Aggregate Stability as Affected by Polyacrylamide Molecular Weight , Soil Texture , and Water Quality

1909 Joint contribution of the Institute of Soil, Water, and Environmental Sciences, ARO (603/2007 Series) and USDA-ARS, National Soil Erosion Research Lab.. Soil Sci. Soc. Am. J. 71:1909–1918 doi:10.2136/sssaj2007.0096 Received 8 Mar. 2007. *Corresponding author ([email protected]). © Soil Science Society of America 677 S. Segoe Rd. Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Sustainable development and use of soil resources requires maintaining soil structure and reducing or eliminating the discharge of sediment and pollutants by runoff and erosion. The favorable effects of the environmentally friendly, nontoxic, anionic polyacrylamide (PAM) as a soil conditioner have recently been reviewed by Sojka et al. (2006). The positive effects of PAM are related to (i) preserving or increasing soil aggregation and pore continuity (Ben-Hur and Keren, 1997; Green et al., 2004; Ajwa and Trout, 2006), (ii) stabilizing the soil surface structure against shear-inducing detachment (Lentz and Sojka, 1994), (iii) increasing water infi ltration and decreasing soil surface sealing (Levy et al., 1992; Shainberg et al., 1992), (iv) controlling runoff generation and soil erosion (Smith et al., 1990; Bjorneberg and Aase, 2000), (v) decreasing the settling time of particles that become suspended in runoff to aid in their deposition (Lentz and Sojka, 1994), and (vi) improving runoff water quality (Lentz et al., 1998; Sojka and Entry, 2000). These potential benefi ts from using PAM for soil aggregate or structural stability are infl uenced through complex relations among polymer properties (e.g., molecular weight [MW], charge type, and density), soil texture and structure, soil salinity, and clay mineralogy (e.g., Ben-Hur et al., 1992; Letey, 1994; Levy and Agassi, 1995; Laird, 1997; Miller et al., 1998; Levy and Miller, 1999; Green et al., 2000, 2004). The effects of PAM as a soil conditioner could be infl uenced by the concentration and composition of the soil solution. The presence of salts in the soil solution enhanced the SO IL & W A ER M A N A G EM EN T & C O N SERV A IO N A. I. Mamedov* USDA-ARS National Soil Erosion Research Lab. 275 S. Russell St. Purdue Univ. West Lafayette, IN 47907-2077