Hopefully you got your soybeans planted during your desired window and into good soil conditions.
Your next task is to scout for emergence, emergence consistency and stand counts. Soybeans aren’t as sensitive to emergence consistency as corn. We know that corn seedlings should all emerge at about the same time, or with 1 or 2 days of each other, so they compete equally and set an equal sized ear.
Soybeans, on the other hand, are compensatory and adjust pod count to accommodate voids in emergence. Generally, growers overplant by 20 to 30% as insurance against seed and seedling loss. This is a good strategy to ensure a good stand with no large gaps or voids. Corn can survive and emerge slowly, but soybeans don’t have that characteristic. Once they germinate they need to get at it and get out of the soil. Delays in emergence quickly reduce their chances of survival. That is why overplanting pays dividends.
So your first step is to have a general idea of when the crop emerged after planting and the weather and soil conditions that might have impacted that planting outcome. Hopefully, the crop will emerge in 6 to 10 days.
Take a quick look for visual symptoms such as blight or damping off, SDS, yellowing, herbicide injury or even early insect feeding. Relate what you observe to soil conditions and weather at planting and emergence rates.
Shaun Casteel at Purdue University recommends this systematic approach to scouting soybean emergence.
1. Track fields once soybean seedlings crack the soil surface. Earlier plantings take longer to emerge, 14 to 21 days, compared to late plantings, when emergence may be in 5 to 10 days.
2. Simply mark off a few rows with flags. Two per 1/10,000th of an acre equals:
- 42 inches of one 30-inch row
- 42 inches of two 15-inch rows
- 42 inches of four 7.5-inch rows
3. Count the number of emerged plants in that area daily or twice a day for finer resolution.
4. Calculate your plant population by dividing total number of plants by 2 and multiplying by 10,000. For example, 26 plants ÷ 2 × 10,000 = 130,000 plants per acre.
5. Compare emergence notes on dates, rates and total stand to weather and soil variables, heat units accumulated from planting to emergence, and from cracking to complete emergence.
This emergence assessment will reveal how well your planting plans and preparations worked out including variety selection, seed treatment planting date, field preparations and weather conditions during planting.
I realize this sounds like a lot of work and it does take a bit of commitment, but the results can reveal valuable information about conditions and preparations, and help better tune your management next year.
Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at email@example.com.