Managing Irrigation-induced Erosion and Infiltration with Polyacrylamide (PAM)

College of Southern Idaho -- Twin Falls, ID -- May 6-8, 1996

Please Note: A printed copy of the proceedings is no longer available. However, each article is now available as a PDF file to be viewed and/or printed. A link to each article is provided at the end of each abstract.

Cover Photo

Table of Contents

• Oral Presentations:

  • The National Irrigation Improvement Initiative, T. Lynott
  • A PAM Primer: A Brief History of PAM and PAM-related Issues, R.E. Sojka and R.D. Lentz
  • Five-Year Research Summary Using PAM in Furrow Irrigation, R.D. Lentz and R.E. Sojka
  • An Integrated Approach For Water Quality: The PAM Connection--West Stanislaus HUA, California, M. McElhiney and P. Osterli
  • Microbial Ecology of Polyacrylamide Application in Agricultural Soils, M.E. Watwood and J.L. Kay-Shoemake
  • Product Stewardship Considerations in the use of Polyacrylamide in Soil Erosion, R. Deskin
  • Reduction of Nutrient and Pesticide Losses through the Application of Polyacrylamide in surface Irrigated Crops, G. Bahr and T. Stieber
  • Agriculture Irrigation Polyacrylamide Application Standard, T.L. Spofford and K.L. Pfeiffer
  • On-Farm Comparison of Polyacrylamide and Straw Mulch on Dry Bean Yield, Irrigation Performance and Erosion, B.A. King, B. Izadi, M.S. Ashraf, R.H. Brooks and W.H. Neibling
  • Need for Solution or Exchangeable Calcium and/or Critical EC Level for Flocculation of Clay by Polyacrylamides, A. Wallace and G.A. Wallace
  • Land Treatment Effects on Soil Erosion, J.K. Mitchell, C. Ray
  • PAM Conformation Effects on Furrow Erosion Mitigation Efficacy, R.D. Lentz, R.E. Sojka
  • Screening of Polymers to Determine their Potential use in Erosion Control on Construction Sites, A. Roa
  • Influence of Structure and Formulation on the Efficacy of Polyacrylamides as Soil Stabilizers, P. Chamberlain* and R. Cole
  • Practical Field Application and PAM Transport in Surface Irrigation, T.D. Stieber and H. Chapman-Supkis
  • Effective Viscosity of PAM Solutions Through Porous Media, J. Letey
  • Net and Tension Infiltration Effects of PAM in Furrow Irrigation, R.E. Sojka*, R.D. Lentz, C.W. Ross and T.J. Trout
  • Fate of Acrylamide Monomer Following Application of Polyacrylamide to Cropland, F.W. Barvenik, R.E. Sojka, R.D. Lentz, F.F. Andrawes and L.S. Messner
  • The Physical Effects of Polyacrylamide on Natural Resources, L.J. Dawson, T.L. Spofford

• Poster Presentations:

  • PAM Spray Effects on Sugarbeet Emergence, G.A. Lehrsch, D.C. Kincaid, and R.D. Lentz
  • Demonstration of Polyacrylamide (PAM) to Reduce Erosion on Onions in the Arkansas River Valley of Colorado, J.C. Valliant

Oral Presentations

The National Irrigation Improvement Initiative

Terry Lynott---NACD office of the Irrigated Ag. Initiative, Lakewood, CO

Over the past several years, public and private sector representatives have been pursuing a more focused approach to address the need for better water and land management in irrigation and non-irrigation applications. Out of these efforts has sprung a National Irrigation Improvement Initiative, a public/private partnership effort, under the general direction of the National Association of Conservation Districts.

The vision for the Initiative is that water for irrigation is being used in harmony with other demands in the most efficient and environmentally acceptable manner possible. It is recognized that some irrigated areas have developed water quality and other environmental problems. Consequently, a priority to resolve these problems and pressure to minimize water usage and negate resulting environmental impacts is intensifying for many agricultural and non-agricultural irrigators. Application of proven and emerging technologies and practices to conserve water and topsoil, to improve and protect water quality, to improve and maintain habitat for fish and wildlife, and to reduce irrigation-induced erosion are primary objectives of the Initiative.

