In situ Determination of K, Ca, S and Si in Fresh Sugar Cane Leaves by Handheld Energy Dispersive X-Ray Fluorescence Spectrometry

A portable energy dispersive X-ray fluorescence spectrometer was evaluated in the in situ analysis of fresh sugar cane leaves for real time plant nutrition diagnosis. Fresh leaf fragments (n = 10 sugar cane varieties; 20 fragments per leaf; 2 measurement sites per fragment) were irradiated and the averaged data from X-ray characteristic emission lines intensities (for K, Ca, S and Si Kα lines) were in close agreement with mass fraction data obtained by a validated comparative method. The linear correlation coefficients (r) ranged from 0.9575 for Ca to 0.9851 for Si. The obtained limits of detection were at least two-fold lower than the critical nutrient levels. Manganese can also be properly determined, but validation still requires more robust calibration models. The proposed method is a straightforward approach towards the fast evaluation of the nutritional profile of plants avoiding time-consuming steps, which involve drying, grinding, weighing, and acid digestion.