Header with SAWC Logo Header middle image Conservation & environmental management
July 04, 2008
SEARCH
HOME CONTACT US JOIN SITE INDEX
Home » Journal of Soil and Water Conservation » Abstracts and Archives » Sept-Oct 2003
Sept-Oct 2003

Journal Logo
September - October 2003: Volume 58, Number 5

Table of Contents

Features

  • The unintentional secret
    By Brian K. Richards, Natalia Peranginangin, Tammo S. Steenhuis, and Larry D. Geohring

Research

Special Research Section – Polyacrylamides (PAM)

Departments

Incorporating economics into the phosphorus index: An application to U.S. watersheds
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R.C. Johansson and J.R. Randall
ABSTRACT: Discharge of excess nutrients into surface water by agricultural production is a significant source of water pollution throughout the United States. A number of mechanisms can be used by policymakers to identify regions for initial abatement programs. One targeting mechanism that is commonly used is the phosphorus index, or P index. This paper develops the concept of an economic P index—one that incorporates into the conventional P index heterogeneous agricultural net returns across watersheds to better target abatement policies for agricultural phosphorus discharge. Using national-level data for phosphorus transport factors, source factors, and net returns, we find that targeting watersheds using an economic P index improves the potential cost-effectiveness of phosphorus abatement efforts by as much as 50% when compared with a conventional P index. Assuming average abatement costs vary in the same direction and magnitude as do agricultural net returns relative to phosphorus discharge potentials, targeting regions using an economic P index in coordination with a conventional P index reduces by more than 60 percent potential average costs of abatement.

Keywords: Nonpoint source pollution, phosphorus index, watershed management

back to top

Nutrient removal by grass components of vegetated buffer systems receiving swine lagoon effluent
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R.K. Hubbard, G.L Newton, and G. J. Gascho
ABSTRACT: Information is needed on nutrient removal mechanisms in vegetated buffer systems to assist in the design of these long-term nutrient removal systems. We determined nutrient removal by grass portions of grass-forest buffer systems receiving swine lagoon wastewater. Cuttings were made at three positions within buffers of coastal Bermuda grass (Cynondon dactylon L.) (Tifton 78) for three years. Wastewater was applied weekly at two rates. The first rate averaged 800 kg N ha-1 yr-1 (714 lb N ac-1 yr-1), 215 kg P ha-1 yr-1 (192 lb P ac-1 yr-1), and 1030 kg K ha-1 yr-1 (920 lb K ac-1 yr-1), and the second rate furnished twice these amounts. Grass buffers 20 m (65.6 ft) in length removed 44% of the nitrogen (N), 19% of the phosphorus (P), and 23% of the kjeldahl (K) as grass biomass from the lesser wastewater application rate. Nutrient removal via uptake (percentage of applied) dropped by a factor of 1.6 when wastewater was applied at the greater rate. Overall, the study showed that while nutrient uptake into the grass biomass accounts for a portion of the nutrient removal in grass-forest buffer systems, the nutrient concentrations in surface runoff and subsurface water exiting these systems as reported previously (Hubbard et al., 1998b), imply that other factors (denitrification, forest uptake, and adsorption) play a greater role in the nutrient assimilation and filtering commonly associated with grass-forest buffer systems. The information on biomass production and nutrient removal by coastal Bermuda grass receiving wastewater in a lower landscape position is important for producers who want to utilize the wastewater nutrients and produce forage on an under-utilized portion of the landscape.

Keywords: Animal wastes, coastal Bermuda grass, nutrient removal, vegetated buffer systems, water quality

back to top

Native warm-season grass establishment on spotted knapweed-infested gravel mine spoils
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

N.W. MacDonald, M.T. Koetje, and B.J. Perry
Abstract: We studied the establishment of native warm-season grasses on gravel mine spoils infested by spotted knapweed (Centaurea maculosa), an exotic perennial that is difficult to control on droughty, infertile sites. We applied factorial combinations of sewage sludge (0 and 11.9 Mg ha-1 [5.3 tons ac-1]) and herbicide (none; 2,4-D; and glyphosate) to evaluate their effects on native grass establishment and on competition between native grasses and spotted knapweed. While native grasses were successfully established with all treatment combinations, sludge application reduced their densities. Warm-season grass biomass subsequently increased rapidly on both sludge and control plots. Both herbicide treatments reduced density and biomass of knapweed during the first two years of the study, but glyphosate and sludge interacted to produce increased knapweed biomass during the third year. For this reason, it may be desirable to delay application of sludge amendments until warm-season grasses are well established in herbicide-treated areas. The response of knapweed to improved soil fertility was dependent on the degree of grass competition, and where this remained high, knapweed dominance was suppressed. While warm-season grasses appeared to compete successfully with spotted knapweed, additional control measures may be required to maintain grass dominance on this and similar knapweed-infested sites.

