Microbial biomass activity of a sodic Lixisol reclaimed with gypsum and clean water irrigation in urban vegetable systems of Burkina Faso

Background

Little is known about the effects of gypsum application to remediate saline–sodic soils in the tropics and the role of microbial indicators in soil reclamation.

Aims

Our study aimed at (1) remediating a highly weathered, irrigated sodic Lixisol under prolonged urban crop production by clean water and gypsum application and (2) to determine the remediation effects on soil microbial indices.

Methods

A three-factorial on-farm experiment with maize (Zea mays L.) was used to study effects on soil microbial biomass of (1) soil degradation at two levels of salinity, (2) irrigation with clean water and wastewater, and (3) the impact of added gypsum during a typical growing season.

Results

At the high-degradation site, the 0.5 M K₂SO₄ extractable carbon (C) content was 40% higher than at the low-degradation site. In addition, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were 20% lower than at the low-degradation site, while fungal ergosterol was even 40% lower, leading to a 33% lower ergosterol/MBC ratio. Wastewater irrigation increased MBN but decreased ergosterol content at the low-degradation site while having no effect at the high-degradation site. Gypsum amendment led to higher MBN at the low-degradation site but to lower MBN at the high-degradation site. Gypsum amendment always increased the ergosterol content whereby this increase was stronger at the low-degradation site, especially in combination with wastewater irrigation.

Conclusions

From a microbial perspective, high soil degradation levels should be avoided by treatment of a saline–sodic wastewater prior to its use for irrigation rather than relying on future remediation strategies of affected field sites.     

Nitrogen use efficiency of microalgae application in wheat compared to mineral fertilizer

Background

Wastewater from sewage treatment plants contains high levels of nutrients, which can be used for plant nutrition. Classical wastewater treatment plants use complex microbial consortia of autotrophic and heterotrophic microorganisms for biological wastewater treatment. Certain autotrophic microalgae (e.g., species of the genera Chlorella, Scenedesmus, and Pediastrum) accumulate nutrients from wastewater very effectively.

Aims

We investigated the potential of microalgae biomass obtained from a prototype wastewater treatment plant as a source of nutrients for crops, focusing on nitrogen.

Methods

We provided wheat plants with different levels of algae biomass equivalent to 60, 120, and 180 kg N per hectare or with mineral fertilizer (N, P, and K) equivalent to the amounts contained in the algal biomass. Physiological and phenotypic traits were measured during growth, including vegetation indices, photosynthetic performance, growth, and nitrogen use efficiency (NUE). In addition, the adundances of Bacteria, Archaea and fungi and genes of ammonium oxidizing Bacteria and Archaea were determined in the rhizosphere of differently fertilized plants.

Results

Microalgal application at fertilizer levels of 120 and 180 kg N ha^–1 showed significantly improved physiological performance, growth, yield and nutrient uptake compared to the unfertilized control. Nevertheless, their yields and NUE were lower than with the application of equal amounts of mineral fertilization, while the adundance of rhizosphere microbes and ammonia-oxidizing microorganisms were not significantly affected.

Conclusions

Microalgae from wastewater treatments form a suitable source of organic fertilizer for wheat plants with only moderate reductions in N use efficiency compared to mineral fertilizer.     

Rural wastewater irrigation and nitrogen removal by the paddy wetland system in the Tai Lake region of China

Background, aim, and scope  

A large area of water eutrophication in the Tai Lake region of China was associated with nitrogen (N) and phosphorus (P) pollution, mainly due to the discharge of untreated rural wastewater (RW) into the surface water (SW) near villages of this region. A field experiment was conducted, using irrigation of RW plus urea fertilization under equal nitrogen (N) rate, namely, black water (BW), domestic wastewater (DW), gray water (GW), SW, and SW without any N application as a control (CK), to elucidate N removal by the paddy wetland system during the rice growing season of 2007.     

Radionuclides and stable elements in the sediments of the Yesa Reservoir,Central Spanish Pyrenees

Purpose  

The sediments accumulated in the Yesa Reservoir (Central Spanish Pyrenees) have greatly decreased its water storage capacity and are a major threat to the sustainability of water resources in the region. This study examines the contents of radionuclides and stable elements in the reservoir sediments and relates their variations with the sediment composition and local sedimentary dynamics, particularly flood frequency and intensity, which are responsible for changes in the main supply and distribution of radionuclides in the basin.     

Herbicide degradation and copper complexation by bacterial mixed cultures from a vineyard stormwater basin

Purpose  

The use of stormwater basins as constructed wetlands for the bioremediation of agricultural runoff waters contaminated with pesticides has great potential. The structure and dynamics of the bacterial community in such system, and its function with respect to contaminant removal, remain to be investigated in detail.     

