Five-year research summary using PAM in furrow irrigation

A previous conference paper (Sojka and Lentz, 1996) presented an historic perspective and some general results of PAM investigations conducted at the USDA-ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho. This paper presents the experimental methods and summarizes results from those studies, conducted over a five year period. Studies initiated since 1991 determined best mode of PAM application. established PAM's effectiveness under different furrow irrigation scenarios and sought to define its potential environmental impacts (Lentz, et al., 1992; Sojka and Lentz, 1993, Sojka et al., 1994; Lentz, 1996; Trout et al., 1995). Kimberly ARS field experiments initially sought to determine the PAM application method that most efficiently and effectively controlled furrow-irrigation induced soil loss and infiltration. We investigated the following PAM application parameters: PAM form — dry granular, stock solution. oil emulsion PAM type — polymer charge type, charge density, molecular weight Application method — standard: PAM added to irrigation water, nonstandard: PAM applied to furrow soil Application strategy — timing, rate, and period of PAM application Irrigation water quality —effect of a water's total salt or sodium adsorption ratio on PAM effectiveness Experiments that examined effects of PAM type on furrow processes are presented in a separate paper (Lentz and Sojka, 1996). A series of studies documented PAM's usefulness over a range of furrow-irrigated field conditions. PAM was tested on different soils, furrow slopes, and using different furrow inflow rates and irrigation waters. Several studies examined PAM's environmental impacts. We first developed an analytical procedure for measuring PAM concentration in irrigation water to document the fate of PAM applied to furrow irrigation inflows. A permanent PAM field site was established to study effects of long-term PAM applications on soil properties. microbiology (Warwood and Kay- Shoemake, 1996), productivity and solute leaching. Another experiment documented PAM s influence on field runoff water-quality. Finally, a plot treated with excessive PAM additions was used to determine the potential for acrylamide-monomer accumulation in crop-tissue (Barvenik et al., 1996)