Mapping Soil Properties With Proximal Soil Fluorescence Sensing.

Precision agriculture aims at optimizing input rates at every location of the field. Optimal input rate usually depends on information coming from both soil and crop. The level of precision with which a farmer can manage his crop is contingent upon the level of precision with which he characterizes it. Soil samples are a good way to measure soil fertility and are widely used to create input prescription maps. However, the spatial range, which consist of the distance beyond which the information from the soil sample is no longer correlated, of most soil parameters is far shorter than the distance between soil sample locations. This prevents the reliable use of spatial interpolation techniques to estimate soil parameters values at every location of the field. Optical characteristics of soil such as fluorescence have the potential to provide reliable estimates of soil physical-chemical properties at a high resolution. The hypothesis of this project was that soil induced fluorescence can be used to estimate soil texture and organic matter content. Soil samples were collected in several fields located in Colorado, USA. At each soil sampling location, induced fluorescence was acquired in situ using the Multiplex3® fluorescence sensor. Results have demonstrated that both organic matter and texture components (sand, silt and clay content) are correlated with fluorescence parameters. These results pave the way for a new set of sensor for proximal soil sensing using fluorescence.