Evaluation of N Fertilization and Algorithm On Corn Under Different Soil Electrical Conductivity Zones In South Carolina.

Due to considerable soil texture variations in the Southeastern U.S., nitrogen (N) application should be based on soil texture. The objectives of this study were to 1) evaluate plant growth and N utilization using optical sensing technology under three soil electrical conductivity (EC) zones in response to N application timing and rate, and 2) test a South Carolina corn algorithm for sidedress N for each soil EC zone and across all zones. A commercially available Veris Technologies® 3100 was used to identify field soil variations and to define three zones based on soil EC levels.  Nitrogen was applied at 45 kg ha^-1 increments from 0 to 180 kg N ha^-1 at two timings (all at plant or split application). During corn vegetation, normalized difference vegetation index (NDVI), leaf area index (LAI) and chlorophyll (SPAD) meter were used to evaluate the crop growth. Plant NDVI readings at about V6 corn stage indicated a different response index (RI) under different soil EC zone and a need for calculating N rates separately for each zone.