Low concentrations of synthetic- or bio-polymers in irrigation water can nearly eliminate sediment, N, ortho- and total-P, DOM, pesticides, micro-organisms, and weed seed from runoff. These environmentally safe polymers are employed in various sensitive uses including food processing, animal feeds, and potable water purification. The most common synthetic polymer is anionic, high purity polyacrylamide (PAM), which typically provides 70-90% contaminant elimination. Excellent results are achieved adding only 10 ppm PAM to irrigation water, applying 1-2 kg ha(-1) per irrigation, costing 4 dollars - 12 dollars kg(-1). Biopolymers are less effective. Using twice or higher concentrations, existing biopolymers are approximately 60% effective as PAM, at 2-3 times the cost. A half million ha of US irrigated land use PAM for erosion control and runoff protection. The practice is spreading rapidly in the US and worldwide. Interest in development of biopolymer surrogates for PAM is high. If the supply of cheap natural gas (raw material for PAM synthesis) diminishes, industries may seek alternative polymers. Also "green" perceptions and preferences favor biopolymers for certain applications.

We measured Escherichia coli, Enterococcus spp. and fecal coliform numbers in soil and on fresh potato skins after addition of solid dairy manure and dairy compost with and without alum (Al(2)(SO(4))(3)) treatment 1, 7, 14, 28, 179 and 297 days after application. The addition of dairy compost or solid dairy manure at rates to meet crop phosphorus uptake did not consistently increase E. coli and Enterococcus spp. and fecal coliform bacteria in the soil. We did not detect E. coli in any soil sample after the first sampling day. Seven, 14, 28, 179 and 297 days after solid dairy waste and compost and alum were applied to soil, alum did not consistently affect Enterococcus spp. and fecal coliform bacteria in the soil. We did not detect E. coli in any soil, fresh potato skin or potato wash-water at 214 days after dairy manure or compost application regardless of alum treatment. Dairy compost or solid dairy manure application to soil at rates to meet crop phosphorus uptake did not consistently increase Enterococcus spp. and fecal coliform numbers in bulk soil. Solid dairy manure application to soil at rates to meet crop phosphorus uptake, increased Enterococcus spp. and fecal coliform numbers in potato rhizosphere soil. However, fresh potato skins had higher Enterococcus spp. and fecal coliform numbers when solid dairy manure was added to soil compared to compost, N and P inorganic fertilizer and N fertilizer treatments. We did not find any E. coli, Enterococcus or total coliform bacteria on the exterior of the tuber, within the peel or within a whole baked potato after microwave cooking for 5 min.

Indigenous soil microorganisms contribute to disease suppression in cropping systems by reducing and competing with pathogen populations, thereby limiting disease severity. Various communities of indigenous microorganisms in any particular soil have adapted to the specific environmental conditions. If the soil around the plant roots could be altered to favor the indigenous soil microorganisms relative to the plant pathogen, the survival and proliferation of indigenous soil microorganisms, and thus effectiveness of biological control, may be increased. Wood chip-polyacrylamide (PAM) cores were used to alter the soil environment in a greenhouse study to favor indigenous soil microorganisms in vegetable and manure compost to reduce Verticillium dahliae infection of potato (Solanum tuberosum L.) plants. Potato plants growing in soils amended with vegetable compost-wood chip-PAM cores had significantly lower visible (V-vis) and isolation (V-iso) V. dahliae infection rates than control soils and soils with dairy or vegetable compvolsst alone. Soils amended with wood chip-PAM-dairy compost cores had significantly lower V-vis and isolation V-iso than control soils and soils with dairy compost. Soils with wood chip-PAM cores and soils with wood chip PAM-vegetable compost had greater microbial biomass/Verticillium dahliae biomass (MB / VB) ratios in soil than control soils or in soils amended with compost alone. MB / VB ratios in wood chip-PAM cores and wood chip-PAM-vegetable compost were greater than in wood chip-PAM-dairy compost cores. V-vis correlated in a quadratic relationship with the MB / VB ratio (r =0.76). As MB / VB ratio increased V-vis decreased. Although field studies with several crops and economic evaluations are necessary, this greenRouse study provides evidence that a wood chip-PAM or wood chip- PAM-vegetable compost soil amendment may be a viable method to control some soil diseases in high value crops.

