Planting corn is a game of inches

COLUMBUS – An extra inch between corn plants can mean a lot in terms of yield loss, said agronomist Peter Thomison, Ohio State University.

With planting season just around the corner, a few hours in the machine shed can save the disappointment of lost yields at harvest, Thomison said. Now’s the time to tune up planting equipment for a uniform seed placement in the furrow, he said.

“Timely planter servicing and adjustment, as well as appropriate management practices, can help prevent many stand uniformity problems,” Thomison said.

Thomison’s counterpart at Purdue University, Bob Nielsen, said many farmers may be losing 5-8 bushels of grain per acre because of uneven planting spacing. These values come from field research conducted over a number of years and locations throughout Indiana, and a survey of Indiana and Ohio fields over nine years, he said.

Other causes.

Spacing alone may not be the cause of yield loss, Thomison said. Other variables, such as less-than-optimal population levels, appear to cut into yields. A University of Illinois study concluded that skips reduce yield in fields where the intended population is at or below the optimum, while doubles increase yield when populations are less than optimum. Therefore, spacing variability caused by doubles may actually be beneficial when seeding rates are suboptimal.

“One conclusion that can be drawn from the Illinois study is that population is the first variable that must be considered in planting time decision making,” Thomison said.

Within-row gaps as large as 6 feet can cut yields by up to 5 percent, Thomison said. That’s a 7.35-bushel-per-acre reduction from a 147-bushel-per-acre corn yield. On the other hand, test weights of two or more tightly grouped plants can drop by as much as a quarter pound.

Stands with varying plant heights are generally related to environmental conditions that delay plant emergence, and out of a farmer’s control. Height irregularities often occur in conservation tillage fields where soils are prone to extended cold and wet soil conditions.

Making adjustments.

Proper planter adjustments and operation can help minimize uneven emergence, Thomison said. Even with uniform within-row plant spacing, emergence delays can lead to yield loss, Thomison said. Expect a 5 percent to 8 percent yield loss if half or more of the stand emerges two weeks late. A 20 percent loss can occur if emergence is delayed by three or more weeks. Thomison offers these tips for improving uniformity of seed placement at planting:

* Avoid excessive tillage trips, especially on wet soils.

* Check seed depth and seed-soil contact often during planting.

* Distribute resides evenly over rows.

* Run planting equipment at speeds between 4.5 mph and 5.5 mph.

* With plate-type planters, match the seed grade with correct planter plate.

* Check for wear on the back plate and brush on finger pickups. Check tension with a feeler gauge and tighten correctly.

* Check for wear on double-disk openers and seed tubes.

* Make sure sprocket settings are correct on the planter transmission.

* Check for worn chains, stiff chain links and tire pressures.

* Lubricate all chains and grease fittings.

* Make sure seed drop tubes are clean and clear.

* Clean seed tube sensors on planters equipped with monitors.

* Properly align coulters and disk openers.

* With air planters, match the air pressure with the weight of seed being planted.

* Make sure press wheels are adjusted to close the seed slot.

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