Soil shrinkage and hydrostructural characteristics of three swelling soils in Shaanxi,China

Purpose  

Knowledge of soil shrinkage is important for a better understanding of water and solute transport in swelling soils. The objective of this study was to investigate the shrinkage processes and characteristics of three typical swelling soils in Shaanxi, China, with different height treatment using a modified core method and to analyze their agronomic properties.     

Spatial and temporal variability of urban soil water dynamics observed by a soil monitoring network

Purpose

Urban soils’ variability in the vertical direction presumably affects hydrological parameters at the timescale. Moreover, horizontal soil alterations at small spatial scales are common in urban areas. This spatio-temporal variability and heterogeneity of soil moisture and the possible influencing factors were to be described and quantified, using data of a soil monitoring network in the city of Hamburg, Germany.

Materials and methods

Soil moisture data from ten observation sites within the project HUSCO was evaluated for two different years. The sites were located within districts with different mean groundwater table depths and characteristic urban soil properties. Soil hydrological simulations with SWAP were calculated for a selected site.

Results and discussion

The temporal evolution of soil water content and tension for the sites was very distinct, related to soil substrate, organic matter content, and groundwater table depth. Impacts of different vegetation rooting depths, the soil substrates’ type, and to some extent the degree of disturbance on soil water dynamics could be identified. An impact of groundwater table depth on the water content of the topsoil during low-precipitation periods could be assumed. The comparison of the results of soil hydrological simulations with empirical data indicated an overestimation of infiltration and percolation for the given soil substrates.

Conclusions

While soil properties are mainly determinant for the long-term progression of soil hydrology, local site factors affect the short-term regime. A shallow groundwater table contributes to more constant water dynamics while the relative decrease of water during a dry phase is diminished.

     

Diurnal Soil Water and Root Water Uptake/Nitrogen Dynamics in the Wastewater-Irrigated Pepper Field

To study the effect of wastewater irrigation in pepper fields, this research analyzed the principle of the water vapor–heat–nitrogen coupling transport and the diurnal rule of root water/nitrate uptake dynamics in wastewater-irrigated pepper fields. In an outdoor experiment, the soil water content, negative pressure head, and temperature at depths of 10, 25, 40, 55, and 70 cm were measured hourly for 480 h in July 2013. The modified HYDRUS-1D code was used to analyze soil water and root water/nitrogen uptake dynamics. The numerical analyses provided insight into the diurnal movement of the soil water and root water/nitrogen uptake dynamics driven by the gradients of the pressure heads and temperatures. The measured and simulated data agree well with each other. When the original nitrate-nitrogen (NO₃-N) content in the soil is high, additional wastewater irrigation will not increase the root uptake of NO₃-N. Thus, excessive wastewater irrigation may cause groundwater nitrogen contamination.     

Soil nitrogen mineralization and fate of (<Superscript>15</Superscript>NH<Subscript>4</Subscript>)<Subscript>2</Subscript>SO<Subscript>4</Subscript> in field-incubated soil in a hardwood plantation of subtropical Australia: the effect of mulching

Background, aim, and scope  

Mulching is frequently used to overcome the drought problem in hardwood plantations that are increasingly being established in lower rainfall areas of Queensland, Australia because of increasing land values. In addition to soil water content, soil nitrogen (N) availability is another critical determinant of plantation productivity in these areas. The purpose of this study was to understand how soil mineral N dynamics, in situ N mineralization, and the fate of fertilized N would be affected by mulching during the early establishment of hardwood plantations.     

Influence of compost of sewage sludge and low-quality water on pesticide uptake by tomato plants grown in an iron mine soil

Purpose

In mine soils, especially from arid or semiarid areas, the use of low-quality water for irrigation is a usual practice. Therefore to fill this gap, different experiments have been carried out to evaluate the effect of compost, pesticide and wastewater on the growth of tomato plants in a mine soil located at an iron extraction area.

Materials and methods

Soils proceeded from Alquife mine wastes whose most outstanding characteristics are alkaline conditions, low organic matter and electrical conductivity and high As concentration. The compost of sewage sludge (CSL) used to amend this soil had a slightly acid pH (6.8), EC 3.0?±?0.07 dS m^-1 (1/10 ratio, m/V) and 10 % organic carbon (OC) content. Irrigation was performed with distilled water (DW) or wastewater (WW) and two pesticides, the insecticide thiacloprid and the fungicide fenarimol, were applied to the soil. Tomato was grown directly from seeds on each pot. Four treatments with addition of pesticides were considered. For comparison purposes, two additional treatments without pesticides were also included.

