Chlorophyll Estimation Using Multispectral Reflectance and Height Sensing

Abstract

Chlorophyll is an indirect indicator of nitrogen status and is used in optical reflectance-based variable-rate chemical application technology. Chlorophyll concentration relates strongly to the photosynthetic potential of a plant and to the physiological and metabolic status of the plant. This research investigated a non-destructive method of determining chlorophyll content and concentration at the individual plant level in Spinacea oleracea (spinach). A multispectral imaging system was used to determine spectral reflectance and to estimate top-view surface area. An ultrasonic distance sensor provided vegetation height estimates. Surface area estimates and height data were included in calculations to estimate plant biomass. The relationships between reflectance, estimated biomass, and laboratory-measured chlorophyll content and concentration were investigated. The product of biomass estimate and normalized difference vegetative index (NDVI670) provided the best estimate of chlorophyll content per plant (R2 = 0.91), while estimates of chlorophyll concentration per unit leaf mass were less accurate (R2 = 0.30).