End‐of‐season corn stalk analysis as a tool to fine‐tune potassium and nitrogen management

Abstract Corn ( Zea mays L.) requires proper nutrient management for optimal growth, and tissue testing plays an important role in refining recommendations. Corn stalk nitrate test (CSNT) is used to evaluate nitrogen (N) management; however, a comparable plant‐based diagnostic tool for potassium (K) is lacking. This study evaluated extractants for stalk‐K and explored K sufficiency threshold concentrations for furrow‐irrigated corn production in Arkansas. Eight field trials were conducted across Arkansas in 2023 and 2024, on silt loam soils with very low (<61 mg K kg −1 ), low (61–90 mg K kg −1 ), and optimum (131–175 mg K kg −1 ) soil‐test K to evaluate corn yield response to K fertilization (0, 37, 75, 112, 149, and 186 kg K ha −1 ). Stalk samples (15–35 cm sections above the soil surface) were collected at physiological maturity and extracted with deionized water and calcium chloride (CaCl 2 ) to measure K and nitrate‐nitrogen (NO 3 ‐N) concentrations. Stalk‐K concentrations consistently increased in response to K fertilization. Deionized water extraction was effective for K and NO 3 ‐N analysis, whereas CaCl 2 produced inflated K values that were weakly related to yield but remained suitable for NO 3 ‐N analysis. Water extractable stalk‐K concentration was significantly associated with relative grain yield ( R 2 = 0.54, p < 0.0001), supporting the preliminary definition of deficient (<3353 mg K kg −1 ), optimum (3353–7142 mg K kg −1 ), and excessive (>7142 mg K kg −1 ) stalk‐K concentration thresholds for irrigated corn production. Our results show corn stalk analysis could be an additional tool for evaluating K and N management in irrigated corn systems.