Effects of incubation temperature on the organic amendment‐mediated control of Fusarium wilt of tomato

Organic soil amendments play important roles in the reduction of plant diseases caused by soil‐borne plant pathogens. This study examined the combined effects of concentrations of organic amendments, temperature and period of incubation in soil on the management of Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (Fol). In an experiment with substrate mixture, Fol reduction was higher when the soils were incubated at 35°C than at 30°C. Disease severity was proportionally reduced as the volume of amendment added increased. Furthermore, disease was significantly lower in substrates incubated for 30 days at both temperatures, as compared to substrates incubated for only 15 days. The most effective control was achieved with pelletised poultry manure (PPM). In experiments with natural sandy soil, the effects of amendments on Fol populations, measured by real‐time quantitative PCR with TaqMan probes, were significant. The highest decreases in Fol DNA resulted when the soil was amended with 2% PPM and incubated at 35°C. The reductions in DNA concentrations was most likely related to the accumulations of high concentrations of NH₃ (27.3 mM) in soils treated with 2% PPM and incubated at room temperature (RT; 23 ± 2°C), or at 35°C. Severity of plants grown in soils incubated at RT decreased by over 40%, and more than 73% when incubated at 35°C, regardless of the rate of PPM. The results indicate that the management with PPM, when combined with heating or solarisation, is an effective control measure against Fusarium wilt of tomato.     

Enhancement of Atrazine Removal by Free and Immobilized Arthrobacter Sp. HB-5 in Soil and Wastewater

In an attempt to remove atrazine in situ, high-efficiency atrazine–degrading Arthrobacter sp. strain HB-5 (HB-5) and HB-5 immobilized on sodium alginate were introduced into two atrazine-polluted soils that are representative of soils in North China. Soil and wastewater with and without (controls) HB-5 or immobilized HB-5 were incubated at 25°C after the addition of atrazine. Soil samples were collected after 0 d, 1 d, 3 d, 5 d, 7 d, 10 d, and 13 d, and wastewater samples were collected after 0 d, 1 d, 3 d, 7 d, 14 d, 21 d, and 28 d. The residual atrazine was extracted from each sample and detected using gas chromatography. The half-life of the atrazine in the in soil samples was less than 3 d, and less than 7 d in the wastewater samples, treated with HB-5 or with immobilized HB-5. The immobilized HB-5 appears to exhibit better self-protection than the free bacteria at different pHs, and its ability to degrade atrazine was less affected by different conditions. Thus, in practice, immobilized HB-5 is better suited to incubations longer than 7 days because of its good adaptability. Both HB-5 and immobilized HB-5 exhibited better degradation of atrazine under conditions similar to the optimal living conditions of HB-5 than under other conditions. A small part of atrazine was removed by adsorption of organic matters, too. This study demonstrates the usefulness of these microorganisms in the bioremediation of soil and water systems polluted with triazine herbicides.     

Bioremediation of a petroleum‐contaminated cryic soil: Effects of phosphorus,nitrogen, and temperature

Bioremediation has been shown to be an effective means of treating petroleum‐contaminated soils in cold areas, although the conditions required to maximize bioremediation in cold region (cryic) soils are not well documented. A laboratory study was conducted to investigate the effects of nitrogen and phosphorus levels and temperature on petroleum bioremediation. A cryic entisol contaminated with diesel fuel was treated with nitrogen (0, 400, 800, or 1200 mg/kg of soil) and phosphorus (0, 60, 120, or 180 mg/kg of soil) and incubated at two temperatures (10 and 20°C). At 10°C, bioremediation rates were not affected by fertility treatments. At 20°C, reaction rates were increased by the addition of P, but unaffected by N. Regardless of fertility regime, the rate of diesel loss was much greater in soil incubated at 20°C than in soil incubated at 10°C.     

