Walking Rows 2025: ISA agronomist update – May 22
May 21, 2025 | Kriss Nelson
Post-planting, farmers are concentrating on crop emergence, pest control and in-season nitrogen applications.
Iowa Soybean Association (ISA) research agronomists urge farmers to diligently scout for weeds to ensure timely post-emergence herbicide application and to check for uniform emergence to determine if replanting is necessary.
Alex Schaffer - Central/South Central Iowa
Planting is close to wrapping up in central and south-central Iowa. With the heat last week, the early-planted fields have grown a lot, and the later-planted or replanted fields are mostly all spiked through the surface. Farmers in my area have shifted their focus to early post-emergence herbicide application on early planted corn. They are happy to get some rain this week and water for the developing crop, and incorporate and "activate" their residual herbicide included in the post-pass.
Overlapping residual herbicides has been one of the major talking points of the agronomy circuit last winter and this spring for controlling weeds in crop fields. Three to four weeks after the first burn down or soil-applied herbicide application is a great time to walk those fields and look for emerging weeds.
Timing that early post-application when you see those first weeds emerging and with a soaking rain in the forecast is a great recipe for a successful weed management program.
Overlapping the residual herbicide applications keeps the majority of weeds from emerging. It puts less pressure on contact and systemic herbicides to control already emerged weeds, leading to cleaner fields and fewer weeds resistant to herbicides.
With the rapid growth last week, many farmers who employ a sidedress nitrogen pass are considering that application. Before making that pass, I would recommend using the N-Fact tool to consult the optimum nitrogen rate based on how the spring has gone for you. Maybe some fields didn't get planted as early as you had hoped, or you have gotten more or less rain than usual. The N-FACT tool accounts for these environmental factors and local multi-rate nitrogen trials to recommend the economic optimum nitrogen rate to apply to a field.
Shane Beck – Northeast/Northern Iowa
Planting is on the home stretch in northeast and northern Iowa. The last couple of weeks of dry weather have allowed many crops to be planted. The crops that are up look good.
I have looked at a couple of soybean fields lately that have had some inconsistent emergence. After digging in the row, I noticed that all the soybeans were there and germinating. The inconsistent moisture they were planted caused them to develop at different rates.
I have heard a little about replanting crops planted around Easter when we received cold rain that caused germination and crusting issues. Stand counts can help decide if replanting needs to happen or not. If stand counts for soybeans are above 80,000, the plants will compensate for this and fill in the thin areas. If the stand counts are below this, adding some additional seed may be of value.
The heavy rain we received in some areas over the last few days could cause some ponding and crusting issues to crops just planted late last week. As soon as we dry out, look at those fields to determine if additional tactics are needed, like a pass with a rotary hoe.
One of the next things to think about is spraying. It is important to be out scouting fields for weeds. Knowing what weeds are in the field and how tall they are can help your herbicide program be very effective. Sometimes we might need to substitute a chemical for another chemical that works better against a particular weed if that is the predominant weed in the field. Or maybe even add another chemical to help ensure the weeds are managed correctly. A general rule of thumb is to apply your herbicides before weeds get larger than a pop can.
Mikaela Connelly Southwest/West Central Iowa
Large portions of the state's western side have been catching much-needed rain this week. I’ve heard roughly 1 to 2 inches in various districts 4 and 7 areas, which is great.
From what I can tell and have heard, farmers finished almost all of the planting due to the warm weather in April and earlier this month. I’ve also seen some growers out making the first cutting of hay.
I’ve seen most soybean fields around the VC or V1 growth stage. The corn has also grown quickly because I have seen V3 and V4 plants this week. Undoubtedly, the warm weather over the last couple of weeks and the moisture will fuel the plants as they grow.
Regarding early-season diseases, I have seen some rhizoctonia in soybean fields. In seedlings, reddish-brown, sunken lesions form on hypocotyls. The resulting firm, dry canker can encircle the seedling and cause it to collapse. Unless the damage is widespread enough to justify replanting, I suggest making note of management decisions to improve the next growing season. Using effective seed treatments and planting resistant varieties can help alleviate the influence of rhizoctonia and other early-season diseases.
