Once springtime arrives, Illinois crop producers begin watching and waiting for optimal soil moisture and temperatures to kick off the 2010 planting season. Soil moisture at the end of March was above average over much of Illinois, according to Bob Scott, meteorologist of the Illinois State Water Survey (ISWS), University of Illinois at Urbana-Champaign.
The ISWS Water and Atmospheric Resources Monitoring (WARM) Program records moisture and temperatures of six layers of soil every hour at 19 sites across the state. Current records show that in the 0- to 6-inch soil layer, moisture values ranged from 80 percent of normal at Stelle to 114 percent at Springfield. The 6- to 20-inch layer was slightly wetter; deeper layers were wet in eastern Illinois, but drier in the central and southwestern parts of the state.
Typically, soil moisture in the type of soils common to most parts of Illinois recharges all fall and winter, and responds quickly to spring rains.
"In Illinois, it is quite rare to enter a growing season with dry soils," Scott said.
Soil moisture tends to decrease once crops have emerged. By summer, moisture levels decrease even more due to evaporation and plants using the water to thrive.
Soil temperatures must be at least 50 degrees F for corn and soybean seeds to germinate. Soil surface temperatures vary less than air temperatures, and on average are slower to warm to the optimal temperatures.
Daily soil moisture and temperature readings indicate how much water is available for crops and show the progression of rising temperatures across the state. With an eye on the calendar, crop producers use this information to determine the best time to start planting. WARM produces daily soil temperature maps for Illinois and monthly soil moisture reports on its Web site, http://www.isws.illinois.edu/warm/.
The Illinois State Water Survey, a division of the Institute of Natural Resource Sustainability at the University of Illinois at Urbana-Champaign, is the primary agency in Illinois concerned with water and atmospheric resources.
