Combine loss: what the beans on the ground cost you
Sigurd Lindquist, Certified Crop Adviser (CCA), Chetek, Wisconsin
Drop a frame behind the combine, count what is inside it, and tap. The page turns the count into bushels an acre and dollars an acre at your bid. Once it is open, the counting works with no signal.
Frame size
Bean size
BeansLoose kernels in the frame, behind the combine
Count loose beans and the beans in any pods on the ground.
Ears on the ground in 1/100 acre
Typical ear
Type your bid, or let the page fill one in.
Count a spot to see the loss.
Yield, acres, and loss ahead of the combine
Ahead of the combine: drop the same frame in crop not yet cut and count what is already on the ground. That part shattered or dropped before the head got there, so the combine did not lose it.
Seed size from a count instead:
Show the math
The rules of thumb
Nebraska CropWatch: in soybeans, 4 beans a square foot is 1 bushel an acre lost for medium beans, 5 for small beans and 3 for large. Their example: 7 beans in a 1 square foot frame is 7 / 4 = 1.75 bushels an acre. Iowa State and NDSU use 4. In corn, 2 kernels a square foot is 1 bushel an acre (Iowa State, NDSU), and one 3/4 pound ear in 1/100 acre is another bushel an acre (UW Extension).
Soybeans: beans that make 1 bushel an acre
| Bean size | Per sq ft | Per 10 sq ft | About seeds a lb |
|---|---|---|---|
| Small | 5 | 50 | 3,630 |
| Medium | 4 | 40 | 2,904 |
| Large | 3 | 30 | 2,178 |
Seeds a pound is the arithmetic behind each rule (beans a sq ft x 43,560 sq ft / 60 lb), not a number from CropWatch. It lets you use a seed count if you have one.
Corn: feet of row that make 1/100 acre
| Head | 20 in rows | 22 in rows | 30 in rows |
|---|---|---|---|
| 6 rows | 43.6 ft | 39.6 ft | 29.0 ft |
| 8 rows | 32.7 ft | 29.7 ft | 21.8 ft |
| 12 rows | 21.8 ft | 19.8 ft | 14.5 ft |
| 16 rows | 16.3 ft | 14.9 ft | 10.9 ft |
1/100 acre is 435.6 square feet. Feet of row = 435.6 / (rows x row width in feet). Pick up every ear across the full head width for that distance.
Questions
How do I measure combine loss in soybeans?
Drop a frame behind the combine and count every bean inside it, loose and in pods. Nebraska CropWatch: 4 medium beans a square foot is 1 bushel an acre lost, 5 if the beans are small, 3 if they are large. In a 10 square foot frame that is 40 medium beans. Count a few spots and average them.
How many corn kernels a square foot is a bushel an acre?
Two kernels a square foot is 1 bushel an acre (Iowa State, NDSU), so 20 kernels in a 10 square foot frame. Count dropped ears on their own: one 3/4 pound ear in 1/100 acre is another bushel an acre.
How do I count dropped ears?
Walk 1/100 acre behind the combine and pick up every ear across the head. 1/100 acre is 435.6 square feet: 29 feet of row behind a 6-row 30-inch head, 21.8 feet behind an 8-row. One 3/4 pound ear in that strip is 1 bushel an acre, and a 1/2 pound ear about 2/3 of a bushel.
How much combine loss is normal?
Iowa State says machine loss in standing corn should run about 1 bushel an acre or less. NDSU aims for 1 to 2 bushels an acre of total loss. Down corn and short beans with low pods lose more, and some of that no setting will fix.
Why count ahead of the combine?
Some loss happens before the head gets there: pods shatter and ears drop. Nebraska CropWatch counts a spot in uncut crop too. Take that count off the count behind the combine and what is left is what the combine lost, the part a setting change can fix.
What is the loss worth?
Bushels an acre times your bid. Two bushels of beans at $10 is $20 an acre, $10,000 on 500 acres. Enter your ZIP for the nearest posted bid, or type your own.
Sources
- Nebraska CropWatch: How to estimate harvest losses in soybean and corn fields (2023). The frame count, 5, 4 and 3 beans a square foot by seed size, the 1.75 bushel example, counting ahead of the combine.
- Hanna, Iowa State ICM: Minimize the amount of corn left on the ground behind the combine (2010). Two kernels a square foot or one ear in 1/100 acre is 1 bushel an acre; about 1 bushel an acre of machine loss in standing corn.
- UW Extension Waupaca County: Fall and winter ag newsletter, 2017-18. One 3/4 pound ear in 1/100 acre is 1 bushel an acre; a 1/2 pound ear about 2/3.
- NDSU Extension: Measuring harvest losses in corn and soybean. Four beans or two kernels a square foot; 1 to 2 bushels an acre of total loss as a target.
Bids: the nearest posted bid comes from the same elevator boards as cash bids near me. The state default is the futures settle less the state's median basis from the basis page, labeled as an estimate.