Optimize N Fertilization in Corn Under Different Soil Electrical Conductivity Zones Using Optical Sensing Technology in South Carolina.

Optical sensing technology can help to determine optimum nitrogen (N) application rate to corn (Zea mays L.) under different soil electrical conductivity (EC) zones. The objectives of this study, conducted at Clemson University, Edisto Research and Education Center (EREC) located near Blackville, South Carolina, was to evaluate N fertilization in corn under different soil electrical conductivity zones using optical sensors and Clemson algorithm. A commercially available Veris Technologies® 3100 was used to identify soil variations. The first part of the experiment consisted of two N application methods (all at once at planting and as a split application with about 35 kg N ha^-1 applied at planting and the rest as a side-dress application at V6 corn stage), and five N rates (0, 45, 90, 135, and 180 kg N ha^-1) under different soil EC zones. In the second part of the experiment, N was applied to corn at 45 kg ha^-1 after corn planting and as side-dress at V6 corn stage. The side-dress N was calculated based on the Clemson algorithm and response index (RI) after recording plant normalized difference vegetation index (NDVI) using GreenSeeker separately for each zone and across all soil EC zones. Calculated N rates for different zones were compared with a standard side-dress rate of 135 kg N ha^-1. The yield results showed that side-dress N rates could be reduced by at least 50% without a significant yield decrease compared to standard side-dress N rate under dryland conditions. Moreover, the side-dress N rate for soil EC zone 1 (light soil texture) needs to be calculated separately from the field average to further optimize N rates and improve N use efficiency.