Oxidation of ethylene by soil bacteria

The course of the biological oxidation of ethylene by soil was dependent on the type of soil used as well as on other factors. As evidenced from an increase in oxidation rate, the ethylene-consuming microorganisms in soil could grow at the expense of ethylene, even when the gas was present at concentrations of 50 ppm or less. Five strains of bacteria strongly resembling each other were isolated from different soils. These pleomorphic, gram-positive, acid-fast, obligate aerobic, ethylene-oxidizing bacteria grew also on saturated alkanes and on ordinary carbon sources. An apparent K_m for ethylene of approximately 40 ppm was estimated for whole-cell suspensions of strain E20 by following the disappearance of the gas from the atmosphere.     

Ethylene Removal by a Biofilter with Immobilized Bacteria

A biofilter which eliminated ethylene (C₂H₄) from the high parts-per-million range to levels near the limit for plant hormonal activity (0.01 to 0.1 ppm) was developed. Isolated ethylene-oxidizing bacteria were immobilized on peat-soil in a biofilter (687 cm³) and subjected to an atmospheric gas flow (73.3 ml min⁻¹) with 2 or 117 ppm of C₂H₄. Ethylene was eliminated to a minimum level of 0.017 ppm after operation with 2.05 ppm of C₂H₄ for 16 days. Also, the inlet C₂H₄ concentration of 117 ppm was reduced to <0.04 ppm. During operation with 2 and 117 ppm of C₂H₄, an increase in the C₂H₄ removal rate was observed, which was attributed to proliferation of the immobilized bacteria, notably in the first 0- to 5-cm segment of the biofilter. The maximal C₂H₄ elimination capacity of the biofilter was 21 g of C₂H₄ m⁻³ day⁻¹ during operation with 117 ppm of C₂H₄ in the inlet gas. However, for the first 0- to 5-cm segment of the biofilter, an elimination capacity of 146 g of C₂H₄ m⁻³ day⁻¹ was calculated. Transition of the biofilter temperature from 21 to 10°C caused a 1.6-fold reduction in the C₂H₄ removal rate, which was reversed during operation for 18 days. Batch experiments with inoculated peat-soil demonstrated that C₂H₄ removal still occurred after storage at 2, 8, and 20°C for 2, 3, and 4 weeks. However, the C₂H₄ removal rate decreased with increasing storage time and was reduced by ca. 50% after storage for 2 weeks at all three temperatures. The biofilter could be a suitable tool for C₂H₄ removal in, e.g., horticultural storage facilities, since it (i) removed C₂H₄ to 0.017 ppm, (ii) had a good operational stability, and (iii) operated efficiently at 10°C.     

Ethylene and carbon dioxide concentrations of soils as influenced by rhizosphere of crops under field and pot conditions

A method for collecting low volumes of soil gas from a small region, and a technique for determining small concentrations of ethylene using an enrichment process are described. Using these methods, it was found that ethylene and carbon dioxide (CO₂) concentrations of soils varied considerably depending on the presence or absence of a rhizosphere. Ethylene was much higher (31–375 nL L^–1; mean: 207) in non-cropped areas (i.e., soils without rhizosphere) than in the rhizosphere region (8–136 nL L^–1; mean: 38) of a field in which maize or soybean were grown. On the other hand, CO₂ concentrations were higher in rhizosphere than in non-rhizosphere soil, especially in pot experiments. The rate of ethylene decomposition was, however, much greater in rhizosphere soil (55 nL g^–1 day^–1) than in non-rhizosphere soil (34 nL g^–1 day^–1). Higher microbial activity was presumed to result in the decrease of ethylene concentration and the increase in CO₂ in rhizosphere regions. The implications of these results in relation to the influence of ethylene in rhizosphere on plant growth, and the role of soil microbes on decomposition of ethylene is discussed.     

