Seeds: Extension Crop Update Newsletter 4-26-21

Iowa State University Extension

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Extension Crop Update
This newsletter, and previous issues from recent years, can be found on-line at:
http://www.extension.iastate.edu/plymouth/info/cropupdate.htm

April 26, 2021
Volume 24, Issue #3

Prepared by
Joel DeJong,
Extension Field Agronomist
Click on photo for contact info

SO, it begins … April has been an interesting weather month. I just calculated growing degree day accumulations for April here in Le Mars and discovered that we had 73 GDD's from April 1 through the 6th. From April 7 through yesterday, April 25, we only accumulated 53 more. Soil temperature averages lately have been below 50 degrees, but today's temperatures (the 26th) will likely get it above that number. Based on forecasts, daily average temperatures should stay there.
This morning I took a photo of a field that I believe was planted April 3. It hasn't gotten far yet, as you can see. It takes about 120 GDD's to emerge normally, but I think I have seen some data showing it takes a little more when we have had a cold period during that time. I know we will all be watching those early planted fields to see how they develop!

We still have a wide window for timely planting of both corn and beans, according to the data summarized from many different research projects. You can read the details in this 4/1/21 ISU ICM News article by ISU Extension Cropping Systems Specialist Mark Licht, titled "Corn and Soybean Planting Date Considerations."

Soil Moistures – I completed my spring soil moisture sampling for the area as of April 15. Below is a map of the results. These samples are pulled at one-foot increments to a depth of five feet. Most had good moisture in the top two to three feet, and some were approaching field capacity of nearly 11 inches. Some sites are lower than average and will likely need more timely rain during the growing season. Paul Kassel wrote a recent ICM Blog about moisture sampling results from eastern NW Iowa, which can be found here. Another article of interest, "Soil moisture benchmark April 19, 2021," from Licht and Archontoulis, uses data and modeling to monitor moisture across the state. Their NW Iowa depth to water table data doesn't look too good right now, but surface moisture data isn't as alarming. While on that page, don't forget to subscribe to those newsletters, too!

Moth trapping network – We have several cooperators across Iowa with pheromone traps deployed to help determine when black cutworm and true armyworm adults are migrating back into the state. Remember, they do not overwinter here, but fly in during the spring and lay eggs that can potentially hatch into harmful pests. The good news so far – NW Iowa has had very limited black cutworm moth and true armyworm captures so far – with just a few early in the month. We will continue to monitor these traps, will let you know when a significant flight occurs, and when the models would indicate that they are big enough to cause damage to crops. So far – no scouting timeline for those pests yet! Updates are being posted weekly on the ISU ICM Blog website, found here.

Alfalfa Update – This morning I was out in a couple of alfalfa fields near Le Mars to see how it handled the cold temperatures of last week. The good news – it grew a couple of inches since then and damage was limited to just a few leaflets of the plant. The growing point at the tops looked unhurt. The growth was only 7" to 8" tall at this time, so I did not start checking it for predicting harvest. I will be watching those fields to do the PEAQ (Predictive Equations of Alfalfa Quality) assessment model that estimates alfalfa Relative Feed Value for the first cutting. I will try to share progress as the alfalfa grows.
If you haven't assessed your stand already, there is enough shoot growth to determine if adequate shoots per square foot are out there. Wisconsin has a great publication on stand assessment which can be found here. Ideally, we want at least 55 stems per square foot, and if crowns are healthy, might still accept down to 40 stems per square foot with somewhat reduced yield.

The 2021 Virtual Crop Scout School is now available and is free to the general public. The scout school consists of 22 webinars from crop protection specialists at eleven Midwest Universities and is offered through the Crop Protection Network (CPN). Crop scouts, farmers, and other users can pick and choose from a variety of diverse subjects to help them become more knowledgeable on crop scouting. Topics are split into digestible bits so crop scouts can interact with subject matter in a way that best suits their time and interest. Go here to register for this free opportunity to learn.