Southwest Michigan field crops update – September 11, 2025
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EmailSeed corn harvest continues, and storage potato harvest started. Commercial corn started to hit black layer.
Weather
Temperatures dropped significantly last weekend and have slowly been warming back up. By this weekend, daytime temperatures will be back in the 80s and will continue there for next week. The past week saw little precipitation, and this upcoming week will continue that trend.
Crops and pests
Soybeans are mostly at late R6 (full seed) and R7, which is where one pod anywhere on the plant has reached mature pod color. Some fields have entered R8 (full maturity). White mold and sudden death syndrome are out in fields. Sudden death syndrome, brown stem rot and red crown rot all have similar symptoms, so don’t hesitate to send in samples for disease confirmation. Watch especially for red crown rot, which has not been confirmed in Michigan yet. Learn more about it from the Michigan State University Extension article, “Red crown rot: A new threat to soybean production.”
Seed corn harvest continued. Commercial corn is mostly at R5 (dent) and approaching R6 (black layer). Some acres have entered R6, which is when a black layer forms on the tip of the kernel where it attaches to the cob. Scrape the tip, and if a hard, black layer is visible, corn has reached physiological maturity.
Potato harvest began in full for both storage and fresh crop. The cool temperatures and dry weather late last week allowed for considerable progress for the first week of storage harvest.
Many growers took advantage of the dry weather this past week to cut alfalfa and forages. As fall approaches, potassium is especially important to help perennial plants overwinter well.
Watch Michigan State University (MSU) forage specialist Kim Cassida’s Virtual Breakfast presentation on potassium for forages for more information.
Weekly water use
Temperatures this week are higher than last week, increasing evapotranspiration. With little to no precipitation expected, you may be questioning whether crops still need water and if it’s time for the last irrigation of the season. Remember, the goal of the final irrigation is to supply enough water for crops to finish strong while leaving the soil in good condition for harvest. For more details, see the recent article “Is it time for the last irrigation?”
Corn at the dent stage is using about 0.14 inches of water per day, dropping to around 0.09 inches at black layer, after which additional irrigation will no longer provide a benefit.
Soybeans at R7 are using about 0.14 inches per day (just under an inch per week). Beyond this stage, soybean water use will drop quickly until the crop reaches full maturity. A newly published MSU Extension bulletin provides guidance on soybean irrigation management.
Monitoring crop stage, soil moisture and weather conditions together will help you make the best decision for the final irrigation. Irrigation Scheduling Tools can help estimate crop water needs and decide timing and application.
Estimated weekly crop water use for field crops in Michigan (inches/week) for the week of Sept. 8-14:
| Crop | Growth stage | Constantine | Entrican | Hart |
|---|---|---|---|---|
| Corn | Reference ET | 0.98 | 0.97 | 0.94 |
| Corn | VT, Silk, Blister, Dough, Begin Dent | 1.08 | 1.06 | 1.03 |
| Corn | Full Dent | 0.98 | 0.97 | 0.94 |
| Corn | Black Layer | 0.65 | 0.64 | 0.62 |
| Soybeans | R5 Begin seed / R6 Full seed | 1.08 | 1.06 | 1.03 |
| Soybeans | Begin Mature | 0.98 | 0.97 | 0.94 |
| Soybeans | R8 95% Pods Mature | 0.2 | 0.19 | 0.19 |
The table above presents estimated crop water use for various field crops across three locations in Michigan. This data helps irrigation management decisions by showcasing potential crop evapotranspiration, calculated based on reference evapotranspiration and crop coefficients for each crop growth stage. It is crucial to note that crop water use values vary across regions due to differences in weather conditions, growth stages, agronomic practices and soil properties.
When using these values for irrigation scheduling, be mindful that they assume all applied irrigation water will be utilized by the plants without any loss. Additionally, these values do not account for any precipitation that may occur during the week of calculation.
Reference evapotranspiration data was obtained from Michigan State University Enviroweather, which also offers a model for determining potential crop evapotranspiration. To access this tool, visit Enviroweather, click on "Crops," select your crop and use the potential evapotranspiration tool by choosing your nearest weather station, the latest date of interest and other crop information.
Field Crops Virtual Breakfast Series
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Grain marketing update, presented by Jon LaPorte, was the topic for the MSU Extension Field Crops Virtual Breakfast this week. He covered marketing decisions such as watching commodity prices, when to sell grain and contract options.
Recordings of this and all the Virtual Breakfast meetings are closed-captioned and available at the Field Crops Virtual Breakfast webpage and the MSU Extension Field Crops Team social media platforms: Facebook, Spotify, YouTube, Apple Podcasts and Twitter/X.
This work is supported by the Crop Protection and Pest Management Program [grant no 2024-70006-43569] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
