Potential yield increase = 5-9%

A corn plant that emerges just four hours after its neighbors will be slightly smaller all season, says Rhett Schildroth, a Williamsburg, Iowa, farmer and product manager for planter-manufacturer Kinze.

“If emergence is delayed on one in four plants by one-and-a-half weeks,”Bassett notes, “yield potential falls by 6%.”The primary causes of non-uniform emergence are uneven planting depths and poor seed-to-soil contact. Consider these tips to improve uniform emergence:

Stay off the field until its ready. If you don’t wait until the soil is fit to work, Bassett says, “your first field pass could cause compaction that will plague the crop the rest of the year.”

Manage tillage. Because of the 2012 drought, “seedbed preparation will be really important this spring,”Zwingman says. In drought-stricken areas, the ground is very hard, even in irrigated fields, he says. Growers who use conventional tillage should pay close attention to spring tillage depth and consistency.

The Rahns employ conventional tillage on most of their fields: fall chisel plow or disk-rip, followed by one or two spring passes with a field cultivator equipped with rolling baskets that smooth and firm the seedbed.

Watch planter down pressure. It’s essential to assure correct seeding depth and adequate seed-to-soil contact, Schildroth says. “You need enough force to get the proper depth, but not so much that you compact sidewalls."

Understand field conditions. Planter tools that sense ground hardness and automatically adjust down pressure on-the-go are helpful in variable fields. The hydraulic weight transfer feature also helps ensure uniform down pressure on row units across the width of the planter.

Check planter parts. “Make sure your opening disks are not worn, and penetrate to the correct depth,”Schildroth says. Adjust the planter’s closing wheels so the soil is firmed around the seed, allowing it to absorb moisture quickly and uniformly.

Match speed to field conditions. This is critical to maintain even seeding depth. “When planting a fully tilled field or into bean stubble in the same direction as the old rows, you can go at a pretty good speed,”Schildroth says “But if it’s a no-till field, corn-on-corn or you are planting at an angle to last year’s rows, slow down.”Zwingman adds: “Excess planter speed is the biggest killer of uniform seeding depth and emergence.”

Various planter speed studies had contradictory results: In a recent Illinois study, planter speeds of up to 8 mph had no yield effect. But a 1998-1999 Wisconsin study showed yield reduction of 7 bu./acre when operating a planter at 8 mph vs. 4 mph, or about 1.8-bu. yield change per 1-mph speed increase. And a yield response to planter speed increases was detected at only 23% of Purdue study sites. The variation in results would seed to emphasize tailoring planter adjustments to field conditions. (For more on this data see http://bit.ly/OhioSeed.)

Manage residue. Uneven residue distribution leads to variable soil moisture and temperature, and non-uniform emergence, Bassett says. “Use row cleaners,”and make sure they are set properly so the soil surface is exposed to sunlight.

Maintain good drainage. All the Rahn fields are pattern tiled, which reduces compaction and produces better soil tilth. “As a result, the soil is more mellow, so we can make a better seedbed,”says Rahn.

Check seed placement. In droughty areas, “we may have trouble this spring getting consistent seed depth,”Zwingman says. “Make sure your planter is running at the correct depth, and if it’s dry, err on the deeper side –at least 2 in. or even a bit deeper.”

Check seed placement when you start planting, Schildroth adds, and check again a couple more times throughout the day, especially if soil conditions change. Interrupting planting to check seed depth is inconvenient, he acknowledges. “But it’s one of the most important things a grower can do to make sure the field is planted correctly.”