CropsCorn
Corn scouting asks a different question at each stage (is the stand even, what is on the ear leaf, will it stand until harvest), and PropelMapper keeps each count with the spot in the field it came from.
“Stand count 32,400 plants/ac across three 1/1000 ac checks, emergence fairly even.”
Example account: Prairie Agronomy
Visual example; transcript only.
Prairie Agronomy
Jorgensen Family Farms › Home Place (Corn)
Stand count 32,400 plants/ac across three 1/1000 ac checks, emergence fairly even.
Gray leaf spot lesions on the third leaf below the ear, maybe 5% of plants.
Tar spot stromata found on two leaves near the waterway, first find this year.
Yield check - Home Place, Sep 15, 2026: “Stand count 32,400 plants/ac across three 1/1000 ac checks, emergence fairly even.” The visit form gets Spoken stand count 32,400 plants/ac, Sampling method Three 1/1000 ac checks, Emergence Fairly even, and the report lists them under Yield check - Home Place.
Farm: Jorgensen Family Farms → Field: Home Place (Corn)
Stages follow the leaf-collar system described by University of Minnesota Extension. Acreage on this page is from the USDA Cropland Data Layer for 2025.
Report outThe inspection question
The grower calls because the low end of the field looks thin. You could walk in, do five counts and report the average. It is better to count the low end and the rest of the field as two areas, three or four counts each, and say so in the report. The grower asked about the low end.
In PropelMapper each count is a note with a pin, so the report shows where the low number came from and where the high one came from. Say the row width and the length you measured with the count, and the stand count lands in the visit form for you to confirm. A photo of the wet corner next to the number answers the next question before anyone asks it.
The grower gets two numbers and a map instead of one number and a guess, and next spring’s planting conversation starts from the pins.
Where it grows
The Cropland Data Layer classified about 97 million acres as corn in 2025, and five states hold more than half of them.
The walkField checks
Vegetative stages count visible leaf collars, and the reproductive stages start at silking. Each row below is a reason to be in the field, with the reading that makes the visit worth writing down.
| Observation | Sampling context | Record |
|---|---|---|
| VE to V4The first few weeks after emergence | Count the stand in several places and note gaps, doubles and late plants. Nebraska Extension counts the plants in 17.4 feet of 30-inch row, one thousandth of an acre, and multiplies by 1,000. Plants more than three leaf stages behind their neighbors rarely produce, so leave them out of the count. | Plants per 1/1000 acre, row width, number of counts, late plants |
| V5 to V10Rapid growth, usually June | Collar stage on the plants you checked, weed escapes by species and height, early leaf disease, and nitrogen color. Pin the patch instead of folding it into the field average. | Stage, weed species and height, symptoms with location |
| VT to R2Tassel, silk and blister | Silks and pollination, rootworm beetles on silks, and leaf disease on the ear leaf and above. Tar spot shows as raised, black stromata that do not rub off; the Crop Protection Network overview shows what else it can be confused with. | Ear-leaf severity, beetles per plant, stage |
| R3 to R6Milk to black layer | Ear and kernel counts for a yield estimate, stalk strength and lodging by area, ear rots, and grain moisture as harvest nears. | Ears per 1/1000 acre, kernel rows and length, stalk test results, moisture |
These are prompts for the record, not treatment thresholds. Use your state’s current guidance for the management decision.
Map layers stop at your field boundaries. They help you decide where to walk; they do not count plants.
Crop historyUSDA NASS Cropland Data Layer
Crop history shows the USDA class for each of the last eight years, so corn-on-corn ground is visible before you walk it. It is a classification, so check it against the grower’s records before you rely on it.
NDVICopernicus Sentinel-2 L2A
Field mean, minimum and maximum
A low-NDVI patch in July is a place to walk to, not a diagnosis. Check the image date against your visit date before you compare them.
SoilUSDA NRCS SSURGO
map units, by share of the field
Soil survey map units show where the wetter, poorly drained soils are, which often explains a thin stand at the low end of a field. A map unit is not a soil test.
Questions
Enough to represent each area you are reporting on. Nebraska Extension suggests counting in several places and averaging. If the field has a problem area, count it separately so the average does not hide it.
No. It is the USDA’s classification from satellite imagery. Check it against the grower’s records before you treat it as fact.
Yes. Notes, photos, video and counts save on the phone and upload when you are back in range. The draft report is made after the upload.
Start with a stand count in two areas and keep going to black layer. By fall, the field’s season is one list of visits.