Tuesday, November 6, 2007 - 9:30 AM
180-1

Cracking Behavior across a Landscape of Shrink-Swell Soil.

Cristine L.S. Morgan, Department of Soil & Crop Sciences, Texas A&M Univ., College Station, TX 77845-2474 and Andrea Kishné, Texas A&M University, Soil & Crop Sciences, College Station, TX 77843-2474.

Watershed hydrology models that include formation of soil cracks for estimating hydrology, usually assume uniform cracking across the landscape. The objective of this study was to measure the uniformity of soil cracking as a function of soil moisture, coefficient of linear extensibility, and landscape position. The area chosen for measurement was a Heiden Clay and Houston Black Clay catena; soil cracking was measured at the summit, shoulder, backslope and footslope. Rebar at different depths was installed at each measurement location to measure vertical soil shrink-swell. On the top of the hill, nine rebar were installed at 30.5 and 65 cm with 3 replicates, and at 90, 150 and 250 cm. Bulk soil electrical conductivity measurements were conducted to select five additional sites. At each of these sites, four rebar were installed at 20, 40, 80 and 120 cm depth along with an access tube for neutron probe moisture measurements. Shrinking-swelling at each depth was measured by leveling using a Pentax AL-320 surveyor's level relative to a monument installed in limestone parent material at 5 m depth. The soil moisture profile was also measured using a neutron soil moisture probe. Results of soil shrink swell associated with landscape position and soil moisture will be presented.