Cornfield Soil Research Articles

Isolation and characterization of atrazine-degrading strain Shewanella sp. YJY4 from cornfield soil.

Atrazine has been used worldwide for over 50years as a chemical herbicide. A strain of bacteria, YJY4 which utilizes atrazine as its sole nitrogen source for growth was isolated from agricultural black soil in northeastern China. 16S rDNA sequencing identified YJY4 as a Shewanella sp. PCR analysis and sequencing confirmed that YJY4 contained atrazine-degrading atzA, atzB and atzC genes. These genes revealed high similarity with those in Pseudomonas sp. ADP and Arthrobacter sp. TC1. The strain YJY4 was observed to degrade atrazine (100mgl(-1) ) to cyanuric acid completely after 36h. To the best of our knowledge, YJY4 was the first reported Shewanella sp. to grow in pure culture with atrazine serving as a sole source of nitrogen. Therefore, YJY4 may help with atrazine biodegradation and may become an abundant resource of atrazine degradation strains. A new isolated strain, YJY4 showed high atrazine-degrading ability, being able to degrade 100mgl(-1) atrazine completely in 36h. Strain YJY4 was identified as Shewanella sp. and contained atrazine-degrading atzA, atzB and atzC genes. This study examined the degradation mechanism and metabolic ability of this strain and for the bioremediation of contaminated environments, provides more strain selection and determines the strain of atrazine bioremediation potential.

Halophilic and thermotolerant Gymnoascus species from several special environments, China

This study introduces three new Gymnoascus species (Gymnoascaceae, Onygenales), G. halophilus, G. stercorarius and G. thermotolerans, isolated from sediments in Chaka Salt Lake, compost and cornfield soil, respectively, in China, based on a polyphasic characterization including morphology, physiology and molecular phylogeny. Phylogenetic relationships were assessed based on the nuclear internal transcribed spacer (ITS = ITS1 + 5.8S + ITS2) region and a combined multilocus alignment of the ITS, 18S subunit rRNA gene and 28S subunit rRNA genes. Our study identified phylogenetic and phenotypic characters that differentiated the three new species from known species in the genus. Salinity and temperature tolerance tests revealed that G. halophilus was an obligate halophile while G. stercorarius and G. thermotolerans were halotolerant and thermotolerant. A key to accepted species of Gymnoascus is provided.

Distribution of terbuthylazine and atrazine residues in crop-cultivated soil: The effect of herbicide application rate on herbicide persistence

Field experiments were carried out to compare the effect of herbicide application rate on the distribution and persistence of atrazine (ATR), terbuthylazine (TBA), and their dealkylated degradation products in two conventionally cultivated cornfield soils: a silt loam soil and a silty clay loam soil, both typical for the crop-producing area of continental Croatia. Herbicides were applied pre-emergence at the registered (R) (1.0–1.5kgha−1), double-registered (2R), and triple-registered (3R) rates. Topsoil (0–30cm) and subsoil (30–60cm) samples were collected periodically during a crop rotation cycle of 17months. Soil microcosm experiments were performed under controlled conditions to investigate the influence of the herbicide application rate on their biodegradation in herbicide-treated cornfield topsoils. The herbicide half-lives (DT50) calculated by using monophasic and biphasic first-order kinetics models were compared. The herbicide sorption intensity in the studied soils was evaluated in terms of the Freundlich sorption isotherm. Under field conditions, TBA was retained within the first 60cm of both agricultural soils at least twice as long as ATR. While ATR residues persisted in soil only until corn harvest (5months), the residues of TBA and its N-deethylated degradation product were still measurable at the end of the crop rotation cycle (17months). The persistence of both herbicides was higher in soil with higher herbicide sorption intensity. ATR and TBA application rates higher than registered generally did not significantly influence the herbicide biodegradation rates or dissipation from the topsoil layers. The enhanced application rate slightly decreased the TBA persistence only in soil exhibiting a rather slow biodegradation. A temperature-leaching potential index for ATR and TBA applied at R rate showed the same leachability class for both herbicides. The leachability class of TBA could be higher than that of ATR in soil with moderate TBA persistence (DT50=30–100days). From an environmental perspective, TBA could pose a similar risk for groundwaters as ATR.

Effect of cropping systems on heavy metal distribution and mercury fractionation in the Wanshan mining district, China: implications for environmental management.

