Nouvelles informations relatives aux variations temporaires de l'activite nitrifiante d'un sol evaluee au laboratoire. incidences d'un apport de matieres organiques

Abstract

The results reported in this paper confirm the seasonal influence on soil nitrifying activity estimated in the laboratory. The variations of this activity depend on different factors: climatic conditions, soil nature, occurence of plants, characteristics of the organic matter added to the soil.

A fresh organic matter (straw, for example) leads to reduced nitrifying activity immediately after its incorporation; its depressive action disappears after a month under laboratory condi‐tions. A decomposed organic matter, as a manure, produces no effect.

This work also shows the seasonal variations of the mineral nitrogen immobilization after addition of a fresh organic matter.     

Effect of four experimental insecticides on enzyme activities and levels of adenosine triphosphate in mineral and organic soils

Abstract

A laboratory study was conducted to determine the effect of four experimental insecticides, DOWCO429X, DPX43898, tefluthrin and trimethacarb, on enzyme activities and levels of adenosine 5'‐triphosphate (ATP) in mineral and organic soils. DOWCO429X decreased urease activity in organic soil after 7 days while a stimulatory effect was observed with most treatments after 14 days. No inhibition on acetylene (C₂H₂) reduction by nitrogenase was evident with any of the insecticides in either soil. With the exception of DOWCO429X and tefluthrin at 7 days in organic soil, none of the insecticide treatments inhibited dehydrogenase activity in either soil. Dehydrogenase activity, measured by formazan formation, was greater in many samples in sandy loam than the control throughout the experiment. No inhibitory effect was observed on amylase activity after 2 or 3 days in sandy soil. A stimulatory effect was apparent in many samples after 2 days in organic soil. All insecticide treatments in sandy soil reduced invertase activity at 2 days. However, none of the experimental insecticides inhibited invertase activity after 3 days. A stimulatory effect in invertase activity was apparent in most cases at 2 days in organic soil and no difference was observed after 3 days. Phosphatase activity in insecticide treated samples was equal to or greater than that of control in sandy soil after 2 h. With the exception of DPX43898, the insecticides depressed phosphatase activity in most organic soil samples. The insecticides did not affect ATP levels in either soil. Results indicated that the chemical treatments at the levels tested did not significantly affect activities of enzymes or level of ATP in both soils.     

Effects of metolachlor on activities of enzymes in a malaysian soil

Abstract

Effects of metolachlor on the activities of cellulase, phosphatase, urease and protease in a loamy sand soil, were evaluated for up to 28 days. Metolachlor at 10 ppm and above caused a reduction in phosphatase and urease activities for the entire period of study. The cellulase activity decreased during the very first day of incubation compared to that of the control but a recovery trend was obvious at all concentrations from day 14 onwards. Protease activity was also reduced in the metolachlor treated soil and the lower activity was observed during the entire study.     

Degradation of Metribuzin in Two Soil Types of Lebanon

The degradation of metribuzin [4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one] as influenced by soil type, temperature, humidity, organic fertilizers, soil sterilization, and ultra-violet radiation was studied in two soil types of Lebanon under laboratory conditions. The two soil types were sandy loam and clay. Deamination of metribuzin in the sandy loam soil to its deaminometribuzin (DA) derivative was basically a result of biological activity. In the clay soil the first metabolite diketometribuzin (DK) was a result of oxidative desulfuration, while diketo-deaminometribuzin (DADK) was the product of reductive deamination. The two soils represented major differences in the pesticide transformation processes. Photodecomposition on the soil surface and in aqueous media was also an important process in the degradation of metribuzin. Furthermore, the increase in soil organic matter enhanced degradation.     

Effect of five insecticides on microbial and enzymatic activities in sandy soil

Abstract

A laboratory study was conducted to examine the effects of five insecticides on microbial and enzymatic activities important to fertility in sandy soil. Cyfluthrin significantly increased bacterial populations after 2 wks. Imidacloprid showed an inhibitory effect on fungal numbers after 2 wks incubation while the others did not affect fungal population. No inhibitory effect was observed on nitrification of soil indigenous nitrogen. All treatments stimulated S‐oxidation after 4 wks. With the exception of cyfluthrin and imidacloprid after 2 wks, denitrification in sandy soil indicated that all treatment inhibited denitrification throughout the experiment. No inhibitory effects on biomass‐c were observed during 2‐wk periods. An inhibitory effect was observed on amylase after 1 wk while significant recovery was observed after 3 wks. With the exception of HgCl₂, no effect was observed on reducing sugar formation for 2 wks with all treatments. Formazan formation resulting from dehydrogenase activity was significantly greater with tebupirimphos and Aztec for 1 wk. All treatments supressed phosphatase activity for 1 wk, while none of the treatments suppressed phosphatase activity after 2 wks. Amitraz, tebupirimphos and Aztec inhibited urease activity for 1 wk. With the exception of tebupirimphos, no treatments affected N₂‐fixation in soil. Although short‐lived inhibitory effects on activities of microbes and enzymes were caused by the insecticides, the soil indigenous microbes can tolerate the chemicals used for control of soil pests.     