Animal wastes are a major contributor of nutrients and enteric microorganisms to surface water and ground water. Polyacrylamide (PAM) mixtures are an effective flocculent, and we hypothesized that they would reduce transport of microorganisms in flowing water. After waste water running at 60.0 1 min(-1) flowed over PAM + Al2(SO4)3, or PAM + CaO in furrows, total coliform bacteria (TC) and fecal coliform bacteria (FC) were reduced by 30-50% at 1 and 50 m downstream of the treatments compared to the control. In a column study, PAM + Al2(SO4)3, and PAM + CaO applied to sandy, sandy loam, loam, and clay soils reduced NH4+ and ortho-P concentrations in leachate compared to the source waste water and the control. PAM + Al2(SO4)3 and PAM + CaO applied to sandy, sandy loam and loam soils reduced both total and ortho-P, concentrations in leachate compared to he source wastewater and control treatment. In a field study, PAM + Al2(SO4)3, or PAM + CaO treatments did not consistently reduce NH4+, NO3-, ortho-P, and total P concentrations in wastewater flowing over any soil compared to inflow wastewater or the control treatment. With proper application PAM + Al2(SO4)3 and PAM + CaO may be able to reduce the numbers of enteric bacteria in slowly flowing wastewater running off animal confinement areas, reducing the amount of pollutants entering surface water and groundwater.

Pollution of surface flow and groundwater from animal waste application to soils has been well 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 and fecal coliforms 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 and fecal coliforms in surface flow, soil, and soil water. Total coliforms in surface flow did not differ when waste was applied to soil, regardless of PAM treatment or days since waste was applied. Total coliforms in surface flow decreased by tenfold over the 7 days after waste regardless of PAM treatment. Fecal coliforms in surface flow decreased by tenfold over the 7 days after waste application and one hundredfold over the 28 days after waste application regardless of PAM treatment. Total coliforms 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 coliforms 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 coliforms in soil were greater in the o to 5 and 5 to 15 cm soil depths when waste was applied to soil, regardless of soil PAM treatment. Fecal coliforms 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 coliforms 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 or fecal coliforms in soils or water.

Irrigation-induced erosion contributes to elevated sediment and nutrient concentrations in irrigation return flow water. Polyacrylamide (PAM). is an effective flocculent widely used to reduced soil erosion. We hypothesized PAM would reduce transport of sediment and nutrients in surface irrigation water flowing over soil. We measured nutrients in irrigation inflow and runoff water and total and extractable nutrients in sediment transported from agricultural fields. Treatments were:(1) PAM application and no PAM (control), (2) three flow rates (7.5, 15:0, and 22.5 L min(-1)), (3) distance along the furrow (1 m below the inflow point and 40 m down furrow), and (4) time during irrigation (0.5, 3.5, and 6.5 h after initial inflow). After irrigation water flowed 40 m, water flowing in furrows receiving PAM treatments reduced the NO3-concentration in runoff by 85% and the total P concentration in water by 90% compared to runoff water in furrows without PAM, regardless of flow rate. Mass export of NH4+, NO3-, dissolved reactive phosphorus (DRP), total P, K, Ca, Mg, Fe, Mn, Cu, B, and Zn in untreated irrigation runoff water increased as the flow rate increased from 7.5 to 22.5 L min(-1). Export of these nutrients, via sediment carried by untreated irrigation runoff water, increased from 2 to 5 fold as the flow rate increased from 7.5 to 22.5 L min(-1). After water flowed 40 m, transport of these extractable nutrients was reduced from 10 to 40 fold in PAM-treated furrows. With proper application, PAM reduces nutrient loss from furrow-irrigated agricultural fields, protecting surface water and groundwater quality.

Increasing the amount of C in soils may be one method to reduce the concentration of CO2 in the atmosphere. We measured organic C stored in southern Idaho soils having long term cropping histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation‐chisel‐tilled crops (ICT), and irrigated pasture systems (IP). The CO2 emitted as a result of fertilizer production, farm operations, and CO2 lost via dissolved carbonate in irrigation water, over a 30‐yr period, was included. Net organic C in ecosystems decreased in the order IP > ICT > NSB > IMP. In this study, if NSB were converted to IMP, 0.15 g C m−2 would be emitted to the atmosphere, but if converted to IP 3.56 g C m−2 could be sequestered. If IMP land were converted to ICT, 0.95 g C m−2 could be sequestered in soil and if converted to IP 3.71 g C m−2 could be sequestered. There are 2.6 × 108 ha of land worldwide presently irrigated. If irrigated agriculture were expanded 10% and the same amount of rainfed land were converted back to native grassland, an increase of 3.4 × 109 Mg C (5.9% of the total C emitted in the next 30 yr) could potentially be sequestered. The total projected release of CO2 is 5.7 × 1010 Mg C worldwide during the next 30 yr. Converting rainfed agriculture back to native vegetation while modestly increasing areas in irrigated agriculture could have a significant impact on CO2 atmospheric concentrations while maintaining or increasing food production.

