THE RELATIONSHIP BETWEEN RED EDGE AND CHLOROPHYLL CONCENTRATION IN THE BROADBALK WINTER-WHEAT EXPERIMENT AT ROTHAMSTED

The concentration of chlorophyll in a crop can be related to both the position of the red edge in a reflectance spectrum and the yield of th at crop. The use of a remotely-sensed red edge to estimate yield is de pendent upon a well-understood relationship between chlorophyll concen tration and yield and a poorly understood relationship between red edg e and chlorophyll concentration. To determine the form of the relation ship between red edge and chlorophyll concentration a field experiment was undertaken using a wheat crop with an exceptionally large range o f chlorophyll concentrations. The non-linear form of the relationship between red edge and chlorophyll concentration meant that estimates of red edge could be used to estimate chlorophyll concentration up to 0. 5 mg g-1 and thereby yield up to 6t ha-1.