阿特拉津降解菌株的分离、鉴定和工业废水生物处理试验

用液体无机盐培养基富集培养法和无机盐平板直接分离法, 从生产阿特拉津的农药厂的废水和污泥混合物中分离到13个能以阿特拉津为唯一氮源生长的细菌菌株。通过16S rRNA基因序列分析, 11个菌株被鉴定为Arthrobacter spp., 2个菌株被鉴定为Pseudomonas spp.。对阿特拉津降解活力最高的Arthrobacter sp. AD30和Pseudomonas sp. AD39的降解基因组成和降解特性进行了详细研究。降解基因的PCR扩增表明, AD30和AD39都含有trzN-atzBC基因, 能将有毒的阿特拉津降解成无毒的氰尿酸。降解实验表明, 向阿特拉津浓度为200 mg/L的无机盐培养基中分别接种等量的AD30、AD39和这两个菌株的混合菌液, 30°C振荡培养48 h以后, 阿特拉津去除率分别为92.5%、97.9%和99.6%, 表明混合菌的降解效果好于单菌。用AD30和AD39的混合菌液接种阿特拉津浓度为176 mg/L的工业废水, 30°C振荡培养72 h以后, 99.1%的阿特拉津被去除, 表明混合菌株在阿特拉津工业废水的生物处理中有很好的应用潜力。     

Organic Amendments to Enhance Atrazine and Metamitron Degradation in Two Contaminated Soils with Contrasting Textures

Among all types of xenobiotics, pesticides such as herbicides play a significant role in soil and water pollution due to their wide usage all over the world. This study addresses the ability of organic amendments to enhance atrazine and metamitron degradation in two herbicide-contaminated soils with contrasting textures under laboratory conditions. Soil samples were collected from surface soils with textures of sandy loam and silty clay, from northeastern Iran. Initial concentration of herbicides was 50 mg · kg^{? 1} soil. Contaminated soil samples were treated with manure, compost and vermicompost at rates of 0, 0.5, and 2% (w/w). Residual concentrations of atrazine and metamitron were determined by HPLC at the end of incubation periods of 20, 40, and 60 days. Residual concentrations of atrazine were 46.5, 38.9, and 36.2 mg · kg^{? 1} after 20, 40, and 60 days incubation, respectively. Residual metamitron concentrations were clearly lower than atrazine. After 20, 40, and 60 days, concentrations of metamitron were 2.9, 1.0, and 0.6 mg · kg^{? 1}, respectively. Organic amendments at the rates of 0.5 and 2% showed similar effects on the enhancement of herbicide degradation in soils. However, no statistically significant effect was observed among types of organic amendments (α = 0.05). Degradation was affected by soil textures. Residual concentrations of herbicides were higher in sandy loam than in silty clay soil.     

Enzyme immunoassay determination of atrazine degradation in soil: Moisture,sterilization, and storage effects

Enzyme immunoassay (EIA) microtiter plate analysis was used to quantify atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5 triazine), fortified at 0, 50, and 500 or 549 ng/g, to Baxter and Maury silt loam soil sampled in 1965 and 1991. In the first experiment, aged soils (sampled in 1965 and stored air‐dried) were fortified with atrazine and then incubated in the dark at 0, 75, 150, 225 and 300 g/kg moisture for 15, 80, 154, and 289 d. In a second experiment, fresh soils were fortified with atrazine and incubated in the dark at 0, 150, and 300 g/kg moisture for 9, 15, 35, 55, 83, and 145 d. One half of the treatments in the second experiment were sterilized with 497 ng/g HgCl₂. Twenty milliliters of acetonitrile: water (9: 1) was used to extract 4 or 5 g of soil by vortex mixing at each sampling date. The soil extract was diluted, 80 μl incubated with antibody‐coated wells, and color development read using a microtiter plate reader. Recovery of atrazine from soil was 98% 5 d after fortification. Pesticide recoveries and first‐order degradation rates were dependent on the freshness and moisture content of the soil sample. Pesticide degradation was slower and recoveries higher in soil that had been air dried and stored since 1965, prior to fortification. More atrazine was extracted from soil maintained at 0 g/kg moisture than from soil maintained at 300 g/kg moisture over time.     