The authors studied the concentration of heavy metals and mercury fractionation in contaminated soil in 2 agricultural land use systems (paddy rice and dry land) at the Wanshan mercury mine in China. The average concentrations of chromium, lead, copper, nickel, and zinc were generally lower in paddy rice soil relative to corn field soil. Soil under corn field production was slightly contaminated with lead (22-100 mg/kg), copper (31-64 mg/kg), and nickel (22-76 mg/kg) and moderately contaminated with zinc (112-635 mg/kg). In both soils, correlation of these metals with the titanium concentration in the soil indicates a geogenic origin for each metal (lead, r = 0.48; copper, r = 0.63; nickel, r = 0.47; zinc, r = 0.48). The mercury and antimony concentration in soil was high under both cropping systems, and future remediation efforts should consider the potential environmental risk presented by these metals. The concentration of bioavailable mercury in soil ranged from 0.3 ng/g to 11 ng/g across the 2 cropping systems. The majority of mercury (>80%) was associated with organic matter and the residual fraction. However, soil under paddy rice production exhibited a significantly lower concentration of Fe/Mn oxide-bound mercury than that under corn field production. This may be a function of the reduction of Fe/Mn oxides in the paddy rice soil, with the subsequent release of adsorbed metals to the soil solution. Sequential change from corn field to paddy rice production, as practiced in Wanshan, should therefore be avoided. Mercury adsorbed to Fe/Mn oxides in corn field soil potentially could be released into the soil solution and be made available for biomethylation under the flooded water management conditions of a rice paddy.

Study on the Residue of Plastic Film in Inner Mongolia Autonomous Region

The study investigated the amount of mulching plastic film residue in corn¡¢potato and vegetable fields in Inner Mongolia Autonomous Region. The result shows that there has been a very serious pollution, and the average amount of residue of mulching plastic film remained in the farmland of Inner Mongolia is 36.3kg/hm2. The average amount of residue of mulching plastic film remained in the corn field soils is 56.25 kg/hm2, the potato fields were38.7kg/hm2, the vegetable fields were 25.05kg/hm2. The results also showed that more than 73% residual film remains in the 0 ~ 10cm plow layer, and the amount of plastic film residue depends on duration of utilization of mulching plastic film, and the longer the duration of utilization, the more plastic film residue is left in the field.

Profiles ofMycobacteriumcommunities under polycyclic aromatic hydrocarbon contamination stress in the Shenfu Irrigation Area, northeast China

Indigenous Mycobacterium communities play an important role in the degradation of polycyclic aromatic hydrocarbons (PAHs), but little is known about Mycobacterium distribution in situ at PAH-contaminated sites. In this study, the diversity and distribution of Mycobacterium communities were investigated in sediments and soils at sites upstream, midstream, and downstream of an oil-sewage irrigation channel, using denaturing gradient gel electrophoresis (DGGE). The results show that heavy PAH contamination in upstream sites negatively affected Mycobacterium community diversity compared with midstream and downstream sites in all 3 sample types (sediments, corn field soils, and rice field soils). There was a correlation between the distribution of Mycobacterium communities and PAH contamination, as indicated by canonical correspondence analysis. Mycobacterium diversity and distribution was found to vary between the 3 sample types.

Biodegradation of alachlor in liquid and soil cultures under variable carbon and nitrogen sources by bacterial consortium isolated from corn field soil

Alachlor, an aniline herbicide widely used in corn production, is frequently detected in water resources. The main objectives of this research were focused on isolating bacterial consortium capable of alachlor biodegradation, assessing the effects of carbon and nitrogen sources on alachlor biodegradation and evaluating the feasibility of using bacterial consortium in soil culture. Kavar corn field soil with a long history of alachlor application in Fars province of Iran has been explored for their potential of alachlor biodegradation. The influence of different carbon compounds (glucose, sodium citrate, sucrose, starch and the combination of these compounds), the effect of nitrogen sources (ammonium nitrate and urea) and different pH (5.5-8.5) on alachlor removal efficiency by the bacterial consortium in liquid culture were investigated. After a multi-step enrichment program 100 days of acclimation, a culture with the high capability of alachlor degradation was obtained (63%). Glucose and sodium citrate had the highest alachlor reduction rate (85%). Alachlor reduction rate increased more rapidly by the addition of ammonium nitrate (94%) compare to urea. Based on the data obtained in the present study, pH of 7.5 is optimal for alachlor biodegradation. After 30 days of incubation, the percent of alachlor reduction were significantly enhanced in the inoculated soils (74%) as compared to uninoculated control soils (17.67%) at the soil moisture content of 25%. In conclusion, bioaugmentation of soil with bacterial consortium may enhance the rate of alachlor degradation in a polluted soil.

