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Jason Clark

Assistant Professor & SDSU Extension Soil Fertility Specialist


Berg Agricultural Hall 310
Agronomy, Horticulture & Plant Science-Box 2207A
University Station
Brookings, SD 57007

Soil fertility guidelines for South Dakota cropping systems

State & Regional Offices

SDSU Campus

Also by Jason Clark

Female producer holding a soil core sampling probe in a harvested soybean field.

Fall Soil Sampling

With fertilizer prices on the rise, it’s more important than ever to understand your soil test levels and crop response to applied fertilizers. Fall is a great time to soil sample before freeze up.

Three soybean fields with yellowing issues due to potassium deficiency, iron deficiency chlorosis and soybean cyst nematode.

What Is Causing Soybeans to Yellow at This Time?

Recently scouted soybean fields were observed with yellowing plants, and one field was found to have plants dying prematurely. Learn some of the factors that may cause soybean plants to yellow at this time in the growing season.

Corn plant with yellowing leaf edges due to potassium deficiency.

Corn Potassium and Drought

For many crop producers, potassium deficiency has become an increased concern, and this year’s drought conditions have resulted in potassium deficiency symptoms showing up in fields where it would normally not occur.