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L. J. Audus 《Plant and Soil》1951,3(2):170-192
Summary (1) The results of experiments on the continuous perfusion of aerated solutions of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2, Methyl-4, chlorophenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) through garden soil indicate that the kinetics of their breakdown are essentially similar.(2) Three phases can be distinguised: (a) an immediate initial adsorption onto soil colloids amounting to 0.167±0.035 mg per g dry soil, (b) a lag phase of varying duration in which there is little or no disappearance of herbicide, (c) a final phase of rapid complete detoxication. Such enriched soils detoxicate subsequent perfusions with the same herbicide molecule at a constant high rate. Enrichment times for 2,4-D, MCPA and 2,4,5-T are roughly of the order or 14, 70 and 270 days respectively.(3) This indirect evidence, from kinetics of detoxication, of the development of a bacterial flora adapted to herbicide breakdown, is strongly supported by experiments in which the detoxicating activity of such enriched soils was completely destroyed by low concentrations (0.01%) of the bacterial poison, sodium azide.(4) Attempts to isolate in pure culture the 2,4-D-decomposing organism were successful. Preliminary classification work relegates the organism to the Bacterium globiforme group. Further confirmatory work is required.(5) Cross perfusion experiments in which 2,4-D enriched soils were perfused with MCPA and vice versa indicate that both can detoxicate the other analogue, although at a somewhat lower rate than the soil directly enriched with that analogue.(6) 2,4-D enriched soil will not detoxicate 2,4,5-T although some activity may be temporarily induced by an intermediate perfusion with MCPA. 相似文献
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Three post-emergence herbicides (2,4-D, picloram and glyphosate) were applied to samples of an Alberta agricultural soil at
concentrations of 0, 2, 20, and 200 μg g−1. The effects of these chemicals on certain microbial variables was monitored over 27 days. All herbicides caused enhancement
of basal respiration but only for 9 days following application, and only for concentrations of 200 μg g−1. Substrate-induced respiration was temporarily depressed by 200 μg g−1 picloram and 2,4-D, and briefly enhanced by 200 μg g−1 glyphosate. It is concluded that because changes in microbial variables only occurred at herbicide concentrations of much
higher than that which occurs following field application, the side-effects of these chemicals is probably of little ecological
significance. 相似文献
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Summary Samples of a sandy loam soil were supplied with normal, 10-fold and 100-fold rates of ioxynil, dalapon, mecoprop, dichlorprop,
MCPA + dichlorprop, picloram, and amitrole-T and incubated at 29°C at 65 per cent of the waterholding capacity. Treated soil
samples were compared with untreated samples. Samples supplied with (NH4)2SO4 and herbicides were used to investigate the effect of the herbicides on the rate of nitrification and the production of nitrite.
In several cases higher numbers of bacteria were found for a longer or shorter period in soil treated with herbicides. There
was some evidence that certain groups of bacteria had adapted to ioxynil in a soil sample supplied with the 100-fold rate
of this chemical.
After 2 or 4 weeks lower numbers ofAzotobacter chroococcum were found at the normal rate of ioxynil, dalapon, mecoprop, and dichlorprop. At the 100-fold rate of application the numbers
of Azotobacter were unfavourably affected by all herbicides.
The production of mineral nitrogen was hardly affected by the normal and 10-fold rates of application.
In the first week the rate of nitrification was slightly depressed in soil samples treated with the normal rates of dichlorprop
and amitrole-T and with the 10-fold rates of dalapon, mecoprop, and MCPA + dichlorprop. Strong inhibition of the nitrification
for at least 7 weeks was shown by the 10-fold rate of amitrole-T. At the 100-fold rate all herbicides, with the exception
of picloram, depressed the rate of nitrification for a longer or shorter period.
During the second week a very small increase of nitrite was found in the samples treated with the normal and 10-fold rates
of dalapon, mecoprop, dichlorprop, and amitrole-T. A small increase of nitrite was noted for 26 weeks in samples treated with
the 100-fold rates of amitrole-T.
A highly significant depression of CO2 evolution was found in the first week in samples treated with the normal rates of ioxynil, dalapon, mecroprop, dichlorprop,
and amitrole-T, also in samples treated with the 10-fold rates of dalapon, mecoprop, dichlorprop, MCPA + dichlorprop, picloram,
and amitrole-T. A highly significant depression of CO2 production was found after 8 weeks in all the samples treated with herbicides at the 100-fold rate with the exception of
the sample treated with picloram.
The decomposition of the herbicides was studied in soil samples treated with the 100-fold rates of herbicides. Only traces
of dalapon and mecoprop were found after 9 months, but 7.2% ioxynil, 29.8% dichlorprop, 39% (MCPA + dichlorprop), 52.1% picloram
and 52.2% amitrole-T were still present in active form. 相似文献
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T. CSERHÁTI, Z. ILLÉS AND S. NEMES-KÓSA. 1992. The effect of some benzonitrile ester herbicides on the growth of Bacillus megaterium, B. cereus var. mycoides, B. polymyxa, B. subtilis, Pseudomonas fluorescens and Azotobacter chrooccum was investigated in the concentration range 20–640 ppm by the agar diffusion method. The zones of inhibition, restricted growth and eventual stimulation were determined. The data matrix was evaluated by principal component analysis. Azotobacter chroococcum was the most resistant to the benzonitrile esters. The influence of benzonitrile esters on the growth of micro-organisms depended equally on the species and on the chemical structure of the herbicides. Chloro substitution considerably modified the effect whereas bromo and iodo substitution resulted in similar biological activity. 相似文献