Study of the Bioremediation of Atrazine under Variable Carbon and Nitrogen Sources by Mixed Bacterial Consortium Isolated from Corn Field Soil in Fars Province of Iran

Atrazine herbicide that is widely used in corn production is frequently detected in water resources. The main objectives of this research were focused on assessing the effects of carbon and nitrogen sources on atrazine biodegradation by mixed bacterial consortium and by evaluating the feasibility of using mixed bacterial consortium in soil culture. Shiraz corn field soil with a long history of atrazine application has been explored for their potential of atrazine biodegradation. The influence of different carbon compounds and the effect of nitrogen sources and a different pH (5.5–8.5) on atrazine removal efficiency by mixed bacterial consortium in liquid culture were investigated. Sodium citrate and sucrose had the highest atrazine biodegradation rate (87.22%) among different carbon sources. Atrazine biodegradation rate decreased more quickly by the addition of urea (26.76%) compared to ammonium nitrate. Based on the data obtained in this study, pH of 7.0 is optimum for atrazine biodegradation. After 30 days of incubation, the percent of atrazine reduction rates were significantly enhanced in the inoculated soils (60.5%) as compared to uninoculated control soils (12%) at the soil moisture content of 25%. In conclusion, bioaugmentation of soil with mixed bacterial consortium may enhance the rate of atrazine degradation in a highly polluted soil.

Effect of Biochar Amendment on Tylosin Adsorption-Desorption and Transport in Two Different Soils

The role of biochar as a soil amendment on the adsorption-desorption and transport of tylosin, a macrolide class of veterinary antibiotic, is little known. In this study, batch and column experiments were conducted to investigate the adsorption kinetics and transport of tylosin in forest and agricultural corn field soils amended with hardwood and softwood biochars. Tylosin adsorption was rapid at initial stages, followed by slow and continued adsorption. Amounts of adsorption increased as the biochar amendment rate increased from 1 to 10%. For soils with the hardwood biochar, tylosin adsorption was 10 to 18% higher than that when using the softwood biochar. Adsorption kinetics was well described by Elovich equation ( ≥ 0.921). As the percent of biochar was increased, the rates of initial reactions were generally increased, as indicated by increasing α value at low initial tylosin concentration, whereas the rates during extended reaction times were generally increased, as indicated by decreasing β value at high initial tylosin concentration. A considerably higher amount of tylosin remained after desorption in the corn field soil than in the forest soil regardless of the rate of biochar amendment, which was attributed to the high pH and silt content of the former. The breakthrough curves of tylosin showed that the two soils with biochar amendment had much greater retardation than those of soils without biochar. The CXTFIT model for the miscible displacement column study described well the peak arrival time as well as the maximum concentration of tylosin breakthrough curves but showed some underestimation at advanced stages of tylosin leaching, especially in the corn field soil. Overall, the results indicate that biochar amendments enhance the retention and reduce the transport of tylosin in soils.

Inhibition of Aspergillus flavus in Soil by Antagonistic Pseudomonas Strains Reduces the Potential for Airborne Spore Dispersal

Pseudomonas chlororaphis strain JP1015 and P. fluorescens strain JP2175 were previously isolated from Mississippi cornfield soil samples and selected for their growth inhibition of Aspergillus flavus in laboratory culture. In this study, the antifungal activity of these bacterial strains against A. flavus in soil coculture was determined. Growth of A. flavus was inhibited up to 100-fold by P. chlororaphis strain JP1015 and up to 58-fold by P. fluorescens strain JP2175 within 3 days following soil coinoculation. A. flavus propagule densities after 16 days remained 7- to 20-fold lower in soil treated with either bacterial strain. Using a bench-scale wind chamber, we demonstrated that treatments of soil with P. chlororaphis strain JP1015 and P. fluorescens strain JP2175 reduced airborne spores dispersed across a 1 m distance by 75- to 1,000-fold and 10- to 50-fold, respectively, depending on soil type and inoculum level. These results suggest that application of these bacterial strains may be effective in reducing soil populations of mycotoxigenic fungi, thereby reducing fungal spore formation, and ultimately reducing the potential for crop plant infection via airborne transmission.

