The Fate of Cryptosporidium Parvum Oocysts in Reclaimed Water Irrigation-history and Non-history Soils Irrigated with Various Effluent Qualities

The present study aimed to look at the fate of protozoan parasite Cryptosporidium parvum oocysts applied through surface drip irrigation on reclaimed water irrigation-history and non-history sandy-loam (Hamra) soil columns. A new and simple isolation method for recovery of oocysts from soil samples was developed and used along this study. The new soil isolation method of oocysts is based on the “two phase separation method” formerly used to recover Clostridium perfringens spores from sediments and soil samples with minor modifications. The range recovery achieved by this method was 64–95% (mean 61.2?±?17.4). The objectives of the second part of this study were to investigate several physical and chemical factors governing transport and survival of C. parvum oocysts in sandy-loam soil columns by breakthrough curves. Comparison of fresh water and reclaimed water irrigation revealed that reclaimed water irrigated-history soil was more hydrophobic allowing water flow through channels with poor oocysts retention and fast flow. Examination of the organic matter effect (originating from reclaimed water irrigation) on oocysts breakthrough revealed that their soil infiltration increased. Calculations of oocysts concentration at different columns depths showed that most of the oocysts were retained in the first 5 cm of soil column. In the present study, comparing the two soil types (history and non-history of effluents irrigation) beside the surface electrostatic charge, one of the main elements found to affect oocysts infiltration and transport in soil columns was soil hydrophobicity caused by soluble organic matter originating from reclaimed water irrigation. Therefore, prior to application in soil irrigation, reclaimed water should be treated to high quality (i.e. membrane technology as the best option) to prevent enhanced transport of various pathogens through those irrigated soils.     

The effect of flow impedance on deposition of Cryptosporidium parvum oocysts with or without a vetiver buffer strip

Cryptosporidium parvum oocysts can be transported in overland flow from faecal deposits of grazing animals causing potential water contamination problems. Deposition of oocysts can occur when overland flow encounters vegetative buffers and its transport capacity is decreased in the upslope backwater region. Deposition of oocysts was investigated using a large rainfall simulator, with and without a vetiver buffer strip. Oocysts-spiked slurries were applied to two contrasting soils and the resultant oocyst/sediment depositions from the flow were compared. The buffers substantially reduced suspended sediment loads from the two soils and increased the oocyst concentration in the soil with >99% of the deposited oocysts measured upslope of the buffer.     

Distribution of carbon and nitrogen in water-stable aggregates and soil stability under long-term manure application in solonetzic soils of the Songnen plain,northeast China

Purpose

Excessive exchangeable sodium and high pH significantly decrease soil structural stability and permeability. Long-term application of cattle manure is an important management practice that can affect water-stable aggregates (WSAs), as well as aggregate stability and distribution of soil organic carbon (SOC) and total nitrogen (TN) in solonetzic soils.

Material and methods

Experiments were carried out in a randomized complete block design comprising five treatments according to the cattle manure application history: corn (Zea mays) with manure applied for 1, 5, 12, and 17 years were used as the experimental treatments and corn without manure application was used as a control. Soil properties, including WSAs, mean weight diameter (MWD), and SOC and TN concentrations in bulk soils and WSAs, were measured across all treatments. The relationships among the measured soil attributes were determined using stepwise regression analysis.

Results and discussion

Results indicated that micro-aggregates mainly accumulated in soils without manure application, while manure application significantly increased macro-aggregates formation. MWD was highest when manure was applied to the soil for 1 year, decreased after 5 years, and increased again after 12 years. SOC and TN concentrations in bulk soils and WSAs increased with the number of years of manure application, with the highest concentrations observed for 17 years in bulk soils. Stepwise regression analysis showed that WSAs 2–5 mm, SOC in WSAs 0.25–0.5 mm, and TN in WSAs 0.1–0.25 mm were dominant independent variables affecting aggregate stability, and that SOC in WSAs 0.25–0.5 mm and TN in WSAs <0.1 mm were dominant independent variables affecting SOC and TN concentrations in bulk soils, respectively.

Conclusions

Long-term application of manure to a solonetz significantly increased macro-aggregates and aggregate stability as well as SOC and TN in bulk soils and all aggregate sizes. These results are likely related to binding agent production as well as C and N accumulation from manure application.     

