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PubMedDate not supplied

[Regulation of the biomass and activity of soil microorganisms by microfauna].

Microcosm experiments showed that the microbial biomass and the respiration activity in soil were regulated by nematodes. Depending on nematode number and plant residue composition, the trophic activity of nematodes can either stimulate or inhibit microbial growth and respiration as compared to soil containing no nematodes. The stimulating effect was observed when nitrogen-free (starch) or low-nitrogen (wheat straw, C:N = 87) organic substrates were applied. Inhibition occurred when a substrate rich in nitrogen (alfalfa meal, C:N = 28) was decomposed and the nematode population exceeded the naturally occurring level. A conceptual model was developed to describe trophic regulation by microfauna (nematodes) of the microbial productivity and respiration activity and decomposition of not readily decomposable organic matter in soil. The stimulating and inhibiting influence of microfauna on soil microorganisms was not a linear function of the rate of microbial consumption by nematodes. These effects are largely associated with the induced change in the physiological state of microorganisms rather than with the mobilization of biogenic elements from the decomposed microbial biomass.

Animals↗
PubMed2005

Studies on nutrient uptake of rice and characteristics of soil microorganisms in a long-term fertilization experiments for irrigated rice.

The ecosystem characteristics of soil microorganism and the nutrient uptake of irrigated rice were investigated in a split-block experiment with different fertilization treatments, including control (no fertilizer application), PK, NK, NP, NPK fertilization, in the main block, and conventional rice and hybrid rice comparison, in the sub block. Average data of five treatments in five years indicated that the indigenous N supply (INS) capacity ranged from 32.72 to 93.21 kg/ha; that indigenous P supply (IPS) capacity ranged from 7.42 to 32.25 kg/ha; and that indigenous K supply (IKS) capacity ranged from 16.24 to 140.51 kg/ha, which showed that soil available nutrient pool depletion might occur very fast and that P, K deficiency has become a constraint to increasing yields of consecutive crops grown without fertilizer application. It was found that soil nutrient deficiency and unbalanced fertilization to rice crop had negative effect on the diversity of the microbial community and total microbial biomass in the soil. The long-term fertilizer experiment (LTFE) also showed that balanced application of N, P and K promoted microbial biomass growth and improvement of community composition. Unbalanced fertilization reduced microbial N and increased C/N ratio of the microbial biomass. Compared with inbred rice, hybrid rice behavior is characterized by physiological advantage in nutrient uptake and lower internal K use efficiency.

Agriculture↗
PubMedDate not supplied

[The effect of biostimulants and fungicides on the growth parameters of natural associations of soil microorganisms].

Biostimulants ivin and emistym take positive effect on the growth characteristics of natural association of soil microorganisms: they increase the specific growth rate, the number of generations, decrease the lag-phase and duration of redoubling the number of microorganisms. Presence of fungicides in the medium inhibits the growth of microorganisms. Under combined use of biostimulants and fungicides one cannot reveal the negative effect of fungicides on the natural associations of microorganisms, however the stimulating action of growth-regulating substances decreases.

Culture Media↗
PubMed1995

Long-term effects of metals in sewage sludge on soils, microorganisms and plants.