Degradation of atrazine by an acclimatized soil fungal isolate

A fungal strain able to use atrazine (2-chloro-4-ethylamino-5-isopropylamino-1,3,5-triazine) as a source of nitrogen was isolated from a corn field soil that has been previously treated with the herbicide. This strain was purified and acclimatized to atrazine at a higher level in the laboratory. A supplemented N was required to trigger the reaction. Atrazine was degraded at a faster rate in inoculated mineral salt medium (MSM) than non-inoculated MSM. Within 20 days, nearly 34% of the atrazine was degraded in inoculated medium while only 2% of the herbicide was degraded in non-inoculated medium. Degradation of atrazine by the isolated fungal strain was also studied in sterile and non-sterile soil to determine the compatibility of the isolated strain with native microorganisms in soil. The degradation of atrazine was found to be more in inoculated sterile soil than in inoculated non-sterile soil. Cell free extract (CFE) of fungal mycelium degraded about 50% of the atrazine in buffer in 96 hours compared to the control. Four atrazine metabolites were isolated and characterized by LCMS. On the basis of morphological parameters the isolate was identified as Penicillium species. Results indicated that the microorganism may be useful for remediation of atrazine-contaminated soil.

Isolation and Identification of Atrazine-degrading Bacteria from Corn Field Soil in Fars Province of Iran

In this study several agricultural fields with a long history of atrazine application in Fars province of Iran have been explored for their potential of atrazine biodegradation. After several subculturing for a period of 300 days acclimation, leads to an enhancement of atrazine biodegradation rate. A successful enrichment culture with a high capability for atrazine degradation was obtained (88%). A combination of enrichment culture technique, in a basal salt medium containing atrazine and carbon sources under nitrogen limitation and plating on indicator atrazine agar, have permitted the isolation of bacterial consortium with high capability of using atrazine as a nitrogen source. Seven gram-negative and one gram-positive bacterial strain, which were able to use this herbicide as a sole source of nitrogen, were isolated from Darehasalouie Kavar corn field soil. Based on physiological, biochemical and nutritional characteristics, the isolated bacteria were identified as Pseudomonas alcaligenes, Acidovorax sp., Pseudomonas putida, Ralstonia eutrophus, Pseudomonas syiringe, Erwinia tracheiphila, Entrobacter agglomerans and Micrococcus varians. Therefore, the bacterial consortium in liquid culture containing carbon sources and atrazine as a sole source of nitrogen, degrade added atrazine more than 80%.

Inoculation Effects of Pseudomonas putida, Gluconacetobacter azotocaptans, and Azospirillum lipoferum on Corn Plant Growth Under Greenhouse Conditions

Alcohol production from corn is gaining importance in Ontario, Canada, and elsewhere. A major cost of corn production is the cost of chemical fertilizers and these continue to increase in price. The competitiveness of alcohol with fossil fuels depends on access to low-cost corn that allows growers to earn a sustainable income. In this study we set out to determine if we can identify root-associated microorganisms from Ontario-grown corn that can enhance the nutrient flow to corn roots, directly or indirectly, and help minimize the use of extraneous fertilizer. Bacteria were isolated from corn rhizosphere and screened for their capacity to enhance corn growth. The bacteria were examined for their ability to fix nitrogen, solubilize phosphate, and produce indole acetic acid (IAA) and antifungal substances on potato dextrose agar. Bacterial suspensions were applied to pregerminated seed of four corn varieties (39D82, 39H84, 39M27, and 39T68) planted in sterilized sand and unsterilized cornfield soil. The plants were grown under greenhouse conditions for 30 days. Three isolates were identified as having growth-promoting effect. These bacteria were identified as to species by biochemical tests, fatty acid profiles, and 16S rDNA sequence analysis. Corn rhizosphere isolates, Gluconacetobacter azotocaptans DS1, Pseudomonas putida CQ179, and Azospirillum lipoferum N7, provided significant plant growth promotion expressed as increased root/shoot weight when compared to uninoculated plants, in sand and/or soil. All strains except P. putida CQ179 were capable of nitrogen fixation and IAA production. Azospirillum brasilense, however, produced significantly more IAA than the other isolates. Although several of the strains were also able to solubilize phosphate and produce metabolites inhibitory to various fungal pathogens, these properties are not considered as contributing to growth promotion under the conditions used in this study. These bacteria will undergo field tests for their effect on corn growth.

