Last week provided another big window for planting and other field activities across Iowa. USDA’s crop progress survey report as of May 3 said 78% of the state’s corn had already been planted and 46% of the soybeans. However, planting progress for the week beginning May 4 has been slowed in some areas due to intermittent rain showers. Also, temperatures have cooled off this week, slowing germination and emergence of corn and soybeans.

It’s time to start scouting fields to check emergence of corn and soybeans. When soil temperatures are lower than 50 degrees F, risk of imbibitional chilling injury to germinating corn seed increases. Also, questions are being raised by farmers this week about preemergence herbicide performance as weed seedlings are emerging.

In alfalfa fields, start watching for adult alfalfa weevils. They become active and start laying eggs as soon as temperatures exceed 48 degrees. For more information, read Alfalfa Weevils Active Throughout Iowa, posted May 6 on Iowa State University’s crop management website.

In their weekly crop roundup, ISU Extension field agronomists report on what they’re seeing and hearing around the state regarding field conditions and planting progress.    

Northwest 

Joel DeJong, Region 1. “The past couple of weeks have allowed for almost nonstop planting in northwest Iowa. It’s hard to find a cornfield that hasn’t been planted, and it appears to me that three-quarters of the beans or more have been planted. My observations from a tour on May 3 gave me an impression that planting here is ahead of what the May 4 USDA crop progress report said. The local weather station has reported three rains since the Easter weekend snow in much of this corner of Iowa, and the biggest of those three precipitation events was one-tenth of an inch.

“Surface conditions started the week of May 4 very dry, but we have received some rain. I had a call from a farmer who had tilled the ground and didn’t plant beans very deep. After one week, there was no evidence of growth. I believe the number of no-till soybean acres has increased this year, and hopefully, that will help reduce the ‘in dry dirt’ calls. Subsoil moisture remains good, but we need to have some moisture in the surface layer to get root systems developed into the zone where moisture is available and to help herbicides control emerging weeds. Overall, this spring is about the earliest date for planting — having this much crop planted by early May — that I’ve ever seen.”

Northeast 

Terry Basol, Region 4. “Planting conditions were very good in northeast Iowa this past week. Pretty much all of the corn is planted in my area, and farmers have a good start on soybean planting. The May 4 USDA crop progress report shows northeast Iowa having 94% and north-central Iowa having 69% of corn planted. On the soybean side, north-central Iowa is at 66% planted and northeast Iowa is at 44% planted. Overall, small grains and hay are looking good for the area. We could use a good shot of moisture (1 to 2 inches of rain) to help with the dry topsoil conditions. This would definitely help get the corn and soybeans off to a good start and would help with the activation of soil-applied herbicides.”

Southwest and West central

Mike Witt, Region 6. “Planting progress in west-central Iowa has continued at a feverish pace this last week. USDA estimates have west-central Iowa at 82% of corn planted and 51% of soybeans as of May 3. This compares to 30% to 40% planted a year ago at this time. Some of the earliest planted corn is beginning to emerge. Soil moisture is a topic of discussion. While subsurface moisture is still adequate, topsoil moisture is more limited. With opportunities for rain this week, things should, hopefully, be improved.

“Lack of topsoil moisture can prevent or limit herbicide activation, reduce the incorporation of surface applied nutrients, and potentially delay emergence. These are things to scout and watch for in your fields. Pastures have started greening up across the region and are in pretty good shape from the winter, with only sporadic problems reported. Overall crop growth is noticeable this first week of May across the region as plants are emerging. This is a good time to get out and start scouting fields.”

Central 

Meaghan Anderson, Region 7. “After another fantastic week for fieldwork, the USDA weekly crop progress report released May 4 showed 76% of corn and 47% of soybeans planted in central Iowa. By middle of last week, some fields were dry enough at the surface that seeds were planted into dry soil at 1.5 or even 2 inches. The rainfall that came May 4 and May 5 were very welcome in central Iowa, even though it brought some colder temperatures with it.

“The earliest planted crops are emerging now, so you should be monitoring these fields for evenness of emergence and spacing between plants, as well as taking stand counts. This is especially important for crops that emerged before we get cold temperatures later this week. Check fields early next week — the week of May 11 — for frosted tissue and monitor those fields for regrowth over the next week or so. Shawn Conley wrote a nice article that describes more about how cold we really need to get to affect soybeans. Calls this week were on pasture management, herbicides and dry soils, weed identification, and seeding rate issues.”

East central, Southeast and South central

Rebecca Vittetoe, Region 8. “This past week was another big week for planting progress across east-central Iowa, with many farmers around the area wrapping up with planting. While it’s been nice to have this big planting window, we could use some rain to help moisten the upper soil profile to help with germination and emergence, as well as to activate preemergence herbicides applied. Crops planted two weeks ago (around April 20) are just starting to emerge. Common questions this past week have been on weed identification (common weed IDs this past week have included wild garlic, wild parsnip, chickweed and yellow rocket), planting issues and considerations, pasture management, and the drier conditions.”

Virgil Schmitt, Region 9. “Rainfall in the last week of April was generally light with less than half an inch of precipitation reported nearly everywhere in the counties I cover. The weather allowed a great deal of fieldwork activity last week, from tillage and fertilizing to spraying and planting. However, many people would like to see a nice rain.

About 75% of the corn is planted in my area as of the first week of May, with a higher percent planted roughly south of Highway 30 and a lower percent planted roughly north of Highway 30. For soybeans, I estimate about 35% are planted, again with a higher percent planted roughly south of Highway 30 and a lower percent planted north of Highway 30. Bluegrass and downey brome are headed out in pastures and yellow rocket is blooming. Questions last week tended to focus on planting issues as well as herbicide and nitrogen application issues.”

Josh Michel, Region 11. “Fieldwork has been ongoing as farmers have taken advantage of ideal planting conditions throughout the region. While some areas did receive 0.10 to 0.25 inch of rain over the past week (the seven-day period ending May 3), that rainfall only briefly paused fieldwork. Approximately 60% of corn and 30% of soybeans acres have been planted, as well as 90% of the oat acres have been planted in this part of the state as of early May.

“Pastures and alfalfa are generally looking good, but many need rain to keep them growing. For those with alfalfa, you should start scouting for alfalfa weevils as they should be active now. The majority of questions this past week have been on weed identification, weed management, cover crop termination and new alfalfa seedings.”

Check out the map to find your local ISU Extension field agronomist and find their contact information here. For rainfall totals as of May 4, visit the National Weather Service.