Application of Soil Magnetic Susceptibility for Monitoring Bioavailable Metals Pollution

Competition between potassiumand ammonium fixationwas studied in somesoilsofthe northern and southernKhuzestan province. Samples were taken from0-30and30-60cmdepthsin cultivation systemssuch assugarcane, rotational cropping, date palm, and uncultivated lands. Then, 0, 50, 100, 200, 400, 600, 800, 1000 mg kg-1 concentrations ofpotassiumand ammoniumwere added to these soil samples. The statistical analysis showed that with increasing concentrations from zero to 1000 mg kg-1 potassium and ammonium for all treatments, potassium and ammonium fixation increased in all systems and depths. In cultivated system, ammonium was fixed from 2007.50 to 1952.08 mg kg-1 in the surface and subsurface layers, respectively, while uncultivated land fixed 1880.62 to 1941.87 mg kg-1 ammonium. In contrast to ammonium, the same trend was not observed for potassium. Ammonium has also more tendency to fixing than potassium due to the presence of smectites and depleted illite clay minerals in these regions. The correlation coefficients between physicochemical properties and fixation showed that organic matter and clay content had negative effect on these cation fixations, but these effects were not statistically significant. Also, soil pH, the amount of lime and sand had insignificant and negative effect on ammonium fixation -0.034, -0.029 and -0.021 and cation exchange capacity and silt percentage show negative effect that was insignificant at -0.068 and -0.017, respectively.