Effect of substrate-dependent microbial ethylene production on plant growth

Various compounds have been identified as precursors/substrates for the synthesis of ethylene (C₂H₄) in soil. This study was designed to compare the efficiency of four substrates, namely L-methionine (L-MET), 2-keto-4-methylthiobutyric acid (KMBA), 1-aminocyclopropane-1-carboxylic acid (ACC), and calcium carbide (CaC₂), for ethylene biosynthesis in a sandy clay loam soil by gas chromatography. The classic “triple” response in etiolated pea seedling was employed as a bioassay to demonstrate the effect of substrate-dependent microbial production of ethylene on plant growth. Results revealed that an amendment with L-MET, KMBA, ACC (up to 0.10 g/kg soil) and CaC₂ (0.20 g/kg soil) significantly stimulated ethylene biosynthesis in soil. Overall, ACC proved to be the most effective substrate for ethylene production (1434 nmol/kg soil), followed by KMBA, L-MET, and CaC₂ in descending order. Results further revealed that ethylene accumulation in soil from these substrates caused a classic “triple” response in etiolated pea seedlings with different degrees of efficacy. A more obvious classic “triple” response was observed at 0.15, 0.10, and 0.20 g/kg soil of L-MET, KMBA/ACC, and CaC₂, respectively. Similarly, direct exposure of etiolated pea seedlings to commercial ethylene gas also modified the growth pattern in the same way. A significant direct correlation (r = 0.86 to 0.97) between substrate-derived C₂H₄ and the classic triple response in etiolated pea seedlings was observed. This study demonstrated that the presence of substrate(s) in soil may lead to increased ethylene concentration in the air of the soil, which may affect plant growth in a desired direction. Published in Russian in Mikrobiologiya, 2006, Vol. 75, No. 2, pp. 277–283. The text was submitted by the authors in English.     

Effect of soil applied L-methionine on growth,nodulation and chemical composition ofAlbizia lebbeck L.

A pot experiment was conducted to evaluate the influence of an ethylene (C₂H₄) precursor, L-methionine (L-MET) added to soil on the growth, nodulation and chemical composition of a leguminous tree,Albizia lebbeck L. Benth (black ciris). L-Methionine (10^-9 to 10^-1 gkg^-1 soil) was applied as a soil drench to established uniform seedlings ofAlbizia lebbeck L. L-MET treatments had significant effects on all the plant growth parameters monitored. Plants responded positively to low to medium L-MET concentrations (10^-9 to 10^-3 gkg^-1 soil) while high levels of L-MET had either negative or no effects. An L-MET treatment of 10^-6 gkg^-1 soil was the most effective in increasing shoot height, plant girth, dry weights of shoot and roots, number and dry weight of nodules and total biomass. The chemical analysis of the plant material revealed that the highest N, P and K contents were present in plants exposed to 10^-6 gL-MET kg^-1 soil, while Ca and Mg contents were maximum with 10^-5 g L-MET kg^-1 soil. A similar trend was observed with the uptake of these elements by the plant. A significant quadratic dose-response relationship was found in all cases when each individual parameter was regressed against log [L-MET] excluding the control. Since, attempts were made to prevent any nutritional and water stress, the plant response to L-MET was most likely caused by substrate-dependent microbial production of ethylene in the rhizosphere. ei]A C Borstlap     

不同树盘覆盖对矮砧苹果园土壤微生物群落结构和多样性的影响

以7年生矮化中间砧苹果为试材,研究了不同材质树盘覆盖对土壤微生物丰度、群落结构和多样性的影响。高通量测序结果表明,防水园艺地布和塑膜覆盖处理提高了0-20 cm土层变形菌门的相对丰度和20-40 cm土层变形菌门的相对丰度,防水园艺地布处理还显著提高了土壤细菌Ace和Simpson指数。相较于防水、塑膜覆盖处理,透水园艺地布不仅提高了0-20 cm土层变形菌门、接合菌门的相对丰度,而且提高了土壤细菌Ace、Chao1和Simpson指数,降低了土壤真菌Ace、Chao1和Simpson指数。树状聚类图结果显示,树盘覆盖显著改变了土壤细菌和真菌群落结构,以透水园艺地布覆盖处理的改变最为显著。综合分析认为,不同覆盖措施均有利于提高土壤细菌群落的丰富度和多样性,降低土壤真菌群落的丰富度和多样性,优化土壤微生物群落结构,其中以透水园艺地布覆盖的效果最好。     