The Initiative is a public and private partnership of organizations, businesses, associations, and agencies working in a coordinated and cooperative effort to assist rural and urban irrigators in improving and maintaining the environment while ensuring effective water and land management practices and sustainable agriculture. As the result of a survey conducted in the first phase of the Initiative, a significant amount of promising activities from a technical, financial, research, and educational perspective are being accomplished, primarily at the local level. A "framework" summarizing this and other germane information is being developed to provide readily usable material about water and land improvement practices focused on environmental protection, ecosystem health, and sustainable agricultural production.

An overriding theme is to not "reinvent the wheel". Rather, learning about and conveying information on success stories is the central theme of these efforts. Emphasis is being given to the use of partnerships formed primarily at the local level. Developing means to reinforce ongoing activities, providing incentives to get other efforts initiated, and broadening the knowledge about dissemination of existing data and information from the vast storehouses of government agencies, associations, and the private corporate sector are major efforts underway. Other forms of assistance, including the provision of technical expertise and guidance, and the attainment of public and private funding for pilot demonstration projects of irrigation water and land improvements, are major anticipated Initiative activities.

Exchanging cogent information about effective irrigation water and land practices will be realized if this Initiative attains its goals and objectives. The National Association of Conservation Districts is continuing to strongly support these efforts. With continued interest from the other key organizations and entities in both the public and private sector, and the generation of interest of others involved in irrigation water and land practices, the overall vision for the National Irrigation Initiative will be realized.

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A PAM Primer: A Brief History of PAM and PAM-related Issues

R.E. Sojka and R.D. Lentz---USDA-ARS, Northwest Irrigation and Soils Research laboratory, Kimberly, Idaho

Polyacrylamide (PAM) and other synthetic soil amendment polymers first saw wide use as road and runway stabilizers in World War II. In the 1950s and 60s numerous polymers were tested for agriculture. Use-strategy required hundreds of pounds per acre, to optimize soil aggregation in the plow layer. High rates restricted use to high return applications. The 1970s and 80s saw occasional renewal of interest in amendments as new polymers were developed. PAMs became available in more sophisticated copolymer formulations and longer chain lengths. A 1975 USSR report described using a polymer dissolved in irrigation water to prevent erosion. The report gave few details and was not widely read. In the 1980's PAM-treated soil and PAM-treated water were used in soil column studies, rain simulators and benchtop rill simulators. A 1991 field test of PAM in Furrow irrigation water lead to use at very low application rates for erosion control and better infiltration. High molecular weight moderately anionic PAM copolymers, regarded safe for sensitive uses by EPA and FDA are recognized by NRCS for soil conservation use under prescribed protocols. Data and insights are given to provide a common understanding of background and general principles of PAM-use.

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Five-Year Research Summary Using PAM in Furrow Irrigation

R.D. Lentz and R.E. Sojka---USDA-ARS, Kimberly, Idaho.

Furrow-irrigation-induced soil erosion is a serious threat to sustainable agriculture globally. Field studies have demonstrated that small concentrations of polyacrylamide (PAM) in irrigation water greatly reduces soil loss from irrigated furrows and increases intake. The PAM used for this application is described, and safety concerns discussed. When used at recommended rates PAM is non-toxic , and it has previous EPA and FDA approval for use in food and water additive applications. PAM effects on furrow irrigation processes are summarized. Optimal PAM treatments reduce furrow soil loss by 94%, increase net infiltration 15%, increase lateral wetting extent 25%, reduce total phosphate losses from fields by 75%, and reduce field losses of some pesticides. PAM's erosion control efficacy decreases as sodium adsorption ratio of the irrigation water increases, but generally it efficacy increases with increasing divalent cation concentration. Studies that examined the fate of PAM added to furrow streams is summarized. During PAM application, runoff from solution-treated furrows contained 6-10 mg/L PAM, while runoff from dry-PAM treated furrows contained 1-6 mg/L. While PAM was being injected into streams, its concentration decreased with distance downstream from the application point. The PAM concentration in solution-treated furrows decreased to the minimum detection limit less than 30 minutes after PAM injection was curtailed. In another study, off-standard PAM treatments were shown to be equally effective as standard approaches, for controlling furrow erosion.