Keywords: Centaurea maculosa, droughty soils, gravel mines, herbicides, land reclamation, sewage sludge, spotted knapweed, warm-season grasses

back to top

No-till spring cereal cropping systems reduce wind erosion susceptibility in the wheat/fallow region of the Pacific Northwest
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)
M.E. Thorne, F.L. Young, W.L. Pan, R. Bafus, and J.R. Alldredge.

ABSTRACT: The dust-mulch fallow phase of winter wheat (Triticum aestivum L.) production in low-rainfall areas of the Columbia Plateau leaves the soil surface loose-structured and exposed to erosion during high winds common to the region, and is a major source of airborne particulate matter. The objective of this research is to evaluate no-till spring cropping as an alternative to traditional winter wheat/dust-mulch fallow in reducing wind erosion susceptibility. Surface residue cover, random roughness, and crop canopy coverage were measured during a 3-year transition period from winter wheat/fallow to no-till spring cereals. These measurements were applied to soil loss ratio models as indices of wind erosion susceptibility. No-till spring cereal rotations reduced erosion susceptibility compared with winter wheat/fallow by maintaining soil cover during spring and fall when erosion is high. Crop canopy cover reduced erosion susceptibility after fall seeding in winter wheat/fallow and after no-till spring seeding. This research indicates that no-till spring cropping would significantly reduce wind erosion in winter wheat/fallow areas.

Keywords: Annual cropping, crop residue cover, random roughness, soil loss ratio

back to top

Tillage impacts on soil property, runoff, and soil loss variations from a Rhodic Paleudult under simulated rainfall
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

C. Truman, W. Reeves, J. Shaw, A. Motta, C. Burmester, R. Raper, and E. Schwab
ABSTRACT: The highly erodible soils of the Tennessee River Valley in northern Alabama have been intensively cropped to cotton (Gossypium hirsutum L.), a low-residue crop, and traditionally managed under conventional tillage practices. Conservation tillage systems have potential as management tools for crop production in this region because they tend to reduce soil loss, to build up organic matter, and to conserve plant available water. Because of changes in tillage (type and timing) and subsequent residue amounts remaining, we evaluated rainfall partitioning and soil loss from a Decatur silt loam (Rhodic Paleudult) cropped to cotton and managed under conventional-till (CT) and no-till systems in November 1999 and June 2000. No-till treatments were evaluated with and without fall paratilling and rye (Secale cerale L.) cover (C, NC). Four tillage-residue treatments evaluated were conventional tillage (fall disk and chisel, spring disk and field cultivated) without paratilling and without cover, no-till without paratilling and without cover, no-till without paratilling and with cover, and no-till with paratill and with cover. Plots

(1 m2) were established on each tillage-residue treatment and exposed to simulated rainfall

(50 mm h-1 for 2 h). For November 1999, runoff was greatest for non-paratilled no-till plots, whereas for June 2000, conventional-till plots had the greatest runoff. For both dates, no-till /paratill/rye plots had 34% to tenfold less runoff than from other tillage systems, while conventional-till plots had 1.5 to 5.4-fold times more soil loss than from other tillage systems. Paratilling influenced runoff and soil loss more so than surface cover. Paratilling no-till plots reduced runoff by at least 67% in November 1999 (13 months after paratilling) and at least 215% in June 2000 (8 months after paratilling) compared with non-paratilled no-till plots. Sediment from no-till /paratill/rye plots decreased by at least threefold in June 2000 compared with that for November 1999. The worst-case scenario evaluated was the conventional-till treatment. The best-case scenario was the no-till /paratill/rye treatment. No-till /paratill/rye plots averaged 11% and 49% more infiltration than conventional-till plots in November 1999 and June 2000, respectively, whereas conventional-till plots averaged 1.8 and 8.7 times more soil loss than no-till /paratill/rye plots, respectively, for the same two dates. No-till coupled with fall paratilling and a rye cover is the best system to increase infiltration and plant available water and reduce runoff and soil loss for the Tennessee Valley region.

