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Take time to evaluate your corn, soybean standTake time to evaluate your corn, soybean stand

ISU agronomists say it’s worthwhile to check population, plant spacing and growth.

Rod Swoboda 1

June 1, 2017

6 Min Read
SOYBEAN STANDS: Some soybeans planted in mid-May have emerged before planned herbicides could be applied to the soil. So some farmers and dealers may need to go with alternative Plan B or Plan C for weed management.

Planting, stand evaluation and spraying is overlapping for some farmers this spring. If you haven’t yet started checking the corn stand in your fields, be sure to begin now. Do a stand evaluation for population, plant spacing and uniformity of growth.

“Now is the time to see and learn what happened this spring and decide what changes you might want to make next year,” says Mark Johnson, Iowa State University Extension field agronomist in central Iowa. “Did you end up with only a few skips? Did you end up with very few doubles? Are the plants evenly spaced? Are they all about the same height? Are you seeing any signs of seedling disease? Are you seeing any emergence problems?”

Corn hybrid evaluation begins now
Much of the corn in central Iowa was planted the last two weeks of April and the first half of May. That is an ideal time, notes Johnson. Now, over the next couple of weeks, you need to find the time to stop and evaluate the new hybrids you planted this spring.

“When looking at a new hybrid, first consider how well it germinates and emerges compared to the hybrids you are more familiar with,” he advises. “If it is the first to emerge in a plot, you know it is a good hybrid for early planting. Next, rate it for early vigor. Once emerged, does it take off and lead the others, is it more like the others, or does it lag a little behind?”

Some farmers still had some corn to plant last week as rain had kept them out of the field. Concerning when he would switch to an earlier-maturing hybrid, he says, “The short answer is right now. Based on ISU research, we recommend farmers stay with full-season corn hybrids through May 20 to 25. But after that, you need to switch to an earlier-maturing hybrid, so the corn can still reach maturity before first killing frost in the fall.

Wet fields held up farmers last week
As of May 25, there were still some farmers who needed to finish planting corn, but more needed to finish planting soybeans in Iowa.

In northwest Iowa, ISU Extension agronomist Joel DeJong says corn didn’t progress much during third and fourth weeks of May, as it was buffeted by wind and rain. Some hail hit but in limited areas. “Most of these corn plants will be fine once they get sunshine and warmer weather; now they are just stressed,” he says. Soybean acreage in northwest Iowa was about two-thirds planted with 15% emerged, as of May 23.

Paul Kassel, an ISU agronomist covering parts of northwest Iowa, says most corn in his area was planted by May 12. Many farmers completed soybean planting by May 23. But about 25% of his area’s bean acreage still needed to be planted as of May 23. Counties he covers had quite a bit of rain the last half of May. “Water is standing and we have some drowned out areas of fields,” Kassel says. “Some of the crop needs to be replanted. Also due to wet weather, farmers are a little behind on herbicide application. They may have to re-evaluate their herbicide program for soybeans and apply a residual herbicide with their first pass of glyphosate.”

Some need to replant drowned-out spots
In north-central Iowa, “we had anywhere from 1.85 inches at Eldora to 3.52 inches of rain at Mason City between May 14 through May 21,” says ISU Extension agronomist Angie Rieck-Hinz. “There are fields with ponds, and a few creeks had low-land flooding. We had hail three consecutive nights in north- central Iowa May 15 through May 17. I received no calls about crop damage. Corn was fairly small and beans were either not planted yet or not emerged.”

SCOUT NOW: Seedling diseases are one reason to use a seed treatment. Each planting season, different weather patterns result in different problems.

In northeast Iowa, “Rain and storms the past couple weeks prevented some farmers from completely getting corn and soybean crops planted by May 22,” says Terry Basol, ISU Extension agronomist at Nashua. “The ISU research farm at Nashua had 3.4 inches of rain May 8 to May 22. Corn could be rowed by May 19. The weekly USDA survey showed 59% of soybeans in our area had been planted by May 22.”