This paper reviews the evidence for impacts of metals on the growth of selected plants and on the effects of metals on soil microbial activity and soil fertility in the long-term. Less is known about adverse long-term effects of metals on soil microorganisms than on crop yields and metal uptake. This is not surprising, since the effects of metals added to soils in sewage sludge are difficult to assess, and few long-term experiments exist. Controlled field experiments with sewage sludges exist in the UK, Sweden, Germany and the USA and the data presented here are from these long-term field experiments only. Microbial activity and populations of cyanobacteria, Rhizobium leguminosarum bv. trifolii, mycorrhizae and the total microbial biomass have been adversely affected by metal concentrations which, in some cases, are below the European Community's maximum allowable concentration limits for metals in sludge-treated soils. For example, N2-fixation by free living heterotrophic bacteria was found to be inhibited at soil metal concentrations of (mg kg-1): 127 Zn, 37 Cu, 21 Ni, 3.4 Cd, 52 Cr and 71 Pb. N2-fixation by free-living cyanobacteria was reduced by 50% at metal concentrations of (mg kg-1): 114 Zn, 33 Cu, 17 Ni, 2.9 Cd, 80 Cr and 40 Pb. Rhizobium leguminosarum bv. trifolii numbers decreased by several orders of magnitude at soil metal concentrations of (mg kg-1): 130-200 Zn, 27-48 Cu, 11-15 Ni, and 0.8-1.0 Cd. Soil texture and pH were found to influence the concentrations at which toxicity occurred to both microorganisms and plants. Higher pH, and increased contents of clay and organic carbon reduced metal toxicity considerably. The evidence suggests that adverse effects on soil microbial parameters were generally found at surprizingly modest concentrations of metals in soils. It is concluded that prevention of adverse effects on soil microbial processes and ultimately soil fertility, should be a factor which influences soil protection legislation.

Bacteria↗
PubMed1976

Products of soil microorganisms in relation to plant growth.

A survey has been made of the range and activity of the organic products of soil microorganisms which have a direct influence on plant growth. Microbial metabolites which effect plants indirectly by the modification of the soil environment are also reviewed. The sources of substrates for the production of metabolites in soil and the farming practices which give rise to them are considered. It is stressed that an interdisciplinary approach is needed in the manipulation of microbiological activity in soil.

Agriculture↗
PubMed1975

A simple fluorescence of staining technique for in situ soil microorganisms.

A simple, rapid straining technique using the magnesium salt of 1-anilino-8-naphthalene sulfonic acid is described. Treatment of soil with an aqueous, membrane-filtered solution (3.5 mg/ml) of the salt causes the soil microorganisms to fluoresce when examined with light from a mercury arc light source.

Anilino Naphthalenesulfonates↗
PubMed1966

Effect of zytron and its degradation products on soil microorganisms.

There was no adverse effect of Zytron, o-2,4-dichlorophenyl o-methyl isopropyl phosphoramidothioate, a herbicide, upon molds, actinomycetes, and soil bacteria in field plots, or upon selected soil microorganisms in model systems. 2,4-Dichlorophenol, a degradation product, was found to be toxic at levels above 10 ppm to molds, but levels this high were not found in soil from treated plots. Aspergillus clavatus degraded both Zytron and 2,4-dichlorophenol. Sodium o-methyl isopropyl phosphoramidothioate, another degradation product of Zytron, stimulated the growth of a species of Penicillium.

Actinomyces↗
PubMed2004

Casuarina cunninghamiana tissue extracts stimulate the growth of Frankia and differentially alter the growth of other soil microorganisms.

Aqueous extracts of host plant Casuarina cunninghamiana tissue altered the in vitro growth of its diazotrophic microsymbiont Frankia and a selection of other soil microorganisms. The growth of actinomycetous Frankia strains, 55005. AvcI1, CesI5, CjI82 001, and Cj was stimulated by aqueous extracts of C. cunninghamiana tissue. Green cladodes (photosynthetic branches), unsuberized roots, and suberized roots were more stimulatory than dry cladodes and seed tissue. Aqueous extracts of green cladodes of C. cunninghamiana most stimulated the growth of Casuarina-derived Frankia strains CjI82 001 and 55005. The growth of isolates of soil bacteria Bradyrhizobium japonicum, Arthrobacter globiformis and Bacillus subtillis and of the soil fungi Penicillium oxalicum and Arthroderma cookiellum was either inhibited or not affected by cladode extracts. Cladode extracts stimulated the growth of the actinomycete Streptomyces albus and the fungus Rhizopus homothallicus. The magnitude (as great as 100%) of the increase in growth caused by tissue extracts for the Casuarina-derived Frankia strains relative to other soil microbes suggests a host-specific enhancement of the microsymbiont.