内蒙草原不同植物功能群及物种对土壤微生物组成的影响

为了分析不同植物群落组成对内蒙古典型草原土壤微生物群落组成的影响,本研究利用植物功能群剔除处理实验平台,采用荧光定量PCR(real-timePCR)和自动核糖体间隔区基因分析(automated ribosomal intergenic spacer analysis,ARISA)技术,对不同植物功能群组成的非根际土壤和常见物种的根际土壤中细菌和真菌的数量及群落结构进行了分析。结果表明,在非根际土壤中,不同植物功能群组成对细菌数量有显著影响,而对真菌数量及细菌和真菌的群落结构影响不明显;在根际土壤中,不同植物物种对细菌、真菌的数量都有显著影响。此外,聚类分析表明,不同物种的根际土中细菌和真菌的群落结构也有所不同,尤其以细菌的群落结构变化较为明显。研究结果表明不同植物物种可以通过根系影响土壤微生物群落组成。     

Influence of Aboveground Biomass Removal on Nitrogen Mineralization in a Restored Tallgrass Prairie

Prescribed burning in prairies influences soil nitrogen (N), which is the primary nutrient that limits plant growth and is an important factor in plant competition and diversity. The primary objective of the experiment described here was to better understand the changes in net N mineralization that occur after a fire. We compared soil properties after a fire with those following vegetation removal by mowing and raking in a restored prairie in southeastern Minnesota. The treatments occurred in the spring of two consecutive years. Calcium oxide, burnt lime, was added to some of the raked plots in the first year to mimic the deposition of basic cations during a fire, which cause an increase in soil pH. Aboveground biomass removal by raking or by burning had similar effects on soil moisture, temperature, and inorganic N. The removal treatments caused warmer and drier soil than in the untreated plots. The change in net N mineralization after raking was unaffected by the addition of lime. In the first year, with low rainfall, removal caused net N mineralization rates similar to those in the untreated controls, but during the second year, with heavy rainfall, net N mineralization rates were significantly higher after removal. We predict that if water is sufficient, increased soil temperature after biomass removal will increase soil microbial activity and net N mineralization, but during drought, water will limit microbial activity. Furthermore, depending on soil N concentrations, which are very high at this study site, altered soil microbial activity will have variable effects on net N mineralization.     

Use of bacterial acc deaminase to increase oil (especially poly aromatic hydrocarbons) phytoremediation efficiency for maize (zea mays) seedlings

Oil presence in soil, as a stressor, reduces phytoremediation efficiency through an increase in the plant stress ethylene. Bacterial 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, as a plant stress ethylene reducer, was employed to increase oil phytoremediation efficiency. For this purpose, the ability of ACC deaminase-producing Pseudomonas strains to grow in oil-polluted culture media and withstand various concentrations of oil and also their ability to reduce plant stress ethylene and enhance some growth characteristics of maize and finally their effects on increasing phytoremediation efficiency of poly aromatic hydrocarbons (PAHs) in soil were investigated. Based on the results, of tested strains just P9 and P12 were able to perform oil degradation. Increasing oil concentration from 0 to 10% augmented these two strains population, 15.7% and 12.9%, respectively. The maximum increase in maize growth was observed in presence of P12 strain. Results of high-performance liquid chromatography (HPLC) revealed that PAHs phytoremediation efficiency was higher for inoculated seeds than uninoculated. The highest plant growth and PAHs removal percentage (74.9%) from oil-polluted soil was observed in maize inoculated with P12. These results indicate the significance of ACC deaminase producing bacteria in alleviation of plant stress ethylene in oil-polluted soils and increasing phytoremediation efficiency of such soils.     

Microbial activities in soil near natural gas leaks

Summary From the present experiments it may be concluded that in the surroundings of natural gas leaks, methane, ethane and possibly some other components of the natural gas are oxidized by microbial activities as long as oxygen is available. This is demonstrated by an increased oxygen consumption and carbon dioxide production, as well as by increased numbers of different types of bacteria. The resulting deficiency of oxygen, the excess of carbon dioxide, and perhaps the formation of inhibitory amounts of ethylene, are considered to be mainly responsible for the death of trees near natural gas leaks. Also the long period of time needed by the soil to recover, may be due to prolonged microbial activities, as well as to the presence of e. g. ethylene.The present experiments suggest that especially methane-oxidizing bacteria of the Methylosinus trichosporium type were present in predominating numbers and consequently have mainly been responsible for the increased oxygen consumption. However, some fungi oxidizing components of natural gas, including methane and ethane may also have contributed to the increased microbial activities in the soil. The same will be true of a possible secondary microflora on products derived from microorganisms oxidizing natural gas components.     

