Engineering Properties of Some Wetland Soils in Trinidad

The physical and engineering properties of six representative wetland soils collected from three major swamps in Trinidad were measured in the laboratory. The study was undertaken to identify suitable crops for large-scale mechanized cultivation in these wetlands. The properties assessed were dry bulk density, water content, Atterberg limits, density-water relations, penetration resistance, shear strength, and compressibility. Most parameters varied according to the soil clay content, which ranged from 47 to 74%. Lower bulk densities and higher field and air-dry water contents were associated with higher clay contents. The soils exhibited liquid limits that were both very high and quite variable, ranging from 56.2 to 122.0%. The mean maximum bulk densities of 5, 15, and 25 Proctor compaction blows decreased from 1.27 Mg m -3 (79 lb ft -3 ) for the soil with the lowest clay content to 1.07 Mg m -3 (67 lb ft -3 ) for the soil with the highest clay content. Mean penetration resistance of the soils obtained after the three Proctor compaction efforts decreased with increasing clay contents of the soils from 7.8 to 4.8 MPa (1131 to 696 lb in. -2 ). The shear strength after five Proctor compaction blows decreased with increasing clay contents from 124 to 96 kPa (18 to 14 lb in. -2 ). The compression index obtained from a standard confined compressibility test increased with increasing clay contents from 0.76 to 0.97. Generally, the soil properties that affect soil workability and trafficability were related to soil clay content. The results indicate that all the soils are ideally suited for mechanized rice cultivation. Moreover, the sugar cane plant, due to its peculiar nature and characteristics, is also a suitable alternative candidate crop for mechanized cultivation on the wetlands of Trinidad.