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United States Department of Agriculture

Agricultural Research Service

Title: Influence of Polyacrylamide Application in Irrigation Furrows on Movement of Microorganisms in Water

Authors
item Sojka, Robert
item Entry, James

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 1999
Publication Date: N/A

Interpretive Summary: Because of the extraordinary efficacy of non-toxic high molecular weight anionic PAMs for removing fine suspended materials in flowing water, we hypothesized that PAM-use would have a significant impact on the removal and/or immobilization of microorganisms in flowing water. Our objective was to test this hypothesis by monitoring the effect of PAM-treatment of furrow irrigation water within an agricultural field on several categories of microbial populations in the inflow and runoff. After water traveled 1 meter at 7.5 liter min**-1, PAM-treatment reduced active bacterial biomass by 64%, reduced total fungal and bacterial biomass by 83 and 90% respectively, reduced algae by 76%, reduced active microbial biomass by 51%, reduced total microbial biomass by 90% relative to the control treatment. After water traveled 40 meters at 7.5 liter min**-1, PAM-treatment reduced active fungal and bacterial biomass by 100 and 60% respectively, total fungal and bacterial biomass by 83 and 90% respectively, algae by 92%, active microbial biomass by 51%, total microbial biomass by 90% and increased the ratio of active fungal biomass/active bacterial biomass (AF/AB) from 39 at 1 meter to 99 at 40 meters. It may not be possible to completely eliminate microorganisms from flowing water with PAM. However, the reductions may significantly reduce the cost, and or use of toxic chemicals, energy or land area required to bring microorganisms down to an acceptable concentration in runoff and ground water from irrigation or other flows. Furthermore, the reduction in phytopathogenic epidemiology from organisms spread in re- used irrigation runoff may significantly reduce the amounts of fungicide or other pesticides applied to crops for the control of plant diseases.

Technical Abstract: Polyacrylamide (PAM) use in irrigation for erosion control has increased water infiltration and reduced soil erosion resulting in runoff water with lower concentrations of nitrogen and phosphorous. Since non-toxic moderate to high molecular weight anionic PAMs have been effective in removing solids and nutrients in flowing water, we hypothesized that PAM-use would effectively remove or immobilize microorganisms in flowing water. We determined the efficacy of PAM-treatment of furrow irrigation water within an agricultural field on several categories of microbial populations in the inflow and runoff. Treatments were: 1) PAM application and a control, 2) three flow rates, 3) two distances from the inflow point, and 4) three sampling times during irrigation. After water traveled 1 meter at 7.5 liter min**-1, PAM-treatment reduced active bacterial biomass by 64%, reduced total fungal and bacterial biomass by 83 and 90% respectively, reduced algae by 76%, reduced active microbial biomass by 51%, reduced total microbial biomass by 90% relative to the control treatment. After water traveled 40 meters at 7.5 liter min**-1, PAM-treatment reduced active fungal and bacterial biomass by 100 and 60% respectively, total fungal and bacterial biomass by 83 and 90% respectively, algae by 92%, active microbial biomass by 51%, total microbial biomass by 90% and increased the ratio of active fungal biomass/active bacterial biomass (AF/AB) from 39 at 1 meter to 99 at 40 meters. Beyond furrow irrigated agriculture, other situations involving overland flow of water causing transmission of microorganisms could potentially see reductions of carried microorganisms. Flowing water carries various plant, animal and human pathogens. Limiting the

Last Modified: 8/22/2014
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