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Deadlines/Dates
September 30: Deadline to Complete Fiscal Year 2026 (FY26) Mid-Contract Management on the Conservation Reserve Program (CRP); Deadline to remove livestock from Non-Emergency Grazing of Conservation Reserve Program; Deadline to apply for the Supplemental Disaster Relief Program (SDRP)  Stage 1, Stage 2, and Stage 1 Quality Loss; Office Fiscal Year Rollover
October 1: Fiscal Year 2027 (FY27) Mid-Contract Management on Conservation Reserve Program (CRP) Opens
December 31: Deadline to Apply for Organic Certification Cost Share Program (OCCSP)

Wait for Dropping Soil Temps Before Applying Fall Fertilizer
Soil and water conservationists with the U.S. Department of Agriculture (USDA), Iowa State University and the Iowa Department of Agriculture are recommending farmers wait until soil temperatures are at least 50°F and falling before applying manure and anhydrous ammonia this fall.
State Climatologist Dr. Justin Glisan has flagged that a very strong El Niño is shaping up in the Pacific Ocean, which historically means warmer and generally wetter fall weather throughout Iowa creating less-than-ideal conditions this harvest season.
These guidelines are recommended by conservationists every fall as a best practice as warmer soils can increase nitrogen mineralization, leading to leaching. Because of the warmer weather predicted for this fall, the date when Iowa fields reach 50°F and falling could be 10-15 days later than usual. For example, central Iowa typically hits 50°F on about November 10, but it could be closer to the week of Thanksgiving this year.
Iowa State University Extension and Outreach has issued the following guidance: “Fifty and Falling: What the Super El Niño Means for Anhydrous Ammonia and Manure Timing this Fall). It is printed below in its entirety.
Some key takeaways from the publication:
• Monitor soil temperatures rather than calendar dates.
• Use nitrification inhibitors with ammonia and manure nitrogen sources.
• Consider planting a cover crop, particularly on fields going to soybeans.
• If manure is applied early, it should be on a field with a cover crop that can reduce nitrate losses to waterways.
• Warm soils can increase nitrogen mineralization. Use precision tools, like fall N soil sampling and N-FACT, to inform and optimize application rates.

FIFTY AND FALLING: WHAT THE SUPER EL NIÑO MEANS FOR ANHYDROUS AMMONIA AND MANURE TIMING THIS FALL

by Mike Castellano, Daniel Andersen, Sotirios Archontoulis, Mitchell Baum, ISU Extension and Outreach Specialists

Iowa State University recommends that fall manure and anhydrous ammonia application not occur until the soil temperature at four inches is 50º and falling. What’s changing this year is when that date is likely to arrive.
The odds of a very strong El Niño (ENSO) this fall and winter are above 90%, with a 69% chance that by October through December it reaches a strength not seen in the ENSO record dating back to 1950. This could help push 2026 toward one of the warmest years on record for Iowa.
The last time ICM News flagged a “very strong El Niño” was the fall of 2023-24 when September-November temperatures were 2.7°F above normal - the 19th warmest fall in 151 years of record. That December, the average temperature was 9.7°F above normal - the third warmest December on record. This year’s ENSO event is forecast to be stronger still. That’s worth planning around.

What does this mean for nitrogen fertilizer and manure management?
Now is the time for adaptive management - for profitability, productivity, and the environment. Ammonium nitrogen, from manure or synthetic nitrogen, is stable in the soil. Nitrate is not; it is easily lost to water and air when soil moisture is high and there is no growing crop to use it. Nitrification, the microbial process that converts ammonium to nitrate, slows sharply once soil temperatures fall below 50°F, though it doesn’t fully stop until soils reach 32°F.
If you apply manure too early into soil that’s still warm enough to drive rapid nitrification, you risk losing enough nitrogen that your hauling costs can exceed the manure value. ISU research consistently shows that early fall manure applications can cost farmers more than 40 bushels of corn compared to late fall or spring application.

What can you do?
Watch soil temperatures rather than calendar dates. Central Iowa typically reaches 50º and falling around November 10. This year that window may land 10 to 15 days later. This is also a year to use nitrification inhibitors with ammonia and manure nitrogen sources. More than two-thirds of Iowa farmers already use a nitrification inhibitor with fall ammonia. Consider planting a cover crop, particularly on fields going to soybeans. If manure is applied early, it should be on a field with a cover crop that can reduce nitrate losses to waterways.
The Iowa Nitrogen Initiative’s N-FACT nitrogen management decision support tool shows the value of retaining fall nitrogen. High fall ammonia and nitrate levels can reduce spring nitrogen needs by more than 50 lbs.

Bottom line
Watch the ground, not the calendar - Iowa State’s Iowa Environmental Mesonet posts real-time four-inch soil temperatures and county-level estimates across the state, and pairing that with the six- to 10-day forecast is the best way to know when “fifty and falling” has actually arrived in your fields. Warmer weather associated with the Super El Niño will likely increase nitrate production - and the potential for loss - from soil organic matter, anhydrous ammonia, and manure.
Good adaptive nitrogen and manure management practices are important every year. But with the Super El Niño taking hold this fall, they may be more important and impactful than ever.