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An Integrated Approach For Water Quality: The PAM Connection--West Stanislaus HUA, California

M. McElhiney and P. Osterli---USDA-NRCS, Modesto, Ca., and Univ. of California, Cooperative Extension, Modesto, Ca.

Irrigation-induced erosion in The West Stanislaus Hydrologic Unit Area (HUA) can potentially contribute a million tons of sediment to the impaired San Joaquin River annually. The HUA project was established by USDA's 1990 "Water Quality Initiative" to promote the implementation of Best Management Practices using an integrated approach of information and education, technical assistance, and cost-sharing. The HUA has served as the test site for the innovative evaluation and use of PAM for reducing significant amounts of sediment and pesticide residues leaving irrigated fields in the watershed. Field trial results in the HUA indicate a 95-98 percent reduction in soil loss and a corresponding reduction in pesticide residues leaving the fields through furrow irrigation. Additionally, a 10-40 percent increase in infiltration was observed in treated furrows.

USDA ARS scientists at Kimberly, Idaho, and scientists from University of California and the PAM Industry have played key roles in assisting with the establishment of the interim NRCS standard and specification in California.

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Microbial Ecology of Polyacrylamide Application in Agricultural Soils.

M.E. Watwood and J.L. Kay-Shoemake---Dept. of Biological Sciences, Idaho State University, Pocatello, ID.

Little is known regarding the microbiological fate of PAM in agricultural fields. We hypothesized that PAM treatment would result in changes in soil microbial communities. PAM treated and untreated soils were collected from bean and potato fields at the USDA ARS Site in Kimberly, ID. Soils were analyzed to determine the impact of PAM additions on soil bacterial numbers, the potential for PAM biotrans-formation as a C or N source, and impact of PAM treatment on inorganic N pools. Few differences were observed between treated and untreated soils with respect to bacterial numbers. PAM treated potato field soil showed significantly higher levels of NO ₃ ^-(3.67 + 0.22 ppm) and NH ₃(0.13 + 0.03 ppm) than untreated soil (1.07 + 0.23 ppm and 0.05 + 0.002 ppm for NO ₃ ^-and NH ₃, respectively). For bean field soil there was no difference between treated and untreated soil N pools. Enrichment cultures generated from PAM treated and untreated soils were able to utilize PAM as sole N source; no enrichment cultures were able to derive C from PAM. Soil microbial consortia utilized acrylamide and acrylic acid.

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Product Stewardship Considerations in the use of Polyacrylamide in Soil Erosion

R. Deskin---DABT. CYTEC Industries Inc., West Paterson, NJ

Product Stewardship is a global term that arises from Responsible Care initiatives originating in the US, Canada and Europe. Product Stewardship is an extension of Product safety programs, the principles of which are applied to all aspects of the product life cycle. The essence of Product Stewardship is the responsible and ethical management of our products from design to final disposition or from cradle to grave. It involves the comprehensive integration of health safety and environmental considerations into all aspects of business and focuses on the product life cycle. At the heart of Product Stewardship is the product Life Cycle which is continuous and includes customer need, raw materials acquisition, product design and development, manufacturing, product distribution, product usage, recycle and reuse and disposal.

A comprehensive Product Stewardship program includes hazard classification at its core. In evaluating risk of a product, one takes into account hazard and exposure, as they both comprise risk. Hazard is a materials intrinsic potential to cause harm. This may include health, physical or environmental hazard. Exposure is the contact a material makes with human, animal, or plant life or with air, water or soil. Risk is the combination of hazard and exposure that establishes the probability of an occurrence of an unwanted adverse effect on human health or the environment.

This paper describes the adherence to the principles of Product Stewardship in the use of Polyacrylamides in soil erosion application. Anionic PAM's have low toxicity to aquatic organisms and do not cause adverse effects on plants, worms, soil nutrients of nitrifying bacteria. The polymer is non-toxic and does not degrade to free monomer.

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Reduction of Nutrient and Pesticide Losses through the Application of Polyacrylamide in surface Irrigated Crops

Gary Bahr and Tim Stieber---Idaho Department of Agriculture and University of Idaho, Coop. Ext. Service, Boise, ID

The benefits of polyacrylamide (PAM) for retaining soil, nutrients, and pesticides was evaluated on three southwest Idaho grower managed fields. SUPERFLOC ^RA836 ³ was applied in the irrigation water during the furrow advance phase of irrigation at 1.0 to 1.25 pounds per acre. Water inflow and outflow rate, furrow advance time, lateral subbing, and sediment content were measured. Water and sediment samples were collected at 15 minutes, 4 h, and 22 h after runoff occurred form the furrows. Sample analysis of nutrients included Kjeldahl N, NO3-N, N02-N, NH3-N, total P, and ortho P. Pesticide analyses included: terbufos, cycloate, EPTC, bromoxynil, chlorpyrifos, oxyfluorfen, and pendimethalin.

