Measuring and modelling the soil shrinkage characteristic curve

Abstract

The macroporosity, and to a lesser extent the microporosity, of swelling and shrinking soils is affected by their shrinkage behaviour. The magnitude of the changes in bulk volume in response to changes in water content is usually described by the soil shrinkage characteristic curve (SSCC), i.e. the relation between the void ratio and the moisture ratio. At present, many techniques have been described for determination of the SSCC. We have applied the core method, the rubber-balloon method and the paraffin-coated method on respectively undisturbed soil samples, disturbed soil samples and soil clods collected from seven horizons of a Vertisol and a Lixisol under sugar cane in the Havana province, Cuba. We demonstrated that the balloon and paraffin-coated method showed similar results, whereas the core method produced less pronounced shrinkage. The latter was due to the anisotropic shrinkage as was confirmed by the change of the geometry factor with the moisture ratio, to a possible reorientation of particles when collecting undisturbed soil cores, and to the occurrence of small cracks upon drying. We have further shown that the core method produced much higher scatter, which was explained by higher measuring errors and crumbling of the samples as they dried out. Because of its superior behaviour, the balloon method was then selected to test nine different parametric models that describe the SSCC. A group of four models which performed best in terms of RMSE, coefficient of determination and Akaike Information Criterion could be distinguished.

Physics of the soil medium organization part 2: pedostructure characterization through measurement and modeling of the soil moisture characteristic curves

“…The well-known methods of this approach are: the resin-coated method (Brasher et al, 1966), the paraffin-coated method (Lauritzen and Stewart, 1942), and the rubber balloon method (Tariq and Durnford, 1993a). In resin-coated and paraffin-coated methods, the soil samples could be clods (Reeve and Hall, 1978), aggregates (Bronswijk, 1991), or soil cores (Crescimanno and Provenzano, 1999;Cornelis et al, 2006). While, in the rubber balloon method, reconstituted soil cores were used in most studies (Tariq and Durnford, 1993a;Cornelis et al, 2006).…”

“…In resin-coated and paraffin-coated methods, the soil samples could be clods (Reeve and Hall, 1978), aggregates (Bronswijk, 1991), or soil cores (Crescimanno and Provenzano, 1999;Cornelis et al, 2006). While, in the rubber balloon method, reconstituted soil cores were used in most studies (Tariq and Durnford, 1993a;Cornelis et al, 2006). In this approach, the soil samples were submerged into water and then the change in the sample volume was determined from the volume of displaced fluid; (ii) physical measurement-based approach: where the soil cores "disturbed or undisturbed" dimensions were measured directly using a vernier caliper (Berndt and Coughlan, 1977;Huang et al, 2011), a linear displacement transducer (Boivin et al, 2004;Braudeau and Mohtar, 2004) or a thin metal stick (Kim et al, 1992); (iii) laser sensors-based approach: where the soil core diameter and height were determined through laser beams such as the retractometer apparatus (Braudeau et al, 1999), (iv) imagebased approach: where the volume of the soil sample (either clod or core) was either scanned with a 3-D optical scanner (Sander and Gerke, 2007) or by a simple standard digital camera (Stewart et al, 2012).…”

“…In this approach, the soil samples were submerged into water and then the change in the sample volume was determined from the volume of displaced fluid; (ii) physical measurement-based approach: where the soil cores "disturbed or undisturbed" dimensions were measured directly using a vernier caliper (Berndt and Coughlan, 1977;Huang et al, 2011), a linear displacement transducer (Boivin et al, 2004;Braudeau and Mohtar, 2004) or a thin metal stick (Kim et al, 1992); (iii) laser sensors-based approach: where the soil core diameter and height were determined through laser beams such as the retractometer apparatus (Braudeau et al, 1999), (iv) imagebased approach: where the volume of the soil sample (either clod or core) was either scanned with a 3-D optical scanner (Sander and Gerke, 2007) or by a simple standard digital camera (Stewart et al, 2012). Several studies have discussed and compared these methods, Cornelis et al (2006) showed that there were significant differences between the Archimedes' principlebased methods "paraffin-coated and rubber balloon methods" and the physical measurement-based methods "vernier caliper method" where the former produced more accurate and reliable data; however, Sander and Gerke (2007) observed some errors in the resin-coated method that affects the measured volume due to inadequate coating or penetration of the coating materials. Crescimanno and Provenzano (1999) highlighted the problem of anisotropy of vernier caliper method due to the use of confined cores.…”

“…Crescimanno and Provenzano (1999) highlighted the problem of anisotropy of vernier caliper method due to the use of confined cores. In general, most of these methods require a continuous measurement follow up for 2-3 weeks (Crescimanno and Provenzano, 1999;Cornelis et al, 2006) and at the end produce 10-20 data pairs.…”

Influence of cracking clays on satellite estimated and model simulated soil moisture

“…Key features of these soils include swelling during wetting periods and shrinking during drying periods, with the potential for cracks to develop under extended dry conditions. The pore volume of vertisol soils varies with moisture condition, increasing the difficulty in accurately estimating moisture content (Cornelis et al, 2006).…”