Mineralization of Nitrogen in Soils Amended with Dairy Manure as Affected by Wetting/Drying Cycles

Abstract

Interest in manure management and its effects on nitrogen (N) mineralization has increased in recent years. The focus of this research was to investigate the N‐mineralization rates of different soil types in Coastal Plain soils and compare them to a soil from Illinois. Soils with and without dairy composted manure addition were subjected to different wetting/drying cycles [constant moisture at 60% water‐filled pore space (WFPS) and cycling moisture from 60 to 30% WFPS] under laboratory conditions at three different temperatures (11°C, 18°C, and 25°C). Samples were collected from three different soil types: Catlin (Mollisols), Bama (Ultisols), and Goldsboro (Utilsols). Soil chemical and physical properties were determined to help assess variations in N-mineralization rates. Addition of composted manure greatly impacted the amount of N mineralized. The amount of manure‐derived organic N mineralized to inorganic forms was mainly attributed to the soil series, with the Catlin (silt loam) producing the most inorganic N followed by the Goldsboro (loam) and then Bama (sandy loam). This was probably due to soil texture and the native climatic conditions of the soil. No significant differences were observed between the constant and cycling moisture regimens, suggesting that the imposed drying cycle may not have been sufficient to desiccate microbial cells and cause a flush in N mineralization upon rewetting. Nitrogen mineralization responded greatly to the influence of temperature, with the greatest N mineralization occurring at 25°C. The information acquired from this study may aid in predicting the impact of manure application to help increase N‐use efficiency when applied under different conditions (e.g., climate season) and soil types.     

尾矿池里添加大理石废料和有机物五年后植被覆盖和土壤生化特性研究

Tailing ponds pose environmental hazards,such as toxic metals which can contaminate the surroundings through wind and water erosions and leaching.Various chemical and biochemical properties,together with extractable and soluble metals were measured five years after reclamation of a polluted soil affected by former mining activities.This abandoned mine site contains large amounts of Fe-oxyhydroxides,sulphates,and heavy metals.As a consequence,soils remain bare and the soil organic matter content is low(< 3 g kg 1).Marble waste,pig manure and sewage sludge were applied in 2004.Plant cover and richness,and soil chemical,biochemical and biological parameters were analysed five years later.Results showed that all soil biochemical properties as well as vegetation cover and richness were higher in treated soils than in the untreated contaminated plots(control),although organic matter,pH values and extractable metals concentrations were similar among treatments.Soluble cadmium and zinc were lower in the amended plots than in control.As a general pattern,soil amended with pig manure showed higher values of most biochemical properties compared to sewage sludge application,while the doses did not have a great effect,being only significant for β-glucosidase,phosphodiesterase and arylsulfatase.Significant correlations were found between vegetation cover,richness and soil biochemical properties,suggesting a high interdependence between plant colonization and reactivation of biogeochemical cycles during five years.This study confirms the high effectiveness of an initial application of the amendments tested to initialize the recovery of ecosystems in bare mine soils under Mediterranean semiarid conditions.This research also shows the high sensitivity of certain biochemical properties in order to evaluate soil quality and reactivation of nutrients cycles in reclaimed mine soils.     

A novel phosphorus biofertilization strategy using cattle manure treated with phytase–nanoclay complexes

The aim of this work was to evaluate the treatment of cattle manure with phytases stabilized in allophanic nanoclays as a potential novel phosphorus (P) biofertilization technology for crops grown in volcanic soils (Andisol). Furthermore, because the optimal pH for commercial phytase catalysis does not match the natural pH of manure, a complementary experiment was set up to evaluate the effect of manure inoculation with an alkaline phytase-producing bacterium. Finally, phytase-treated soil, manure, and soil–manure mixtures were evaluated for their P-supplying capacity to wheat plants grown under greenhouse conditions. Treating cattle manure with phytases stabilized in nanoclays resulted in a significant (P?≤?0.05) increase of inorganic P in soil extracts (NaOH-EDTA and Olsen). The use of phytase-treated cattle manure increased dry weights by 10 % and the P concentration by 39 % in wheat plants grown under greenhouse conditions, which is equivalent to a P fertilizer rate of about 150 kg of P per hectare. The inoculation of cattle manure with β-propeller phytase-producing bacteria led to an ～10 % increase in inorganic P in the manure extracts. However, applying inoculated manure to soil did not significantly increase wheat yield or P acquisition responses. Our results suggest that the novel approach of incubating cattle manure with phytases stabilized in nanoclay enhances the organic P cycling and P nutrition of plants grown in P-deficient soils.     

