Iowa State University recently completed their fall survey of subsoil moisture levels across northwest Iowa.
Subsoil moisture levels are a concern as we look ahead to the 2012 cropping year. The amount of subsoil moisture is well below average. The level of subsoil moisture in Dickinson, Clay and Pocahontas Counties ranges from 1.4 inches to 5.0 inches of plant available moisture.
Typical Iowa soils have the potential to hold from 10.0 to 11.0 inches of moisture in the top five feet of soil.
The dry conditions late summer and fall left the soil moisture reserve very low. Soil moisture readings from the ten sites where ISU personnel analyzed soil moisture averaged 4.1 inches of moisture as of November 1, 2011.
These results confirm what is expected in terms of reserve soil moisture. Most of the area had a full profile of soil moisture in mid-summer. However, a large part of the area received little rain in late summer and early fall. Rainfall amounts since mid-July have been six to nine inches below normal.
Some areas -- like the sampling site near Rossie - show the results of some late season rainfall and the fact the corn and soybean crop did not use soil moisture past mid-September.
A frost event on Sept. 15 effectively brought the growing season to a close and the crop did not use any soil moisture after that date.
This level of subsoil moisture is very low when compared to levels of subsoil moisture the past few years. Therefore, the area will be very dependent on rainfall this fall and next spring. There is more concern if rainfall is not received this fall or next spring.
Crop production will then be very dependent on summer rainfall without a reserve of soil moisture going into the summer crop growth time period.
Future rainfall during November, March and April will also contribute to subsoil moisture. Typical rainfall for those months is three to five inches.
We can expect about 80% of that rainfall to contribute to subsoil moisture reserves.
Cherokee in Cherokee County, 5.6 average inches; 2011 soybean; available moisture 3.9 as of Nov. 1.
Marcus in Cherokee County, 5.6 average inches; 2011 soybean; available moisture 2.4 as of Nov. 1.
Rossie in Clay County, 5.7 average inches; 2011 soybean; available moisture 5.0 as of Nov. 1.
Spirit Lake in Dickinson County, 5.7 average inches; 2011 soybean; available moisture 1.4 as of Nov. 1.
Sutherland in O'Brien County, 5.9 average inches; 2011 soybean; available moisture 4.5 as of Nov. 1.
Melvin in O'Brien County, 5.9 average inches; 2011 corn; available moisture 5.1.
Rolfe in Pocahontas, 6.0 average inches; 2011 corn; available moisture 3.3.