Abstract

A portable plant nutrition test instrument with global positioning system (GPS) module was designed for the fast and noninvasive measurement of the field crop nutrition content and distribution. Two Light Emitting Diode (LED) light resources at 650 and 940 nm were used to obtain the transmittance spectra of leaves. The chlorophyll content prediction model was established according to the relationship between transmission spectra and SPAD value. The nitrogen content prediction model was established according to the relationship between transmission spectra and the nitrogen contents obtained by combustion method. The water content prediction model was established according to the relationship between transmission spectra and the water contents obtained by weight method. The results indicated that correlation coefficients (R²) for chlorophyll content, nitrogen content and water content were 0.92, 0.91, and 0.76, respectively. With GPS module, the portable instrument can support the nutrition and position information of the sampling points to the GIS software in the management computer to do the nutrition distribution analysis. The portable instrument is helpful to provide a high efficient and scientific way for the management and operation in precision agriculture.

Key words: Spectroscopy, chlorophyll content, nitrogen content, water content, global positioning system (GPS).