除草剂阿特拉津对土壤脲酶活性的影响

研究了阿特拉津对4种典型施肥处理的土壤脲酶活力的影响。结果表明,处理初期,低浓度阿特拉津对土壤脲酶有一定刺激作用,高浓度处理在整个试验过程中对脲酶有明显抑制作用,阿特拉津对不同肥力土壤中脲酶的影响有明显差异,对照土壤和NPK肥土壤中脲酶活力较低,脲酶受抑制明显,抑制率分别高达30．35％和28．89％;NPK+秸秆和NPK+有机肥土壤的脲酶活力高,脲酶抑制率低,最高抑制率分别为21．35％和16．86％,不同肥力土壤在整个处理过程中,脲酶抑制率均为先逐渐增大到最大值,然后又逐渐降低;高肥力土壤脲酶抑制率最大值出现的时间比低肥力土壤迟,表明高肥力土壤对阿特拉津有较强的耐受能力。     

Mineralization Potential of Atrazine and Degradation Intermediates from Clustered Characteristics in Inoculated Soils

Soil properties impact pesticide persistence. Because these characteristics operate together in situ, identification of their clustered associations can help explain pesticide fate. Factor analysis was used to reduce the dimensionality of soil characteristics by grouping them into clustered independent factors, which were then related to the mineralization of atrazine and selected degradation intermediates. A Sharpsburg silty clay loam, Ortello sandy loam, and Hord silt loam were inoculated with a Hord soil that had a high capacity for atrazine mineralization. The soils were spiked with ¹⁴C-radiolabeled atrazine, deethylatrazine, hydroxyatrazine, N-isopropylammeline, N-isopropylammelide or cyanuric acid and sampled during incubation for 80 d (atrazine) or 40 d (degradation intermediates) at 22°C. Low mineralization in uninoculated soils demonstrated that the absence of atrazine-mineralizing microorganisms was most limiting. In inoculated soils, regression analysis indicated mineralization of atrazine (R² = 0.88) and its degradation intermediates (R² ≥ 0.89) was related to factors associated with bioavailability and microbial activity. For atrazine, this relationship indicated mineralization may be positively influenced by higher pH and available phosphorus, lower NO₃-N, organic carbon and clay contents, and lower adsorption. Our results show how factor analysis can be used in conjunction with multiple regression to determine mineralization potential and thus help identify soils with limited degradation capacities and possible long-term persistence.     

Rapid laboratory measurement of the temperature dependence of soil respiration and application to changes in three diverse soils through the year

Determining the temperature dependence of soil respiration is needed to test predictive models such as Arrhenius-like functions and macro-molecular rate theory (MMRT). We tested a method for rapid measurement of respiration using a temperature gradient block, cooled at one end (~2 °C) and heated at the other (~50 °C) that accommodated 44 tubes containing soil incubated at roughly 1 °C increments. Gas samples were taken after 5 h incubation and analysed for CO₂. The temperature gradient block allowed rapid assessment of temperature dependence of soil respiration with the precision needed to test models and explore existing theories of how temperature and moisture interact to control biochemical processes. Temperature response curves were well fitted by MMRT and allowed calculation of the temperature at which absolute temperature sensitivity was maximal (T_inf). We measured temperature response of three soils at seven moisture contents and showed that the absolute rate and sensitivity of respiration was partly dependent on adjusted moisture content. This result implied that comparisons between soils need to be made at a common moisture content. We also measured potential changes in the temperature dependence (and sensitivity) of respiration for three different soils collected at one site throughout a year. T_inf ranged from 43 to 51 °C for the three soils. T_inf and temperature sensitivity were not dependent on soil type collected but was partly dependent on time of year of collection. Temporal changes in temperature response suggested that the microbial communities may tune their metabolisms in response to changes in soil temperatures.     

Eradication of Polymyxa betae by Thermal and Anaerobic Conditions and in the Presence of Compost Leachate

The abiotic conditions required for eradication of Polymyxa betae, the vector of Beet necrotic yellow vein virus in sugar beet, were investigated. Survival of resting spores of P. betae was determined under aerobic (30 min, 4 days and 21 days) and anaerobic (4 days) conditions under several temperature regimes in a water suspension and in leachate extracted from an aerobic compost heap. In water under aerobic conditions the lethal temperature was 60, 55 and 40°C for exposure times of 30 min, 4 days and 21 days, respectively. The effect of compost leachate and/or anaerobic conditions on survival of P. betae depended on temperature. After incubation for 4 days at 20°C, no significant effects of anaerobic conditions or leachate on the survival of P. betae were found. However, at 40°C for 4 days under anaerobic conditions, survival of P. betae was significantly lower than survival under aerobic conditions in water as well as in leachate. In leachate taken from an aerobic compost heap, aerobically incubated at 40°C for 4 days, survival of P. betae was significantly lower than survival in water at the same temperature. As anaerobic spots are prevalent in aerobic compost heaps, especially during the thermophilic phase, actual inactivation temperatures under composting conditions are likely to be lower than the temperatures we found for eradication in water under aerobic conditions.     