Respiration induced by substrate and bacteria diversity after application of diuron,hexazinone, and sulfometuron-methyl alone and in mixture

Abstract

After application, herbicides often reach the soil and affect non-target soil microorganisms, decreasing their population, diversity or affecting metabolic activity. Therefore, laboratory studies were performed to evaluate the effects of diuron, hexazinone and sulfometuron-methyl alone and mixed upon carbon transformation by soil microorganisms in clayey and sandy soils and the effect on bacterial diversity and structure. Control treatment without herbicide application was also performed. Sub-samples from the control and herbicide treatments (10?g – in triplicate) were collected before herbicide application and 7, 14, 28 and 42?days after treatment (DAT), then 1?mL of ¹⁴C-glucose solution was applied. The released ¹⁴CO₂ was trapped in 2?M NaOH solution and the radioactivity was analyzed by liquid scintillation counting (LSC), 12?h after glucose application. The effect of herbicides on bacterial diversity was evaluated by T-RFLP. The experiment was conducted in a complete randomized design. Hexazinone did not affect ¹⁴CO₂ evolution. Diuron showed a greater ¹⁴CO₂ evolution in sandy and clayey soil, while sulfometuron-methyl led to an increase in sandy soil, at 42 DAT. A greater evolution of carbon was observed in the treatment with herbicide mixture in sandy soil, compared with the same treatment in clayey soil or control. However, the herbicide mixture application did not affect the soil biological activity measured by the respiration rate induced by substrate. On the other hand, the herbicide mixtures affected the bacterial diversity in both soils, being the strongest effect to diuron and sulfometuron-methyl in clayey soil and hexazinone in sandy soil.     

Persistence of azadirachtin A and B in soil: Effects of temperature and microbial activity

Abstract

The persistence of two insecticidally active compounds from the neem tree, azadirachtin A and B, was determined at two different temperatures (15 and 25°C) in the laboratory after application of the commercial neem insecticide, Margosan‐O, to a sandy loam soil. The influence of microbial activity on degradation was also examined by comparing autoclaved and non‐autoclaved soils also at 15 and 25°C. Temperature influenced degradation rates. The DT ₅₀ (time required for 50% disappearance of the initial concentration) for azadirachtin A was 43.9 and 19.8 d for non‐autoclaved soil kept at 15 and 25°C, respectively. The DT ₅₀ for azadirachtin B was 59.2 and 20.8 d for non‐autoclaved soil kept at 15 and 25°C, respectively. Microbial activity was also responsible for faster degradation because DT ₅₀ ’s for autoclaved soil were much longer than for non‐autoclaved soils. DT ₅₀ ‘_s for azadirachtin A in autoclaved soil were 91.2 (15°C) and 31.5 d (25°C). DT50’s for azadirachtin B in autoclaved soil were 115.5 (15°C) and 42.3 d (25°C). Two degradation products of azadirachtin were detected, but were not identified. Higher levels of the two degradation products were detected in non‐autoclaved soil.     

The rate of soil reduction as affected by levels of methyl parathion and 2, 4‐D

Abstract

A simple technique was demonstrated for determining the potential for synthetic organics to stress microbial populations. Oxidized Crowley and Cecil soil materials were amended with varying concentrations of 2,4‐D and methyl parathion, flooded, and then analyzed for changes in pH, redox potential, and levels of soluble plus exchangeable Fe, Mn, and Zn, all of which may be directly or indirectly influenced by the activity of soil microorganisms. At the concentrations tested (up to 75 ppm), there was little effect of 2,4‐D, but methyl parathion apparently did affect microbial activity contributing to changes in the measured soil properties upon flooding. This approach may be a useful technique for screening various compounds for their potential to stress microbial activity that, for many researchers, would be easier than direct observations of microbial parameters such as population numbers and classifications, and enzyme levels.     