The majority of plants have mycorrhizal fungi associated with them. Mycorrhizal fungi are ecologically significant because they form relationships in and on the roots of a host plant in a symbiotic association. The host plant provides the fungus with soluble carbon sources, and the fungus provides the host plant with an increased capacity to absorb water and nutrients from the soil. Adverse conditions are a pervasive feature in both natural and agronomic soils. The soil environment is constantly changing with regard to moisture, temperature and nutrient availability. In addition, soil properties are often manipulated to improve crop yields. In many cases, soils may be contaminated through disposal of chemicals that are toxic to plants and microorganisms. The formation and function of mycorrhizal relationships are affected by edaphic conditions such as soil composition, moisture, temperature, pH, cation exchange capacity, and also by anthropogenic stressors including soil compaction, metals and pesticides. Arbuscular mycorrhizal fungi are of interest for their reported roles in alleviation of diverse soil-associated plant stressors, including those induced by metals and polychlorinated aliphatic and phenolic pollutants. Much mycorrhizal research has investigated the impact of extremes in water, temperature, pH and inorganic nutrient availability on mycorrhizal formation and nutrient acquisition. Evaluation of the efficacy of plant–mycorrhizal associations to remediate soils contaminated with toxic materials deserves increased attention. Before the full potential benefits of arbuscular mycorrhizal fungi to reclaim contaminated soils can be realized, research advances are needed to improve our understanding of the physiology of mycorrhizae subjected to adverse physical and chemical conditions. This paper will review literature and discuss the implications of soil contamination on formation and function of arbuscular mycorrhizal associations.

Waste streams associated with a variety of agricultural runoff sources are major contributors of nutrients, pesticides and enteric microorganisms to surface and,round waters. Water soluble anionic polyacrylamide (PAM) was found to be a highly effective erosion-preventing and infiltration-enhancing polymer, when applied at rates of 1-10 g m(-3) in furrow irrigation water. Water flowing from PAM treated irrigation furrows show large reductions in sediment, nutrients and pesticides. Recently PAM and PAM + CaO and PAM + Al(SO4)(3) mixtures have been shown to filter bacteria, fungi and nutrients from animal wastewater. Low concentrations of PAM [175-350 a PAM ha(-1) as PAM or as PAM + CaO and PAM + Al(SO4) mixture] applied to the soil surface, resulted in dramatic decreases (10 fold) of total, coliform and fecal streptococci bacteria in cattle, fish and swine wastewater leachate and surface runoff. PAM treatment also filtered significant amounts of NH4, PO4 and total P in cattle and swine wastewater. This points to the potential of developing PAM as a water quality protection measure in combination with large-scale animal feeding operations. Potential benefits of PAM treatment of animal facility waste streams include: (1) low cost, (2) easy and quick application, (3) suitability for use with other pollution reduction techniques. Research on the efficacy of PAM for removal of protozoan parasites and viruses and more thorough assessment of PAM degradation in different soils is still needed to completely evaluate PAM treatment as an effective waste water treatment. We will present analysis and feasibility of using PAM, PAM + Al(SO4)(3), and PAM + CaO application for specific applications. Our results demonstrate their potential efficacy in reducing sediment, nutrients and microorganisms from animal production Facility effluents. Published by Elsevier Science Ltd.

Large-scale deposition of animal manure can result in contamination of surface and ground water and in potential transfer of disease-causing enteric bacteria to animals or humans. We measured total coliform bacteria (TC), fecal coliform bacteria (FC), NO3, NH4, total P, and PO4 in ground water flowing from basalt and sand aquifers, in wells into basalt and sand aquifers, in irrigation water, and in river water. Samples were collected monthly for 1 yr. Total coliform and FC numbers were always higher in irrigation water than in ground water, indicating that soil and sediment filtered most of these bacteria before they entered the aquifers. Total coliform and FC numbers in ground water were generally higher in the faster flowing basalt aquifer than in the sand aquifer, indicating that the slower flow and finer grain size may filter more TC and FC bacteria from water. At least one coliform bacterium/100 mL of water was found in ground water from both basalt and sand aquifers, indicating that ground water pumped from these aquifers is not necessarily safe for human consumption according to the American Public Health Association and the USEPA. The NO3 concentrations were usually higher in water flowing from the sand aquifer than in water flowing from the basalt aquifer or in perched water tables in the basalt aquifer. The PO4 concentrations were usually higher in water flowing from the basalt aquifer than in water flowing from the sand aquifer. The main concern is fecal contamination of these aquifers and health consequences that may arise from human consumption.

