Dr. Dan Talks Agronomy

Some fields and regions of the Corn Belt are just fine, but others had fields whose soils stayed cool for weeks after planting. Others were pounded with too much rain after emergence, then faced drown-outs and the possibility of replanting and potentially lost nitrogen. Fortunately, one of the scenarios growers won't face this season is delayed corn planting or prevented planting since most corn acres were planted in the optimal window.

COOL SOIL TEMPERATURES

Some corn acres were planted by April 15, and then soil temperatures stayed cool -- below 55 degrees Fahrenheit -- for the next three weeks before emergence occurred. On our family farm in northeast Nebraska, our DTN weather station recorded soil temperatures at 50 degrees about mid-April. Temperatures for the following 30 days hovered between 48 and 55 degrees. Those are not ideal temperatures for germination and emergence.

During that period, we also had frequent rains exceeding 8 inches. So the soil was both cool and wet but not necessarily saturated for extended periods of time. Corn planted in mid-April still hadn't emerged three weeks later, but I consider their prospects good because we did not experience chilling rains or extended periods of saturation.

Today's corn seed and seedlings are better adapted to stress conditions that come with early planting such as cold soils and surviving delayed emergence. In addition, today's seed treatments protect against seedling diseases and soil-borne insects that can damage seeds the longer they remain in the soil. That means seed can sit in the soil, progressing slowly, and emerge three weeks later and still yield.

However, even with the best genetics and seed treatments, and depending on soil conditions and potential for crusting, seedlings may twist below the soil surface and not emerge. If you notice gaps in your stands as the crop emerges, dig up some seeds and look for the presence of dead seed or twisted seedlings below the surface. This is evidence that the seed or seedlings were probably damaged by the extended cool and/or wet period.

SATURATED SOILS

The recent frequent, heavy rains saturated the upper soil profile for extended period, and even caused water ponding in many areas. Short-term saturation is common and not really a risk if the soil drains within a day. When floodwater or ponding remains, the oxygen supply in the soil will be depleted in about 48 hours. Germinating seeds and young seedlings will not survive more than two or three days underwater. Emerged young plants can withstand four or five days underwater if air temperatures remain below 70 degrees. If air temperature is warm, survival goes down drastically. Fortunately, air temperatures have remained moderate -- in the 50s and 60s -- enabling recovery.

After water recedes and the soil naturally drains, plant survival can be confirmed by examining the color of the growing point. In the seedling stage, both the root and shoot (coleoptile) should be white or cream colored. For emerged plants, wait a few days as the soil dries to see if growth resumes. Cut open the shoot to see if the growing point at the bottom of the plant is white. If it is brown or necrotic, that seedling will die.

Water ponding is an annual risk whenever corn is planted in heavier soils in a level landscape. Every year, some fields somewhere will experience flooding after a heavy or frequent rainfall event. Problems with extended periods of saturation are much less today due to extensive tiling that has taken place in most of these vulnerable landscapes.

To learn more about the impact of water ponding on corn, see this Purdue article: https://www.agry.purdue.edu/…

Dan Davidson can be reached at AskDrDan@dtn.com

Follow Dan Davidson on Twitter @dandavidsondtn

(GH/AG/CZ)

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