A Survey on Distribution of Aspergillus Section Flavi in Corn Field Soils in Iran: Population Patterns Based on Aflatoxins, Cyclopiazonic Acid and Sclerotia Production

Soil isolates of Aspergillus section Flavi from Mazandaran and Semnan provinces with totally different climatic conditions in Iran were examined for aflatoxins (AFs; B and G types), cyclopiazonic acid (CPA) and sclerotia production. A total of 66 Aspergillus flavus group strains were identified from three species viz. Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius in both locations. A. flavus (87.9%) was found to be the prominent species followed by A. nomius (9.1%) and A. parasiticus (3.0%). Only 27.5% of A. flavus isolates were aflatoxigenic (B(1) or B(1) and B(2)), out of which approximately 75% were capable to producing CPA. All the A. parasiticus and A. nomius isolates produced AFs of both B (B(1) and B(2)) and G (G(1) and G(2)) types, but did not produce CPA. Sclerotia production was observed in only 4 isolates of A. flavus among all 66 isolates from three identified species. A. flavus isolates were classified into various chemotypes based on the ability to produce aflatoxins and CPA. In this study, a new naturally occurring toxigenic A. flavus chemotype comprising of two strains capable of producing more AFB(2) than AFB(1) has been identified. A relatively larger proportion of aflatoxigenic A. flavus strains were isolated from corn field soils of Mazandaran province which indicate a possible relationship between high levels of relative humidity and the incidence of aflatoxin-producing fungi. The importance of incidence of Aspergillus section Flavi in corn field soils regard to their mycotoxin production profiles and crop contamination with special reference to climatic conditions is discussed.

Development of a New Most-probable-number Method for Enumerating Methanotrophs, Using 48-well Microtiter Plates.

We developed a new most-probable-number (MPN) method for enumeration of methanotrophs, using 48-well microtiter plates. With this method, a microtiter plate which has been inoculated with serial dilutions of a sample is placed in a plastic desiccator containing methane and shaken. The proposed method gave estimates of population densities of a pure culture of Methylocystis sp. strain M and of methanotrophs in a paddy soil sample similar to those obtained by a conventional MPN method using serum bottles. The new microtiter plate MPN method with an additional replica-plating technique made it possible to enumerate small populations of methanotrophs in cornfield and forest soils. It also requires less equipment, labor, and time than the conventional serum bottle MPN method.

Soil respiration and methane flux in adjacent forest, grassland, and cornfield soils in Hokkaido, Japan

Soil respiration and methane flux from adjacent forest, grassland, and cornfield were measured by using the closed chamber method from June to November, 1999 in Shizunai, Hokkaido, Japan, where the soil was an Aquic Humic Udivitrands derived from volcanic ash. The forest soil absorbed methane, at arate ranging from -0.12 to -0.02 mg C m-2 h-1, while the grassland soil emitted methane, at a rate ranging from undetectable levels to 0.18 mg C m-2 h-1. In the cornfield soil methane flux ranged from -0.01 to 0.04 mg C m-2 h-1. The soil respiration rate varied from 3 to 230 mg C m-2 h-1, 27 to 372 mg C m-2 h-1, and 29 to 156 mg C m-2 h-1 for the cornfield, grassland, and forest soils, respectively. Linear regression analysis demonstrated that the methane flux rate was positively correlated with the soil water-filled pore space (WFPS), and negatively correlated with the relative gas diffusion coefficient (D/D o) and air-filled pore space (AFPS). Soil respiration rates were positively correlated with the soil temperature at all the sites. The Q 10 value was 4.8, 3.3, and 1.9 for the cornfield, grassland, and forest soils, respectively.

