Worn back plates and brushes. Rust buildup. Broken belts.

Those are the problems Dan McKeon sees most often as he tests the accuracy of corn planter metering units using his new computerized planter stand.

McKeon, a crop consultant with DDM Crop Service in North Platte, NE, bought the computerized Row Unit Tester in February.

"Without the planter stand, there's no way to accurately test planter units," explains McKeon, who uses it on John Deere finger and vacuum metering units and Kinze finger units.

By having their units tested and then calibrated, McKeon hopes corn growers will get their desired plant population and even seed spacing. That should maximize yields, he says.

"If a producer wants to drop 30,000 seeds per acre, and his planter units are operating at 85% efficiency, only 25,500 seeds are planted. Then, with a 5% allowance for germination figured in, that number drops to 24,225.

"You can apply the correct amount of fertilizer and other chemicals, choose the right seed, plant at the optimum time, etc. But if your planter meters aren't calibrated correctly, it goes to waste because you don't have the stand to equal your yield potential," says McKeon.

To get started, McKeon plugs the following information from each customer into the computer: row width, desired population, planting speed and seed size. Then he attaches a metering unit from the farmer's planter to the stand and runs 100 kernels through it. A 100-cell gated belt catches the seed after it's run through the metering unit.

Ideally, each cell should catch one kernel. But if the unit isn't running at 100% accuracy, some cells contain two or three kernels or no kernels at all.

The stand's computer calculates each unit's percentage of accuracy.

"Most units run at about 85-95% drop accuracy before we work on them."

Next, McKeon and his assistant, Tim Storm, tear the units apart. They adjust tension, clean all parts and replace any that are worn. They keep a big supply of brushes, back plates and other parts on hand to speed service.

They spray the inside of finger-unit frames with liquid graphite to prevent rust and keep them running smoothly.

After taking the above steps, they test the unit a second time. If accuracy is less than 99%, they repeat the procedure.

The entire process takes 35-40 minutes per row.

McKeon, who hopes to work on 350 units this season, charges $18.95 per row for finger units and $8.95 for vacuum units. He charges more for finger pickup units because they have more moving parts.

He says each planter unit should be checked annually or after planting 500 acres.