Spatial distribution of roots and cracks in soils cultivated with sunflower

The aim of this research was to investigate the spatial distribution of roots and cracks in two clay soils cropped with sunflower under different inter-row spacing in order to identify the optimal management. A latin square experimental design was applied to compare bare soil and soil cropped with sunflower, with three plant densities, obtained by keeping constant the number of plants on the row (3 plants m^?1) and varying the row spacing (0.4, 0.6, 0.8 m). The presence of the crop and the different distance between rows influenced soil moisture content as well as the root spatial distribution and thus the structural features of cracks. Increasingly lower values of moisture were found in both soils as the distance between rows decreased; an opposite trend was observed for both root density and crack size. The volume of cracks in the soil grown with sunflower at 0.4 m row spacing was 201.4 m³ ha^?1, thus 8 times higher than the value on the bare soil and 2.5 times higher compared to the one grown at 0.8 m between rows. Optimal results in terms of root density, soil moisture and crack size were obtained with an inter-row spacing of 0.6 m.     

Copper/Zinc Bioaccumulation and the Effect of Phytotoxicity on the Growth of Lettuce (<Emphasis Type="Italic">Lactuca sativa</Emphasis> L.) in Non-contaminated,Metal-Contaminated and Swine Manure-Enriched Soils

Copper/zinc bioaccumulation and the effect of phytotoxicity on the growth of lettuce (Lactuca sativa L.) were studied in plastic vessels containing (i) non-contaminated soil, (ii) copper-contaminated soils at concentrations of 75.0 and 125.0 mg kg^?1, (iii) zinc-contaminated soils at concentrations of 1200 and 2400 mg kg^?1, and (iv) soil enriched with swine manure. Copper and zinc concentrations in lettuce leaves were determined by flame atomic absorption spectrometry during 42 days of growth. Copper concentrations from 0.92 to 13.06 mg kg^?1 were found in lettuce leaves grown in copper-contaminated soils and zinc concentrations from 58.13 to 177.85 mg kg^?1 were found in lettuce leaves grown in zinc-contaminated soils. Copper and zinc concentrations in lettuce leaves grown in swine manure-enriched soils ranged from 0.82 to 8.33 and 0.68 to 13.27 mg kg^?1, respectively. Copper and zinc bioaccumulation caused a decrease in lettuce growth in metal-contaminated soils and an increase in phytotoxicity effects when compared to growth in non-contaminated and manure-enriched soils. These findings were confirmed by measuring leaf areas and biomasses. Copper was less toxic to lettuce than zinc due to the different concentrations in the soil. Lettuce growth and development was better in the swine manure-enriched soil than non-contaminated soil, which indicates that swine manure is a safe agricultural biofertilizer when used in appropriate amounts to avoid metal bioaccumulation in soil and plants.     

Movement of the protozoan pathogen Cryptosporidium parvum through three contrasting soil types

The potential for transfer of the protozoan pathogen Cryptosporidium parvum through soil to land drains and, subsequently, water courses following the application of livestock waste to land was monitored in the laboratory using simulated rainfall and intact soil cores. Following irrigation over a 21-day period, Cryptosporidium parvum oocysts applied to the surface of soil cores (initial inoculum concentration 1×10⁸ oocysts core^–1) were detected, albeit in low numbers, in the leachates from clay loam and silty loam soils but not in that from a loamy sand soil. Variations in leaching patterns were recorded between replicate cores. At the end of the study soil cores were destructively sampled to establish the location of oocysts remaining within the soil. Distribution within cores was similar in all three soil types. The majority (72.8+-5.2%) of oocysts were found in the top 2 cm of soil, with numbers decreasing with increasing depth to 13.2±2.8%, 8.39±1.4%, and 5.36±1.4% at depths of 10, 20, and 30 cm, respectively.     