川西亚高山针叶林土壤微生物及酶对林下植物去除的响应

生物多样性与生态系统功能的关系是生态学领域研究的热点与难点。但因受研究手段的限制,有关森林物种组成及其多样性变化对土壤微生物数量和酶活性影响的研究少有报道。采用人工去除灌草层的实验方法,研究了川西亚高山针叶林灌草层丧失对土壤微生物数量和酶活性的影响。结果表明:1)灌草层去除后,土壤细菌和真菌数量以CK(对照)RH(除草)RS(除灌),而土壤放线菌数量则以RHCKRS;2)灌草层去除后,土壤微生物群落构成发生改变,真菌比例有所下降;3)灌草层去除后,土壤酶活性随之发生变化,各种酶活性均以CKRHRS。表明林下灌草层去除,尤其是灌木层去除,导致土壤微生物数量下降、群落构成发生变化以及土壤酶活性下降,从而在一定程度上影响到森林生态系统的物质循环功能。     

Soil microbial communities in restored and unrestored coastal dune ecosystems in California

Most restoration projects involving invasive plant eradication tend to focus on plant removal with little consideration given to how these invasives change soil microbial communities. However, soil microorganisms can determine invasibility of habitats and, in turn, be altered by invasives once established, potentially inhibiting native plant establishment. We studied soil microbial communities in coastal dunes with varying invasion intensity and different restoration approaches (herbicide, mechanical excavation) at Point Reyes National Seashore. Overall, we found evidence of a strong link between bacterial and fungal soil communities and the presence of invasives and restoration approach. Heavily invaded sites were characterized by a lower abundance of putatively identified nitrifiers, fermentative bacteria, fungal parasites, and fungal dung saprotrophs and a higher abundance of cellulolytic bacteria and a class of arbuscular mycorrhizal fungi (Archaeosporomycetes). Changes in soil microbiota did not fully dissipate following removal of invasives using herbicide, with exception of reductions in cellulolytic bacteria and Archaeosporomycetes abundance. Mechanical restoration effectively removed both invasives and soil legacy effects by inverting or “flipping” rhizome‐contaminated surface soils with soils from below and may have inadvertently induced other adverse effects on soils that impeded reestablishment of native dune plants. Land managers should consider additional measures to counteract lingering legacy effects and/or focus restoration efforts in areas where legacy effects are less pronounced.     

Effect of modified Fenton's reaction on microbial activity and removal of PAHs in creosote oil contaminated soil

This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified Fenton's reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H(2)O(2) on was studied. In both experiments the H(2)O(2) dosage was 0.4 g H(2)O(2)/g soil. In completely H(2)O(2)-saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column. In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially saturated soil, with only 25% in 10 days. The effect of the modified Fenton's reaction on the microbial activity in the soil was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards Vibrio fischeri increased as a result of the modified Fenton's reaction. The activities of the microbial extracellular enzymes acetate- and acidic phosphomono-esterase were lower in the incubated modified Fenton's treated soil compared to extracellular enzyme activities in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation of soil in serum bottles at 20 degrees C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation of organic compounds. In untreated soil 20-30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil.     

Phytoremediation: synergistic use of plants and bacteria to clean up the environment

Phytoremediation is a relatively new approach to removing contaminants from the environment. It may be defined as the use of plants to remove, destroy or sequester hazardous substances from the environment. Unfortunately, even plants that are relatively tolerant of various environmental contaminants often remain small in the presence of the contaminant. To remedy this situation, plant growth-promoting bacteria that facilitate the proliferation of various plants especially under environmentally stressful conditions may be added to the roots of plants. These bacteria have been selected to lower the level of growth-inhibiting stress ethylene within the plant and also to provide the plant with iron from the soil. The net result of adding these bacteria to plants is a significant increase in both the number of seeds that germinate and the amount of biomass that the plants are able to attain, making phytoremediation in the presence of plant growth-promoting bacteria a much faster and more efficient process.     