Keywords: Conservation tillage, infiltration, paratill, simulated rainfall

back to top

Polyacrylamide quantification methods in soil conservation studies
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

J. Lu and L. Wu
ABSTRACT: Polyacrylamide (PAM) application in soil conservation has gained rapid acceptance in recent years. Determination of PAM concentration in waters containing soil constitutes (defined as soil waters in this paper)—such as runoff water, irrigation tail water, and soil solution and PAM content in soil matrix is important for improving PAM application efficiency, understanding PAM conditioning depth, and assessing PAM’s fate in the environment. Methods for quantifying PAM concentration in soil waters should be sensitive and reliable at low concentrations (0.1 to 10 mg L-1, or 0.1 to 10 ppm) and invulnerable to interferences from dissolved salts and organic matter. There are about 11 groups of PAM analytical methods in literature. In this article we discuss and review the principles, lower detection limits, major interferences, advantages, and limitations of these methods. The N-bromination method (a PAM analytical technique based on spectrophotometry) is satisfactory for quantification of polyacrylamide in both soil waters and organic-matter-removed soil.

Keywords: Quantification, soil water, substrate-borne polyacrylamide, water-borne polyacrylamide

back to top

Polyacrylamide for coliform bacteria removal from agricultural wastewater
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R. Spackman, J.A. Entry, R.E. Sojka, and J.W. Ellsworth
ABSTRACT: Pollution of surface flow and groundwater from animal waste application to soils has been documented. Polyacrylamide (PAM) has reduced total coliform (TC) and fecal coliform (FC) bacteria in animal waste water flowing in irrigation furrows. We measured efficacy of PAM dissolved in water and as a “patch” application to soil to remove total coliform and fecal coliform from: 1) water flowing over dairy waste in furrow-irrigated, ungrazed forage production systems; 2) soil water after it flowed through 1 m of soil; and 3) influence of PAM on survival of total coliform and fecal coliform in surface flow, soil, and soil water. Total coliform in surface flow did not differ when waste was applied to soil, regardless of PAM treatment or days since waste was applied. Total coliform in surface flow decreased by tenfold over the 7 days after waste regardless of PAM treatment. Fecal coliform in surface flow decreased by 10-fold over the 7 days after waste application and one hundredfold over the 28 days after waste application regardless of PAM treatment. Total coliform in soil decreased by tenfold over the 7 days after waste was applied, one hundredfold over the 28 days after waste was applied and one thousandfold over the 63 days after waste was applied, regardless of PAM treatment or soil depth. Total coliform did not differ in control soils and soils receiving waste, regardless of soil depth or PAM treatment over the 28 and 63 days after dairy waste was applied. Fecal coliform in soil was greater in the 0 to 5 and 5 to 15 cm soil depths when waste was applied to soil, regardless of soil PAM treatment. Fecal coliform in all three soil depths decreased as much as one thousandfold over the 28 and 63 days after waste and PAM treatments were applied. In all treatments, except the waste application x PAM patch treatment, total coliform in soil water showed a tenfold decrease over the 28 and 63 days after waste was applied. PAM may not provide additional protection to surface water from waste applied to ungrazed forage production systems, but the compound does not enhance survival of total coliform or fecal coliform in soils or water.

Keywords: Anionic polyacrylamide, dairy waste, fecal coliforms, furrow irrigation runoff, soil water, total coliforms

back to top

Using polyacrylamide with sprinkler irrigation to improve infiltration
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

D.L. Bjorneberg, F.L. Santos, N.S. Castanheira, O.C. Martins, J.L. Reis, J.K. Aase, and R.E. Sojka

ABSTRACT: Center-pivot irrigation systems often apply water at rates greater than the soil infiltration rate. Applying high molecular weight, water-soluble, anionic polyacrylamide (PAM) to the soil can improve infiltration and reduce soil erosion The objective of this study was to determine whether single and multiple PAM applications with sprinkler irrigation improved infiltration under field conditions. A two-year study conducted near Kimberly, Idaho, used a solid-set sprinkler system, and a one-year study conducted in Monte dos Alhos near Alvalade do Sado, Portugal, used a center pivot. At Kimberly, applying PAM with four irrigations (total applied PAM was 2.1 kg ha-1 in 2000 and 3.0 kg ha-1 in 2001) significantly reduced total measured runoff, from 5.9 mm (2000) and 9.2 mm (2001) for the control to 2.0 and 2.1 mm. Total measured soil erosion was also reduced from 52 and 34 kg ha-1 for the control to 21 and 5 kg ha-1 for the multiple PAM treatment. Applying similar or greater amounts of PAM with a single irrigation reduced erosion, but not runoff, compared with the control. In the Monte dos Alhos study, runoff was reduced by applying a total of 0.3 kg PAM ha-1 with a single irrigation (43 mm runoff) or three irrigations (65 mm runoff) compared with the control (111 mm runoff). Measured soil erosion was not significantly different among treatments. Applying PAM with multiple irrigations extended its effectiveness as long as the application rate was great enough to adequately stabilize the soil surface during the first irrigation.

