Subsoil moisture nonexistent in southeast South Dakota

Subsoil moisture nonexistent in southeast South Dakota Soil samples taken in soybean stubble at the Southeast South Dakota Experiment Farm this fall showed soil is dry down to four feet.

That's a report from Jim Gerwing, Extension soils specialist at South Dakota State University.

Gerwing said there is some moisture between four and five feet and more moisture deeper than five feet.

"Current dry soil conditions may reduce yields in 2000 due to the lack of water storage if significant rains don't come this spring," Gerwing warns.

Soils at this research farm are heavy and hold about two or two-and-a-half inches per foot. It will take eight to 10 inches of rain or snow melt soaking into the soil to recharge the soil profile completely for maximum yield potential next year.

"If recharge does not occur before planting, crops will be very dependent on in-season rainfall and that makes them susceptible to short-term dry periods of two weeks or less," Gerwing said.

The last time soil moisture was this short at Beresford was the fall of 1987. Corn yields on many experiments the following year were less than 50 bushels per acre. October soil sampling at the SDSU Central Research Station in Highmore and the Brookings Agronomy Farm showed fall rains recharged soil to a depth of two to two-and-a-half feet. At these locations three or four inches of rain would be needed to recharge soil completely.

The northern and western areas of South Dakota had adequate late summer and fall rain to recharge soils almost completely although the surface couple inches are dry from several months of dry weather.

"Subsoil moisture is extremely important to carry crops through dry periods many summers," Gerwing said. "Most crops use one-quarter to one-third of an inch of water per day in mid summer. If it doesn't rain significantly every week they must reach down into the subsoil for stored water."

Corn, soybean, winter wheat, and sunflowers often root to a depth of four or five feet, depending on yield. Spring-seeded small grains regularly root to three-and-a-half feet.

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