Polyacrylamide to Improve Water Flow and Salt Removal in a High Shrink-Swell Soil
- M. Malik,
- C. Amrhein and
- J. Letey
Reclamation of salt-affected high shrink-swell soils using chemical amendments combined with deep loosening and tile drainage is very expensive. As an alternative, the utilization of cracks as pathways for water and salts is possible if these cracks could be stabilized by the application of a polyacrylamide (PAM) polymer and their complete closure prevented upon rewetting. A laboratory column study was conducted on two soil samples with exchangeable sodium percentages (ESP) of 8 and 25 from a heavy-textured, swelling soil. The soil samples were packed into columns, ponded with irrigation water for 24 h, then drained and dried to create cracks. After drying, the soil samples were ponded for 24 h with irrigation water containing 0, 25, 75, and 200 mg L−1 of an anionic polyacrylamide polymer, allowed to drain, and dried. The treated soils were then ponded without drainage for 1, 6, 12, and 24 h to allow crack closure and the hydraulic conductivity (HC) and effluent salinity were measured. The experiment was repeated except that the polymer solution was added to the soil without initially creating the cracks. An additional study was carried out to test the durability of the polymer when subjected to wetting and drying cycles. Increasing the amount of polymer significantly increased the HC and salt removal in the cracked soils. When the polymer solution was applied directly onto soils without initially creating cracks, there was no increase in HC on the ESP 8 soil and a small increase on the ESP 25 soil. The polymer had a stabilizing effect on soil cracks, but the increase in HC did not persist through several wetting and drying cycles.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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