Researchers recommend that soil temperatures at the 4-inch depth are 50° F and cooling before applying fall anhydrous ammonia or manure with a high ammonium nitrogen (N) content, such as with liquid swine manure.
Looking at the current 4-inch soil temperatures across the state, we did drop below that 50° F mark this weekend.
However, the weather forecast is calling for warmer temperatures this upcoming weekend, which may result in soil temperatures warming back up into the low to mid-50s again before dropping below 50° F again. You can monitor the 3-day history average soil temperatures in every Iowa county and forecasted 4-inch soil temperatures here on the ISU Environmental Mesonet website.
Historically, the soil temperatures at the 4-inch depth cool below 50° F in the northern third of the state the first week of November. For central and southern Iowa, soil temperatures cool below 50° F during the second week and third weeks of November, respectively.
Additional Resources:
Rebecca Vittetoe Field Agronomist in EC Iowa
Rebecca Vittetoe is an extension field agronomist in east-central/southeast Iowa serving Iowa, Jefferson, Johnson, Keokuk, Poweshiek, and Washington counties. Vitteoe works with farmers, landowners, and ag retailers to answer agronmy-related questions. Her areas of expertise include general ...
Meaghan Anderson Field Agronomist in Central Iowa
Meaghan Anderson is a field agronomist in central Iowa and an extension specialist at Iowa State University Extension and Outreach. Educational programming is available for farmers, agribusinesses, pesticide applicators, certified crop advisors, and other individuals interested in crop ...