Subordinate plant species impact on soil microbial communities and ecosystem functioning in grasslands: Findings from a removal experiment

Despite their low relative abundance, subordinate plant species may have larger impacts on ecosystem functioning than expected, but their role in plant communities remains poorly understood. The aim of this study was to test how subordinate plant species influence the functioning of a species-rich semi-natural grasslands. A plant removal experiment was set-up in the mountain grasslands of the Jura Mountains (Switzerland) to test the impact of subordinate plant species on soil microbial communities and ecosystem functioning. The experiment included three treatments: removal of all subordinate species, partial biomass removal of dominant species, and a no biomass removal control. After 2 years of treatments, we determined soil microbial community (bacteria and mycorrhizal fungi) by T-RFLP analysis and measured litter decomposition, soil respiration, soil inorganic nitrogen (DIN) availability and throughout above-ground biomass production as measures of ecosystem function. The removal of subordinate plant species strongly affected bacterial and weakly influenced mycorrhizal fungi communities and decreased rates of plant litter decomposition, soil respiration and DIN availability with larger effects than the partial loss of dominant biomass. The removal of subordinate plant species did not modify plant community structure, but it did reduce total above-ground biomass production compared to the control plots. Collectively, our findings indicate that the loss of subordinate species can have significant consequences for soil microbial communities and ecosystem functions, suggesting that subordinate species are important drivers of ecosystem properties.     

Comparison of release and transport of manure-borne Escherichia coli and enterococci under grass buffer conditions

AIM: To test the hypothesis that Escherichia coli and enterococci bacteria have similar release rates and transport characteristics after being released from land-applied manure. METHODS AND RESULTS: Turfgrass soil sod was placed into 200 cm long boxes that had the top two 25 cm sections separated to monitor the release and infiltration of bacteria, which affected bacteria transport in the rest of the box. Dairy manure with added KBr was broadcast on the top two sections. Boxes with either live or dead grass stand were placed under a rainfall simulator for 90 min. Runoff and infiltration samples were collected and analysed for Br, E. coli, enterococci and turbidity. Significant differences in release kinetics of E. coli and enterococci were found. A change from first-order release kinetics to zero-order kinetics after 1 h of rainfall simulation was observed. CONCLUSION: Differences in release rates but not in the subsequent transport were observed for E. coli and enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Because both E. coli and enterococci are currently used as indicator organisms for manure-borne pathogens, the differences in their release rates may affect the efficiency of using these organisms as indicators.     

Microbiological and chemical properties of soil associated with macropores at different depths in a red-duplex soil in NSW Australia

Some agricultural soils in South Eastern Australia with duplex profiles have subsoils with high bulk density, which may limit root penetration, water uptake and crop yield. In these soils, a large proportion (up to 80%) of plant roots maybe preferentially located within the macropores or in the soil within 1–10 mm of the macropores, a zone defined as the macropore sheath (MPS). The chemical and microbiological properties of MPS soil manually dissected from a 1–3 mm wide region surrounding the macropores was compared with that of adjacent bulk soil (>10 mm from macropores) at 4 soil depths (0–20 cm, 20–40 cm, 40–60 cm and 60–80 cm). Compared to the bulk soil, the MPS soil had higher organic C, total N, bicarbonate-extractable P, Ca⁺, Cu, Fe and Mn and supported higher populations of bacteria, fungi, actinomycetes, Pseudomonas spp., Bacillus spp., cellulolytic bacteria, cellulolytic fungi, nitrifying bacteria and the root pathogen Pythium.In addition, analysis of carbon substrate utilization patterns showed the microbial community associated with the MPS soil to have higher metabolic activity and greater functional diversity than the microbial community associated with the bulk soil at all soil depths. Phospholipid fatty acids associated with bacteria and fungi were also shown to be present in higher relative amounts in the MPS soil compared to the bulk soil. Whilst populations of microbial functional groups in the MPS and the bulk soil declined with increasing soil depth, the differentiation between the two soils in microbiological properties occurred at all soil depths. Soil aggregates (< 0.5 mm diameter) associated with plant roots located within macropores were found to support a microbial community that was quantitatively and functionally different to that in the MPS soil and the bulk soil at all soil depths. The microbial community associated with these soil aggregates thus represented a third recognizable environment for plant roots and microorganisms in the subsoil.     