Studies on the ecology of actinomycetes in an agricultural soil amended with organic residues: II. Assessment of enzymatic activities of <Emphasis Type="Italic">Actinomycetales</Emphasis> isolates

The main objective of this investigation was to study the enzymatic activities of Actinomycetales strains isolated from an agricultural soil amended with different amounts of municipal solid waste compost (MSWC) or farmyard manure (FM). For this purpose, the hydrolytic activities of carboxymethyl cellulase, xylanase, pectinase, amylase, chitinase and protease were tested for 75 isolates of Sterptomyces, Amycolatopsis and Nocardioides from different sources (unamended soil, amended soil with FM or MSWC, FM and MSWC) at temperature ranging between 30 and 50°C. It was shown that the highest rate of enzymes producer’s strains was registered at 30°C, and decreased gradually to annul at 50°C, with the exception of the MSWC strains origin. It was also shown that the percentage of strains producers of enzymes isolated from soil amended with MSWC appeared higher than the one registered for those isolated from control and amended with FM soils. Application of MSWC increases the number of enzymes producer-actinomycetes in the soil and then it improves its fertility.     

Effect of compost,nitrogen salts,and NPK fertilizers on methane oxidation potential at different temperatures

The effects of compost, nitrogen salts, and nitrogen–phosphorous–potassium (NPK) fertilizers on the methane oxidation potential (MOP) of landfill cover soil at various temperatures were assessed. For this, we used batch assays conducted at 5°C, 15°C, and 25°C with microcosms containing landfill cover soil slurries amended with these elements. Results indicated variable impacts dependent on the type of amendment and the incubation temperature. For a given incubation temperature, MOP varied from one compost to another and with the amount of compost added, except for the shrimp/peat compost. With this latter compost, independent of the amount, MOP values remained similar and were significantly higher than those obtained with other composts. Amendment with most of the tested nitrogen salts led to similar improvements in methanotrophic activity, except for urea. MOP with NPK fertilizer addition was amongst the highest in this study; the minimum value obtained with NPK (20–0–20) suggested the importance of P for methanotrophs. MOP generally increased with temperature, and nutrient limitation became less important at higher temperatures. Overall, at each of the three temperatures tested, MOP with NPK fertilizer amendments provided the best results and was comparable to those observed with the addition of the shrimp/peat compost. The results of this study provide the first evidence of the following: (1) compost addition to improve methanotrophic activity in a landfill cover soil should consider the amount and type of compost used and (2) the importance of using NPK fertilizers rather than nitrogen salts, in enhancing this activity, primarily at low temperatures. One can also consider the potential beneficial impact of adding these elements to enhance plant growth, which is an advantage for MOP.     

Effect of Organic Residues and Liming Materials on Metal Extraction from a Mining-Contaminated Soil

Incubation tests were used to assess the effectiveness of three different organic residues and three different liming materials, alone or in combination, in the remediation of a mine contaminated soil. The organic residues tested were sewage sludge from a municipal wastewater treatment plant (SS), compost from the organic fraction of unsorted municipal solid waste (MSWC), and garden waste compost (GWC), applied at 100 and 200 Mg ha^{? 1}. The liming materials tested were agriculture limestone (6.4 Mg ha^{? 1}), calcium oxide (3.7 Mg ha^{? 1}), and sugar beet sludge (12.2 Mg ha^{? 1}) from the sugar manufacturing process. The soil and mixtures of soil and amendments were adjusted to 70% of the maximum water holding capacity and incubated for 28 days in a controlled-temperature room at 20°C ± 1°C. At the end of the incubation, samples were analyzed for pH, electrical conductivity, organic matter content, CaCl₂-extractable, and' NH4Ac/HAc+ EDTA–extractable metal fractions (Cu, Zn, and Pb). Correlations among the variables and/or similarities among the treatments were identified by principal component analysis and hierarchical cluster analysis. The amendments tested decreased the CaCl₂-extractable Cu and Zn fractions, considered as mobile metal fractions, to below analytical detectable limits, providing organic matter to the soil with levels between 1% and 2% at the end of the experiment, significantly different relatively to the original soil. pH and electrical conductivity reached high values when using 200 Mg ha^{? 1} SS or 200 Mg ha^{? 1} MSWC, with any of the liming materials tested, making these application rates excessive for this particular situation. Furthermore, the treatments using MSWC increased the NH4Ac/HAc+ EDTA–extractable Cu, Pb, and Zn fractions, considered as mobilizable metal fractions, as did the 200 Mg ha^{? 1} SS for Pb and Zn. Considering the overall results, the compost made from garden waste decreased metal solubility in the soil and increased soil pH and organic matter content, without the addition of large amounts of soluble salts, and without increasing the mobilizable metal content. Of the organic materials tested, this was the only one that can be considered adequate for remediation of the contaminated soil under study, at the application rates tested.     