Keywords: Center pivot, erosion, PAM, runoff, sprinkler irrigation

back to top

Inhibiting water infiltration with polyacrylamide and surfactants: Applications for irrigated agriculture
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R.D. Lentz

ABSTRACT: Efficiencies of surface irrigation systems are often limited by infiltration conditions. Treatments that decrease infiltration into unlined canals, reservoirs, and the inflow end of furrows relative to outflow ends would reduce seepage losses and improve application uniformity. Several laboratory studies evaluated effects of high molecular weight (10 to 15 Mg mol-1), water-soluble, anionic polyacrylamide (PAM), alone and combined with anionic surfactants, on the hydraulic conductivity (KSAT) of soils. Dry soils were treated with one or two treatment solutions and subjected to conditions that simulated those in an irrigation furrow or pond. The KSAT of soil packed in columns was measured with a constant head apparatus for 19 hours. PAM treatment concentrations > 125 mg L-1 applied to dry soils preceding flooding reduced KSAT by 25%, and a 10 mg-L-1 PAM + 29 k-mg-L-1 sodium-lauryl-sulfate surfactant application reduced KSAT by 70%, relative to controls. Miniflume tests then applied the treatments only to the inflow end of the mini-furrows. The 125 and 250 mg L-1 PAM treatments significantly improved water application uniformity: Cumulative infiltration was reduced in the upper half of miniflume furrows and increased in the lower, relative to controls. When applied to dry soils and allowed to dry overnight, as may be done when treating irrigation ponds, the 1,000 mg L-1 PAM solution reduced KSAT by 60% to > 90% in silt loam and clay loam soils. Either the single or combination treatments could potentially be used to increase the uniformity of furrow water applications and reduce seepage from unlined irrigation ponds and canals.

Keywords: Furrow irrigation, infiltration, irrigation uniformity, PAM, polyacrylamide, sealing

back to top

Using polyacrylamide to control erosion on agricultural and disturbed soils in rainfed areas
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

D.C. Flanagan, L.D. Norton, J.R. Peterson, and K. Chaudhari

ABSTRACT: Use of anionic polyacrylamide (PAM) as an erosion control soil amendment has been studied at the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), National Soil Erosion Research Lab since the early 1990s. An initial field experiment in Indiana using simulated rainfall on a sloping silt loam soil found that 20 kg ha-1 of PAM could reduce sediment loss by more than 60% from the first storm event from an agricultural silt loam soil, as well as provide control from rill detachment for inflows of water up to 60 L min-1. More recent studies have examined use of PAM on areas prone to excessive erosion (highway embankments, landfill caps, etc.) to provide control while vegetation is being established. A simulated rainfall study found that 80 kg ha-1 PAM application on a 3:1 silt loam soil embankment reduced runoff by 86% and soil loss by 99% in a severe storm event (69 mm h-1 for 1 hour) on initially dry soil. The PAM continued to be effective at controlling runoff and soil loss through a series of simulated rainfall applications, reducing runoff by an average of 40% and soil loss by an average of 83% over the entire experiment. Two associated natural rainfall studies found similar erosion control benefits, as well as improved vegetation establishment. Polyacrylamide at 80 kg ha-1 was also found to be effective at preventing earthen channel erosion and degradation on a preformed trapezoidal channel at a 1% slope at inflows of water up to 760 L min-1. Application of PAM as a liquid spray that is allowed to dry on the soil surface is more effective than an application of dry PAM granules for immediate erosion control. Recent laboratory experiments have been targeted toward determining the optimal rates of PAM to control rill erosion and minimize cost.

Keywords: PAM, polyacrylamide, soil amendments, soil erosion control

back to top

Polyacrylamide and straw residue effects on irrigation furrow erosion and infiltration
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R.D. Lentz and D.L. Bjorneberg