Animal wastes are a major contributor of nutrients and enteric microorganisms to surface and ground water. Since polyacrylamide (PAM) is an effective flocculent, we hypothesized it would reduce transport of microorganisms in flowing water. We measured total coliform bacteria (TC) and fecal coliform bacteria (FC) in water flowing at 15.5 1 min(-1) in furrows over 9.91 cattle, fish or swine manure and then (PAM)+Al(SO4)(3) or PAM+CaO. After water flowed over manure and then PAM+Al(SO4)(3), or PAM+CaO, TC and FC were reduced by 0.5 to 1000 fold in water flowing 1 and 27 in downstream of the treatments compared to the control treatment. PAM+Al(SO4)(3) and PAM+CaO should be able to reduce the numbers of enteric bacteria in animal wastewater running off animal confinement areas, reducing the bacteria entering surface and ground waters.

Swine (Sus scrofa) wastewater was applied to three separate 4 m wide x 30 m long riparian filterstrips consisting of 20 m grass and 10 m forest, 10 m grass and 20 m forest, and 10 m grass and ttl m maidencane (Panicum hemitomon Schult,) in Southern Georgia during each season. Total and fecal coliform numbers in the applied wastewater pulse did not decline as water moved downslope regardless of vegetation type or season. The pulse of applied wastewater did not move beyond 15 m in any treatment in autumn or summer (dry seasons) and only moved beyond 7.5 m in the 20 m grass-10 m forest treatment in the summer. Total and fetal coliform numbers in soil water and shallow ground water declined by approximately 10-Fold every 7 d for the First 14 d regardless of vegetative treatment or season. Soil temperature and soil moisture correlated with total coliform bacteria in both 1.5 m wells (r(2) = 0.89) and 2.0 m wells (r(2) = 0.89), and with fecal coliform bacteria in 1.5 (r(2) = 0.82) and 2.0 m (r(2) = 0.76) wells. Animal production operations may need to locate in warm-dry climates so animal waste can be applied to lands to help ensure enteric bacteria input to surface and ground water will not occur.

Despite the ability of aquifers to filter bacteria in wastewater, application rates exceeding the land's capacity to adsorb enteric microorganisms may result in contamination of water resources. We measured total coliform(TC) and fecal coliform bacteria (FC) in groundwater flowing from basalt and sand aquifers in wells into aquifers, irrigation water and river water monthly for one year. TC and FC numbers were higher in irrigation water than groundwater indicating that soil and sediment filtered most of these bacteria before it entered the aquifers. TC and FC numbers in groundwater were generally, but not always higher in the faster flowing basalt aquifer than the sand aquifer. At least one coliform bacteria was found in groundwater from both basalt and sand aquifers showing that groundwater is not necessarily safe for human consumption. FC bacteria were several fold lower in groundwater than river water showing that groundwater is safer than surface water.

Polyacrylamide (PAM) use in irrigation for erosion control has increased water infiltration and reduced soil erosion. This has improved runoff water quality via lower concentrations of nitrogen, phosphorous, and pesticides, and decreased biological oxygen demand. Since non-toxic high molecular weight anionic PAMs removed clay size sediment particles in flowing water, we hypothesized that PAM would effectively remove or immobilize microorganisms in flowing water. In an agricultural field, we determined the efficacy of PAM-treatment of furrow irrigation water to remove several categories of microorganisms 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 times during each irrigation. After water traveled 1 m at 7.5 and 15.5 l min(-1), PAM-treatment reduced total bacterial and microbial biomass and total fungal biomass relative to the control treatment. After water traveled 40 m at 7.5, 15.5, and 22.5 l min(-1), PAM-treatment reduced algae, the numbers active and total bacteria, active and total fungal length, and total bacterial biomass, total fungal and microbial biomass relative to the control treatment. Although specific organisms were not identified or monitored in this study, the results clearly have implications for controlling the spread of soil-borne plant pathogens and other classes of harmful organisms within and among fields via irrigation water and in re-utilized return flows. Beyond furrow-irrigated agriculture, new methods to manage overland transmission of harmful microorganisms could potentially help control transport of pathogens from animal waste in runoff and groundwater.