The influence of previous plant cultivation on soil nitrification

Summary Studies have been made on the effect of previous cultivation of different plants on soil nitrification. Greater effects were obtained when the soil was incubated at 29°C and under natural conditions in the open that at 18°C. The rate of nitrification was usually lower in previously uncultivated than cultivated soils except in the cases of pea, timothy grass and onion when increased rates were found.     

Survival of Plasmid-Containing Bacillus subtilis Released into Mushroom Compost

Abstract The survival of a plasmid-containing Bacillus subtilis released into mushroom compost was investigated. The indigenous Bacillus population of mushroom compost exhibited an antibiotic-resistance profile that was distinguished by almost complete absence of chloramphenicol resistance. Bacillus subtilis containing the chloramphenicol-resistance plasmid pC194 was released into mushroom compost microcosms and populations were monitored at different incubation temperatures. The organism colonized both sterile and untreated compost at 37°C, and to a lesser extent at 50°C, but was eliminated after 30 d at 65°C. Although sporulation of the B. subtilis population occurred within compost, the population was maintained for up to 13 weeks at 50°C, largely as vegetative cells. Experiments in which the B. subtilis host strain, without plasmid, was released demonstrated that plasmid carriage had no effect on the ability of the bacterium to colonize and survive in compost. Furthermore, the size and composition of the indigenous bacterial population was unaffected by the presence of the introduced B. subtilis strain. Virtually no loss of plasmid pC194 from the B. subtilis population in compost was observed, and experiments at low growth rates in chemostats confirmed the stability of this host/vector system in the absence of positive selection pressure. Received: 9 July 1997; Accepted: 20 October 1997     

Temperature responses of carbon mineralization in conifer forest soils from different regional climates incubated under standard laboratory conditions

¹⁴C‐labelled straw was mixed with soils collected from seven coniferous forests located on a climatic gradient in Western Europe ranging from boreal to Mediterranean conditions. The soils were incubated in the laboratory at 4°, 10°, 16°, 23° and 30 °C with constant moisture over 550 days. The temperature coefficient (Q₁₀) for straw carbon mineralization decreased with increasing incubation temperatures. This was a characteristic of all the soils with a difference of two Q₁₀ units between the 4–10° and the 23? 30 °C temperature ranges. It was also found that the magnitude of the temperature response function was related to the period of soil incubation. Initial temperature responses of microbial communities were different to those shown after a long period of laboratory incubation and may have reflected shifts in microbial species composition in response to changes in the temperature regime. The rapid exhaustion of the labile fractions of the decomposing material at higher temperatures could also lead to underestimation of the temperature sensitivity of soils unless estimated for carbon pools of similar qualities. Finally, the thermal optima for the organic soil horizons (Of and Oh) were lower than 30 °C even after 550 days of incubation. It was concluded that these responses could not be attributed to microbial physiological adaptations, but rather to the rates at which recalcitrant microbial secondary products were formed at higher temperatures. The implication of these variable temperature responses of soil materials is discussed in relation to modelling potential effects of global warming.     

