Corn yields and leaf samples were obtained from experimental plots receiving varying rates of N, P, and K. Yields were placed in two groups. One group consisted of yields < 134 bu/A, and a second group consisted of yields ≥ 134 bu/A. Within each group yields were regressed on leaf levels of N, P, K, Ca, Mg, B, Cu, Fe, Mn and Zn as independent variables in a second order polynomial. Using stepwise regression procedures the fit of the polynomial was determined for each set of observations, and statistical significance of various effects was determined.