Theses and Dissertations

Issuing Body

Mississippi State University


Cox, Michael S.

Committee Member

Golden, Bobby R.

Committee Member

Bond, Jason A.

Committee Member

Irby, Jon Trenton

Committee Member

Dodds, Darrin M.

Date of Degree


Document Type

Dissertation - Campus Access Only


Plant and soil Science

Degree Name

Doctor of Philosophy (Ph.D)


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Potassium (K) deficiency of soybean [Glycine max (Merr.) L.] is common throughout the Mid-Southern region of the United States. Visual symptoms of K deficiency may be absent or subtle during early and mid-reproductive growth stages. Correcting K deficiency in-season is problematic due to limited research. Information regarding soybean yield response to in-season fertilizer K application time is limited to growth stages prior to the onset of R1. Research is also limited on new higher yielding soybean cultivars. The objective of this study was to evaluate influences of in-season K application timing during reproductive growth stages on soybean yield. Field experiments were established in 2019, 2020, and 2021 to evaluate the effect of soybean potassium rate and timing during reproductive growth stages. Four independent experiments were established to: (1) determine the effect of applying K fertilizer to sufficient soils at different times in-season on yield and plant K status on two different soil textures, (2) determine the effects of K timing, K rate, and dicamba rate on yield and plant stress, and (3) determine the effects of K timing and desiccation on yield and plant stress. Results indicate that potassium application rate and timing during soybean reproductive growth stages do not increase yield on soils with adequate K present. Soybean trifoliate leaf tissue K analysis and petiole sap K analysis had no response during reproductive growth stages when K fertilization occurred on soils with ample K. Potassium fertilization did not aid soybean recovery after dicamba injury.