PAM application reduced sediment loss from 35 to 99 %, increased infiltration form 7 to 49%, and increased lateral soil wetting by 1 to 13%. Total N and P concentrations leaving the furrows was reduced by over 90% with PAM treatment; ortho P was reduced by 50%. Nitrate-N in runoff water was also reduced through PAM application but average concentrations never exceeded 1.0 ppm.

PAM treatment reduced pesticide concentration in tailwater by 0 to 98% depending on the compound. Concentration of nutrients and pesticides were greatest with initial outflow water and least at the end of the irrigation. Concentration and incidence of pesticides in sediment were greater than in tailwater. PAM application reduced sediment pesticide concentration, although sample collection was limited for some fields.

If PAM applications and irrigation are managed properly there can be significant reductions in sediment loss while preventing significant losses of nutrients and pesticides. Infield crop production benefits appear to be significant while protecting water quality. Grower involvement during trials and field demonstration tours has been important for practice adoption.

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Agriculture Irrigation Polyacrylamide Application Standard

T.L. Spofford and K.L. Pfeiffer---USDA-NRCS, Portland, OR

An interim conservation practice standard was developed by the Natural Resources Conservation Service, in conjunction with the ARS, to address environmental safety concerns of polyacrylamide applications on surface irrigated croplands. This standard establishes criteria for the reduction of irrigation induced erosion from surface irrigation using polyacrylamide materials in quantities that treat the problem and minimize off field impacts. Current research and documentation of site and application information, material effectiveness, and offsite impacts will be used to evaluate, revise and enhance this standard.

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On-Farm Comparison of Polyacrylamide and Straw Mulch on Dry Bean Yield, Irrigation Performance and Erosion

B.A. King, B. Izadi, M.S. Ashraf, R.H. Brooks and W.H. Neibling--Univ. of Idaho, Aberdeen, Univ. of Idaho, Moscow, Univ. of Idaho, Moscow, Univ. of Idaho, Burley and Univ. of Idaho, Twin Falls.

Polyacrylamide (PAM) and straw mulching were evaluated in an on-farm study to obtain site-specific information on erosion control and irrigation performance. The specific objective was to document the potential of Pam under continuous flow furrow irrigation and straw mulch under surge flow furrow irrigation to reduce soil erosion and improve irrigation performance under two slope conditions. A randomized block experimental design consisting of three treatments and six replications was established in a commercial dry bean field on a 0.8% and 1.6% slope. The treatments consisted of conventional continuous flow furrow irrigation (control), continuous flow with liquid PAM injection until runoff began, and straw mulch with surge irrigation. The PAM treatment reduced sediment loss by 78% and the straw treatment reduced sediment loss by 95% compared to the control. Dry bean yield was significantly increased by both treatments at the top and middle of the field on the 1.8% slope and was not significantly increased on the 0.8% slope compared to the control.

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Need for Solution or Exchangeable Calcium and/or Critical EC Level for Flocculation of Clay by Polyacrylamides.

Arthur Wallace and Garn A. Wallace---Wallace Laboratories, El Segundo, CA 90245.

We have frequently observed in our field work that coapplication of gypsum with polyacrylamide leads to increased flocculation of soil. Various techniques have been used in the laboratory to evaluate the possible importance of either or both calcium bridging and solute concentration (EC) on the flocculation process. A calcareous soil of pH over 8 and slightly saline was leached with deionized water to an EC of 0.08 ds/m in the leachate. An acid clay soil of pH near 4 was studied with and without cation neutralization with Ca(OH) ₂. The EC in the systems was varied with gypsum and with NH ₄NO ₃. Polyacrylamides used had around 20, near 2, and near 0 anionic charges. Full flocculation was exceedingly difficult to achieve in the very low solute soils. There may be a two-component effect. Neutralization of the acid soil dramatically increased flocculation. Both gypsum and NH ₄NO ₃were effective in enhancing the flocculation and almost equally. The absolute need for calcium as a bridging agent was not eliminated in the tests, but there were strong indications of the need for minimal EC to obtain most effective flocculation. Only small differences were noted for the polymers of variable charge indicating the importance and function of the amide groups in flocculation and perhaps indicating that calcium bridging is not the main factor in flocculation with these materials.