In southwest and west-central Iowa, ISU’s Aaron Saeugling says lack of sunshine caused some yellow corn during mid-to-late May. A few fields showed signs of cold stress emergence in May, but overall corn in his area looks good. After recent heavy rains, some bean fields need replanting.

Aggressive burndown herbicide applications
In south-central Iowa, ISU’s Clark McGrath says the few acres left to be planted will probably go to beans. Corn stands generally look good. But there have been some cornfields that had issues with corkscrew emergence, leafing out underground and other cold, wet weather issues. “Considering the stress we’ve had this spring, today’s corn genetics are pretty amazing,” notes McGrath.

He says soybean burndown and residual herbicide applications on no-till acres have been hit-and-miss. There are some aggressive burndown applications being made. Double-check product labels for recommendations on planting intervals, weed size and soybean emergence restrictions to avoid crop injury and poor performance.

In southeast and south-central Iowa, ISU’s Rebecca Vittetoe says when soybeans started to emerge the last two weeks of May, she saw some issues. If you used ILeVO seed treatment, you may notice soybean cotyledons looking yellow or brown around the outer edge. She’s had a few calls on this. “Other things to be watching for include seedling diseases in corn and insect activity [black cutworm, armyworm and bean leaf beetles],” says Vittetoe. “In regard to forages, alfalfa is starting to bloom and should be ready for first cutting once we dry out.”

Scout for insect pests, weed control
In east-central Iowa, ISU’s Meaghan Anderson says while corn may be looking a little tough right now after wind and hail storms, it’s a good time to get out and check stands, scout for pests and check on weed control. “I’ve checked several fields that will be ready for a timely postemergence herbicide application as soon as the soils dry out,” she says. Seedling diseases will be showing up soon as well and will probably appear as wilted or yellow plants, or plants with dying leaves. 

“Almost every corn stand I checked in mid-May had at least one plant that unfurled underground,” says Anderson. “This is likely the effect of chilling after the seed had germinated and began to produce a radicle. Most soybeans I’ve seen are getting to the point where we could take stand counts and start checking for bean leaf beetle feeding or other early-season issues.”

In southeast Iowa, over the last three weeks, fields received from 2 to 4 inches of rain, says ISU’s Virgil Schmitt. Corn was mostly planted, and what was planted in the April 22 to April 25 window was at V2 to V4 stage as of May 22. It’s generally healthy, but some doesn’t have a full green color due to lack of sunny days. Bean acreage in southeast Iowa was over half planted, and a few fields had emerged by May 22. There are soybeans planted May 15 to 16 that emerged before planned soil-applied herbicides could be applied. So some farmers, dealers and consultants may need to go with alternative Plan B or Plan C for weed management.


About the Author(s)

Rod Swoboda 1

Editor, Wallaces Farmer

Rod, who has been a member of the editorial staff of Wallaces Farmer magazine since 1976, was appointed editor of the magazine in April 2003. He is widely recognized around the state, especially for his articles on crop production and soil conservation topics, and has won several writing awards, in addition to honors from farm, commodity and conservation organizations.

"As only the tenth person to hold the position of Wallaces Farmer editor in the past 100 years, I take seriously my responsibility to provide readers with timely articles useful to them in their farming operations," Rod says.

Raised on a farm that is still owned and operated by his family, Rod enjoys writing and interviewing farmers and others involved in agriculture, as well as planning and editing the magazine. You can also find Rod at other Farm Progress Company activities where he has responsibilities associated with the magazine, including hosting the Farm Progress Show, Farm Progress Hay Expo and the Iowa Master Farmer program.

A University of Illinois grad with a Bachelors of Science degree in agriculture (ag journalism major), Rod joined Wallaces Farmer after working several years in Washington D.C. as a writer for Farm Business Incorporated.

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