Date of Graduation

7-2026

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Drescher, Gerson

Committee Member

Kelley, Jason

Second Committee Member

Fernandes, Samuel

Third Committee Member

Roberts, Trenton

Keywords

Corn; Fertilization; Potassium; Yield

Abstract

Potassium (K) deficiency is an increasingly important yield-limiting factor for irrigated corn (Zea mays L.) in Arkansas, where below optimum soil-test K (STK) acreage is increasing and visible K deficiencies or hidden K hunger threaten yield and profitability. Improving K management for modern, high-yielding hybrids require refining soil-test-based fertilizer recommendations and defining growth-stage-specific tissue-K sufficiency ranges that diagnose deficiency before irrecoverable yield loss occurs. This research aimed to i) quantify corn grain yield and yield component responses to K fertilization across a wide range of STK levels; ii) determine the frequency and magnitude of agronomically and economically meaningful yield responses to K; iii) correlate relative grain yield to tissue-K concentrations across key vegetative and reproductive growth stages; and iv) establish dynamic critical tissue-K concentrations for furrow-irrigated corn to improve K nutritional diagnosis and support refinement of fertilizer-K recommendations. From 2022 through 2024, sixteen field trials (12 single-site-year and 4 long term experiments) were conducted on silt loam soils, with preplant STK values spanning Very Low to Above Optimum categories. Potassium was applied as muriate of potash at 0 to 187 kg K ha⁻¹, and corn was grown under furrow irrigation. Whole plants (V6), uppermost collared leaves (V10, V12), and ear leaves (VT) were sampled to determine tissue-K concentrations. Grain yield and individual yield components (ears per plant, kernel rows per ear, kernels per row, and 1000 kernel weight) were measured at maturity. Corn grain yield responded positively to K fertilization in 6 of 16 trials, all on Very Low or Low STK soils, where yield increases ranged from modest gains to more than fourfold above the unfertilized control, whereas sites testing Medium or Optimum in STK showed negligible yield response to additional K. Across responsive sites, K fertilization primarily increased kernels per row and 1000-kernel weight (up to 14-56% and 24% increase, respectively, compared to the no-K control), indicating that K sufficiency supports kernel set and filling, while rows per ear were less affected and more strongly governed by hybrid genetics. Tissue-K concentrations increased with STK and fertilizer-K rate at all growth stages. Relative corn grain yield increased with tissue-K until approaching a plateau. The linear plateau model predicted maximum yield potential with tissue K concentrations of 29 g K kg-1 at V6 (R2 = 0.34), 13 g K kg-1 at V10, and 14 g K kg-1 at V12, and VT (R2 = 0.56, 0.38, and 0.41, respectively). The decline in critical tissue-K concentrations with crop development demonstrates that fixed sufficiency ranges are inadequate and that growth-stage-specific thresholds are needed for accurate K diagnosis. Collectively, these findings show that K fertilization substantially improves grain yield and yield components of furrow-irrigated corn on Very Low and Low STK soils but provides minimal benefit once STK reaches the Optimum category. Dynamic critical tissue-K concentrations can make tissue testing a sensitive and practical tool to complement STK information, guide in-season corrective K applications, and refine fertilizer-K recommendations for more precise, profitable, and efficient K management in Arkansas corn production systems.

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