GEOPHYSICAL ELECTROMAGNETIC SURVEY METHODS APPLIED TO AGRICULTURAL WASTE SITES

This paper reports the use of electromagnetic (EM) instrumentation for surveying agronomic and waste treatment sites at locations previously profiled by soil coring for evaluation of nutrients in the soil profi le. Surveys were made using a geophysical EM instrument capable of mea suring conductivity 3 to 6 m below the surface of the ground with hori zontal or vertical polarization. Two specific sites were analyzed to e valuate the effects of management practices: (i) An animal waste compo sting site with one section in use since 1985 and with expanded operat ion to another section in 1989 and (ii) A waste storage pond (operatio nal in 1973) holding precipitation runoff from a cattle feedlot. Corre lation analysis between the EM conductivity measurements and chemical analysis at both sites (concentrations of NH4+, NO3-, CL-, and P) show significant (P < 0.05) correlations for the ions while P did not show a significant correlation. The Ehl measures were able to distinguish the 6-yr-old site from the 10-yr-old site (P < 0.05). The results indi cate that EM methods provide useful information for shallow subsurface surveys of livestock waste management facilities.