Bacteria↗
PubMed1976

Utilization and degradation of lindane by soil microorganisms.

Of 147 microorganisms isolated from a loamy sand, 71 showed good growth with lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane) and produced chloride in an aqueous medium. Thirteen soil microorganisms were selected to study the utilization of lindane. Lindane was metabolized by the microbes to gamma-2,3,4,5,6-pentachloro-1-cyclohexene (gamma-PCCH), alpha-3,4,5,6-tetrachloro-1-cyclohexene (alpha-TCCH), beta3,4,5,6-tetrachloro-1-cyclohexene (beta-TCCH), gamma-3,4,5,6-tetrachloro-1-cyclohexene (gamma-TCCH), and pentachlorobenzene (PCB). Cells of Pseudomonas sp. No. 62 grown on lindane simultaneously adapted to gamma-PCCH, alpha-TCCH, beta-TCCH, gamma-TCCH, PCB, 1,2,3,4,-tetrachlorobenzene (1,2,3,4-TCB) and 1,2,4,5-tetrachlorobenzene (1,2,4,5-TCB). The bacteria degraded each of these chemicals at least partially as indicated by an increased rate of oxygen consumption.

Actinomycetales↗
PubMed1983

Testing and evaluating some methods to investigate side effects of environmental chemicals on soil microorganisms.

Some methods of measuring soil biological activities (dehydrogenase activity, short- and long-term respiration, ATP content, nitrogen transformation, and straw decomposition) were used to assess their suitability for testing side effects of environmental chemicals on microbial activities. Reproducibility and, especially, the sensitivity of the methods (and activities) were important. In these investigations, the chemicals Aretit (herbicidal ingredient dinoseb acetate), pentachlorophenol, and sodium dodecyl sulfonate (LAS) were applied at different dosages. The trials were run under laboratory and field conditions to examine agreement between the results. The activities tested varied in their sensitivity to the chemicals. Dehydrogenase activity, short-term respiration, ATP content, and, in some cases, nitrogen transformation were the most sensitive, whereas straw decomposition and long-term respiration needed higher dosages for inhibitory effects. Dinoseb acetate was particularly effective. The effects of all chemicals were strongly modified by the soil type, while temperature and moisture had fewer effects. Inhibitory effects lasted several months under laboratory conditions. Agreement between laboratory and field trials was best with dehydrogenase activity.

Adenosine Triphosphate↗
PubMed1971

Solubilization of iron-containing minerals by soil microorganisms.

Eighty-eight strains of microorganisms were isolated from soils collected in northern and southern Chile, and 10 fungi which showed the highest solubilizing action upon the iron in granodiorite were then selected. These fungi were incubated with the following iron-containing minerals: augite, hornblende, biotite, magnetite, hematite, and the igneous rock granodiorite. The solubility of iron in these minerals depended on their nature, crystalline structure, the concentration of metabolic products, or all three. Complex formation could be the mechanism involved, as a strong cation-exchange resin was not able to extract Fe from culture solutions. This conclusion is also confirmed by the R(F) values obtained by thin-layer chromatography of iron-containing culture solutions.

Acremonium↗
PubMed1991

Effect of the herbicide Bentanex on soil microorganisms and their activity.

The effect of the herbicide Bentanex, especially of its effective component bentazone, on selected soil bacteria and fungi, on their growth and reproduction and on some important physiological activities ensuring a regular nutrient cycle in nature was investigated. Bentazone affected growth and reproduction of soil bacteria and micromycetes in dependence on the concentration and species of the microorganism. Physiological and biochemical activities of bacteria with respect to nitrogen fixation, nitrification and CO2 production were negatively influenced by high concentrations of the herbicide. These concentrations were used to observe the effect on selected activities of soil microorganisms and were much higher than those actually used in agriculture.

Bacteria↗