Heavy Metal Concentration Survey in Soils and Plants of the Les Malines Mining District (Southern France): Implications for Soil Restoration

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg^?C1 Zn, 90,000 mg kg^?C1 Pb, 9,700 mg kg^?C1 of As and 245 mg kg^?C1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metal-tolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg^?C1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.     

Long-term and legacy effects of manure application on soil microbial community composition

We analyzed soil prokaryotic and fungal community composition in soils with varying histories of cattle manure application. The manure treatments were (i) annual application for 43 years (MF), (ii) annual application for 14 years followed by 29 years without application (MF14), and (iii) annual application for 30 years followed by 13 years without application (MF30). An annual application of chemical nitrogen (N) fertilizer (CNF) and a non-amended control (Con) were also included. Soil prokaryotic evenness and diversity significantly decreased in MF relative to other treatments in fall, but were similar to the other fertilizer treatments in spring and summer. Distinct prokaryotic and fungal community composition was observed in MF compared to other treatments across fall, spring, and summer seasons. The MF treatment significantly increased the relative abundance of Firmicutes, Gammaproteobacteria, and Gemmatimonadetes, but significantly decreased the relative abundance of Acidobacteria. In fall, the soil prokaryotic and fungal community composition with MF30 was significantly different than the other fertilization treatments. Overall, the study showed that annual manure application (MF) led to a different microbial community composition than the other fertilizer treatments. Soil without manure application for 13 years (MF30) had a significantly different microbial community composition from other fertilizer treatments in fall, while the soil without manure application for 29 years (MF14) resembled a microbial community that had never received manure.     

Nitrification and acidification from urea application in red soil (Ferralic Cambisol) after different long-term fertilization treatments

Purpose

Long-term manure applications can prevent or reverse soil acidification by chemical nitrogen (N) fertilizer. However, the resistance to re-acidification from further chemical fertilization is unknown. The aim of this study was to examine the effect of urea application on nitrification and acidification processes in an acid red soil (Ferralic Cambisol) after long-term different field fertilization treatments.

Materials and methods

Soils were collected from six treatments of a 19-year field trial: (1) non-fertilization control, (2) chemical phosphorus and potassium (PK), (3) chemical N only (N), (4) chemical N, P, and K (NPK), (5) pig manure only (M), and (6) NPK plus M (NPKM; 70 % N from M). In a 35-day laboratory incubation experiment, the soils were incubated and examined for changes in pH, NH₄ ⁺, and NO₃ ^?, and their correlations from urea application at 80 mg N kg^?1(?80) compared to 0 rate (?0).

Results and discussion

From urea addition, manure-treated soils exhibited the highest acidification and nitrification rates due to high soil pH (5.75–6.38) and the lowest in the chemical N treated soils due to low soil pH (3.83–3.90) with no N-treated soils (pH 4.98–5.12) fell between. By day 35, soil pH decreased to 5.21 and 5.81 (0.54 and 0.57 unit decrease) in the NPKM-80 and M-80 treatments, respectively, and to 4.69 and 4.53 (0.43 and 0.45 unit decrease) in the control-80 and PK-80 treatments, respectively, with no changes in the N-80 and NPK-80 treatments. The soil pH decrease was highly correlated with nitrification potential, and the estimated net proton released. The maximum nitrification rates (K _max) of NPKM and M soils (14.7 and 21.6 mg N kg^?1 day^?1, respectively) were significantly higher than other treatments (2.86–3.48 mg N kg^?1 day^?1). The priming effect on mineralization of organic N was high in manure treated soils.

Conclusions

Field data have shown clearly that manure amendment can prevent or reverse the acidification of the red soil. When a chemical fertilizer such as urea is applied to the soil again, however, soil acidification will occur at possibly high rates. Thus, the strategy in soil N management is continuous incorporation of manure to prevent acidification to maintain soil productivity. Further studies under field conditions are needed to provide more accurate assessments on acidification rate from chemical N fertilizer applications.     

