Effects Of Wastewater Irrigation Research Articles

Effects of wastewater irrigation on soil sodicity and nutrient leaching in calcareous soils

Soil column studies were conducted with two soils to assess the effects of irrigation with wastewater on soil and groundwater quality. Upon the application of wastewater, exchange occurred between solution sodium (Na +) and exchangeable cations (Ca 2+, Mg 2+, K +), whereby these cations were released into solution. The average exchangeable sodium percentage (ESP) of the soils increased during leaching from 9 to 21 and 28.8 to 29.7 after applying 5.0 and 3.5 l (about 7 and 6 pore volumes) of wastewater to the soils columns, respectively. Adverse effect of high Na + concentration in the wastewater on raising ESP was less pronounced in the soil having initial high ESP than in the soil with low initial ESP. Salinity of the soils was also increased with the application of wastewater and Mg 2+ and K + were leached from the soils. These losses would be more severe on soils having a low cation exchange capacity and if, uncorrected could lead eventually to their deficiencies for plant growth. When the soil columns were leached with distilled water the flow rate of one soil decreased to zero after 2.2 pore volume indicating damage to soil structure. Irrigation with wastewater, which is generally more sodic and saline than regional groundwater, increases the rate of soil sodification of shallow groundwater. A relatively simple chromatographic model was used to estimate final ESP profiles in the soils assuming the condition of local equilibrium. This approach had a limited success for one of the soil. Since the final leached concentrations are in good agreement with those of wastewater, we attribute these differences to non-uniform flow through the column. In terms of practical soil and water management, our study reveals that relatively simple means can be useful to predict the water quality in soils, their discharge to ground water, and the hazard of soil structure deterioration.

Long term effect of wastewater irrigation of forage crops on soil and plant quality parameters

In this study, sites irrigated with wastewater for 10, 5, and 2 years and site not irrigated were sampled for soil and plant chemical analysis to evaluate its long term effect. Long term wastewater irrigation increased salts, organic matter and plant nutrients in the soil. Soil pH was not consistently affected. Soil Cu was not affected by wastewater application while Zn, Fe and Mn was not consistently affected. Wastewater irrigation had no significant effect on soil heavy metals (Pb and Cd) regardless of duration of wastewater irrigation. The barley biomass increased with added wastewater and nutrients provided with the wastewater. However, longer period of wastewater application (10 years) resulted in lower biomass production but remained higher than that of the control plants. Plant essential nutrients (Total-N, NO 3, P, and K) were higher in plants grown in soils irrigated with wastewater. Plant Cu, Zn, Fe, Mn increased with 2 years of wastewater irrigation, then reduced with longer period. Plant Pb and Cd increased with wastewater irrigation and their levels were higher the longer the period of wastewater irrigation. Based on these results, it can be concluded that proper management of wastewater irrigation and periodic monitoring of soil and plant quality parameters are required to ensure successful, safe, long-term wastewater irrigation.

Effect of irrigation water quality on organic matter, Cd and Cu mobility in soils of central Mexico

Untreated wastewater has been used for irrigation since 1912 at the Irrigation District 03, Central Mexico. Accumulated heavy metals are dominantly bound to the organic soil fraction. In a field study we evaluated the effect of wastewater irrigation on the quality of soil organic matter and the amount of water extractable Cu and Cd. In a column experiment we tested if water treatment affects the leaching of both metals and dissolved organic carbon (DOC) out of soils that have been irrigated for more than 90 years with untreated wastewater. The field study shows that long term irrigation increases the mineralizable carbon fraction and the DOC concentrations. The water extractable Cu and Cd concentrations also increase and correlate with DOC. In the column leachates the Cu concentrations also correlate with DOC, the Cd concentrations correlate with the sum of cations, chloride and DOC concentrations. Water treatment reduced Cd leaching, but it did have no substantial effect on Cu leaching.

