Predicting Nitrogen Requirements for Maize with the Dark Green Color Index under Experimental Conditions

Core Ideas Current N fertilizer recommendations for maize based on yield goals and soil texture do not account for native soil fertility. Assessing plant nitrogen status using the dark green color index may allow for more targeted N fertilizer recommendations. The dark green color index method averaged between 92 and 112 kg N ha−1 less than standard extension recommendations in low residual N soils. Grain yield was similar between treatments based on the dark green color index method and standard extension recommendations. Nitrogen fertilizer recommendations for maize (Zea mays L.) should be adequate to ensure high yields but should be both economical and environmentally sound. Previous research developed algorithms using a digital camera to determine the dark green color index (DGCI) that predicted N recommendations from leaves of maize between V6 and V10. This study evaluated those algorithms by comparing them with recommendations from the University of Arkansas Cooperative Extension Service. There were no significant differences in yield between recommendations for N using the DGCI method between V6 and V10 and extension recommendations on fields with either low‐ or medium‐residual N. The DGCI method averaged about 112 and 92 kg N ha−1 less than extension recommendations in low residual N soils when 67 and 0 kg N ha−1 was applied preplant, respectively. Future research should simplify the DGCI method for use in the field and evaluate DGCI method recommendations over a range of soils and environments.