Which Corn Will Yield Best This Year?

Which Corn Will Yield Best This Year?

Will it be early planted corn that went into the ground the first-half of April? Or corn planted first week of May? Best time to plant varies year-to-year, depending on weather and soil conditions. "We may not have seen our best planting date yet for this year," says ISU agronomist Roger Elmore.

Due to wet, cold soil during most of April farmers in Iowa didn't get hardly any corn planted and had to wait until the first few days of May to really begin planting in earnest. But just because you didn't get much corn, or any corn at all, planted in April, that doesn't mean your yields in 2011 will be poor.

The best time to plant varies from year-to-year depending so much on weather and soil conditions at planting, says Iowa State University Extension corn agronomist Roger Elmore. "We may not have even seen our best planting date yet this year," he said on May 6.

Iowa farmers were finally able to get into fields this week, as soil dried out enough to allow them to plant in early May. However, soil temperature at planting depth was quite cold overnight and in the mornings during the week ending May 7. "It certainly was cold on several of the mornings. Fortunately, we don't have a lot of corn up and growing yet in Iowa. It's still in the soil, where the seed is protected from the cold weather," says Elmore.

See any problems with corn seedlings sitting in cold, frigid soils?

Are you noticing any problems with corn seedlings that were sitting in cold soil, as freezing temperatures of 32 degrees F or slightly below hit some of the newly planted fields? "So far, so good, but you need to be looking," says Elmore. "There was hardly any corn that had emerged from the ground yet on those cold mornings this past week. The growing point within the plant was still well below ground. So even if the corn leaves on the plants do get frozen off, the corn plants will grow back and recover, as long as the growing point is not damaged."

He adds, "The only significant concern is that our heat unit accumulation has been slow because of the cold temperatures in Iowa this spring. Emergence of the corn crop that was planted or will soon be planted is going to be slower than we like. The longer you leave corn seed in cold ground, the more chance there is for poor emergence or variable emergence. It's not good for increasing yield."

Farmers have made quite a bit of progress in the last five to seven days in getting corn planted in Iowa. There were a lot of planters in the fields this past week and soil conditions across the state were generally good. Some fields and portions of fields were avoided, because they were still too wet to plant, but a lot of Iowa's 2011 corn crop did get planted from May 1 to May 7.

Corn plants looking a little yellow when they emerge this year

A farmer near Cambridge in central Iowa had corn emerging on May 4. It was planted April 8. The farmer says they're a little yellow, but the corn plants are coming up. "Young corn plants will be yellow due to cold and wet soils, which are not good conditions for corn to be emerging from," says Elmore. "Particularly if you have some of the early planted corn, it's now time to get out there in the field and evaluate the corn emergence."

Elmore looked at a field on May 3 that was planted on April 13 and it still had the roots first coming out of the seed. "And the coleoptile, which is the first shoot, was just coming out of the seed," says Elmore. "So, the corn seedlings were still basically sitting at planting depth, or about 2 inches below the soil surface. We need warmer temperatures to get that seed up and out of the ground and growing. It takes about 90 heat units to accumulate for that to happen."

Watch your emerging corn, and note the uniformity of emergence

Once you get 90 heat units or growing degree days accumulated, the corn seed that you planted should be coming up, says Elmore. "Check your stand for variability and uniformity of stand, and note how well it emerges," he advises.

Does Elmore have any thoughts on possible yield loss that may have already occurred this spring for the 2011 Iowa corn crop, as of May 7, due to delayed planting? "I don't think we can talk about yield losses yet," he answers. "On average, we're still in good shape and we have 95% to 98% of our yield potential on the corn that's planted by May 10 or so in Iowa. Also, you must remember every year is different in terms of the type of growing season we will have."

He also points out that "The numbers we cite in terms of percent of potential yield if planted by a certain date are averages based on research over the years. And in any given year that average moves around quite a bit. In fact, we may not have seen our best planting date yet for corn this year."

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