Results and discussion

Addition of compost of sewage sludge led to a significant and sustained increase of soil OC content and dehydrogenase activity, while irrigation with wastewater had a slight or negligible effect on both properties. The plant species responded negatively to wastewater irrigation when this practice was undertaken with the application of both pesticides. No detectable amounts of thiacloprid, a relatively unstable and polar insecticide, were found in soil. The concentration of fenarimol in soil was higher after amendment with compost, but was not modified by irrigation with wastewater. In tomato shoots, the amounts of both pesticides were inversely correlated with final soil organic carbon, indicating that this soil property is relevant for their plant uptake. Besides, fenarimol concentrations in the soil and the tomato shoots were inversely related (r?=??0.836).

Conclusions

Tomato was not able to grow healthy in Alquife mine soil without compost addition. The irrigation with wastewater only reduced plant growth when used in combination with pesticides. Uptake of both pesticides by tomato plants was negligible according to the low bioaccumulation factor values, but was almost doubled for wastewater irrigation. Caution should be taken with the use of treated wastewater, because it may reduce plant growth in tomato that is a species sensitive to salinity.

     

Arbuscular mycorrhizal association is beneficial for growth and detoxification of xenobiotics of barley under drought stress

Background, aim, and scope  

Plant growth and productivity under abiotic stresses such as water shortage or pollution are major problems which currently worry scientists in the field of food production and plant health. Since the intensification of livestock production with its associated increased demand for fodder has encouraged farmers to rely more heavily on chemical fertilizers, very often, municipal waste and wastewater sludge is considered a possible source of plant nutrients, although it might carry a significant amount of anthropogeneous pollutants. The extent to which plants react to drought, as well as how pollutants are taken up or how they act on plants, might depend on rhizosphere processes such as mycorrhizal symbioses. Therefore, it seemed timely to investigate plant defense reactions in the presence of arbuscular mycorrhizal fungi (AMF) toward a possible dangerous sewage sludge pollutant under the influence of drought.     

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

Purpose  

Properties of Fe oxides are poorly understood in soils with fluctuating water tables and variable redox conditions. The objective of this research was to (a) characterize the mineralogical composition of Fe oxides and (b) determine the relationship to the stable Fe isotope ratio in a soil with temporally and spatially sharp redox gradients.     

Reservoir sedimentation and its mitigating strategies: a case study of Angereb reservoir (NW Ethiopia)

Purpose  

The Angereb dam in northwestern Ethiopia was commissioned in 1997 to serve as a domestic water supply for 25 years. However, its sustainability is being threatened by rapid sedimentation. The overall objective of this study was to understand reservoir sedimentation in this tropical highland watershed and to propose its mitigating strategies that would contribute to the improved planning and management of reservoirs in similar regions.     

Impact of controlled redox conditions on nickel in a serpentine soil

Purpose  

Serpentine soils exist in many regions around the world; they are naturally enriched with nickel (Ni). An adequate understanding of soil processes determining Ni solubility is a special need particularly since less research has been addressed to Ni behavior under dynamic and controlled redox conditions. Our aim was (1) to characterize the properties of a serpentine soil and (2) to determine the impact of predefined redox windows on the mobility and dynamics of Ni in a serpentine soil.     

Spatial distribution of sediments and transfer properties in soils in a stormwater infiltration basin

Purpose  

The aim of our study was to characterise the heterogeneity of sediment distribution in a stormwater retention/infiltration basin (Pont de Cheviré, Nantes, France) and to determine the impact of this distribution on water transfer properties in the soil.     

Effects of 15-year application of municipal wastewater on microbial biomass,fecal pollution indicators,and heavy metals in a Tunisian calcareous soil

Purpose

Water shortage in most countries of the southern Mediterranean basin has led to the reuse of municipal wastewater for irrigation. Despite numerous advantages for soil fertility and crop productivity, recycling wastewater in the soil also has several ecotoxicological and sanitary problems. To evaluate the chronic soil contamination and the cumulative impact of wastewater, we compared seven plot sites irrigated with treated wastewater 1, 2, 7, 9, 13, and 15 years and one nonirrigated taken as control, and these were sampled for soil analysis.

Materials and methods

Soil samples were analyzed for pH, electrical conductivity (EC), total Kjeldahl nitrogen (TKN), total organic matter, and total concentrations of Cu, Zn, Fe, Ni, Pb, and Cd. Microbial biomass and enteric bacteria (fecal coliforms and fecal streptococci) were determined in all soil samples.