Degradation of Pyrimethanil in Soil: Influence of Light,Oxygen, and Microbial Activity

The research was carried out in order to verify the influence that light, oxygen, and microbial activity have on the degradability of pyrimethanil (PYR) in soil. The products of degradation were also identified and their evolution in time evaluated. The results indicate that the molecule is more persistent in the absence of light, oxygen, and microbial activity. The order of importance of these three factors is as follows: light < microbial activity < oxygen. The following products of degradation were identified: (1) benzoic acid, (2) cis,cis-muconic acid, (3) hydroxyl-4,6-dimethyl-2-pirimidinamine, (4) N′-ethyl-N-hydroxyformamidine, and (5) 4,6-dimethyl-2-piridinamine, which appeared different from those reported in literature for the degradation of PYR in abiotic conditions. This result suggests that the degradation in soil is mainly biotic.     

Moist Olive Husks Addition to a Silty Clay Soil: Influence on Microbial and Biochemical Parameters

To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, β-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 × 10³ (D), 16 × 10³ (2D) and 80 × 10³ (10D) kg ha^?1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO₂ suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO₂ data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation.

o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, β-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 × 10³ kg ha^?1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 × 10³ kg ha^?1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.     

Phytotoxicity of atrazine and alachlor in soil amended with sludge,manure and activated carbon

Abstract

Greenhouse studies were conducted to determine the influence of waste‐activated carbon (WAC), digested municipal sewage sludge (DMS), and animal manure on herbicidal activity of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐trazine] and alachlor [2‐chloro‐2’,6'‐diethyl‐N‐(methoxymethyl)acetanilide] in a Plainfield sandy soil. Amendments generally reduced bioactivity against oat (Avena sativa L.) and Japanese millet (E. crus‐galli frumentacea). The extent to which herbicide phytotoxicity was inhibited depended upon the application rate and the kind of soil amendment. WAC, applied at the loading rate of 2.1 mt C/ha, showed a significant inhibitory effect on both herbicides. In DMS‐ and manure‐amended soil, the reduction of atrazine activity was not significant at the rate of 8.4 mt C/ha, but reduction of alachlor activity was significant at the rate of 4.2 mt C/ha. Despite inhibition of herbicidal activity, the ED₅₀ of atrazine and alachlor was below 2 ppm in most of the amendment treatments. Before adopting carbon‐rich waste amendments as management practices for controlling pesticide leaching in coarse‐textured soils, further studies are needed to characterize how alterations in sorption, leaching and degradation may affect herbicidal activity.     

Impact of long‐term pesticide applications on some soil biological parameters

Abstract

The soil oxidative and anaerobic processes, as well as, the microbial biomass were followed during three years in a cotton farm (Tatuí) where the recommended pesticides have been used for several years, and in an experimental field (São Paulo) treated first time with the same pesticides. The oxidative process was monitored by the dehydrogenase (DHA)‐activity using triphenyltetrazolium chloride (TTC) as substrate. The anaerobic process was followed by the iron‐oxide reduction, and the microbial biomass was estimated by the substrate (glucose)‐indiced respiration. Increases in DHA‐activity and in the microbial biomass occurred only in the farm soil, with concomitant decreases in iron‐reduction. In the experimental field soil, the increases in DHA‐activity were followed only by decreases in iron‐reduction. Soil characteristics were the determining factor for different biological parameters after pesticide inputs. All the pesticides produced at least one clear but transient effect.     

Effect of a mixture of flufenacet and isoxaflutole on population numbers of soil-dwelling microorganisms,enzymatic activity of soil,and maize yield

Abstract

This study was aimed to evaluate the effect of a mixture of flufenacet?+?isoxaflutole on counts of microorganisms, ecophysiological diversity index (EP), colony development index (CD) and on the enzymatic activity of soil and maize growth. The experiment was conducted with sandy clay, to which the tested herbicide was administered in doses of: 0.25, 5.0, 10, 20, 40, 80 and 160?mg/kg. Soil without the addition of the mixture served as the control. Results demonstrated that the tested mixture contributed to a decrease in numbers of Azotobacter, organotrophic bacteria, actinobacteria and fungi. The negative effect of the herbicide could also be noticed in the case of the enzymatic activity of soil. Soil contamination contributed to suppressed activities of dehydrogenases, catalase, urease, alkaline phosphatase and arylsulfatase. In turn, the initial increase in the activity of β-glucosidase was followed by its decline observed with time. The flufenacet?+?isoxaflutole mixture affected also maize plant growth, reducing maize dry matter yield when used at doses from 5.0 to 160?mg/kg. In summary, it may be concluded that mixture evokes a negative effect on the microbiological and biochemical activity of soil and that their excess in the soil leads to plant decay as at the seeding stage.     

