Search results for "Gradation"

Offsetting land degradation through nitrogen and water management during maize cultivation under arid conditions

2018

All-Optical Measurement of Background, Amplitude and Timing Jitter for high speed pulse trains or prbs sequences using autocorrelation function

2006

We present a simple method for all-optical measurements of background, amplitude- and timing-jitter of ultra high speed pulse trains or prbs sequences using the jitter dependences of the intercorrelation-peak shape.

Impact of distribution heterogeneity of microorganisms and 2,4-D on biodegradation processes in soil : experiment and modelling

2013

Impact of distribution heterogeneity of microorganisms and 2,4-D on biodegradation processes in soil : experiment and modelling. Conference on Pesticide Behaviour in Soils, Water and Air (York 2013)

Variability of pesticide mineralization in individual soil aggregates of millimeter size

2002

The aim of this study was to compare the 2,4-D mineralization in individual aggregates of millimeter size (3 size classes and 96 aggregates per size class). 14 CO 2 coming from the mineralization of 14 C ring-labeled 2,4-D and evolved by each aggregate incubated in microtiter plates was trapped with barium hydroxide on filters and measured using a Phosphorimager. We observed an important variability of mineralization in aggregates of each size class and in the different size classes of aggregates. The main factors responsible for these fluctuations could be a heterogeneous distribution of degrading microorganisms or of available carbon necessary for cometabolism.

Microbial aspects of atrazine biodegradation in relation to history of soil treatment

1999

Among 15 soils with different cropping practices, seven which had an history of repeated atrazine applications showed accelerated degradation of this herbicide. By contrast, grassland or agricultural soils with no recorded atrazine application, at least for the last three years, had a low degradation potential. No direct relation was found between the rate of atrazine mineralisation and the size of the microbial biomass. In adapted soils, the amounts of extractable residues were lowered and the very high percentages of radioactivity from [ring-14C]atrazine recovered as [14C]carbon dioxide demonstrated that N-dealkylation and deamidation were the only processes for micro-organisms to derive …

Indicateurs pour l'évaluation de l'impact de produits phytosanitaires sur la composante microbienne de la qualité biologique des sols

2011

National audience

Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin…

2002

A greenhouse study was conducted to investigate the ability of four crops (wheat, corn, oilseed rape and soybean) to influence the degradation of bentazone, diclofop-methyl, diuron, isoproturon and pendimethalin in soil. The present study showed that microbial biomass-carbon was significantly higher in planted soils than in bulk soil, especially with wheat and corn, after several cropping cycles. The biomass in corn and soybean planted soils was adversely affected by bentazone but recovered after three cropping cycles. In wheat-planted soils, diclofop-methyl application resulted in persistent increase of the amount of microbial biomass. Bentazone did not show accelerated degradation even af…

Monitoring of atrazine treatment on soil bacterial, fungal and atrazine-degrading communities by quantitative competitive PCR

2003

We report the development of quantitative competitive (QC) PCR assays for quantifying the 16S, 18S ribosomal and atzC genes in nucleic acids directly extracted from soil. QC-PCR assays were standardised, calibrated and evaluated with an experimental study aiming to evaluate the impact of atrazine application on soil microflora. Comparison of QC-PCR 16S and 18S results with those of soil microbial biomass showed that, following atrazine application, the microbial biomass was not affected and that the amount of 16S rDNA gene representing 'bacteria' increased transitorily, while the amount of 18S rDNA gene representing fungi decreased in soil. In addition, comparison of atzC QC-PCR results wit…

Degradation of 2,4‐D, 2,4‐Dichlorophenol, and 4‐Chlorophenol in Soil after Sorption on Humified and Nonhumified Organic Matter

1999

Soil organic matter (SOM) primarily governs sorption processes and therefore affects the availability of organic chemicals to degrading microorganisms. Transformations of 14 C-ring-labeled 2,4-dichlorophenoxyacetic acid (2,4-D); 2,4-dichlorophenol (2,4-DCP); and 4-chlorophenol (4-CP) sorbed on organic materials with increasing degrees of humification (wood, fresh straw, composted straw, ligain, and humic acid) and on a reference mineral sorbent (Al-oxide) were studied during soil incubation experiments. Chemicals previously sorbed on the different sorbents were applied to the soil. Mineralization kinetics, analysis of water and methanol extracts and measurements of the nonextractable radioa…

Isoproturon

2010

Frequent use of phenylurea herbicide isoproturon (IPU) in agricultural fields has resulted not only in the contamination of the natural resources including soil and water but also in the adaptation of the soil microflora to its rapid degradation. However, up to now, the mechanisms underlying this microbial adaptation are not well elucidated. The aim of this study was to explore the processes and factors implicated in IPU degradation from the agricultural field to the genes coding for catabolic genes. The study carried out at the experimental field of Epoisses cropped with a winter wheat / barley / rape seed crop rotation indicated that as a result of its periodically repeated use, the soil …