Short-term assay of soil urease activity using colorimetric determination of ammonium
TL;DR: In this paper, a rapid assay for soil urease in the absence of bacteriostatic agents has been developed, which comprises incubation of soil with an aqueous or buffered urea solution, extraction of ammonium with 1 N KCl and 0.01 NHCl and colorimetric NH4+ determination by a modified indophenol reaction.
Abstract: A rapid assay for soil urease in the absence of bacteriostatic agents has been developed. The method comprises incubation of soil with an aqueous or buffered urea solution, extraction of ammonium with 1 N KCl and 0.01 NHCl and colorimetric NH4
+ determination by a modified indophenol reaction. The method is characterized by high sensitivity and stability of the coloured complex formed. Measurements obtained by this method showed that no change in urease activity occurred when field-moist samples of soils were stored at −20°C for as long as 5 months. Air-drying of field-moist soil samples may lead to an increase in urease activity.
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TL;DR: The discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers, and the genome of this chemolithoautotrophic organism encodes the pathways both for ammonia and nitrite oxidation.
Abstract: Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered to be a two-step process catalysed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetically advantageous. This functional separation has puzzled microbiologists for a century. Here we report on the discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers. The genome of this chemolithoautotrophic organism encodes the pathways both for ammonia and nitrite oxidation, which are concomitantly activated during growth by ammonia oxidation to nitrate. Genes affiliated with the phylogenetically distinct ammonia monooxygenase and hydroxylamine dehydrogenase genes of Nitrospira are present in many environments and were retrieved on Nitrospira-contigs in new metagenomes from engineered systems. These findings fundamentally change our picture of nitrification and point to completely nitrifying Nitrospira as key components of nitrogen-cycling microbial communities.
1,648 citations
TL;DR: The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L.
Abstract: B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.
1,506 citations
01 Jan 2015
TL;DR: The abstract should follow the structure of the article (relevance, degree of exploration of the problem, the goal, the main results, conclusion) and characterize the theoretical and practical significance of the study results.
Abstract: Summary) The abstract should follow the structure of the article (relevance, degree of exploration of the problem, the goal, the main results, conclusion) and characterize the theoretical and practical significance of the study results. The abstract should not contain wording echoing the title, cumbersome grammatical structures and abbreviations. The text should be written in scientific style. The volume of abstracts (summaries) depends on the content of the article, but should not be less than 250 words. All abbreviations must be disclosed in the summary (in spite of the fact that they will be disclosed in the main text of the article), references to the numbers of publications from reference list should not be made. The sentences of the abstract should constitute an integral text, which can be made by use of the words “consequently”, “for example”, “as a result”. Avoid the use of unnecessary introductory phrases (eg, “the author of the article considers...”, “The article presents...” and so on.)
1,229 citations
TL;DR: In this paper, the authors conducted a study to determine the effects of long-term addition of organic and inorganic fertiliser amendments at low rates on soil chemical and biological properties.
Abstract: The effect of organic and inorganic fertiliser amendments is often studied shortly after addition of a single dose to the soil but less is known about the long-term effects of amendments. We conducted a study to determine the effects of long-term addition of organic and inorganic fertiliser amendments at low rates on soil chemical and biological properties. Surface soil samples were taken from an experimental field site near Cologne, Germany in summer 2000. At this site, five different treatments were established in 1969: mineral fertiliser (NPK), crop residues removed (mineral only); mineral fertiliser with crop residues; manure 5.2 t ha −1 yr −1 ; sewage sludge 7.6 t ha −1 yr −1 or straw 4.0 t ha −1 yr −1 with 10 kg N as CaCN 2 t straw −1 . The organic amendments increased the C org content of the soil but had no significant effect on the dissolved organic C (DOC) content. The C/N ratio was highest in the straw treatment and lowest in the mineral only treatment. Of the enzymes studied, only protease activity was affected by the different amendments. It was highest after sewage amendment and lowest in the mineral only treatment. The ratios of Gram+ to Gram− bacteria and of bacteria to fungi, as determined by signature phospholipid fatty acids, were higher in the organic treatments than in the inorganic treatments. The community structure of bacteria and eukaryotic microorganisms was assessed by denaturing gradient gel electrophoresis (DGGE) and redundancy discriminate analyses of the DGGE banding patterns. While the bacterial community structure was affected by the treatments this was not the case for the eukaryotes. Bacterial and eukaryotic community structures were significantly affected by C org content and C/N ratio.
876 citations
TL;DR: It is shown that Bacteria rather than Archaea functionally dominate ammonia oxidation in an agricultural soil, despite the fact that archaeal versus bacterial amoA genes are numerically more dominant.
Abstract: Agricultural ecosystems annually receive approximately 25% of the global nitrogen input, much of which is oxidized at least once by ammonia-oxidizing prokaryotes to complete the nitrogen cycle. Recent discoveries have expanded the known ammonia-oxidizing prokaryotes from the domain Bacteria to Archaea. However, in the complex soil environment it remains unclear whether ammonia oxidation is exclusively or predominantly linked to Archaea as implied by their exceptionally high abundance. Here we show that Bacteria rather than Archaea functionally dominate ammonia oxidation in an agricultural soil, despite the fact that archaeal versus bacterial amoA genes are numerically more dominant. In soil microcosms, in which ammonia oxidation was stimulated by ammonium and inhibited by acetylene, activity change was paralleled by abundance change of bacterial but not of archaeal amoA gene copy numbers. Molecular fingerprinting of amoA genes also coupled ammonia oxidation activity with bacterial but not archaeal amoA gene patterns. DNA-stable isotope probing demonstrated CO(2) assimilation by Bacteria rather than Archaea. Our results indicate that Archaea were not important for ammonia oxidation in the agricultural soil tested.