The lack of consistent success of biological control of soilborne plant pathogens may be due to the introduction of the organism into a foreign environment. We hypothesized that wood chip-polyacrylamide (PAM) cores surrounding host plant roots could alter the soil environment to favour growth of introduced biocontrol microorganisms, thereby reducing Verticillium dahliae infection of potato ( Solanum tuberosum L.) in a greenhouse. A 7cm diameter 2 15cm deep hole (core) was drilled in the center of a 20 2 30cm deep pot (1.9 kg) containing soil infested with V. dahliae inoculum. Cores were then filled with wood chip-PAM-biocontrol organism mixtures. Soils that had Streptomyces lydicus inoculated into wood chip-PAM cores had lower levels of V. dahliae symptoms ( V vis ) and V. dahliae isolations ( V iso ) than all other treatments in three soils. V vis and V iso on plants growing in soils amended with S. lydicus or Pseudomona corrugata inoculated into the soil itself (without wood chip-PAM cores) did not differ from soils that were unamended with these biocontrol organisms. V. dahliae biomass was lower in wood chip-PAM cores inoculated with S. lydicus than control or wood chip-PAM cores without biocontrol bacteria. Soils with wood chip-PAM cores inoculated with S. lydicus or P. corrugata generally had higher microbial biomass/ V. dahliae biomass (MB/VB) ratios than control soils, or soils with S. lydicus or P. corrugata inoculated into the soil. Wood chipPAM cores alone and wood chip-PAM cores inoculated with S. lydicus had higher MB/VB ratios than wood chip-PAM cores inoculated with P. corrugata . V vis and V iso were curvilinearly correlated with the MB/VB ratios in negative relationships, respectively (r 2 = 0.68, r 2 = 0.68). As the MB/VB ratio increased, V vis and V iso decreased. Although field studies and economic evaluations are necessary, amending soil with wood chips-PAM and a biocontrol bacterium may be a valuable method to increase the effectiveness of biocontrol organisms.

Microcosms were used to determine the influence of N additions on active bacterial and active fungal biomass, cellulose degradation and lignin degradation at 5, 10 and 15 weeks in soils from blackwater and redwater wetlands in the northern Florida panhandle. Blackwater streams contain a high dissolved organic C concentration which imparts a dark color to the water and contain low concentrations of nutrients. Redwater streams contain high concentrations of suspended clays and inorganic nutrients, such as N and P, compared to blackwater streams. Active bacterial and fungal biomass was determined by direct microscopy; cellulose and lignin degradation were measured radiometrically. The experimental design was a randomized block. Treatments were: soil type (blackwater or redwater forested wetlands) and N additions (soils amended with the equivalent of 0, 200 or 400 kg N ha –1 as NH 4 NO 3 ). Redwater soils contained higher concentrations of C, total N, P, K, Ca, Mn, Fe, B and Zn than blackwater soils. After N addition and 15 weeks of incubation, the active bacterial biomass in redwater soils was lower than in blackwater soils; the active bacterial biomass in blackwater soils was lower when 400 kg N ha –1 , but not when 200 kg N ha –1 , was added. The active fungal biomass in blackwater soils was higher when 400 kg N ha –1 , but not when 200 kg N ha –1 , was added. The active fungal biomass in redwater wetland soils was lower when 200 kg N ha –1 , but not when 400 kg N ha –1 , was added. Cellulose and lignin degradation was higher in redwater than in blackwater soils. After 10 and 15 weeks of incubation, the addition of 200 or 400 kg N as NH 4 NO 3 ha –1 decreased cellulose and lignin degradation in both wetland soils to similar levels. This study indicated that the addition of N may slow organic matter degradation and nutrient mineralization, thereby creating deficiencies of other plant-essential nutrients in wetland forest soils.

