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Around the County

Frequent information updates for agricultural audiences

June 30, 2010

Yield Potential of Ponded Corn - from Mike Roegge

How much yield potential is there for these wet areas in corn fields that have corn that's only knee high or less, when the good looking corn is head high? Good question. And what can you do to potentially improve those areas?

The problem is that the plant can't grow because there is no air in the soil. The soil is saturated with water. And until there is air in the root zone, the plant will continue to decline. Perhaps the best option is to open the ground up with a toolbar or row cultivator as soon as conditions allow. Of course the concern is that you'll damage the good corn getting back to the wet areas. You'll need to weigh the options on how much damage you'll cause by the tillage trip. But the heavy rains that fell on saturated soils have created a somewhat impervious layer that won't allow much passage of air. Until that is broken up, don't expect much in the way of corn growth.

What is the yield potential of those wet areas? Much depends upon how long those areas were saturated with water and how soon the corn plant will respond to more favorable growing conditions. I don't think some of these areas have much in the way of yield potential. Especially those earlier planted fields where the wet areas are less than knee high while the good areas are above your head. These wet areas have just been too wet for too long and the plants don't have much of an opportunity to produce yield. The biggest question is how long will it take for the wet areas to respond. The sooner that happens, the more likely for yield.

We've also noted the first emergence of western corn rootworm beetles. We've seen the populations of these insects decline over the past three years. Hopefully, the wet weather we had thus far (which is detrimental to larvae survival) plus Bt protected corn, will keep these in check. Time will tell. But be watchful for silk clipping by the rootworm beetles as well as Japanese beetles.

Posted by John Fulton at 10:50 AM | Permalink |

June 3, 2010

What's with the nutrient deficient looking corn? - from Fabian Fernandez

URBANA – Growing season conditions may be the biggest contributor to poor crop appearance today, rather than inadequate soil fertility, said Fabián Fernández, University of Illinois Extension specialist in soil fertility and plant nutrition.

"Environmental conditions play an important role in nutrient availability," Fernández said. "Plants obtain most of their nutrients and water from the soil through their root system. Any factor that re­stricts root growth and activity has the potential to restrict nutrient availability."

Fernández said four factors may be causing this season's observed deficiencies.

· Excess water in the soil depletes oxygen and builds up carbon dioxide levels. While oxygen is needed by the roots to grow and take up nutrients, high carbon dioxide levels are toxic and limit root growth and activity.

· Temperature influences how nutrients are absorbed. Under cool soil temperatures, chemical reactions and root activity decrease, rendering nutrients less available to the crop. Plant nutrients are taken up as roots extract soil water to replenish water lost through the leaves. Cool air temperatures can lower evapotranspiration and reduce the convective flow of water and nutrients from the soil to the root.

· Light intensity affects nutrient availability. Many days in this growing season have been characterized by low light intensity due to cloudiness. Low light intensity reduces photosynthetic rates and nutrient uptake by the crop.

· Immobilization of nitrogen occurs when plant-available nitrogen becomes temporarily unavailable as microorganisms breakdown crop residue. This has been observed in corn fields planted on previous corn. As crop residue and soil organic matter starts to mineralize, nitrogen will become available to the plant. If the full amount of nitrogen has not been applied yet, a sidedress application of urea ammonium nitrate (UAN) can help provide the nitrogen the plant needs at this time.

"As growing conditions improve, most nutrient deficiency symptoms will disappear without additional fertilization," he said.

In Illinois there are instances in which calcium, magnesium, sulfur, and a few micronutrients may be deficient, but these deficiencies are not widely seen, he said.

"The use of micronutrient fertilizers should be limited to areas of known deficiency, and only the deficient nutrient should be applied," Fernández said. "Exceptions to this are situations in which producers already in the highest yield bracket try micronutrients experimentally in fields that are yielding less than would be expected under good manage­ment, which includes an adequate N, P, and K fertility program and a favorable pH."

If a nutrient deficiency is suspected, he encourages producers to collect plant samples and send them to a laboratory for nutrient analysis.

When diagnosing a fertility problem through plant analysis, select paired samples of compa­rable plant parts representing the abnormal and normal plants. After collecting the samples, deliver them immediately to the laboratory. Samples should be air-dried if they cannot be delivered immediately or if they are going to be shipped.

Soil factors (fertility status, temperature, and moisture) and plant factors (cultivar and development stage) may complicate the interpretation of plant analysis data. The more information provided concerning a par­ticular field, the more reliable the interpretation will be.

"Because growing season conditions accentuate problems that might not be as evident in other years, this is a good time to learn about field conditions or management practices that should be adjusted to prevent or lessen problems in the future," he said.

Posted by John Fulton at 3:36 PM | Permalink |