SPAD Meter Measurements and Cotton N Management

SPAD meter could be a fast and easy tool to guide cotton N management. In this study, SPAD readings were taken from ten leaves on main stems in a field experiment with four cotton varieties and five N rates to develop a guideline for N application.  The differences in varietal SPAD meter readings were significant, indicating that a calibration system is needed to use the SPAD reading for N recommendations. Calibration by different leaf positions in the same plant could be a useful tool to develop a universal guideline for different varieties.