By Mark Licht
Weather this past weekend had people thinking about planting corn and soybean. I’ve already heard a rumbling or two about planting soybean during the next warm up. As spring planting approaches, soil temperature becomes one of the most important factors influencing successful corn and soybean planting. While it’s tempting to roll into the field the moment soils look fit, making decisions based on both soil temperature and soil moisture can make the difference between a strong stand and a season-long struggle.
Why Soil Temperatures Matter
For corn and soybean germination, early-season growth and seedling vigor is influenced dramatically by soil temperature. Germination is optimal when soil temperature rises above 50°F. I encourage farmers not to look at soil temperature alone, but to also consider the 3 to 7 day forecast having a warming trend to avoid chilling injury. From late March through mid-April there can be rapid air and soil temperature swings. Residue cover, soil color, and drainage all affect daily soil temperature fluctuations.
Where to Find Current Soil Temperatures in Iowa
ISU Soil Temperature Maps (4-inch depth): The Iowa Environmental Mesonet (IEM) provides daily soil temperature analysis maps using ISU Soil Moisture Network observations combined with bias-corrected NWS forecast model analysis. Trends can be viewed for the past 3 days as well as forecasted into the future using the GFS forecast model outputs.
ISU Soil Moisture Network (live station data): The ISU Soil Moisture Network provides real-time observations at four depths, including dedicated soil temperature plots for the 4-inch depth. This data comes from weather stations that are fully instrumented with air temperature, solar radiation, precipitation, humidity, soil moisture, soil temperature, wind speed, and wind direction.
Source : iastate.edu