planting.

In this study, seeding during the second week of May maximized yield potential while avoiding cold soil and the risk of late spring frost.

Click here to access these, and other frost maps from Manitoba Agriculture and Resource Development.

Success with Seed Inputs

Inoculants contain living bacteria, so proper storage and application is important to maintain viability:

  • Keep cool and out of direct sunlight. Follow manufacturer recommendations.
  • Check compatibility of seed-applied inoculants with seed treatments. Apply seed treatment first and allow it to dry before applying inoculant to the seed.
  • If using liquid or peat inoculants, seed soon after application.

Seed treatments can help improve crop establishment by protecting seedlings from early-season pests. They are available as a fungicide-only or combined with an insecticide:

  • Fungicide seed treatments are most likely to provide a return on investment if planting into cool, wet soils or into fields with a history of root rots.
    • For peas, there are now seed treatments available (Intego and Rancona Trio) to help suppress Aphanomyces early in the season during the seedling stage. Consider these if your field has a history of Aphanomyces. But note that they will only provide early-season protection from the disease.
  • Insecticide seed treatments are most likely to provide a return on investment in fields with a history of insect pressure. Insecticide seed treatments for peas and faba beans are available to protect against wireworms, pea leaf weevils and cutworms.

Early Season Considerations for Pea Leaf Weevil

  • Larvae of pea leaf weevil (PLW) feed on root nodules of field peas and faba beans. Excessive nodule feeding can inhibit N-fixation.
  • PLW appears to be established in the northwest region of Manitoba, with weevils found near Swan River in 2019 and near Kenville, Minitonas, Gilbert Plains and Dauphin in 2020 due to trapping efforts led by Manitoba Agriculture and Resource Development. PLW has not been found outside of this region. Monitoring will continue in 2021.
  • Insecticide seed treatment (chlorantraniliprole, imidacloprid or thiamethoxam) is available for preventative control. However, only use seed treatment if you know this pest will be a problem in your field based on past PLW populations and damage. It is unlikely that seed treatment would be cost-effective at this time, given the current PLW levels in Manitoba.
  • In-season scouting for leaf notching is the best way to determine if you have a PLW problem, since larvae (left) and adults (right) are difficult to find. Use this growing season to look for any potential damage and inform next year’s spring input decisions. Keep reading The Bean Report for more tips throughout the season.
Pea leaf weevil larva.
Adult pea leaf weevil.

Additional Resources:

Pea Leaf Weevil – Government of Saskatchewan Web Page
Integrated Management of Pea Leaf Weevil in North Dakota – NDSU Extension Service Fact Sheet

On-Farm Network – Returning to the Scene of the Crime: Wireworm Worries, Year Two

Trapping for Wireworms

Source: Wireworms in Manitoba and a Guide to Scouting your Fields by Ivan Drahun and Dr. Bryan Cassone, Brandon University, Spring 2020 Pulse Beat

New! Organic Field Peas – Production Guidelines