Effectiveness of crop straws,and swine manure in ameliorating acidic red soils: a laboratory study

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg^?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH₄⁺) and nitrate plus nitrite (NO₃^??+?NO₂^?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg^?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol₍₊₎ kg^?1 compared to 2.82 and 4.19 cmol₍₊₎ kg^?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol₍₊₎ kg^?1 per pH unit increase for both straws compared to 6.25 cmol₍₊₎ kg^?1 per pH unit from the manure. The NO₃^??+?NO₂^? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.

     

Bacterial diversity as affected by application of manure in red soils of subtropical China

A plot experiment was conducted to understand the response of the soil bacterial community to manure application rates and the relationship between the composition of bacterial community and soil chemical properties. The experiment involved gradients of manure combined with chemical fertilizer in red soils from granite, red sandstone and red clay between 2013 and 2015. The soil bacterial community composition was significantly affected by different manure rates. The relative abundances of Burkholderiaceae, Micrococcaceae and Streptomycetaceae were higher at low manure rates (1.75 to 3.5 t·ha^?1·yr.^?1), whereas the relative abundance of Xanthomonadaceae was higher at high manure rates (7 to 28 t·ha^?1·yr.^?1). Manure application increased the bacterial abundance but decreased the diversity when its rates were higher than 7, 14 and 14 t·ha^?1·yr.^?1 in soils from granite, red sandstone and red clay, respectively. Redundancy analysis revealed that soils from different parent materials had different bacterial communities with soil pH and available phosphorus (AP) being determinant factors. The peanut yields exhibited significantly positive correlations with the bacterial diversity in soil, implying the importance of bacterial diversity for soil productivity. Soil AP was correlated with bacterial diversity by parabolic equations and probably AP may be an indicator of declining bacterial diversity at high manure rates. The critical value were 39.71, 65.75 and 90.16 mg·kg^?1 in soils from granite, red sandstone and red clay, respectively. This study suggests the importance of maintaining soil bacterial diversity under moderate and balanced applications of manure.     

Utilizing Composted Beef Cattle Manure and Slaughterhouse Waste as Nitrogen and Phosphorus Fertilizers for Calcareous Soil

Effectively utilizing composts requires that their nitrogen (N) and phosphorus (P) contents be used as fertilizer, but how this is best accomplished is not fully understood. The authors' objective was to quantify N and P availability of a calcareous clay loam soil receiving composts derived from four contrasting beef cattle feedlot feedstocks applied at 50, 150, and 450 mg total P kg^?1 and supplemented twice with fertilizer N for a 42-week greenhouse plant bioassay. Three composted manures from beef cattle fed distinct diets and a composted mix of slaughterhouse and construction waste were applied. Inorganically fertilized and non-amended soils were included as controls. Canola (Brassica napus L.) and pea (Pisum sativum L.) were grown in pots containing 1.5 kg air-dried soil for six alternating 7-week cycles. Soils amended with composted manure from beef cattle fed typical finishing diets had the lowest apparent N recovery (31%) and the greatest soil nitrate after 42 weeks (25 mg N kg^?1). Phosphorus availability was greater with composted manure from beef cattle fed distillers' dried grains than composted manure from beef cattle fed typical finishing diets and a composted mixture of slaughterhouse and construction waste. Apparent P recovery (66%) was greatest from composted manure of beef cattle fed corn (Zea mays L.) distillers' dried grains applied at 50 mg total P kg^?1. Composted manure from beef cattle fed distillers' dried grains had greater P availability than conventional composted beef cattle feedlot manure. Overall, performance of the composted mixture of slaughterhouse and construction waste was similar to the composted beef cattle manures.     

