Premature corn planting can lead to greater yield losses

By: Agriculture.com Staff 04/09/2007 @ 2:57pm

Growers anxious to get this spring's corn crop in the ground may be struggling with weather-driven delays to fieldwork. But, they'll end up much better off waiting on warmer, drier conditions than trying to force the crop in, according to an Iowa State University ag meteorologist.

Current damp, cool conditions follow a months-long trend of volatility in weather, according to S. Elwynn Taylor. Going back as far as September, both average monthly temperatures and precipitation levels have skewed from average one way or another by as far as 20 degrees and four inches.

"December started out cooler than usual and ended warmer than usual by 10 degrees and had double the normal precipitation," Taylor says. "January started off 23 degrees warmer than usual and ended 16 degrees colder than usual and slightly on the dry side.

"We're bouncing back and forth on this thing," he adds. "People forget about what the weather's been doing this winter. We've been going through these extremes, setting record highs and lows."

What does this mean going further into this spring planting season? Taylor says research in his department indicates a clear pattern: Volatile fall and winter weather patterns typically precede difficult or delayed spring planting seasons, mainly because of continued volatility well into the growing season.

"These extremes are likely to continue. Let's say that the crop is adapted to average conditions, and if you set a new record somewhere out on the edge of those conditions and the crop is not adapted to it well, there will probably be some problems," Taylor says. "We have found that when we have months that set records for both high and low temperatures, it's generally not positive for the coming crop season."

Despite this volatile weather outlook, Taylor advises growers to allow conditions to warm and dry up before entering the fields for planting. Doing so prematurely can lead to greater yield losses than those brought on by later planting dates. The first concern is with moisture and the damage fields can incur when planted when too wet.

"[Soil moisture] is the highest it's been in the past 12 years, maybe longer than that. Ninety-two percent of tiles are reported to be running across the Corn Belt, from the center of Indiana to the center of Nebraska. That's the highest number we've seen since we started surveying this nine years ago," Taylor says. "With a lot of water in the soil, there's a lot of opportunity to damage your soil by driving around on it. We'll pay for it in reduced yields coming from compactions or other problems that can cause poor rooting."

Taylor adds a 2002 study by his department indicates a corn yield loss of 17 1/2 bushels per acre in a field where compaction had led to root depths of 19 inches versus 4 1/2-foot root depths in soil without compaction.

"This goes on year-to-year, and it's difficult to get out of it," he says.

Trying to plant before soil temperature is as the right level can be equally detrimental to corn stands. For planting, 50 degrees is the typical target for soil temperature, a target that's still a ways off, at least in much of Iowa.

"This time of year, we're normally running in the 40s, but we're running in the 30s at the present time," Taylor says. "Corn begins to grow when temperatures exceed 50. Until we start getting 50-degree days, I don't think the soil temperatures move appreciably above 40."

Soil temperature concerns don't end once the seed is in the ground, and it's not important only at the depth where the seed is planted. Root and stem development can only take place when soil is above 50 degrees as well. If planted in a sub-50-degree seedbed, the corn's growth will be slowed or stopped. But, that won't stop the onslaught of pathogens and harmful microorganisms.

"It's not just the soil temperature where the seed is. The roots have to go down, and if they hit a 'block of ice,' they quit growing," Taylor says. "It's better off in the bag, because at least there, there's not disease working on it. The diseases in the soil don't quit at these temperatures like the corn does."

In general, Taylor says considering the potential corn yield loss from field compaction and early-season pests, it's better to wait to plant until soil temperature and moisture conditions improve.

"Get on the soils when the moisture's right so you don't damage it. We'll assume the soils will warm up the first week of May or last week of April. So, the real concern is the well-being of the soil itself," Taylor says. "The second concern is if you put plants in cold soil, they won't grow but will be susceptible to microorganisms attacking it."

Growers anxious to get this spring's corn crop in the ground may be struggling with weather-driven delays to fieldwork. But, they'll end up much better off waiting on warmer, drier conditions than trying to force the crop in, according to an Iowa State University ag meteorologist.