Iowa State University has completed its spring survey of subsoil moisture in northwest Iowa. Subsoil moisture levels are surveyed in pre-determined areas each spring and fall, says Joel DeJong, Iowa State University Extension field agronomist.
The April rains have contributed greatly to subsoil moisture levels. Subsoil moisture levels in the northwest corner of Iowa have increased an average of five inches since these sites were sampled last fall. The level of subsoil moisture at the soil moisture sites in Lyon, Osceola, Sioux, O'Brien, Plymouth, Cherokee, Woodbury, Ida and Monona Counties range from 4.8 inches near Akron to 9.8 inches of plant available moisture south of Marcus (table 1) as of the end of April.
The amount of moisture in the subsoil is now at or above normal in several locations. The exceptions are west of Sibley, along with northern Plymouth and southern Sioux County sites. Sites in O'Brien, Cherokee, Ida and Woodbury Counties are approaching field capacity at this time, if early May precipitation is included.
Typical soils in northwest Iowa have the potential to hold from 10.0 to 11.0 inches of moisture in the top five feet of soil. The dry conditions last summer and last fall left the soil moisture reserve very low. Soil moisture readings from sites ranged from 1.2-inches in Monona County to 7.8-inches in eastern Cherokee County last fall.
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