Polyacrylamide (PAM) is an effective flocculent and we hypothesized that it would reduce transport of microorganisms and nutrients in water flowing over and through soil. We measured nutrients, total coliform bacteria, fecal coliform bacteria, fecal streptococci, active and total fungi, and active and total bacteria in eater leached through cattle, fish, and swine manure, PAM, PAM + Al(SO4)(3), or PAM + CaO mixtures, and 25-cm sand columns. In the laboratory study, PAM, PAM + At(SO4)(3), and PAM + CaO treatments reduced total coliform bacteria, fetal coliform bacteria, and fecal streptococci by 10-to 1000-fold in water leached through sand columns. Polyacrylamide + Al(SO4)(3) and PAM + CaO treatments reduced the concentration of NH4, total P, and PO4 by 20 to 60% in leachate when cattle and swine manure were applied. In a field study, after water flowed over all three manure sources and then PAM, PAM + AI(SO4)(3), or PAM + CaO in furrows, total coliform bacteria, fecal coliform bacteria, and fecal streptococci were reduced by 10- to 1000-fold in water flowing 1 and 27 m downstream of the treatments compared with the control treatment. When mater flowed over rattle manure and then PAM + Al(SO4)(3) or PAM + CaO, PO, concentration was reduced by 50 to 70% and total P concentration was reduced by 0 to 75% in water 27 m downstream of the treatments compared with the PAM atone treatment. Polyacrylamide + Al(SO4)(3) and PAM + CaO should be able to reduce the numbers of enteric microorganisms and nutrient concentration in animal wastewater running off animal confinement areas, reducing the amount of these pollutants entering surface and ground waters.

Survival of total and fecal coliform bacteria was measured in the 0 to 5,5 to 15, and 15 to 30 cm soil depths at 1, 3, 7, 14, and 90 to 120 d after swine (Sus scrofa) wastewater application to riparian filterstrips in southern Georgia during each season of the year. Vegetative treatments evaluated were: (i) 20 m grass-10 m forest, (ii) 10 m grass-20 m forest, and (iii) 10 m grass-20 m maidencane (Panicum hemitomon Schult.). During winter, spring, and summer vegetation type in riparian filterstrips did not affect survival of total and fecal coliform bacteria. Total and fecal coliform bacterial numbers were usually higher in the top 0 to 5 cm of soil than in the 5 to 15 and 15 to 30 cm soil depths in all treatments. Total and fecal coliform numbers in the 0 to 5, 5 to 15, and 15 to 30 cm depths declined approximately 10-fold every 7 to 14 d after waste application in all seasons of the year. At 90 to 120 d after waste application, total and fecal coliform numbers in the three soil depths did not differ from riparian filterstrips that did not have animal waste applied. Total coliform bacteria in the 0 to 5, 5 to 15, and 15 to 30 cm soil depths correlated with temperature and moisture in a curvilinear relationship (r(2) = 0.80 , 0.77, and 0.64, respectively). Fecal coliform bacteria in 0 to 5, 6 to 15, and 16 to 30 cm of soil also correlated with temperature and moisture in a curvilinear relationship (r(2) = 0.56, 0.53, and 0.53, respectively).

Polyacrylamide (PAM) has been available commercially since 1995 for reducing irrigation-induced erosion and enhancing infiltration. The first series of practical field tests was conducted in 1991. PAM used for erosion control is a large water soluble (non-crosslinked) anionic molecule (12-15 megagrams per mole) containing < 0.05% acrylamide monomer, In controlled field studies PAM eliminated, on average, 94% (80-99% range) of sediment loss in field runoff from furrow irrigation, with a typical 15-50% relative infiltration increase on medium to fine textured soils compared to untreated controls. Similar but less dramatic results have been seen with sprinkler irrigation. Under some conditions infiltration is unchanged or can even be slightly reduced, e.g. in sandy soils or where PAM application rates are very high. Results are achieved with per irrigation field application rates of about I kg per hectare, for furrow irrigation, and 2 to 4 kg per hectare for sprinkler irrigation. Cost of PAM is $7 to $13 per kg. Seasonal application totals vary from 3 to 7 kg per hectare. Farmer field sediment control has been around 80% of test plot results. Substantial runoff reductions have been documented for nutrients, pesticides, microorganisms, BOD, and weed seed. No adverse effects have been seen for soil microbial populations. Crop yields have not been widely documented, though evidence exists for yield increases related to infiltration improvement. High effectiveness, low cost, and case of application, compared to traditional conservation measures, has resulted in rapid technology acceptance in the US and internationally. PAM-use for runoff water quality protection is one of the most potent new irrigation environmental technologies in the market place. New uses in construction and dryland erosion control are being developed rapidly. This paper discusses new insights and understanding of PAM-use and potential for future developments.