Relationship of DGCI and SPAD Values to Corn Grain Yield in the Eastern Corn Belt

Abstract

Crop sensors may help growers identify nitrogen (N) deficiencies and optimize grain yield in corn (Zea mays L.), but limited research is available on using these technologies in the Eastern Corn Belt where sidedress applications are more common. Field studies in Ohio (four site‐years) and Michigan (two site‐years) were conducted to evaluate the relationship of the dark green color index (DGCI) to soil plant analysis development (SPAD) values at the V4, V6, and R1 to R2 growth stages, as well as the relationship to ear‐leaf N concentration and grain yield. Five N rates (0–240 lb N acre−1) were evaluated in Ohio, and six N rates (0–250 lb N acre−1) were evaluated in Michigan. A linear relationship was observed between relative measurements of DGCI and SPAD in all but one site‐year at V4 and V6, and in all site‐years at R1 to R2. At V6, N application was detected by SPAD in four site‐years and by DGCI in two site‐years as compared with no N application. At the R1 to R2 stage, both DGCI and SPAD detected color differences in all six site‐years. Across all site‐years, both relative DGCI and relative SPAD measurements exhibited a linear relationship (P < 0.01) to relative yield at V6 (r2: 0.05–0.23) and R1 to R2 (r2 = 0.51–0.75), but the r2 values were 0.18 to 0.24 greater for SPAD than for DGCI. Ear‐leaf N concentration exhibited similar yield predictions as both SPAD and DGCI at R1 to R2. Results suggest that detection of N deficiencies may be location dependent, but detection of differences between treatments was more frequent using the relative SPAD measurements as compared with the relative DGCI measurements.