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5 steps to an efficient harvest

You check behind your six-row combine and find two corn ears dropped every 30 feet or so. Compound this by counting scattered kernels on the ground that average 4 per square foot.

Pretty good, right?

That depends. With a six-row machine at 30-inch rows, that 30-foot stretch with two dropped ears equals about 1∕100 acre. That’s 200 dropped ears per acre. With average-size ears, losses tally 2 to 3 bushels per acre, says Mark Hanna, Iowa State University Extension agricultural engineer.

Meanwhile, those ground kernels add up, too. Four per square foot equals about a 2-bushel-per-acre loss.

All these losses add up to 4 to 5 bushels per acre left behind with your combine. At $5 per bushel, you do the math!

“You are never going to get to zero,” says Hanna. “The American Society of Agricultural Engineers says 1% is the maximum acceptable threshing loss for corn and soybeans. In 200-bushel corn, that’s just 2 bushels. I know from experience that some combines in good standing crop have losses of under .5 bushel an acre. A good goal is to get to under 1 bushel per acre.”

Hanna gives five tips to help you fine-tune your combine and slice corn harvest losses.

1. Measure how you’re doing.

Look behind the combine and count the whole ears in a 30-foot stretch (or with a 12-row head, 15 feet is 1∕100 acre). Use this formula as a rule of thumb: One dropped ear equals 1 bushel per acre lost. If you see more dropped ears than you like, you know it’s a problem at the front end of the combine. Hanna says about 60% of corn harvest losses occur at the header.

In that stretch of harvested ground behind the combine, dig deeper -- down to ground level -- and look for scattered kernels. Count them in several 1-square-foot areas to get an average.

“It’s important to do this across the head and across the field,” Hanna says. “The variability can be high.”

If you find your total harvest loss is less than 1 bushel per acre and that’s your goal, don’t change a thing and keep harvesting, he says.

2. Find the culprit.

If the loss is unacceptable, determine where it’s occurring. If the problem is whole ears, look closely at header operation. Walk ahead into unharvested crop. You may see that most of the dropped whole ears are on the ground ahead of the combine. You can’t blame the combine for that.

To check for shelling losses on stalk rolls, combine into a section of standing crop for 15 feet to 30 feet, then back up and look at each row individually. This will tell you if you are losing kernels at the header rather than out the back of the combine due to a threshing or separating problem. You may be able to see that shelling losses are coming from one or two rows, so you can concentrate on fixing them, says Hanna.

If you determine you have a header problem, Hanna says to follow this checklist:

  • Set deck plates 1.25 inches apart.

  • Set snouts to just touch the ground.

  • Make sure ear savers, chains, rollers, and trash knives are all in good condition and are adjusted to manual specifications.

3. Get inside.

If the loose kernels are not present in front but are coming out the back, the problem is internal.

Start with threshing adjustments, says Hanna. For example, a normal rotor speed on some combines is 300 to 375 revolutions per minute (rpm), so start at the low end and adjust upward in 25-rpm increments. The reason you start at the low speed is because the faster the rotor goes, the greater the amount of cracked and split kernels there will be.

Ditto for concave settings between the rotor and cylinder. Start at the widest setting with the least crop damage. Check for grain losses or poor separation and adjust narrower as needed. Adjust in small increments until you bring losses into your acceptable area.

“While you are making these settings, check for chips or sharp edges on rasp bars and augers,” says Hanna. “Those can crack seed coats and split seeds.”

4. Make it flow.

The separator area needs optimal fan power. Start at the highest fan setting. If it blows kernels out the back, slice it in small increments.

Look at the tailings at the bottom of the combine for salvaged kernels, partial kernels, and trash that may be rerouted back through the thresher. There should be few whole kernels in the tailings.

If you see whole kernels, open sieves to get more of them into the clean grain auger. Many tailings show excess grain damage, and you are probably losing bushels out the back as fines and dust.

5. Find that sweet spot.

“Threshing is done by the violence of the crop and by the crop residue threshing against each other and against the rasp bars in the rotor,” says Hanna. “If you run the machine too full, you can slug it or pass material through unthreshed. If it’s not full enough, it beats up the crop and lowers grain quality. You have to find the sweet spot between too much and too little, where the machine is running full and you get maximum efficiency.

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