Modification and testing of a domestic freezer for use in studies of plant growth and survival at low temperatures

Modifications of a domestic freezer are described, which convert it to a versatile controlled environment chamber capable of maintaining temperatures between ambient and - 18 °C and therefore useful in investigations both of plant growth at low positive temperatures and of survival of sub-zero temperatures. The temperature control mechanism can provide a wide range of diurnal temperature regimes and of cooling and warming rates. Measurements in two such chambers showed air temperatures were always uniform to within ° 1 °C of set temperature except in a 6 cm band round the inside walls, where they were lower by 0°6 °C, at most; CO₂ concentration was always close to 300 v.p.m.; relative humidity was usually in the range 80–90% and photon flux densities during the light period were 180 ° 10 μmol m^-2 s^-1. The uniformity of environmental conditions within each chamber was confirmed by measurements of leaf growth and plant survival of tillers of a single genotype of perennial ryegrass growing in pots of compost. These tests also confirmed the lower temperature of the 6 cm band adjacent to the chamber walls. Although temperature settings were identical, air and compost temperatures were 0°3 °C higher in one of the two chambers tested. Although this difference did not result in significant differences in plant survival, significant differences in leaf lamina extension were found between cabinets. Problems encountered in the design and testing of the chambers are discussed.     

Swimming performance of hatchling green turtles is affected by incubation temperature

In an experiment repeated for two separate years, incubation temperature was found to affect the body size and swimming performance of hatchling green turtles (Chelonia mydas). In the first year, hatchlings from eggs incubated at 26°C were larger in size than hatchlings from 28 and 30°C, whilst in the second year hatchlings from 25.5°C were similar in size to hatchings from 30°C. Clutch of origin influenced the size of hatchlings at all incubation temperatures even when differences in egg size were taken into account. In laboratory measurements of swimming performance, in seawater at 28°C, hatchlings from eggs incubated at 25.5 and 26°C had a lower stroke rate frequency and lower force output than hatchlings from 28 and 30°C. These differences appeared to be caused by the muscles of hatchlings from cooler temperatures fatiguing at a faster rate. Clutch of origin did not influence swimming performance. This finding that hatchling males incubated at lower temperature had reduced swimming ability may affect their survival whilst running the gauntlet of predators in shallow near-shore waters, prior to reaching the relative safety of the open sea.     

Fruit-body production of a luminous mushroom,Mycena chlorophos

Cultural conditions for fruit-body production ofMycena chlorophos were investigated with the aim of using the mushroom for study of bioluminescence, scientific exhibition, and ecological conservation. A small glass jar having a cap with a microfilter was used as a culture vessel. A compost powder mixed with rice bran in proportion of 20% (fw/fw) and adjusted to 70% (w/w) in moisture content was used as production medium. Casing with 2 g/jar of moistened compost powder was necessary for fruit-body formation. Mycelium was grown in a culture chamber at 27°C, relative humidity (RH) of 80% for 4 wk, then transfered to a culture chamberat 21°C, 90% RH and light intensity of 300–800 lx after casing its, and incubated for 3 wk to produce fruit-bodies. The mean yield was 31 fruitbodies, i.e., 150 mg dry weight per jar.     

Effects of diurnal temperature variation on microbial community and petroleum hydrocarbon biodegradation in contaminated soils from a sub‐Arctic site

Contaminated soils are subject to diurnal and seasonal temperature variations during on‐site ex‐situ bioremediation processes. We assessed how diurnal temperature variations similar to that in summer at the site from which petroleum hydrocarbon‐contaminated soil was collected affect the soil microbial community and the extent of biodegradation of petroleum hydrocarbons compared with constant temperature regimes. Microbial community analyses for 16S rRNA and alkB genes by pyrosequencing indicated that the microbial community for soils incubated under diurnal temperature variation from 5°C to 15°C (VART5‐15) evolved similarly to that for soils incubated at constant temperature of 15°C (CST15). In contrast, under a constant temperature of 5°C (CST5), the community evolved significantly different. The extent of biodegradation of C10–C16 hydrocarbons in the VART5‐15 systems was 48%, comparable with the 41% biodegradation in CST15 systems, but significantly higher than CST5 systems at 11%. The enrichment of Gammaproteobacteria was observed in the alkB gene‐harbouring communities in VART5‐15 and CST15 but not in CST5 systems. However, the Actinobacteria was abundant at all temperature regimes. The results suggest that changes in microbial community composition as a result of diurnal temperature variations can significantly influence petroleum hydrocarbon bioremediation performance in cold regions.