Assessment of nutrient concentrations and validation of reference sufficiency ranges for current corn (Zea mays L.) hybrids under rainfed and irrigated conditions

Plant analysis is a useful tool for determining crop nutritional status in modern agricultural production. The current Reference Sufficiency Ranges (RSR) for the southern region of the United States, used in Tennessee, were established based on decades-old research and have been utilized with limited modification. Due to substantial changes in corn/maize traits and management practices, evaluating and validating the RSR is warranted. This study aimed to assess concentrations of Nitrogen (N), Phosphorus (P), and Potassium (K) and validate the RSR using current hybrid corn (Zea mays L.). Field studies using a split-split-plot design were conducted in 2021 and 2022. The main plot factor was assigned to water treatments which included rainfed and irrigated conditions. Each main plot included six corn hybrids in separate subplots. Fertilizer was applied as a split-split-plot factor with each corn hybrid evaluated under four fertilizer treatments. Compared with rainfed conditions, N concentration under irrigation improved from the early vegetative to tasseling stages, leading to significant (p < 0.05) yield increases across N-fertilizer treatments. Generally, P concentrations were significantly (p < 0.05) higher in seedling and early vegetative plant tissues when P-fertilizer treatment was applied under rainfed conditions. Although the established RSR occasionally diagnosed deficiency correctly in the absence of fertilizer in this study, it also occasionally diagnosed concentrations as insufficient despite adequate fertilizer application. Overall, the RSR at the seedling stage is too low for current corn hybrids and too high at maturity, indicating a need for an update to the RSR in corn production.