Soybean crop update and scouting activities

Manitoba Pulse & Soybean Growers Bean Report for June 1

Soybeans

The majority of soybeans have been seeded in Manitoba. Depending on how quickly fields dry up, there may be some late planting or change in acres. Early planted fields are nearing the unifoliate stage (V-C), while those planted May 20 or later are still emerging. Emergence is taking a little longer in some cases due to deeper planting and cool conditions. There were concerns about dry soils and impact on seed viability (how long can seed sit in dry soil?) and seeding depth (≥1.5”). Soybeans are emerging from 2” depths but are taking longer (10-12 days). Assessing seeding depth at emergence can help diagnose emergence issues such as deep seeding (long, thin hypocotyl) or soil crusting (swollen hypocotyl). Seed that sat in dry ground is also emerging: seed mortality can be a concern if seed imbibes some moisture, begins the germination process but then dries up. Soybean seed must maintain 20 per cent seed moisture throughout germination.

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We are now dealing with excess moisture conditions. Soybean seedlings will be more tolerant to saturated soil conditions than seed. Seedlings can generally survive submerged conditions for 48-96 hours. However, if flooding occurs within 1-3 days of seeding/initial seed uptake, germination and emergence can be severely affected depending on temperature and duration of flooding. Studies have shown a reduction in germination by 15-30 per cent and up to 40 per cent when flooding occurred for 1-24h and 48h, respectively, 1-3 days after seed imbibition. Assessing plant stands will be critical. A desired soybean plant stand is 120-160,000 plants/ac, however 60-120,000 plants/ac can still produce 76-95 per cent optimum yield. Use the MPSG Bean app.

Severe soil erosion from strong winds occurred during the week of May 15 and rolled bean fields were particularly impacted. While providing benefits for harvest management, rolling breaks soil aggregates, increasing risk of soil erosion from wind and water, and can reduce water infiltration. If land rolling is required for harvest management, post-emergence rolling at V1 (first trifoliate) is a viable option. Some farmers are moving towards this to minimize negative impacts on soil. MPSG is looking for feedback on land rolling soybeans—take our survey!

Dry beans

Majority of edible beans are seeded and got a good start before the rain but some acres will be on hold. Yield potential of dry beans can be maintained into early June. Soil crusting impeding emergence and excess moisture may be concerns moving forward, weed control should be top of mind.

Field peas

Herbicide applications in field pea were underway prior to the rain, although some decided to hold off until after. Field peas have been advancing well and are currently in the 3 to 6 node stage. Once field peas have advanced beyond the 6th node stage, the application window for group 2 herbicides is closed. Plants are noticeably shorter than normal due to dry conditions early in the season. After herbicide applications, assessing nodulation and monitoring for root rots are key scouting activities. If poor emergence and/or nodulation is evident, look for root rot symptoms such as discoloured roots. Root rots in field pea and lentil can be a production limitation in wet soil conditions. Peas will begin flowering 40-50 days after planting, at which time fungicide applications should begin.

Click here to read the full June 1 Bean Report on the Manitoba Pulse & Soybean Growers website.

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