I haven’t heard of or seen many corn diseases thus far in the growing season. I think the moisture this week and somewhat cooler temperatures could change that over the next few weeks. I would be looking for black cutworm in corn for pests, as Missouri and Illinois have reported some pressure. With the potential for diseases and pests, I would encourage growers to scout their fields, assess stand counts, and continue to scout as crops emerge. This time of year is when crops are arguably the most vulnerable.
I have heard of some replanting occurring due to crusting in fields. I recommend replanting soybeans if your stand count is below 75,000 plants per acre. Soybeans do a phenomenal job of branching and setting lots of pods, so the lower soybean populations can often make up yield. With a replant, I would encourage farmers to consider the cost and the likelihood of increased disease and insect pressure. If you opt not to replant, I would be vigilant of weeds in your fields and minimize the pressure to maximize yield.
Craig Woods – Northwest Iowa
In northwest Iowa, conditions have taken a turn for the wetter, to the point where some ponding has already occurred in some fields with low spots and slower infiltration. With ponding, it will be important to evaluate plant populations to help determine if replanting will be necessary. If you want to keep better notes on ponding issues for specific fields and want to address them when conditions improve, taking photos and captioning them is an option.
Along with ponding, rain brings possible fungal and disease pressure on recently emerged plants. Scouting may be beneficial, especially with cooler, wet conditions promoting susceptibility.
Depending on the infection rate, possible adjustments in fungicide application may need to be made later in the season.
While scouting, evaluating the effectiveness of your seed treatments could help adjust future programs.
Soybeans in district 1 are still being planted. Those earlier planted soybeans have nearly 80% emerged and are at the V1 growth stage. Corn has mainly emerged to the V1 to V2 stages.
Evan Brehm - Southeast/Eastern Iowa
Farmers are reporting that planting conditions have been ideal. Outside of planter malfunctions, stand counts have been what they’ve expected.
Soybean planting is nearing the finish line as early planted soybeans have been a trend the past 6 to 7 years. Districts 6 and 9 are on par with this week’s Iowa Crop Progress report of soybean planting being two weeks ahead of the 5-year average. Earlier-planted soybean fields have entered the V2 stage.
Field conditions in my area have recovered from D4 drought across the districts last fall to None or D0 (abnormally dry) drought condition categories.
Corn planting is primarily wrapped up, with most fields emerging. A few reports of replanted corn acres were addressed last week before the recent rain showers we received this weekend, Monday, and Tuesday. Most corn in eastern and southeastern Iowa is entering the V3 growth stage.
When it comes to insects, scouting should remain a priority, especially in cover crop or weed-infested fields. There have been a few reports of slug feeding.
Slugs prefer cool, wet soil conditions and coverage. As a mollusk, chemical management can be a barrier. The best method is to plan for the future. Crop rotation and tillage are cultural practices that break up the slug life cycles. Although something to be aware of, there have been very few reports of slugs, other than along waterways in low-lying areas.
Black cutworm emergence has occurred, and cutting dates in districts 6 and 9 are predicted around May 17. Be on the lookout for black cutworm in the coming weeks.
Cover crop termination is gaining traction for later applications. The reason is for moisture retention, longevity of the cover crop to maximize the full soil health benefits, and suppression of weeds. Earlier-terminated cover crop fields in mid-April show flushes of waterhemp and giant ragweed. Those soybeans are a full stage ahead of soybeans that were planted green. Later-terminated cover crop fields have two things growing out there: soybeans and slowly dying cover crops. Few weeds are to be seen with cereal rye that is knee high, thus showcasing its benefits of weed suppression.
Farmers should scout for corn lacking nitrogen or sulfur. With cool, wet conditions, corn fields may need a boost. Warmer temperatures will correct this, but consider a split application of nitrogen. Be cautious not to overapply your UAN or urea nitrogen source, and make the best management decisions to boost corn yield.
Conservation in Action Tour is in its third year in eastern Iowa. Spanning three counties, field signs showcase conservation practices across fields such as no tillage, strip tillage, cover crops, planting green, waterways, denitrifying bioreactors, saturated buffers and wetlands. To view maps and learn more, click here.
Soil amendments and biologicals have hit the market in the past decade. Two farmers in Eastern Iowa are testing a product from Fish Head Farms in Rhode Island. Haney Soil health tests have and will be performed along with in-season tissue sampling. This product is derived from composted fish manure aimed at boosting soil health, which, in the end, we hope contributes to profitability for the farmer. Stay tuned for those results.
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