Effects of Treated Wastewater Effluent Irrigation on Terrestrial Salamanders

Since 1983, State Game Lands 176 in Centre Co.,Pennsylvania, U.S.A., has been spray irrigated withtreated wastewater effluent as an alternative to thedirect discharge of treated effluent into surfacewaters. Although the effects of wastewater irrigationon birds and mammals had been studied, its effects onamphibians were unknown. We examined the physiological and behavioral responses of juvenile Jefferson salamanders (Ambystoma jeffersonianum Green) to effluent-irrigated soils and wastewater effluent in the field and laboratory to assess the effects of wastewater irrigation on the terrestrial phase of this species. Salamanders confined to irrigated soils for 35 d showed no difference in six physiological parameters (growth, body water concentration, and body sodium, potassium, calcium, and magnesium levels) compared to those enclosed on unirrigated soils. Salamanders on wastewater effluentsoaked substrates for the same duration in thelaboratory had higher body sodium concentration thanthose on deionized water soaked substrates, likely dueto elevated sodium levels in wastewater effluent.Salamanders demonstrated no `preference' for irrigatedor unirrigated soils over three days when allowed achoice between the two substrates in behavioral tests. These results suggest wastewater effluent irrigationis not acutely toxic to terrestrial A.jeffersonianum under natural conditions. Long-termadverse effects wastewater irrigation on terrestrialJefferson salamanders are still possible, andexaminations of salamander growth and survival overlonger durations are needed to assess the holisticimpacts of wastewater spraying on this species.

The effects of wastewater irrigation on groundwater quality in Mexico

The main aim of this research was to determine the environmental effects of wastewater irrigation on the subsurface at two locations in Mexico; Leon and the Mezquital Valley. Freshly-drilled subsurface sediment samples (both sites) and groundwater samples (Mezquital Valley) were taken at various depths. These were analysed for a range of physico-chemical and microbiological parameters using standard methods. Elevated concentrations of faecal and total coliforms were recorded at both sites indicating that faecal bacteria had been transported through the subsurface. The level of subsurface contamination was affected by both spatial and temporal factors with higher coliform concentrations occurring at shallower depths (<10 m below the surface) and at the top of the water table, and during the wet season. Elevated nitrate concentrations were found in all of the Mezquital Valley groundwaters. Thus, wastewater irrigation appears to have had a negative impact on groundwater quality. In order to mitigate this, treatment of wastewater prior to irrigation and careful irrigation management is recommended. The potential effects of groundwater degradation on public health, and the need for guidelines to protect groundwater quality, are discussed.

WASTE WATER IRRIGATION AND N AND P FERTILISATION ON HCN AND NO, CONTENT OF FODDER

A field experiment was conducted to study the effect of waste water irrigation. and graded levels of N and P fertilisation on hydrogen cyanide (ICN) and nitrate NO, contents of fodder sorghum var. co.27. The HCN and NO, contents were high in waste water irrigated fodder and the highest value was registered with cattle shed wash. Application of N increased and that of P decreased these toxic components in fodder. As crop growth advanced, a decrease in HCN and NO, contents were observed. The trends observed suggest that a delayed harvest of the fodder would certainly prove more safe.

The effects of wastewater irrigation on groundwater quality in Mexico

The main aim of this research was to determine the environmental effects of wastewater irrigation on the subsurface at two locations in Mexico; Leon and the Mezquital Valley. Freshly-drilled subsurface sediment samples (both sites) and groundwater samples (Mezquital Valley) were taken at various depths. These were analysed for a range of physico-chemical and microbiological parameters using standard methods. Elevated concentrations of faecal and total conforms were recorded at both sites indicating that faecal bacteria had been transported through the subsurface. The level of subsurface contamination was affected by both spatial and temporal factors with higher conform concentrations occurring at shallower depths (<10 m below the surface) and at the top of the water table, and during the wet season. Elevated nitrate concentrations were found in all of the Mezquital Valley groundwaters. Thus, wastewater irrigation appears to have had a negative impact on groundwater quality. In order to mitigate this, treatment of wastewater prior to irrigation and careful irrigation management is recommended. The potential effects of groundwater degradation on public health, and the need for guidelines to protect groundwater quality, are discussed.