Ecological impacts of the N-viro biosolids land-application for wild blueberry (Vaccinium angustifolium. Ait) production in Nova Scotia

Land application of biosolids from processed sewage sludge may deteriorate soil, water, and plants. We investigated the impact of the N-Viro biosolids land-application on the quality of the soil water that moved through Orthic Humo-Ferric Podzols soil of Nova Scotia (NS) at the Wild Blueberry Research Institute, Debert, NS Canada. In addition, the response of major soilproperties and crop yield was also studied. Wild blueberry (Vaccinium angustifolium. Ait) was grown under irrigated and rainfed conditions in 2008 and 2009. Four experimental treatments including (i) NI: N-Viro irrigated, (ii) NR: N-Viro rainfed, (iii) FI: inorganic fertilizer irrigated, and (iv) FR: inorganic fertilizer rainfed (control) were replicated 4 times under randomized complete block design. Soil samples were collected at the end of each year and analyzed for changes in cation exchange capacity (CEC), soil organic matter (SOM), and pH.Soil water samples were collected four times during the study period from the suction cup lysimeters installed within and below crop root zone at 20 and 40 cm depths, respectively. The samples were analyzed for a range of water quality parameters including conductance, hardness, pH, macro- and micronutrients, and the infectious pathogens Escherichia coli (E. coli) and salmonella. Berries were harvested for fruit yield estimates. Irrigation significantly increased CEC during 2008 and the soil pH decreased from 4.93 (2008) to 4.79 (2009). There were significant influences of irrigation, fertilizer, and their interaction, in some cases, on most of the soil water quality parameters except on the infectious bacteria. No presence of E. coli or salmonella were observed in soil and water samples, reflecting the absence of these bacteria in biosolids used in this experiment. Nutrient concentration in the soil water samples collected from the four treatments were higher in the sequence NI > NR > FI > FR. The irrigation treatment had significant effect on the unripe fruit yield. We conclude that the comparable performance of N-Viro biosolids and the increasing prices of inorganic fertilizers would compel farmers to use economically available N-Viro biosolids that, coupled with the supplemental irrigation, did not deteriorate the studied soil properties, soil water quality, and the wild blueberry yield during this experiment.     

Soil Persistence of Triasulfuron Herbicide as Affected by Biotic and Abiotic Factors

Persistence of triasulfuron [3-(6-methoxy-4methyl-1,3,5-triazin-2-yl)-1-{2-(2-chloroethoxy)-phenylsulfonyl}-urea] in soil was studied under wheat crop and laboratory conditions. Field experiment was conducted in the farms of Agronomy Division, Indian Agricultural Research Institute (IARI), New Delhi. Randomized block design (RBD) was followed with four replicates and two rates of treatments along with control and weedy check. Triasulfuron was applied as post-emergent application to wheat crop at two rates of application viz., 15 g and 20 g a.i. ha^?1. Soil samples at 0 (3 h), 1, 3, 5, 7, 10, 15, 20, and 30-day intervals after application were drawn, extracted, cleaned up, and analyzed for herbicide residues by high performance liquid chromatography (HPLC) using C₁₈ column and methanol: water (8:2) as mobile phase at 242 nm wave length. Effect of microbial activity and soil pH was studied under laboratory conditions. Dissipation of triasulfuron followed a first-order-rate kinetics. Residues dissipated from field soil with half-life of 5.8 and 5.9 days at two rates of application. The study indicated biphasic degradation with faster rate initially (t _1/2 = 3.7 days), followed by a slower dissipation rate at the end (t _1/2 = 9.4 days). Similar trend was observed with non-sterile soil in laboratory with a longer half-life. Acidic pH and microbial activity contributed toward the degradation of triasulfuron in soil.     

Effect of Pencycuron on Microbial Parameters of Waterlogged Soil

A laboratory study was conducted to monitor the effect of pencycuron [1-(4-chlorobenzyl)-1-cyclopentyl-3-phenylurea] on microbial parameters of alluvial (AL) soil (Typic udifluvent) and coastal saline (CS) soil (Typic endoaquept) under waterlogged condition. Pencycuron at field rate (FR), 2FR and 10FR affected the microbial biomass C (MBC), soil ergosterol content and fluorescein diacetate hydrolyzing activity (FDHA) differentially. The DCM amendment did not seem to have any counteractive effect on the toxicity of pencycuron on the microbial variables. The change in microbial metabolic quotient (qCO₂) and microbial respiration quotient (Q_R), indicated pencycuron induced disturbance at 10FR. Present study revealed that the metabolically activated microbial population was more suppressed compared to the dormant population.     

