ABSTRACT
Geoelectrical resistivity, hydrogeochemical and soil properties analysis methods were used for chemical fertilizer monitoring in sandy soil at a palm oil plantation in Machang, Malaysia. The time lapse monitoring was done using these methods five times within a three-month period. The hydrogeochemical analysis was conducted over three auger holes to a depth of 1 meter and sampled at 25 centimeter intervals. Chemical fertilizer was applied to the 21 x 21 square meter area after the first data set measurement. Areas outside of this fertilized zone are considered a non-fertilized zone. The other four data sets were acquired at about equal time intervals, thus giving a four-post fertilization data set. The hydrogeochemical measurements indicate that the cations content are relatively similar for every time lapse measurement. However, relatively higher changes of anions content occur at the surface level to a depth of 1 meter. Of particular interest is the nitrate concentration above the limit for safe human consumption as it returns to the initial value about 100 days after fertilization. The geoelectrical model prior to fertilization showed similar resistivity values at near surface to a depth of about 75 centimetres with no significant occurrences of low resistivity values. Lower resistivity values were obtained during the second, third, fourth and fifth measurements within the chemically fertilized zone. In the last measurement, the resistivity values in the fertilized zone are almost similar to the non-fertilized zone. This indicates that the contaminant has dissolved into the surrounding environment within this time period