EVALUATING DRAINAGE DESIGN PARAMETERS FOR WASTEWATER IRRIGATION APPLICATIONS TO MINIMIZE IMPACT ON SURFACE WATERS

DRAINMOD, an agricultural water management computer model, was used to evaluate the hydrology for anirrigation scenario for an Ohio community using treated wastewater as the water supply. This model was used to simulatethe runoff potential of the proposed site under drainage and wastewater irrigation, to evaluate subsurface drainagesystem design parameters and irrigation interval, and to evaluate the effect of wastewater irrigation on potential cropyield. Constituent concentrations of the wastewater were within normal recommendations for agricultural irrigation, andwere not the focus of the study. A 40-year climatic record and USDA Soils5 data were used as inputs to the model toevaluate hydrologic response over a range of input values of irrigation rate and interval, and drain spacing and depth.Simulation results indicate that an irrigation interval of 1 or 2 days could meet the annual irrigation application criteriaof 67 cm (26 in.). Frequency analysis of runoff over the 40-year period for the 2-day irrigation interval revealed thatapproximately 99% of all days produced zero runoff. A response surface of average annual irrigation depth for the 2-dayirrigation interval indicated that the target depth of 67 cm could be attained with a range of drain spacing (7.5 to 12.5 m;25 to 50 ft) and depth (85 to 150 cm; 33 to 60 in.) combinations. Within the range of drain spacing and depths evaluatedwith wastewater irrigation at the 2-day irrigation interval, relative crop yield increased when an increase in drain depthwas coupled with a decrease in drain spacing.

Influence of Pulp and Paper Mill Wastewater on Chrysomela scripta (Coleoptera: Chrysomelidae) Performance and Populus Plant Traits

The effect of wastewater irrigation on resistance of poplar trees to the cottonwood leaf beetle, Chrysomela scripta F., was investigated. Five Populus clones were tested in a greenhouse for their effects on the survival, fresh pupal weight, and development time (from egg to adult) of the cottonwood leaf beetle when they were irrigated with either wastewater or freshwater. Foliar concentrations of nitrogen, mineral elements (P, Mn, Mg, Ca, Na, K), phenolic glycosides, and leaf toughness also were measured to understand the potential mechanisms of resistance to the cottonwood leaf beetle. C. scripta performance was negatively affected by irrigation with wastewater; both survival and pupal weight were reduced. Performance also varied among clones and was the worst on Populus fremontii Watson variety wislenzensii , a native species. Leaf toughness and foliar N level were not affected by the irrigation treatment and were not correlated with larval growth and survival. Among minerals, foliar concentrations of sodium increased with wastewater irrigation, and were related negatively to pupal weights. Foliar magnesium also was influenced by the irrigation treatment but it was not correlated with C. scripta performance. Manganese varied with clone, but not with the type of water used for irrigation, and was correlated negatively with survival and related positively to development time. Differences in phenolic glycosides were observed between treatments and among clones, but there were no detectable relationships between phenolic glycosides and C. scripta performance.

Monitoring of groundwater in Gabal el Asfar wastewater irrigated area (Greater Cairo)

In arid to semi-arid countries water scarcity on a national level is seemingly contradicted by the local occurrence of sometimes large amounts of domestic wastewater. Consequently, in many countries this wastewater is considered as an additional source of water, particularly for irrigation purposes. The government of Egypt is planning to use wastewater in land reclamation in many areas on the Eastern and Western fringes of the Nile Valley and Delta. A preliminary survey on the effects of wastewater irrigation was carried out by the Research Institute for Groundwater (RIGW) in the Gabal el Asfar area (Greater Cairo) in 1990-1991. A general framework of reuse of sewage effluent for irrigation in Egypt was discussed. The hydrogeological setting of the Gabal el Asfar area, the groundwater flow system and the thickness of the unsaturated zone were described. The impact on groundwater quality from sewage effluent irrigation has been assessed and the migration of pollution was evaluated. The main objective of the present study is to analyze and explain changes in groundwater quality between 1991 and 1994. The study is executed within the framework of the Environmental Management Groundwater Resources project.