Effect of Agricultural Antibiotics on the Persistence and Transformation of 17β-Estradiol in a Sequatchie Loam

A laboratory incubation study was conducted to investigate the effect of agricultural antibiotics (sulfamethazine, tylosin, and chlortetracycline) on the persistence and transformation of 17β-estradiol in Sequatchie loam. We measured concentrations of 17β-estradiol and its primary metabolite (estrone) in soils spiked with antibiotics and 17β-estradiol. Dehydrogenase activity (DHA) was also measured as an indicator of the total microbial activity of the soils. The presence of antibiotics significantly decreased transformation of 17β-estradiol to estrone. There was a positive correlation between the DHA and the concentrations of estrone in soil spiked with 17β-estradiol only, implying that the reaction is mainly catalyzed by dehydrogenases. However, the positive correlation was weakened in soil spiked with 17β-estradiol and antibiotics together. We recommend that any study evaluating the fate and transport of estrogenic hormones in soil should include the effect of agricultural antibiotics because antibiotics and estrogenic hormones are commonly excreted together in environmental samples.     

Migration of heavy metals and migration-degradation of phenanthrene in soil using electro kinetic-laccase combined remediation system

Abstract

In order to solve the problem of heavy metal-organic compound soil pollution, in this paper, we developed a highly efficient electro kinetic-laccase combined remediation (EKLCR) system. The results showed that the EKLCR system had an obvious migration effect on heavy metals (copper and cadmium) and good migration-degradation effect on phenanthrene. The migration rates of copper and cadmium were 48.3% and 40.3%, respectively. Especially, with the presence of laccase, the removal rate of phenanthrene on Cu²⁺-contaminated soil was higher than that of Cd²⁺-contaminated soil due to the significant effect of heavy metals on the enzymatic activity of laccase. The average migration-degradation rate of phenanthrene by EKLCR system was 45.4%. Finally, gas chromatography-mass spectrometry (GC/MS) was used to analyze the degradation intermediates of phenanthrene in the soil, which included 9,10-Phenanthrenequinone, phthalic acid, and 2,2-Biphenyldicarboxylic Acid. In addition, we give the possible degradation pathways of phenanthrene, 2,2-Biphenyldicarboxylic Acid is further degraded to produce phthalic acid. The products of the phthalic acid metabolic pathway are protocatechuic acid, pyruvic acid or succinic acid, the final products of these organic acids are carbon dioxide and water.     

Effect of the veterinary ionophore monensin on the structure and activity of a tropical soil bacterial community

Abstract

Monensin (MON) is a coccidiostat used as a growth promoter that can reach the environment through fertilization with manure from farm animals. To verify whether field-relevant concentrations of this drug negatively influence the structure and activity of tropical soil bacteria, plate counts, CO₂ efflux measurements, phospholipid fatty acids (PLFA) and community-level physiological profiling (CLPP) profiles were obtained for soil microcosms exposed to 1 or 10?mg kg^?1 of MON across 11?days. Although 53% (1?mg kg^?1) to 40% (10?mg kg^?1) of the MON concentrations added to the microcosms dissipated within 5?days, a subtle concentration-dependent decrease in the number of culturable bacteria (<1 log CFU g^?1), reduced (?20 to ?30%) or exacerbated (+25%) soil CO₂ effluxes, a marked shift of non-bacterial fatty acids, and altered respiration of amines (1.22-fold decrease) and polymers (1.70-fold increase) were noted in some of the treatments. These results suggest that MON quickly killed some microorganisms and that the surviving populations were selected and metabolically stimulated. Consequently, MON should be monitored in agronomic and environmental systems as part of One Health efforts.     

Effects of conditioning,cross‐conditioning,and microbial growth on development of enhanced biodegradation of insecticides in soil

Abstract

Pretreatment of a Drummer‐Catlin soil mixture with granular formulations of carbofuran or trimethacarb enhanced biodegradation of subsequent treatments with the technical formulations. Degradation of carbofuran was enhanced by pretreatments with trimethacarb, and degradation of trimethacarb was enhanced by pretreatments with carbofuran. Bendiocarb degradation was enhanced by pretreatments of soil with carbofuran or trimethacarb. In bioassays with southern corn rootworm larvae, biological activity of carbofuran, trimethacarb, and bendiocarb was rapidly lost in soils pretreated with granular formulations. Pretreatment of soil with granular terbufos did not enhance the biodegradation of subsequent applications of technical terbufos. Several microbial biomass assays showed an increase in specific carbofuran‐degrading bacteria in soils that were pretreated with carbofuran. Bacteria were isolated that could grow on carbofuran and apparently degrade it when present with another carbon source.