Spatial Modeling of Soil Nutrients: A PXRF Approach.

The use of commercial fertilizers on farms in Louisiana pose a threat to water quality as a nonpoint source of nutrient enrichment of surface waters. Given high annual rainfall, nutrients have a propensity to move off-site into bayous and surface streams. The dynamics of such movement are site specific and strongly related to topography, vegetative cover, soil texture, and management practices. Until now, sporadic soil sampling and laboratory testing of nutrients has given farmers a cursory sense of nutrient levels in their fields, but with little understanding of spatial variability or temporal movement of nutrients. This study uses GPS referenced field portable x-ray fluorescence (PXRF) spectrometry to rapidly assess a variety of different nutrients at hundreds of locations in a single field. Three fields in St. Landry Parish, Louisiana were evaluated using this technique. Scanning and interpolation analysis was completed in the field, on-site using Innov-X PXRF equipment and a laptop computer GPS/GIS system. Results clearly show the ability of this system to provide farmers with high resolution nutrient distribution maps on-site, which can be used for precision application of future fertilizer in response to crop needs.