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Land Treatment Effects on Soil Erosion

J. Kent Mitchell, Chittaranjan Ray---University of Illinois, Ag. Engr. Dept., Illinois State Water Survey, Urbana, Illinois

Small fallow plots (10' x 35') on 3 to 5 percent slopes have been monitored for runoff and sediment yield from natural rainfall. The plot treatments include two levels of polyacrylamides (PAM) applicating grass strip, and a single stiff grass row. Significant differences in runoff and sediment yield have been observed.

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PAM Conformation Effects on Furrow Erosion Mitigation Efficacy

R. D. Lentz, R. E. Sojka---USDA-ARS, Kimberly, Idaho.

Previous experiments have shown that an initial application of 5-10 ppm polyacrylamide, to furrow irrigation water, can substantially reduce sediment loss in treated furrows. Our objective was to determine whether polyacrylamide conformational factors, such as charge type, charge density, and molecular weight (MW) influence PAM's ability to control furrow erosion. Two studies were conducted on a 0.6 ha plot located near Kimberly, Idaho. Soil was Portneuf silt loam (coarse-silty, mixed, mesic, Durixerollic Calciorthid). The study area was planted to field corn in rows spaced at 0.76 m intervals, or beans spaced at 0.56 m. Only wheel track furrows were irrigated. Furrow length was 176 m and slope was 1.5%. Inflow rate was 23 L min ^-1during furrow advance, and 15 L min ^-1for the balance of the irrigation. Polyacrylamides with contrasting charge type (neutral, anionic, cationic)and charge density (0, 8, 19, 35%) were employed in the first study. Polymers were applied at a concentration of 10 ppm during the initial 30 min of each treated irrigation, and a 10 min additional application was introduced every 4 hrs (twice) during the remainder of the irrigation. Only the first and third irrigations were treated. In the second study, anionic PAMs with varying molecular weights (6, 13, 15 million daltons) were applied to irrigation inflows at 10 ppm only during the furrow advance, and all irrigations were treated. Anionic and neutral PAMs were more effective than cationics for erosion control. High to moderate charge density (19-35%) PAMs were more effective than low charge density counterparts. Among anionic PAMs, those having MWs > 12 million daltons controlled erosion slightly more effectively than those of 6 million dalton MW.

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Screening of Polymers to Determine their Potential use in Erosion Control on Construction Sites

Aicardo Roa---Dane County Land Conservation, Madison, WI

Conventional agriculture appears to be decreasing in energy efficiency and have some adverse effects on the environment. Technology that protects the environment is desirable to be tested. Erosion control needs to be addressed in a serious scientific way in order to maintain the level of food production to feed the people. Soil erosion reduces the productive potential of most agricultural lands, and the resulting sediment decreases the utility of receiving waters. Polyacrylamides (PAMs) have been found to have significant capacity of soil binding for highly erodile soils, and therefore, for reducing erosion. PAMs may be used to stabilize critical sites against erosion until such sites can be more permanently stabilized through vegetation. The purpose of this study was to evaluate and demonstrate the use of PAMs on stability of aggregates and the ability to clarify suspended solids from contaminated waters. The first test was based on stability of aggregates and percentage of retention of soil on sieves of different openings. A second test was the settling rates based on the fact that the velocity of sedimentation is a function of the soil particle size. Based upon the laboratory results, five polymers were selected for further study on a commercial test.

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Influence of Structure and Formulation on the Efficacy of Polyacrylamides as Soil Stabilizers

P. Chamberlain* and R. Cole---Allied Colloids Ltd, Bradford, England and Allied Colloids Inc, Suffolk, VA.

Polyacrylamides may reduce soil erosion by a combination of factors including crumb stabilization and flocculation of suspended particles, whilst water infiltration may be influenced by surface stabilization and by the properties of deposited flocs.

