Agricultural Geophysics: Past, Present, and Future

Abstract

Geophysical methods are becoming an increasingly valuable tool for agricultural applications. Agricultural geophysics investigations are commonly (although certainly not always) focused on delineating small- and/or large-scale objects/features within the soil profile (~ 0 to 2 m depth) over very large areas. The three geophysical methods predominantly employed for agricultural applications, both past and present, are resistivity, electromagnetic induction (EMI), and ground penetrating radar (GPR). Some of the more important past developments for agricultural geophysics include: soil water content monitoring using resistivity methods beginning in the 1930s and 1940s; soil salinity assessment with resistivity and EMI methods beginning in the 1960s and 1970s; updates and improvements in U.S. national program soil survey mapping using GPR beginning in the late 1970s and on into the 1980s; and for precision farming purposes, the delineation of spatial variations in soil properties with resistivity and EMI methods beginning in the 1990s. There has been significant recent advancements in agricultural geophysics, with resistivity, EMI, GPR, and other geophysical methods presently being used or evaluated for applications ranging from soil hydrologic characterization, determination of clay-pan depth, soil nutrient monitoring at confined animal feeding operation sites, crop/tree root biomass surveying, subsurface drainage system infrastructure detection, identification of subsurface flow pathways, soil compaction evaluation, etc. However, before agricultural geophysics can reach its full potential, new developments are needed, such as: expanding possible agricultural applications for resistivity, EMI, and GPR methods; greater employment of geophysical methods that have not traditionally been applied to agriculture; construction of multi-sensor geophysical equipment platforms, perhaps integrated with agricultural machinery; development of agricultural geophysics expert system computer software; etc. Achieving these future advancements in agricultural geophysics will require close collaboration between those in both the agricultural and environmental/engineering geophysics communities.