Effect of wastewater irrigation on mineral com‐position of corn and sorghum plants in a pot experiment

Abstract Effect of wastewater irrigation was investigated on mineral composition of corn and sorghum plants in a pot experiment. The ranges for the concentration of different minerals in corn plants were 0.67–0.89% calcium (Ca), 0.38–0.58% magnesium (Mg), 0.09–1.29% sodium (Na), 0.81–1.87% nitrogen (N), 1.81–2.27% potassium (K), 0.12–0.16% phosphorus (P), 190–257 mg/kg iron (Fe), 3.5–5.6 mg/kg copper (Cu), 37.1–44.5 mg/kg manganese (Mn), 21.6–33.6 mg/kg zinc (Zn), 1.40–1.84 mg/kg molydbenum (Mo), 11.0–45.7 mg/kg lead (Pb), and 2.5–10.8 mg/kg nickel (Ni). Whereas for sorghum plants, the ranges were: 0.56–0.68% Ca, 0.19–0.32% Mg, 0.02–0.27% Na, 0.69–1.53% N, 1.40–1.89% K, 0.10–0.14% P, 190–320 mg/kg Fe, 3.8–6.0 mg/kg Cu, 29.2–37.6 mg/kg Mn, 21.1–29.9 mg/kg Zn, 2.2–3.7 mg/kg Mo, 12.3–59.0 mg/kg Pb, and 2.5–15.2 mg/kg Ni. Heavy metals such as cobalt (Co) and cadmium (Cd) were below detection limits at mg/kg levels. The concentrations of Ca, N, K, P, Cu, and Mn in corn plants were in the deficient range except...

Monitoring of groundwater in Gabal El Asfar wastewater irrigated area (Greater Cairo)

In arid to semi-arid countries water scarcity on a national level is seemingly contradicted by the local occurrence of sometimes large amounts of domestic wastewater. Consequently, in many countries this wastewater is considered as an additional source of water, particularly for irrigation purposes. The government of Egypt is planning to use wastewater in land reclamation in many areas on the Eastern and Western fringes of the Nile Valley and Delta.A preliminary survey on the effects of wastewater irrigation was carried out by the Research Institute for Groundwater (RIGW) in the Gabal el Asfar area (Greater Cairo) in 1990–1991. A general framework of reuse of sewage effluent for irrigation in Egypt was discussed. The hydrogeological setting of the Gabal el Asfar area, the groundwater flow system and the thickness of the unsaturated zone were described. The impact on groundwater quality from sewage effluent irrigation has been assessed and the migration of pollution was evaluated.The main objective of the present study is to analyze and explain changes in groundwater quality between 1991 and 1994. The study is executed within the framework of the Environmental Management Groundwater Resources project.

Changes in Infiltration and Drainage during Wastewater Irrigation of a Highly Permeable Soil

AbstractThe effects of wastewater irrigation on hydraulic properties of a highly permeable, volcanic‐ash soil are presented. Ponded infiltration rate, water content, and drainage were measured by the instantaneous profile technique in a 5‐m3, 2.3 m deep isolated soil monolith. This was done both before and after 32 mo of irrigation with secondary‐treated wastewater. Irrigation then continued for a further 4 mo. After 8 mo of no irrigation, a third set of measurements was made. Ponded infiltration rate decreased by 50% from 8.3 × 10−5 to 4.1 × 10−5 m s−1 after 32 mo of wastewater irrigation. A further decrease to 1.7 × 10−5 m s−1 was found 1 yr later. Three years of wastewater irrigation resulted in a 25‐mm decrease in the amount of water stored by the soil to a depth of 2.3 m after 20 d of drainage. This decrease was mainly at depths less than 1 m and may be due to restricted wetting of the soil. An identical decrease was found in the amount of water that drained from the soil during these 20 d. However, the water content at depth 0.1 m after 20 d of drainage was increased by 0.1 m3 m−3. This increase in water content and the concomitant decrease in infiltration rate appear to be caused by clogging of soil pores.

