2019 ASHS Annual Conference

Real-time data on elemental nutrients and heavy metals in native soil, fertilizers, treatments and their uptake by plants is of great value to horticulturists striving to optimize the growth of healthy, local and sustainable fruits, vegetables and herbs.

Nutrients (e.g., P, K), secondary nutrients (e.g., Ca, Mg, S) and micro nutrients (e.g., Cu, Fe, Mn, Mo, Zn) in natural or manufactured agents allow plants to develop into large, appetizing and healthy products. Conversely, heavy metals (e.g., As, Cd, Hg, Pb) present in outdoor or indoor growth media can damage plants and develop hazardous products.

With today’s interest in both sustainable and precision agriculture of healthy foods, many organizations now monitor the growth media and plant uptake of nutrients and heavy metals using portable X-ray fluorescence (pXRF) spectrometry. This elemental analysis method is nondestructive and can be taken into the field or greenhouse to rapidly screen soil, powders, liquids, solids and plant tissue for fast actionable results.

PXRF has long been used for elemental analysis of soils for environmental stewardship as well as for geological studies such as mineral exploration. Two well-known environmental methods for this application are US EPA 2007 SW-846 Test Method 6200 and ISO 13196:2013. Additionally, the “USDA Soil Survey Field and Laboratory Methods Manual (2014, No. 51, V.2)” describes the pXRF method for major and trace elemental analysis in the “Soil Mineralogical Analyses” section.

Real-time nutrient diagnostics and heavy metal screening with portable elemental analyzers help horticulturists optimize plant characteristics and maintain product safety at any stage of the growing cycle. This capability enables growers to make better decisions about their plants’ progress in real time without having to send large quantities of samples out to a lab.

The technology of pXRF will be described; the trade-offs between screening samples as-is and analyzing samples which have been prepared will be discussed; and data correlated with ICP analysis will be presented.