Revisiting Relationships Between Mid-Season Ear-Leaf Nutrient Concentrations and Corn Grain Yields.

Historically, corn (Zea mays L.) ear-leaf N concentration at mid-silking has been positively correlated with final grain yield (GY) in numerous studies. Various state and regional publications have published suggested “nutrient sufficiency ranges” or threshold nutrient concentrations for N (as well as other nutrients) in ear leaves sampled at silk emergence, but these are based on studies conducted decades ago. Recent information about relationships between ear-leaf nutrients other than N and final GY are limited, especially for modern hybrids in high-yielding environments. Several field studies conducted near West Lafayette, IN from 2010 to 2013 involved collection of corn ear-leaf samples at mid-silking. These field studies often involved comparison of multiple hybrids, plant densities or tillage systems plus their corn response to nutrient management alternatives (e.g. macronutrient rates, placement, and timing). The ear-leaf samples were analyzed for nutrient concentrations (N, P, K, Ca, Mg, S, Zn, Mn, Fe, Cu, B, and Al), and each plot’s nutrient concentration data were subjected to regression analysis to evaluate their relationship with plot level GY responses. Variation in ear-leaf P, N, and Fe concentrations explained >50%, while S and Cu explained >40% of the variation in GY. However, these nutrients (N, P, S, Fe, and Cu) also correlated positively with each other (R² ranged from 0.365 to 0.863). When the field experiments involved multiple N rates, ear-leaf N concentrations were more directly impacted (mean R²=0.571) by N rates than by other ear-leaf nutrient concentrations (R²= 0.057- 0.458). The overall relationships of ear-leaf nutrient concentrations with GY suggest that revisions in state recommendations for “nutrient sufficiency” based on ear-leaf sampling may be warranted for some nutrients .