CropsAlfalfa and hay
Alfalfa and hay scouting by cutting
An alfalfa field runs on a cutting schedule instead of a leaf-stage calendar, and PropelMapper keeps each weevil stem check, leafhopper sweep and readiness reading with the field and the cutting it belongs to.
- Stages
- Vegetative, bud and flower, within each cutting
- CDL class
- 36 · Alfalfa (37 · Other hay)
- Scouting
- Spring green-up to the last fall cutting
Insect thresholds are University of Minnesota Extension’s. Harvest timing follows Iowa State’s PEAQ method. Acreage is from the USDA Cropland Data Layer for 2025.
The walkField checks
Alfalfa scouting calendar by cutting
University of Minnesota Extension names two insects behind most of the economic damage to its alfalfa: alfalfa weevil in spring and potato leafhopper through the summer. Harvest readiness is the third reason to walk a hay field.
- Alfalfa weevil, Before first cutting, then on the stubble
Pick 50 to 100 stems from five spots and check the tips for feeding. Before first cutting, Minnesota’s threshold is feeding on 35 percent of tips in a weak stand or 40 percent in a vigorous one, or two live larvae per stem. After harvest it is eight or more larvae per square foot of stubble.
Record: Stems checked, percent with feeding, larvae per stem
- Potato leafhopper, Second and third cuttings
Take three to five sets of ten pendulum sweeps per spot. The threshold climbs with plant height: 0.3 leafhoppers per sweep under 3 inches, 0.5 at 3 to 7, 1.0 at 8 to 12 and 2.0 above 12. Skip it in wind over 10 mph or wet alfalfa, and stop 7 to 10 days before cutting.
Record: Sweeps, leafhoppers, plant height, yellow V-shaped leaf tips
- Cutting readiness, The week before each harvest
PEAQ estimates relative feed value from the height of the tallest stem and its stage, measured in five representative spots. Iowa State’s target for a milking herd is about 150 RFV, so for haylage you cut when PEAQ reads about 165, to allow for harvest losses.
Record: Tallest stem, stage, PEAQ RFV at each spot
- Stand and winter survival, Spring green-up and late fall
Stems per square foot, crown and root condition, heaving, and the date of the last fall cutting. An old stand thinning in the low spots is the usual start of the rotate-or-keep conversation.
Record: Stems per square foot, crown condition, cutting dates
These thresholds are Minnesota’s and may differ in your state. They belong in the record next to the count, not in place of your judgment on the field.
Where it grows
Where alfalfa is grown
The Cropland Data Layer classified about 13 million acres as alfalfa in 2025, led by Montana and Wisconsin. Another 10.7 million acres were classed as other hay.
Report outThe inspection question
Leafhopper counts tied to each cutting
A hay field’s season is a run of short cycles: green-up, scout, cut, regrow, scout, cut. A useful record ties every count to the cutting it belongs to. Six leafhoppers in ten sweeps on 8-inch regrowth is under the line; the same count on 2-inch stubble is well over it.
In PropelMapper the field is a place and each walk is a visit with its date. Say "second crop, eight inches, ten sweeps, six leafhoppers" and the plant height and count land in the visit form for you to confirm. When the nutritionist asks why the third cutting tested low, the scouting notes and the cutting dates are on the same field page.
Plenty of alfalfa feeds a herd on the same operation. Put the hay fields and the barns under the same farm, and the forage side and the cattle side share one history.
Alfalfa stand age, NDVI and soil drainage
A hay field changes every few weeks, so the layers are worth reading against your cutting dates.
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Crop historyUSDA NASS Cropland Data Layer
- Alfalfa class 36
- Other hay (not alfalfa) class 37
Eight years of crop history show how old a stand is and what grew there before, which helps when the grower is deciding whether to rotate out.
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NDVICopernicus Sentinel-2 L2A
Field mean, minimum and maximum
NDVI drops at every cutting and climbs with the regrowth, so read it against the harvest dates. A patch that stays low after regrowth is worth walking.
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SoilUSDA NRCS SSURGO
map units, by share of the field
Alfalfa does poorly on wet ground. Poorly drained map units in the soil survey often line up with the thin spots in an old stand.
Who scouts alfalfa and hay
- Agronomists and crop consultantsInsect counts and cutting recommendations for the grower.Who scouts it
- Pest control advisersWeevil and leafhopper counts against the thresholds.Who scouts it
- DairyForage quality that ends up in the ration.Who scouts it
- Beef and ranchHay supply and pasture on the same ranch.Who scouts it
Questions
Alfalfa and hay questions
Does PropelMapper calculate PEAQ?
No. Measure the height and stage the way Iowa State describes, read the RFV from the PEAQ table or stick, and say it in the note. The reading is stored with the field and the date.
Can I keep cuttings apart in the record?
Each walk is a visit with a date, so say which cutting it is in the note. You can also add the cutting number as a metric so it shows in its own column on the Metrics grid.
Alfalfa scouting before the next cutting
Walk a field before the next cut, record the sweeps and the PEAQ reading, and read the report before the swather goes in.