828 citations
Cites methods from "Short-term assay of soil urease act..."
...N content of 100 mg NH4-N/g d.w.s. Nitrogen-free controls received the same amount of distilled water....
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...The soil filtrate of each replicate was used for colorimetric measurement of NH4-N (Kandeler and Gerber, 1988), NO3-N (Schlichting and Blume, 1966) and pH....
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...The plots had been fertilized with 160 kg N ha-1, which is equivalent to 70 mg NH4-N/g d.w.s assuming an effective soil depth of 20 cm....
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...N (Kandeler and Gerber, 1988), NO3-N (Schlichting and Blume, 1966) and pH. Soil NO2-N was measured by ion chromatography and found to be below the detection limit....
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References
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TL;DR: WALKLEY as discussed by the authors presented an extension of the DEGTJAas discussed by the authorsF METHOD for determining soil organic matter, and a proposed modification of the CHROMIC ACID TITRATION METHOD.
Abstract: AN EXAMINATION OF THE DEGTJAREFF METHOD FOR DETERMINING SOIL ORGANIC MATTER, AND A PROPOSED MODIFICATION OF THE CHROMIC ACID TITRATION METHOD A. WALKLEY;I. BLACK; Soil Science
17,132 citations
26 Oct 2015
3,503 citations
TL;DR: The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L.
Abstract: B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.
1,506 citations
"Short-term assay of soil urease act..." refers background in this paper
...The numerous pub l i shed me thods for the de t e rmina t i on o f soil urease ac t iv i ty differ widely in t ime o f incuba t ion , subs t ra te concent r a t ion and choice o f buffer (Burns 1978; Gosewinkel and B r o a d b e n t 1984)....
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...The wide d iscrepancy in the cond i t ions used and the defects in the me thods a d o p t e d for assay o f urease ac t iv i ty have caused m a n y o f the divergent f indings in research on soil urease (Burns 1978)....
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TL;DR: In this article, a simple and precise method of assaying urease activity in soils is described, which involves determination of the ammonium released by urea-fixing activity when soil is incubated with tris(hydroxymethyl)aminomethane (THAM) buffer, urea solution, and toluene at 37°C for 2 h, ammonium release being determined by a rapid procedure involving treatment of the incubated soil sample with 2.5 M KC1 containing a urea inhibitor (Ag 2 SO 4 ) and steam distillation of
Abstract: A simple and precise method of assaying urease activity in soils is described. It involves determination of the ammonium released by urease activity when soil is incubated with tris(hydroxymethyl)aminomethane (THAM) buffer, urea solution, and toluene at 37°C for 2 h, ammonium release being determined by a rapid procedure involving treatment of the incubated soil sample with 2.5 M KC1 containing a urease inhibitor (Ag 2 SO 4 ) and steam distillation of an aliquot of the resulting soil suspension with MgO for 3.3 min. Studies reported showed that the optimal buffer pH and substrate (urea) concentration for assay of soil urease activity using THAM buffer are 9.0 and 0.02 M, respectively, and that the method described is satisfactory for assay of urease activity in ammonium-fixing soils.
776 citations
"Short-term assay of soil urease act..." refers methods in this paper
...To test the colorimetric method adopted for the determination of NH~, this method was compared with steam distillation and acidimetric titration of the distillate (Tabatabai and Bremner 1972)....
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...Com!Sarison of two methods for estimation of ammonium: Steam distillation (Tabatabai and Bremner 1972) and modified colorimetric method (Wagner 1969)....
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...1976), s team dis t i l l a t ion (Tabatabai and Bremner 1972) and e lec t roconduc t iv i ty using a s teady-s ta te f low system across a m e m b r a n e (Gosewinkel and Broadben t 1984)....
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TL;DR: In this article, the results obtained by a buffer method of assaying urease activity were markedly higher than those obtained by non-buffer method, and studies reported that it provided a much better index than the buffer method for the ability of soils to hydrolyze urea under natural conditions.
Abstract: Analyses of 16 soils selected to obtain a wide range in properties showed that the results obtained by a buffer method of assaying urease activity were markedly higher than those obtained by a non-buffer method. Both methods gave reproducible results, but the non-buffer method was the more precise, and studies reported showed that it provides a much better index than the buffer method of the ability of soils to hydrolyze urea under natural conditions. The buffer method detects urease activity that does not occur when soils are treated with urea in the absence of buffer. This is a disadvantage if the purpose of the assay is to obtain an index of the ability of soils to hydrolyze fertilizer urea, but is an advantage if the purpose is to detect urease in soils or soil fractions. Use of toluene to inhibit microbial activity in assay of urease activity by the non-buffer method described did not significantly affect the results obtained by this method, but it is decreased the precision of the method.
255 citations