PAM APPLICATION TECHNIQUES AND MOBILITY IN SOIL

High application rates (50-200 mg Kg-1 soil) and strong adsorption to soil aggregates severely limit polyacrylamide (PAM) application as a s oil conditioner below the top soil. Limited penetration, 0 to 20 cm, w as obtained upon introducing tritium-labeled PAM-2J into a clayey and sandy loam, respectively. This low penetration rate is related to the adsorption of the polymer to the surface of soil particles. This study tested the potential effect of modifying PAM application management b y lowering the viscosity of the applied PAM solution, thus increasing the efficiency of polymer subsurface penetration under reduced applica tion rates. One way of enhancing PAM penetrability may be a temporary reduction in adsorption. A significant reduction (up to five fold) in the viscosity of polymer solution flowing through narrow capillaries, caused by the addition of NaCl or CaCl2 to the solution, was observed in the laboratory. The application of PAM affected soil structure by r edistributing soil pore sizes, as indicated by changes in water conten t under different pressures.