The objective of this study was to investigate the influence of PAM's of differing anionic character and molecular weight on some of the above factors.

Laboratory data will be presented for a range of soil types to illustrate the influence of polymer structure on three factors: crumb stability as determined by clay dispersion, speed and completeness of flocculation as determined by clarity tests, and water retention and porosity of soil flocs.

The implications of the above results will be discussed, with particular relevance to current field practice and to development of improved formulations.

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Practical Field Application and PAM Transport in Surface Irrigation

T. D. Stieber and Heidi Chapman-Supkis---University of Idaho

Producers are rapidly adopting PAM technology in southwest Idaho. Some application problems have been encountered and PAM losses in tailwater has been raised as an issue. Application methods were evaluated on eleven fields and PAM tailwater losses were measured on six fields. Analytical procedures for determining PAM concentration in collected samples was adapted to a Hach 2000 spectrophotometer. Calibration curves using standards (r ²= 0.98) were generated for this test. Losses of applied PAM to mud conveyance ditches ranged from 16 to 34 percent while losses in concrete systems were generally less than 5 percent. Lower quarter average application uniformity was 89 percent for liquid and 65 percent for dry application methods. PAM losses in irrigation runoff averaged 5 percent for liquid and 15 percent for dry methods when an advance phase water treatment approach was utilized. Total seasonal PAM losses from five applications (1 lb/acre rate) would range from 0.25 to 0.75 pounds PAM per acre. Irrigation management practices that limit runoff to less than 25 percent of total applied water will greatly reduce losses of sediment, nutrients, and PAM in furrow runoff.

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Effective Viscosity of PAM Solutions Through Porous Media.

J. Letey---University of California Riverside.

Saturated hydraulic conductivity, K, of soils depends on the pore size distribution and the density and viscosity of the solution. PAM solutions can enhance soil flocculation and aggregate stability with a consequent effect of increased pore size and hydraulic conductivity. Laboratory studies revealed that addition of PAM to water increases the effective viscosity of the solution as it flows through porous media and that the effect is of greater magnitude in finer materials. The increased effective viscosity partially offsets the increased pore size effect and should be considered in developing the optimal PAM treatment strategy.

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Net and Tension Infiltration Effects of PAM in Furrow Irrigation

R.E. Sojka*, R.D. Lentz, C.W. Ross and T.J. Trout---USDA-ARS, Northwest Irrigation and Soils Research Laboratory, Kimberly, ID; Landcare New Zealand, Ltd, Palmerston North, New Zealand; USDA-ARS Irrigation Management Research Unit, Fresno, CA

Using polyacrylamide (PAM) following the NRCS conservation practice standard increases net infiltration. PAM prevents detachment, transport, and deposition of soil in furrows. Furthermore, any sediment entrained in the flow is flocculated by PAM and settles to the furrow bottom in loose pervious structures. We hypothesized that depositional surface seals that block pores at the soil water interface are greatly reduced. On Idaho Portneuf silt loams (coarse-silty, mixed, mesic Dirixerollic Calciorthid) net infiltration has generally increased 15%. Net increases on finer textured soils are higher. Research in 1995 utilizing tension-infiltrometry confirmed that PAM's maintenance of open pores to the furrow surface provides the infiltration increase mechanism. Infiltration rates at 40 and 100 mm tension in PAM-treated furrows were roughly double the rates of control furrows. In another study, recirculating infiltrometer data showed a 30% infiltration increase with infiltration inversely related to maximum sediment concentration in the flow.

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Fate of Acrylamide Monomer Following Application of Polyacrylamide to Cropland.

F.W. Barvenik, R.E. Sojka, R.D. Lentz, F.F. Andrawes and L.S. Messner ^---Cytec Industries, Stamford, CT, and USDA-ARS, Kimberly, ID.

Although polyacrylamides (PAMs) exhibit little toxicity and do not degrade to release acrylamide (AMD) monomer, commercial PAMs may contain up to 0.05% residual AMD from manufacturing. PAMs are used in treatment of potable water, wastewater discharging to surface streams, and FDA sanctioned food contact applications. The environmental fate of AMD monomer will be reviewed in this paper. AMD is not adsorbed significantly by soil, and is chemically and biologically labile in natural environments, especially under aerobic conditions. There is no literature evidence of AMD uptake by plants, except for rice grown hydroponically in the presence of extremely high AMD levels. In addition, recent work with field crops showed no uptake. Potatoes, beans, corn and sugar beets, were grown in the presence of very high dosages of PAM, and AMD was analyzed by gas chromatography. AMD was not detected in the crops (detection limit <100 ppb). Reactivity of AMD was demonstrated by spiking studies, in which freshly added AMD rapidly dropped to undetectable levels.

