Measuring Potassium in Plant Tissues Using near Infrared Spectroscopy

Abstract

Near infrared (NIR) spectroscopy is routinely used to determine constituents with organic bonds which absorb electromagnetic radiation in the region 1100 to 2500 nm. The nitrogen fertilizer requirements of cereal crops are determined from the analysis of vegetative samples by NIR spectroscopy. Simultaneous determination of other plant-essential elements would enhance the value of the analysis. Compared to nitrogen, other essential elements are either present at a lower concentration in the tissue or present largely in an inorganic form which is not detectable by NIR spectroscopy. In this paper we report NIR spectroscopic calibrations for potassium in grape petioles, grape leaves, rice shoots and orange leaves. When tested against a set of verification samples the NIR spectroscopic calibrations accounted for 96, 89, 93 and 85% of the concentration of K with standard errors of performance of 0.16, 0.12, 0.18 and 0.17%K respectively.