Results and discussion

The soil pH values were not consistently affected. Soil salinity, measured as EC, appeared significantly high and proportional to the duration of wastewater irrigation. Also, concentrations of total Ni, Zn, Cu, Pb, and Cd increased significantly (P?≤?0.05) according to the number of irrigation years but are usually under Tunisian standards. The concentration of heavy metals (Ni, Zn, Cu, Pb, and Cd) showed a significant decrease in the soil profile. The microbial biomass carbon (MB_C) is 1.5 times larger in the soil irrigated for 15 years with treated wastewater as compared to the one taken as control. The growth of microorganisms might be explained by the ready source of easily degradable compounds in the oligotrophic soil environment brought about by wastewater irrigation. Soil bacteriological analysis showed that the number of fecal coliforms (FC) and that of fecal streptococci (FS) were affected appreciably (P?≤?0.05) by the duration of wastewater application (number of years) and by the soil depth (0–20, 20–40, and 40–60 cm).

Conclusions

Treated wastewater irrigation led to changes in physicochemical and microbiological soil properties. The magnitude and specificity of these changes significantly correlated with the duration of such practice. It can be concluded, based on these results, that the proper management of wastewater irrigation and periodic monitoring of soil fertility and quality parameters are required to ensure successful, safe, and long-term reuse of wastewater irrigation.     

Implications of municipal wastewater irrigation on soil health from a study in Bangladesh

This study evaluated soil health in fields of wheat (Triticum aestivum L. cv Shatabdi) and potatoes (Solanum tuberosum L.) irrigated by different blends of municipal wastewater (hereafter called wastewater). The crops were grown with and without added fertilizers over three consecutive years. The wastewater contained high concentrations of organic carbon (C), nitrogen (N), phosphorus (P), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), zinc (Zn) and boron (B). It also contained negligible concentrations of a few heavy metals. Irrigation by wastewater resulted in an increase in the porosity of the surface soil and thus a reduced bulk density. Wastewater enhanced the saturated hydraulic conductivity and water retention capacity of the soils. The organic carbon, total N, available P and S, and exchangeable Na, K, Ca and Mg of the soils increased proportionately with the quantity of applied wastewater. C, N and K increased significantly (α = 0.05) when fields were irrigated using raw wastewater after applied fertilizers; the other elements accumulated in the soil insignificantly under both fertility levels. Electrical conductivity (EC) and pH of the upper 0–20 and 20–40 cm soil layers increased with the application of wastewater; the increase was significant only under raw wastewater irrigation. In the 40–60 cm soil layer, both EC and pH remained unchanged. The applied inorganic fertilizers raised EC but reduced soil pH. The wastewater contained large counts of total coliform (TC: 17.2 × 10⁶ cfu/100 mL) and faecal coliform (FC: 13.4 × 10³ cfu/100 mL). Irrigation using municipal wastewater is proposed for improving soil fertility as well as for alleviating water scarcity with the exception of some crops whose edible parts come in direct contact with wastewater and/or are eaten uncooked.     

Sorption and persistence of wastewater-borne psychoactive and antilipidemic drugs in soils

Purpose  

Although the ubiquity of pharmaceuticals in treated wastewater has now been well documented, their fate and risk during beneficial wastewater reuse are far less understood. Soil sorption and degradation are important processes affecting the leaching potential of trace contaminants in irrigated soil. To this end, we examined the sorption and attenuation of six psychoactive and antilipidemic drugs, i.e., carbamazepine, diazepam, Dilantin, meprobamate, primidone, and gemfibrozil, in a loam (LVL) and a loamy sand representative of golf course soils in the southwestern United States.     

Light Weight Aggregates made from Dredged Harbour Sediments

Goal  

Annually, 400.000 m₃ harbour sediments are dredged to maintain the water depth in the harbours of Bremen and Bremerhaven. The sediment contains organic and inorganic pollutants and hence is deposited on a landfill. Because of the limited capacity of that landfill alternative treatment techniques are investigated. This study aims to evaluate the production of Light Weight Aggregates (LWA) from harbour sediments with respect to the product quality and environmental aspects of the use of the LWA.     

Impacts of long-term inorganic and organic fertilization on lignin in a Mollisol

Purpose  

Fertilization is an essential management method to maintain and increase soil organic carbon (SOC) content in agroecosystems. Fertilizer application is known to markedly influence the turnover of labile and refractory SOC components. However, the dynamics of lignin in response to different types of fertilization remains unclear. This study addresses the impact of long-term fertilization on lignin accumulation in an arable soil.