ABSTRACT: Water-soluble anionic polyacrylamide (PAM) is a highly effective erosion deterrent in furrow irrigation, but little is known about the effect of plant residues on PAM efficacy. We hypothesized that increasing plant residue in irrigation furrows may alter PAM’s ability to control erosion. Furrows with 10 g m-1 (485 kg ha-1) on treated area and 30 g m-1 (1490 kg ha-1) wheat straw applications, irrigated with PAM or untreated water, and conventionally irrigated furrows (no PAM and no straw) were used. Five irrigations were monitored on a field with 1.5% slope and silt loam soil (Durinodic Xeric Haplocalcids). PAM was applied as a granular patch at the furrow inflow end (33 g or 1 kg active ingredient ha-1). Compared to controls, individual straw and PAM+straw treatments reduced sediment loss in all irrigations by 64% to 100%, but increased infiltration (1.3x to 2.5x) only for irrigation one, when furrows were fresh. Adding more straw to low straw (with or without PAM) treatments increased average sediment loss reduction from 86% to 94% in the first two irrigations, but provided no extra benefit in subsequent irrigations (relative to controls). Adding PAM to low and high straw treatments increased average sediment loss reduction from 80% to 100% in the first two irrigations, and from 94% to 99.8% in subsequent irrigations. Combining plant residue and PAM in furrows produced greater erosion control and larger infiltration enhancements than with straw alone. An important additional benefit of PAM is that it greatly reduced detachment, transport, and redistribution of residue in furrows, which helped prevent furrow blockage and attendant overflow problems, allowing farmers to use conservation tillage in furrow irrigated fields.

Keywords: Erosion, furrow irrigation, infiltration, sediment discharge, straw residue

back to top

Weed seed transport and weed establishment as affected by Polyacrylamide in furrow-irrigated corn
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

R.E. Sojka, D.W. Morishita, J.A. Foerster, and M.J. Wille

ABSTRACT: Polyacrylamide (PAM) has been used successfully to reduce erosion and increase infiltration on nearly a half million hectares of United States irrigated farmland. PAM is a potent and environmentally safe flocculent that greatly accelerates separation of suspended solids from water. It also improves particle cohesion, stabilizing soil structure. We hypothesized that in irrigation furrows, PAM prevents loss of weed seed and might affect weed establishment and management practices. We grew corn (Zea mays L.) in plots without herbicides, or that were treated with either Eradicane® (EPTC + dichlormid) or Dual® II (S-Metolachlor) and irrigated in furrows that had either no PAM, or that were treated either with 10 g m-3 (10 kg ML-1 or 10 ppm) dissolved PAM during water advance, or with PAM applied as a powder patch at the furrow head. As in previous studies, erosion was greatly reduced with PAM and infiltration was increased. PAM use also reduced runoff loss of weed seeds (barnyardgrass, kochia, redroot pigweed, common lambsquarters, and hairy nightshade) 62% to 90%. Interactions of herbicide treatments and PAM on erosion, infiltration, and weed seed loss were related to the mulching effect of weed vegetation. PAM is an effective and environmentally safe means of reducing weed seed distribution in furrow irrigation water while simultaneously reducing erosion and increasing infiltration in weed-free crop production.

Keywords: Dichlormid, EPTC, erosion, infiltration, metolachlor, return flows, runoff, seed bank, surface flow, water quality

back to top

Scanning electron micrographs of polyacrylamide-treated soil in irrigation furrows
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 5)

C.W. Ross, R.E. Sojka, and J.A. Foerster
ABSTRACT: Polyacrylamide (PAM) is used at rates of 1 to 2 kg ha-1 per irrigation on a half million hectares of United States irrigated farmland to prevent 94% of irrigation-induced erosion and to enhance infiltration by 15% to 50% on medium to fine-textured soils. The polyacrylamides used for this application are large (12 to 15 megagrams per mole), water-soluble anion molecules applied in the irrigation stream. Erosion prevention has been shown to result from stabilized soil structure in the 1 to 5 mm veneer of surface soil that regulates infiltration, runoff, and sediment loss on water application. We hypothesized that this could be confirmed from scanning electron micrographs (SEMs) of PAM-treated soil. Both untreated and PAM-treated soils form surface seals in irrigation furrows, but the stable surface structure of PAM-treated furrows is more pervious. This is thought to result from a greater number of continuous unblocked pores at the soil-water interface. SEMs of PAM-treated and untreated soil microstructures are presented from thin surface samples of Portneuf silt loam, collected from furrows immediately following an irrigation, and freeze-dried. SEMs of PAM-treated soil showed net or web-like microstructural surface coatings about 1 mm thick on soil mineral particles, giving a glue-like porous appearance. Individual strands of PAM were about 0.2 mm in diameter. Strands of PAM aggregated the soil by ensnaring and bridging mineral particles while untreated soil had poorly aggregated, unconnected particles. Thus, microstructural differences between PAM-treated and untreated soil from irrigation furrows were consistent with erosion and infiltration results.

Keywords: Irrigation-induced erosion, polyacrylamide, scanning electron microscopy, soil microstructure
Privacy Feedback Print Friendly Top
© 2004-2008 Soil and Water Conservation Society
All Rights Reserved.
945 SW Ankeny Road
Ankeny, Iowa 50023
P 515-289-2331
F 515-289-1227

Powered by SiteViz