Carbofuran transfer and persistence in drained agricultural soils related to their structure and adsorption properties

Carbofuran (Curater 5G) behavior was studied in two drained cornfield soils, clay and loamyclay, for 2 successive years. Different dissipations were observed in each soil for the same time period (8 weeks in 1985, 9 weeks in 1986). The authors found drained water from organic matter-rich soil to possess a higher carbofuran content, with 7.1–13.7 and 2.5–5.0% of the applied dose for clay and loamy-clay soils, respectively. The major part of these percentages arose from the drained waters associated with rainfall occurring during the first 2–3 weeks after application. Laboratory experiments confirmed the influence of the soil structure and its properties on carbofuran adsorption, and consequently on carbofuran leaching under field conditions.

Persistence and degradation of PP993 pyrethroid, fonofos, and chlorpyrifos in a Quebec cornfield's soil

Persistence and degradation of PP993 pyrethroid, fonofos, and chlorpyrifos in a Quebec cornfield's soil

Relationship Between Land‐Use Practices and Fecal Bacteria in Soils

AbstractFecal and other bacteria populations in soils from pasture, cornfield, and forest sites were assessed at the Rhode River watershed. Total coliform (TC), fecal coliform (FC), total streptococci (TS), fecal streptococci (FS), and aerobic heterotrophic bacteria (TVC) numbers were determined seasonally. They were also determined with depth to 25 cm in soils from the pasture. Bacterial numbers per gram of pasture soil from the surface 1 cm were: 252‐1,603 TC, 10‐3% FC, 317‐2,270 TS, 163‐1,330 FS, and 1.6‐65.1 × 106 TVC. The numbers declined markedly with depth, except that TS and TVC numbers remained near the surface values. Fecal coliform numbers varied seasonally, from 22 to 396 MPN/g soil in fall and spring when cattle were grazing, and from 10 to 50 MPN/g soil in winter and summer when cattle were absent from the pasture. The cornfield and forest surface soils contained equally low FC numbers ranging from 3 to 27 MPN/g soil. Aerobic heterotrophic bacteria were similar in magnitude at all three land‐use sites. No readily discernable seasonal pattern was noted. The proportion of coliform bacteria differed with land use. In pasture soils 67% of isolates were confirmed as Escherichia coli, 22% were Enterobacter aerogenes, and 11% belonged to other species. In cornfield soils only 8% were E. Coli, 77% E. aerogenes, and 15% other species. In forest soils only E. coli were the dominant species. Thus, the pro‐ portion of E. coli was directly related to the degree of fecal pollution of the soils, and the proportion of E. aerogenes increased with remoteness of the soil from potential polluting agents.

Dissipation of the Herbicides Atrazine and Alachlor in a Maryland Corn Field

AbstractAtrazine and alachlor are commonly used in Maryland corn fields (Zea mays L.), primarily as pre‐emergence herbicides. This research was part of a watershed program designed to monitor nonpoint source pollution due to runoff of chemicals from agricultural lands. Atrazne (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and alachlor (2‐chloro‐2′,6′‐diethyl‐N‐methoxymethyl acetanilide) were sprayed on a corn field at rates of 1.7 kg/ha and 2.3 kg/ha, respectively. Soil cores were taken from sites at four elevations in the field. At the highest elevation, atrazine underwent a decrease in the surface 5‐cm layer, but a fraction of atrazine was leached into the deeper soil profile. At the middle altitude, atrazine concentrations in the 2.5‐ to 30‐cm soil profile changed very little during the growing season. At the lowest elevation, where soil moisture was rather high, atrazine had an even distribution in the soil profile. Thus, the data on field soil indicated both downward and lateral movement of atrazine. Alachlor remained in the top 8 cm of the soil. Low teachability of alachlor in field soil is believed to result from a strong affinity of alachlor molecules for soil organic matter. Runoff losses were detected at a weir situated near the bottom of the drainage channel of the watershed. During the 1976 growing season, 17 g/ha of atrazine and 3.6 g/ha of alachlor were discharged. About 60% of the discharged herbicides were in the dissolved phase. Flow‐weighted mean herbicide concentrations in the runoff water were 16.9 µg/liter (atrazine) and 0.6 µg/liter (alachlor). Atrazine carryover detected in the corn field soils was generally from 0.09 to 0.56 µg/g. Between 5 and 13% of the atrazine applied to the fields was estimated to be carried over to the next growing season.