Response of the bacterial diversity and soil enzyme activity in particle-size fractions of Mollisol after different fertilization in a long-term experiment

Particle-size soils were fractionated for evaluating changes in the composition of bacterial community and enzyme activity in response to 13 years of fertilization. This study focused on Mollisol and its particle-size fractions of 200–2,000 μm (coarse sand sized), 63 to 200 μm (fine sand sized), 2 to 63 μm (silt sized), and 0.1 to 2 to μm (clay-sized). Long-term chemical fertilization lowered the pH of all particle fractions, whereas organic fertilizer application mitigated soil acidification. Nutrient concentrations depended on both fertilizer treatment and particle fractions and enzymes were unevenly active throughout the soil. Generally, the highest enzyme activities were observed in the silt and clay fractions of control soil and the soil treated with chemical fertilizer (N, P, and K (NPK)) and in the sand-sized fraction of soil treated with manure and chemical fertilizer (MNPK). Except for acid phosphomonoesterase, the other tested enzyme activities in coarse-sized fractions of MNPK soil were significantly higher than those of the control and NPK soils. Fertilization and soil fraction interactively (p?<?0.05) affected the enzyme activity. Denaturing gradient gel electrophoresis analysis showed that the bacterial community structure significantly differed in different particle sizes with a higher bacterial diversity in small-sized than in coarse-sized fractions. Dominant bands were excised and sequenced. We have found the following bacterial groups: Actinobacteria, γ-proteobacteria, and Acidobacteria. In addition, enrichment of organic matter in coarser fractions was related to greater bacterial diversity than any other treatment. Principal component analysis showed a smaller variability among fractions of the organic amended treatment. Redundancy analysis showed that the tested properties significantly affected the composition of bacterial community with the exception of C/N and available P. No significant correlation between enzyme activity and bacterial community composition was detected, whereas positive correlations between other soil properties and enzyme activities were observed to various extents. Probably, enzyme activities might be affected by specific functional bacterial communities rather than by the overall bacterial community. We concluded that the long-term application of organic manures contributed to the increase of soil organic matter content of particles higher than 200 mm, with higher bacterial diversity and increases in most of the enzyme activities.     

Effects of Soil Amendments on Growth and Metal Uptake by Ocimum gratissimum Grown in Cd/Zn-Contaminated Soil

Hydroponic and pot experiments were conducted to assess the uptake of heavy metals (Cd and Zn) by a common crop plant, African basil, Ocimum gratissimum. In addition, the effects of soil amendments, hydroxyapatite (HA) and cow manure on plant growth and metal accumulations were compared. In the hydroponic study, plants were exposed to various concentrations of Cd (2.5 and 5 mg L^?1) and Zn (10 and 20 mg L^?1) for 15 days. O. gratissimum was shown to be a Cd accumulator more than a Zn accumulator. Cadmium concentration in its shoots exceeded 100 mg kg^?1. In the pot experiments, soils from a heavily Cd-contaminated site (Cd 67.9 mg kg^?1 and Zn 2,886.8 mg kg^?1) were treated with cow manure and HA at the rates of 10% and 20% (w/w), and 0.75 and 1.5% (w/w), respectively. Plants were grown in the greenhouse for 3 months. The addition of cow manure resulted in the highest biomass production and the lowest accumulations of Cd in plant parts, while HA was more efficient than cow manure in reducing Zn uptake. Leaves of African basil showed a decreased Cd concentration from 1.5 to 0.3 mg kg^?1 (cow manure) and decreased Zn concentration from 69.3 to 34 mg kg^?1 (HA). This clearly demonstrates the efficiency of HA and cow manure in reducing metal content in leaves of plants grown on high metal-contaminated soil to acceptable or close to acceptable values (0.2 mg kg^?1 for Cd, 99.4 mg kg^?1 for Zn).     

Effect of Nitrogen Fertilizers on Zinc Accumulation in Fescue

Abstract

This research evaluated effects of nitrogen fertilizers on availability of zinc (Zn) in soils. Two slit loams of the Hadley series (Typic Udifluvents) were used. Zinc sulfate was mixed with the soils to give Zn at 125, 250, 500, or 1,000 mg/kg and incubated for 14 days. Fertilizers (compost, cow manure, urea) were mixed with the soils to supply N at 200 mg/kg. Fourteen days after the fertilizers were mixed with the Zn‐treated soils, soil samples were taken for analysis of plant‐available Zn by extraction with Morgan's solution or water. After the soil samples were taken, fescue (Festuca arundinacea Schreb.) seeds were placed into pots to assess germination, growth, and Zn accumulation. Higher concentrations of Morgan's extractable Zn were detected in soils treated with compost (201 mg/kg) than with calcium nitrate (179 mg/kg), manure (153 mg/kg), or urea (152 mg/kg). However, with water extraction, higher Zn concentrations were detected in soils treated with calcium nitrate (36 mg/kg) with the lowest concentrations being extracted from soils treated with urea (8 mg/kg). Extraction of Zn by Morgan's solution or water increased as the soil‐Zn levels increased. Fescue germinated and grew at all of the soil‐Zn levels. The highest concentration of Zn occurred in plants grown in soils amended with calcium nitrate or urea, and the lowest concentration was in plants grown in soils amended with compost or manure. Fescue grown in soils amended with urea had the largest dry mass, and plants grown with compost or manure had the smallest. Zinc concentration and accumulation for fescue shoots increased as the soil‐Zn levels increased. These results suggest that accumulation of Zn in fescue can be enhanced by selection of nitrogen‐containing fertilizers that affect the solubility of Zn in soils.     

