Electrical conductivity of some soils in Trinidad as affected by density, water and peat content

The apparent bulk electrical conductivity (σa) of eleven soils from Trinidad tropic region was measured in the field and the laboratory with a portable Field Scout soil water content/electrical conductivity probe. The effect on σa of compacting three of the soils (a sandy loam, clay loam and clay) to three or four bulk densities (1.1, 1.3 and 1.5 and 1.7 t m−3), each with four levels of peat (0, 4%, 8%, and 12% by mass) at four gravimetric water contents (5, 12, 19 and 26%) was further investigated in the laboratory. The σa measured in the field ranged from 0.09 to 0.75 dS m−1 and was within 0.05 dS m−1 of the corresponding laboratory-measured values for the individual soils. Electrical conductivity of the laboratory-compacted soils, which ranged from 0 to 0.66 dS m−1, increased with increasing bulk density, water and peat contents. The clay soil exhibited greater values of σa than the clay loam or sandy loam soils, at given values of bulk density, water and peat contents. Good agreement was found between the field and laboratory measurements of σa as well as electrical conductivity of the saturated water extracts from individual soils. Apparent bulk electrical conductivity was significantly affected by the interaction between soil type and water content, and between peat content and water content. A multiple linear regression equation was developed from experimental data to determine the relative importance of the experimental parameters on σa.