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The Physical Effects of Polyacrylamide on Natural Resources

L.J. Dawson, T.L. Spofford---USDA-NRCS, Madison, WI, USDA-NRCS, Portland, OR

The physical effect polyacrylamide (PAM) has on irrigation induced erosion is very graphic and intuitively a good effect. Less dramatically, polyacrylamide also effects many aspects of the soil, water, and animal resources. Many, but not all effects are desirable.

Through awareness and management, the desirable effects can be accented and the undesirable effects minimized.

By considering if and how PAM can effect potential resource concerns shown on the Conservation Practice Physical Effects matrix developed by the NRCS, awareness can be enhanced in the less intuitive areas.

PAM can have physical effects on 33 natural resources concerns, rarely if ever all at one site, and all at one time.

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Poster Presentations

PAM Spray Effects on Sugarbeet Emergence

G.A. Lehrsch, D.C. Kincaid, and R.D. Lentz---USDA-ARS, Kimberly, ID.

Polyacrylamide (PAM) stabilizes surface soil under furrow irrigation and may also reduce aggregate slaking caused by sprinkler drop impact, thus minimizing crust formation and increasing sugarbeet (Beta vulgaris L.) emergence. We evaluated the effects of a moderately anionic PAM and sprinkler droplet energy on sugar beet emergence in the field. In 404 L of solution ha ¹, rates of 10 and 25 kg PAM ha ¹were sprayed in 25-mm-wide bands over newly planted rows in a Portneuf silt loam (Durixerollic Calciorthid) near Kimberly, ID, on 25 July 1995. A linear-move irrigation system applied water at droplet energies of 5 and 15 J kg ¹to the plots five times. At the above rates, the PAM we studied did not increase sugarbeet emergence. In fact, emergence was greatest, albeit slightly, in plots sprayed with only tap water. Emergence was slightly better (P<0.016) in tap water-treated and control (not treated) plots, 32.8%, than in PAM-treated plots, 29.8%. This finding was likely related to PAM's inability, as applied, to stabilize surface soil aggregates under high droplet energies. When droplet energies increased three-fold, emergence decreased by over 12%. To increase sugarbeet emergence, reduce droplet energy striking the soil surface after planting.

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Demonstration of Polyacrylamide (PAM) to Reduce Erosion on Onions in the Arkansas River Valley of Colorado

J.C. Valliant---Colorado State Univ. Extension, Rocky Ford.

Soil loss due to erosion can be high when onions are furrow-irrigated from 7 to 15 times during the growing season in the Arkansas River Valley of Colorado. Polyacrylamide (PAM) treated irrigation water was applied to onions on three dates in 1995 to reduce soil loss and improve quality of return flow to the river. On the first date, soil loss was reduced 83%, from 477 pounds per acre on the untreated areas to 80 pounds per acre on the PAM-treated areas. This reduction in soil loss was obtained even though the flow rate was increased from 16.5 GPM per furrow on the untreated areas to 29.0 GPM per furrow on PAM-treated areas. On the two other dates, applying 16.5 GPM per furrow on all areas, PAM reduced soil loss 29% and 77%, respectively. Reduction in soil loss on the 1400 foot long field of silty clay loam soil averaged 58.5% on five irrigations indicating a carryover effect of PAM when untreated irrigation water was used on all areas. Total runoff was reduced from 3.7 on the untreated areas to 2.5 inches per acre on the PAM-treated areas indicating a greater lateral movement and/or a higher infiltration rate due to the PAM. Similar onion yields of 628 and 611 sacks (50 pound) per acre were produced on the untreated and PAM-treated areas.

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A printed copy of the proceedings is no longer available. However, each article is now available as a PDF file to be viewed and/or printed. A link to each article is provided at the end of each abstract.

Last updated on 20 June 2002 by Jim Foerster and Lynn Heinemann