Effects of wastewater irrigation of pastures on the health of farm animals and humans

Wastewater recycling and reuse through agricultural irrigation can provide an economical means of preventing pollution of surface water sources, while conserving water resources and valuable nutrients for increased crop production and grazing pastures. With proper methods of wastewater treatment, health risks to farmers and farm animals as well as to the public who consume agricultural produce can be prevented. The possibility of transmission of the beef tapeworm Taenia saginata, Salmonella sp. and Mycobacteria sp. to farm animals grazing on wastewater-irrigated pasture is evaluated. While such transmission is possible when raw, untreated wastewater is used for irrigation, the risk is greatly reduced and essentially eliminated with effluent treated to meet the new World Health Organisation (WHO) recommended microbial guidelines for effluent. These guidelines call for one or less helminth eggs per litre and a mean of 1,000 faecal coliform bacteria per 100 ml. In warm climates and where land is available, one of the most economical methods of achieving this standard is the use of multi-cell stabilisation ponds designed for a 25-day detention period. In colder climates and where land is a limiting factor of wastewater treatment, conventional secondary biological treatment followed by disinfection can also be applied to meet this standard.

Community Structure and Composition of Breeding and Wintering Birds in a Wastewater-Irrigated Oak Forest

We compared avian community structure and composition between 4 forested sites irrigated with wastewater (chlorinated sewage effluent) and 4 nonirrigated forested sites in central Pennsylvania during 1 breeding season and 2 winters. Compared to nonirrigated sites, irrigated sites had higher densities of all species combined and higher species richness (S) in the breeding season and in the winters. In the breeding season, 9 species were significantly (P < 0.05) more abundant on irrigated sites, whereas only 1 species was more abundant on nonirrigated sites. In winter, 4 species were more abundant on irrigated sites, but none was more abundant on nonirrigated sites. Because irrigation resulted in dense herbaceous growth, species that foraged or nested in vegetation near (<3 m) ground level were particularly abundant on irrigated sites. We conclude that community structure and composition of breeding and wintering avifauna were not negatively affected by wastewater irrigation, but breeding populations of species that forage or nest in leaf litter may be affected negatively by irrigation. J. WILDL. MANAGE. 54(3):493-500 Approximately 22 of 2,000 municipal sewage systems in the United States that apply treated wastewater directly on land do so in forests (W. E. Sopper, pers. commun.; Urie 1986). But this practice is expected to increase as small, localized facilities are needed in nonagricultural areas, on steeply sloping terrains, or where crop irrigation is not necessary (Nutter and Red 1986). Application of wastewater to land is attractive for several reasons (Sopper 1968); but irrigation of forest habitats, in particular, results in higher soil infiltration rates, less runoff and erosion, lower land acquisition costs, and fewer potential human health risks than irrigation of agricultural lands (U.S. Environ. Prot. Agency 1981, Burd 1986). Changes to forests irrigated with wastewater have been well-documented. Wastewater application alters the structure and species composition of forest understory plants, abundance of invertebrates, and occurrence of fruit-producing vegetation (Sopper and Kardos 1973, Lewis 1977, Mastrota et al. 1989). Thus, irrigation directly affects the resources (e.g., nesting sites, food, or cover) available to forest birds. Yet little is known about the effects of wastewater irrigation on community structure and omposition of forest birds (Rollfinke 1988). Three previous studies of breeding avian communities associated with wastewater irrigation (Savidge and Davis 1971, Snider 1974, Lewis and Samson 1981) were conducted on sma l forested plots within The Pennsylvania State University's (PSU) Wastewater Renovation System with irregular or partial-year irriga ion schedules (Rollfinke 1988). The PSU system was expanded from 40 to 200 ha and began using a year-round irrigation schedule in 1983. We compared community structure and composition of breeding and wintering birds on irrigated and nonirrigated forested sites after the expansion of this irrigation system. ' Present address: Friends School, 5114 N. Charles Street, Baltimore, MD 21210. This content downloaded from 207.46.13.120 on Wed, 14 Sep 2016 04:56:46 UTC All use subject to http://about.jstor.org/terms 494 IRRIGATED FORESTS * Rollfinke and Yahner J. Wildl. Manage. 54(3):1990 We thank E. D. Bellis and J. A. Kurland for comments on the manuscript. Our research was supported by the Pennsylvania Agriculture Experiment Station and the Max McGraw Wildlife Foundation.

