In situ estimates of waterhyacinth leaf tissue nitrogen using a SPAD-502 chlorophyll meter

► The SPAD-502 meter measures relative chlorophyll levels in Eichhornia crassipes leaves. ► The readings serve as a proxy allowing non-destructive in situ estimates of leaf nitrogen levels. ► SPAD readings provide accurate estimates when properly calibrated (e.g., for location, herbivory, etc.). Previous investigations with Eichhornia crassipes and its biological control agents Neochetina bruchi and N. eichhorniae identified leaf tissue nitrogen (N) as a driver in their interactions. However, traditional methods for determining plant tissue N content are cumbersome, time-consuming, and destructive–and thus unsuited for rapid in situ evaluations. We therefore tested the utility of a hand-held chlorophyll meter as a means of producing in situ estimates of N in the leaves of this floating aquatic weed. The Minolta SPAD-502 chlorophyll meter provided excellent estimates (F=385.96, P