Manipulation of ethylene biosynthesis

The plant hormone ethylene is involved in many plant processes ranging from seed germination to leaf and flower senescence and fruit ripening. Ethylene is synthesized from methionine, via S-adenosyl-L-methionine (SAM) and 1-amino-cyclopropane-1-carboxylic acid (ACC). The key ethylene biosynthetic enzymes are ACC synthase (ACS) and ACC oxidase (ACO). Manipulation of ethylene biosynthesis by chemicals and gene technology is discussed. Biotechnological modification of ethylene synthesis is a promising method to prevent spoilage of agricultural and horticultural products.     

A Previously Unexposed Forest Soil Microbial Community Degrades High Levels of the Pollutant 2,4,6-Trichlorophenol

2,4,6-Trichlorophenol (2,4,6-TCP) is a hazardous pollutant that is efficiently degraded by some aerobic soil bacterial isolates under laboratory conditions. The degradation of this pollutant in soils and its effect on the soil microbial community are poorly understood. We report here the ability of a previously unexposed forest soil microbiota to degrade high levels of 2,4,6-TCP and describe the changes in the soil microbial community found by terminal restriction fragment length polymorphism (T-RFLP) analysis. After 30 days of incubation, about 50% degradation of this pollutant was observed in soils amended with 50 to 5,000 ppm of 2,4,6-TCP. The T-RFLP analysis showed that the soil bacterial community was essentially unchanged after exposure to up to 500 ppm of 2,4,6-TCP. However, a significant decrease in richness was found with 2,000 and 5,000 ppm of 2,4,6-TCP, even though the removal of this pollutant remained high. The introduction of Ralstonia eutropha JMP134 or R. eutropha MS1, two efficient 2,4,6-TCP degraders, to this soil did not improve degradation of this pollutant, supporting the significant bioremediation potential of this previously unexposed, endogenous forest soil microbial community.     

Effects and persistence of baygon (Propoxur) and temik (Aldicarb) insecticides in soil

Summary The effects of two carbamate insecticides, Baygon and Temik, on microbial processes in soil were investigated. Total plate counts revealed that Baygon and Temik at field rate applications (5 ppm) did not greatly influence the microbial populations in the soil. At a concentration of 500 ppm the fungal and actinomycete populations showed a marked increase in response to Temik and Baygon.Nitrification was severely inhibited by the granular (formulated) Baygon and Temik at 500 ppm, but was much less inhibited with the technical grade (technical) insecticides. The discrepancy appeared due to metabolism of the corn cob grits carrier, the resulting immobilization of nitrogen causing an apparent inhibition of nitrification. At the approximate field rate applications of 5 ppm, only slight inhibition was observed with formulated Baygon or Temik. An accumulation of nitrite was noted, especially with technical Baygon at 500 ppm.Populations of the autotrophic nitrifying bacteria were depressed for 2–3 weeks by application of either Baygon or Temik to the soil at 500 ppm. Pure culture studies on Nitrobacter agilis and Nitrosomonas europaea indicated that Baygon and Temik were toxic to both organisms, but particularly the latter. The toxicity to Nitrosomonas was more severe in pure cultures than in soil.Oxygen uptake studies showed that formulated Baygon (but not Temik) added to soil at 500 ppm resulted in high respiratory activity, mostly due to metabolism of the carrier. The technical insecticides had little effect on respiration as measured by carbon dioxide evolution, although there were indications that Temik was being metabolized during the interval from 16 to 30 days. Baygon was found to be quite resistant to degradation in the test soil. Temik residues decreased by about 50% during the 30-days test period.Published with the approval of the Director of the North Dakota State Agricultural Experiment Station as Journal Article 487. Portion of a thesis presented by the senior author in partial fulfillment of the requirements for the M.S. degree in Bacteriology at North Dakota State University