Vesicular-arbuscular mycorrhizae in a wastewater-irrigated oldfield ecosystem in Michigan

The incidence of vesicular-arbuscular mycorrhizae (VAM) in wastewater irrigated and non-irrigated oldfield soils in Michigan was studied. Soil and root samples were taken monthly from field plots on the second and third years of consecutive irrigation with municipal wastewater at rates of 0, 5 and 10 cm wk−1. The oldfield ecosystem contained a high VAM fungal spore population density, but low species diversity. The most common VAM fungal species were Glomus mosseae and G. fasciculatum. Both spore density and root colonization were higher in irrigated than in non-irrigated plots. Irrigation effects were largest early in the growing season. In addition to increasing VAM incidence, wastewater irrigation shifted VAM fungal species composition. Irrigation favored G. mosseae over G. fasciculatum. Bioassays using either Sorghum vulgare or Daucus carota, an oldfield native species, indicated that the VAM systems were still functioning after the third year of consecutive wastewater irrigation. The data from experiments using nutrient solutions at wastewater concentrations suggest that the effects of wastewater irrigation on VAM are due to the effects of both water and nutrients. Since VAM are a very important component of the plant's water and nutrient uptake system and equally important in structuring plant communities under limiting growth conditions, it is suggested that the stimulatory effect of wastewater irrigation on VAM in an oldfield ecosystem enhances the ecosystem's ability to function as a living filter for wastewater clean up.

SALINITY AND ALFALFA YIELD UNDER EFFLUENT IRRIGATION IN SOUTHWESTERN SASKATCHEWAN

The effect of wastewater irrigation on soil salinity and crop yield was determined in a study at Swift Current, Saskatchewan. A toposequence consisting of the Orthic Regosol series, Calcareous Brown series, Orthic Brown series and Cumulic Orthic Brown series of the Birsay Association was seeded to alfalfa and irrigated with effluent from a secondary sewage lagoon. Since the applied effluent had a mean EC of 2.6 dS/m, soil salinization was a major concern. For 8 yr the four soils were sampled for salinity to a depth of 150 cm each fall. During the 8-yr period, alfalfa was sampled for dry matter yield twice each year from each soil. The results indicate that irrigation by 10–15% more than the normal recommended application rate (i.e., when low saline surface water is used for irrigation) will ensure sufficient leaching to maintain salt content in the root zone at a level not deleterious to plant growth. After 8 yr of effluent irrigation, new steady state salinity profiles were developed in the Orthic Regosol, Calcareous Brown and Orthic Brown series. At this steady state condition the salt contents in the upper 60 cm of the root zone in these three soil series were generally similar. They increased from the initial low ECe value of 0.6 dS/m to 2.5 dS/m. Salinity increased with depth toward the bottom of the root zone where the Orthic Brown series had an ECe value of 4.0 dS/m, while the Orthic Regosol and Calcareous Brown series had values of 6.0 dS/m. Effluent irrigation resulted in a small net reduction of salts in the 150-cm profile of the Orthic Regosol and the Calcareous Brown series, but caused an increase of salts in the Orthic Brown profile. In the Cumulic Orthic Brown series the salt content throughout the profile increased continually from a very low initial level, and had not reached a steady state condition after 8 yr of irrigation. The development of a high water table in this area resulted in salt movement into the root zone of the Cumulic Orthic Brown series that was distinctly higher than those of the other three series and caused alfalfa yields to decline from being highest at the start of this study to only about 80% of yields on the Orthic Brown series at the end. The observed yield reductions emphasize the importance of having adequate drainage to effect salt removal by leaching when crops are irrigated with saline sewage effluent. Key words: Wastewater irrigation, soil salinity, alfalfa yield

Effects of Wastewater Irrigation and Plant and Row Spacing on Soybean Yield and Development1