Genetic diversity of bacterial β-glucosidase-encoding genes as a function of soil management

This study is the first approach to evaluate the diversity of bacterial β-glucosidase-encoding gene sequences, aiming to identify the main environmental factors structuring bacterial β-glucosidase genetic diversity in semiarid soils. Two agricultural management systems, soils under spontaneous cover vegetation vs. noncovered herbicide-treated soils, were tested. The weed biomass generated in the former was estimated around 2,600 kg?ha^?1?year^?1, whereas leaves and root exudates from olive trees were the only input of C biomass in the latter. Dendrograms generated from polymerase chain reaction–denaturing gradient gel electrophoresis profiles of bacterial β-glucosidase-encoding genes revealed two clusters determined by soil treatment and sharing <20 % similarity. The sequences of a total of 59 DNA fragments, representing 39 operational taxonomic units, were successfully determined. The Proteobacteria phylum clearly dominated all the soil samples, but representatives of Chloroflexi, Deinococci, Actinobacteria, Thermotogae, and Firmicutes class were also detected. Management strategies favoring the presence of spontaneous vegetation determined a higher genetic diversity of β-glucosidase-encoding genes of soil bacteria. However, since there is little information of β-glucosidase gene sequences available in databases, it is difficult to establish particular relationships between bacterial networks for C degradation and land use. Results from canonical correspondence analysis indicated that bacterial metabolic networks for oligomeric C substrates utilization were affected by the physicochemical properties of the soil; the uppermost 10 cm of covered soil clustered together and were positively correlated with some chemical properties related to soil fertility, whereas less influence of soil texture was observed for the deeper layers of bare soils.     

The Effects of Cow Manure and Vermicompost on Availability and Desorption Characteristics of Zinc in a Loamy Calcareous Soil

The application of organic fertilizers in soils not only increases soil organic matter but also introduces essential nutrients to soil. Therefore, applying these fertilizers can affect the availability and desorption characteristics of nutrients. The main objective of this research is to study the effects of cow manure (CM) and vermicompost (VC) on availability and desorption characteristics of zinc (Zn) in a loamy calcareous soil. In this study, concentration of available Zn (using DTPA-TEA, AB-DTPA, and Mehlich 3) and desorption characteristics of Zn (using successive extraction with DTPA-TEA For 1–504 h at 25 ± 1°C) in amended soil with 0, 0.5, and 1% (w/w) of CM and VC were investigated in a completely randomized design. Results of this research showed that concentration of Zn extracted by using three methods was higher in amended soils with 1% CM and VC than those with 0.5% of these fertilizers. Furthermore, the difference between concentration of available Zn in amended soils with CM and VC was not found to be significant (p > 0.05). The results of kinetics study illustrated that the effect of organic fertilizers on Zn desorbed after 504 h was found to be significant (p < 0.01). Amount of cumulative of Zn desorbed in amended soils was significantly (p < 0.05) higher than unamended soil. Concentration of Zn desorbed after 504 h in 0.5 and 1% of CM and VC compared with unamended soil increased 26, 54, 12, and 46%, respectively. In addition, Zn desorption rate in amended soils with CM was higher than those with VC. It can be concluded that organic fertilizers applied to loamy calcareous soils enhance source of available Zn for the plant. Moreover, the results of this study showed that the ability of amended soils with VC to supplying Zn for plants was lower than those with CM.