CropsSoybeans
Soybeans hide their problems once the rows close, so PropelMapper keeps the May stand check, the July aphid counts and the August white mold notes pinned to the spot where you made each one.
“Pod count 38 per plant on 10 plants, 3 beans per pod average.”
Example account: Prairie Agronomy
Visual example; transcript only.
Prairie Agronomy
Ortega Ridge › Marcy Quarter (Soybeans)
Pod count 38 per plant on 10 plants, 3 beans per pod average.
Soybean aphids averaging 80 per plant, below threshold, recheck in 7 days.
Frogeye leaf spot moderate on upper canopy in the south end.
Pod count - Marcy Quarter, Sep 5, 2026: “Pod count 38 per plant on 10 plants, 3 beans per pod average.” The visit form gets Pods per plant 38, Plants sampled 10, Beans per pod 3 average, and the report lists them under Pod count - Marcy Quarter.
Farm: Ortega Ridge → Field: Marcy Quarter (Soybeans)
Stages follow the V and R system described by University of Minnesota Extension. Acreage on this page is from the USDA Cropland Data Layer for 2025.
The walkField checks
Soybeans make up for a thin stand better than corn does, by branching and setting more pods. That makes the stand check less about one number and more about gaps, timing and what else the field is telling you.
VC to V2
Iowa State measures one thousandth of an acre (17 feet 5 inches of 30-inch row) or tosses a hoop and multiplies by a factor. Replant usually comes up below about 75,000 plants an acre for early plantings, or 50,000 to 60,000 for plantings in late May and June. Note the gaps, not just the average.
Record: Plants per acre, method, gap lengths
V2 to R1
Escapes after the post pass, by species and height, each with a pin. Bean leaf beetle feeding on young plants, and how much leaf area is gone.
Record: Species, height, patch size, defoliation
R1 to R5
The University of Minnesota threshold through R5 needs all three: an average of 250 aphids per plant, more than 80 percent of plants infested, and numbers rising. Count whole plants across the field, away from borders and hot spots.
Record: Aphids per plant, plants checked, percent infested, change since the last visit
Flowering in cool, wet weeks
A closed canopy and cool, wet weather at flowering set up white mold. Split stems, look for white growth and black sclerotia, and note where in the field you found them.
Record: Plants affected out of plants checked, location
R5 to R6
Pods per plant and seeds per pod for a yield estimate, plus late disease and defoliation.
Record: Pods per plant, seeds per pod, plants counted
Thresholds come from extension guidance and get revised. Check your state’s current numbers before acting on one.
Where it grows
About 77 million acres were classified as soybeans in the 2025 Cropland Data Layer. Illinois and Iowa together hold about a quarter of them.
Report outThe inspection question
The aphid threshold is an average per plant, and the average depends on how many plants you looked at and where. The plants by the buckthorn on the field edge give a different average than plants spread across the field. Say the count and how you got it.
In PropelMapper each stop is a pinned note. Say "twenty plants, about one-ninety a plant, eighteen of twenty infested" and the readings land in the visit form for you to confirm. Next week’s count goes in the same column of the Metrics grid, so the rising-or-falling part of the threshold is right there.
Your report gives the grower the count, the method and your call. If the call is to wait and recount in a few days, that becomes a task with a date on it.
The layers are most useful for choosing where to walk and for explaining a pattern you already found on foot.
Crop historyUSDA NASS Cropland Data Layer
Eight years of crop history make the corn and soybean rotation easy to see, and so is the year somebody broke it. Double-crop wheat and soybeans has its own class.
NDVICopernicus Sentinel-2 L2A
Field mean, minimum and maximum
Before the canopy closes, NDVI mostly sees the soil between rows. It earns its keep in July and August, when a low patch can point you toward something worth walking to.
SoilUSDA NRCS SSURGO
map units, by share of the field
Iron deficiency chlorosis tends to follow high-pH soils, and the soil survey shows where those map units fall in the field.
Questions
Both are on Iowa State’s list. A hoop suits narrow rows and drilled beans; a measured row length suits wide rows. Write down which one you used and its multiplier.
University of Minnesota’s published threshold runs through beginning seed. After that, it gives no formal threshold.
No. The phone keeps notes, photos and counts without a connection and sends them when you are back in range.
Keep the stand check and the aphid counts on the same field, and the season explains itself when the grower asks about yield.