AbstractConsiderable research has demonstrated that soybean [Glycine max (L.) Merr.] yields can be increased with the addition of supplemental water during reproductive stages, but little information is available concerning the use of municipal wastewater as the water source. Variables included in this field study were: three water regimes‐municipal wastewater, well water and no water; two row spacings‐51 and 76 cm; two in‐row spacings‐20 and 32 plants/m and two cultivars‐Nebsoy and Harcor. Soybeans planted on a Miami silt loam soil (fine‐loamy, mixed, mesic Typic Hapludalf) received a total of 9.8 cm of wastewater or well water as overhead spray irrigation in 1979 and 9.4 cm in 1980. Data were collected on seed yield, agronomic characteristics, dry matter production, leaf photosynthesis, and leaf chemical analysis. Seed yields were significantly different for water treatments in 1979 with 2,430, 2,580, and 2,790 kg ha−1 for no water, well water and wastewater, respectively. Yields generally increased as plant population increased with the greatest yield for both cultivars occurring at the highest plant population (645,500 plants ha−1). Irrigated plants were 4 to 5 cm taller, matured 5 to 6 days later, had larger seeds and lodge slightly more than nonirrigated plants. The two cultivars responded differently to the wastewater, with Harcor exhibiting a better response than Nebsoy. The 1980 growing season was wetter than normal and there was little or no yield response to irrigation. Under the conditions of soil type, climate and wastewater quality found during this experiment, wastewater was generally superior to well water in increasing yields.

Effect of Waste Water Irrigation and Leaching Percentage on Soil and Ground Water Chemistry

AbstractIrrigation with sewage waste water for six seasons produced greater salinity under alfalfa (Medicago sativa L.) than under reed canary grass (Phalaris arundinacea L.) or fallow. Irrigation rates were designed to produce high and low leaching percentages (LP). The high irrigation rate (I2) was double the low irrigation rate (I1). Leaching percentages were estimated from the soluble Na concentration at the 90‐ to 150‐cm depth of the soil profile. At the 90‐ to 150‐cm depth of the soil profile, Na reached a steady state for the conditions of the irrigation season by the fall of each year in the first 2 crop years and by the end of the second irrigation season in the last 4 crop years. At the water table depth (2–4 m), Cl in the ground water was close to an annual steady‐state concentration by the end of each irrigation season in the first 2 crop years and by the end of the second irrigation season in the last 4 crop years. Sodium and Ca + Mg approached equilibrium during the final 3 crop years.High LPs (&gt;34%) in the first 2 years reduced original salinity levels [electrical conductivity (EC) 3.99 to &lt;1.39 mmhos/cm]. When irrigation rates were reduced in the last 4 years, salinity increased, but the salt levels were well below those (EC &lt;2.13 mmhos/cm) that would significantly reduce crop yield.Ground water calculations at low LP (&lt;10%) showed that EC and sodium adsorption ratio (SAR) values were high, but CaCO3 precipitation was balanced by gypsum dissolution. By comparison, at high LPs (&gt;15%) the EC and SAR values were low, but there was a potential danger of a large net transfer of salt to ground water because of gypsum dissolution.

STATUS OF INORGANIC PHOSPHORUS IN SOILS IRRIGATED WITH MUNICIPAL WASTEWATER1

A cooperative study was conducted with Pennsylvania State University to assess the effects of wastewater irrigation on the status of soil phosphorus. The major objectives of the research were to evaluate the influence of wastewater irrigation on changes in soil organic carbon, nitrogen, and phosphorus and the sorption of orthophosphate (P). Soil samples were obtained in 1974 and 1975 from Hublersburg silty clay loam cropped to corn (Zea mays L.), Reed canarygrass (Phalaris arundinaceae L.), or a mixed forest and from a Morrison sandy loam with a mixed forest stand. The sites had been irrigated with secondary effluent for 11 to 12 years. Soil analyses indicated that the majority of phosphorus added to soils during wastewater irrigation remained in the upper 30 cm of the Hublersburg clay loam soil. In contrast, appreciable amounts of P had leached to the 30 to 60-cm depth in the Morrison sandy loam. The equilibrium phosphate concentration (EPC) increased markedly at the 0 to 15-cm depth as a result of wastewater irrigation, due to sorption of P added in the wastewater. As expected, the maximum P sorption capacity of soils was decreased by wastewater irrigation. A comparison of soluble P levels in leachate samples collected in the field at a 120-cm depth with soluble P predicted by EPC measurements indicated that laboratory measurements overestimate the ability of a soil to remove P from wastewater. Thus, wastewater may not interact with all potentially available P sorption sites in soils. The EPC and P sorption capacity of soils irrigated with wastewater was reduced by extracting soils with oxalate and citrate-dithionite-bicarbonate. These results indicated the significance of hydrous iron oxides in P retention by soils irrigated with wastewater.