scholarly journals Evolutionary implications of microplastics for soil biota

2019 ◽  
Vol 16 (1) ◽  
pp. 3 ◽  
Author(s):  
Matthias C. Rillig ◽  
Anderson Abel de Souza Machado ◽  
Anika Lehmann ◽  
Uli Klümper
Keyword(s):  
Aquatic Ecosystems ◽  
Soil Microorganisms ◽  
Soil Microbes ◽  
Soil Biota ◽  
Microbial Populations ◽  
Selection Pressures ◽  
Soil Microbial ◽  
Anthropogenic Stressor ◽  
Evolutionary Consequences ◽  
Harmful Effects

Environmental contextMicroplastic particles are increasingly recognised as human-caused pollutants in soil with potential harmful effects on soil microorganisms. Microplastics may also have evolutionary consequences for soil microbes, because the particles may alter conditions in the soil and hence selection pressures. Including an evolutionary perspective in an environmental assessment of microplastics could lead to new questions and novel insights into responses of soil microbes to this anthropogenic stressor. AbstractMicroplastic pollution is increasingly considered to be a factor of global change: in addition to aquatic ecosystems, this persistent contaminant is also found in terrestrial systems and soils. Microplastics have been chiefly examined in soils in terms of the presence and potential effects on soil biota. Given the persistence and widespread distribution of microplastics, it is also important to consider potential evolutionary implications of the presence of microplastics in soil; we offer such a perspective for soil microbiota. We discuss the range of selection pressures likely to act upon soil microbes, highlight approaches for the study of evolutionary responses to microplastics, and present the obstacles to be overcome. Pondering the evolutionary consequences of microplastics in soils can yield new insights into the effects of this group of pollutants, including establishing ‘true’ baselines in soil ecology, and understanding future responses of soil microbial populations and communities.

scholarly journals Influence of Repeated Application of Wetting Agents on Soil Water Repellency and Microbial Community

2019 ◽  
Vol 11 (16) ◽  
pp. 4505 ◽  
Author(s):  
Enzhan Song ◽  
Xiaowei Pan ◽  
Robert J. Kremer ◽  
Keith W. Goyne ◽  
Stephen H. Anderson ◽  
...  
Keyword(s):  
Soil Water ◽  
Soil Microorganisms ◽  
Water Repellency ◽  
Organic Coatings ◽  
Wetting Agent ◽  
Microbial Populations ◽  
Repeated Application ◽  
Soil Water Repellency ◽  
Soil Microbial ◽  
Wetting Agents

Wetting agents are the primary tool used to control soil water repellency (SWR) and localized dry spot (LDS), especially on sand-based soils. However, the effect of repeated applications of wetting agents on soil microbial populations is unknown. This two-year field experiment investigated six wetting agents representing different chemistry effects on a creeping bentgrass (Agrostis stolonifera L.) putting green with existing SWR. Four out of the six wetting agents improved soil volumetric water content in the second growing season, while others showed no effect. This result was negatively correlated to the development of LDS, and positively correlated to occurrence of an air-borne turf disease. Soil microbial populations, determined by soil phospholipid fatty acid (PLFA) analysis, found that none of the treatments applied caused a shift in microbial populations between fungi and bacteria, or gram-positive and gram-negative bacteria. The stress indicators such as saturated to mono-unsaturated fatty acids were not affected by the wetting agents applied as well. However, the wetting agent that contains alkyl block polymers (ABP; Matador) with proven capability for removal of soil organic coatings showed inhibition of microbial populations at one evaluation timing. This result suggested a temporary restriction in soil carbon availability for soil microorganisms following repeated ABP application, which likely contributed to the elevated LDS development observed. Another wetting agent, a combined product of a nonionic surfactant plus acidifiers (NIS; pHAcid), which is designed to reduce inorganic carbonates while enhancing wetting, elevated all soil microbial populations tested at the end of the experiment, indicating a desirable improvement in soil health. However, repeated application of NIS did not reduce SWR at the conclusion of this experiment, which, in combination with a previous report, suggested a minimal disturbance of soil organic coatings of the hydrophobic sand. Overall, this experiment suggested that soil microbial populations can be affected by wetting agents which may further influence SWR, yet the actual effect on soil microorganisms varies depending on the chemistry of the wetting agents.

scholarly journals Bacteriological Assessment of Soil Treated with Pesticide and Herbicide in Birnin Kebbi Metropolis of Kebbi State, Nigeria

2019 ◽  
pp. 1-13
Author(s):  
Joseph A. Famubo ◽  
Bunmi B. Oladunjoye
Keyword(s):  
Soil Microorganisms ◽  
Mean Value ◽  
Microbial Populations ◽  
Control Soil ◽  
Soil Microbial ◽  
Bacillus Spp ◽  
The Mean ◽  
Staphylococcus Spp ◽  
Lactobacillus Spp ◽  
Herbicide Glyphosate

The present study was carried out on the effect of pesticides on soil microorganisms at half (x0.5) recommended rate (x1.0), and one and a half (x1.5). One commonly used insecticide Sniper as pesticide and herbicide Glyphosate were used on some physicochemical parameters and microbial populations. The mean value of pH for Sniper (x0.5) was 7.0; Sniper (x1.0) was 6.9; Sniper (x1.5) was 6.8; Glyphosate (x0.5) was 6.9; Glyphosate (x1.0) was 6.8: Glyphosate (x1.5) was 6.8 and for control soil was 7.3 respectively. The conductivity was ranged with a mean of 308.1 mS for Sniper x0.5, 410.3 mS for Sniper x1.0, 388.1 mS for Sniper x1.5, 197.8 mS for Glyphosate x0.5, 117.4 mS for Glyphosate x1.0, 223.85 mS for Glyphosate and 185.7 mS for the control soil. The soil organic matter was taken immediately after the treatments, and after the four weeks of treatment, the values were 1.50 g at week 0 and 0.72 g at week 4 for Sniper x0.5; 1.35 g at week 0 and 0.42 g at week 4 for Sniper x1.0; 1.71 g at week 0 and 0.50 g at week 4 for Sniper x1.5; 1.21 g at week 0 and 0.75 g at week 4 for Glyphosate x0.5; 1.05 g at week 0 and 0.86 g at week 4 for Glyphosate x1.0; 1.67 g at week 0 and 1.01 g at week 4 for Glyphosate x1.5 and 1.90 g at week 0 and 1.45 g at week 4 for the control soil. A total of 8 bacteria species were identified, such as Bacillus spp (50%), Lactobacillus spp (8.3%), Proteus spp (5.6%), Staphylococcus spp (11.1%), Actinomycetes spp (8.3%), Micrococcus spp (2.8%), Pseudomonas spp (8.3%) and Flavobacterium spp (5.6%). The effect of these findings shows that pesticides might be affecting the soil microbial load by reducing it.

scholarly journals Effects of Oxidation-Reduction Potentials on Soil Microbes

Agricultura ◽  
2019 ◽  
Vol 16 (1-2) ◽  
pp. 35-42
Author(s):  
Gabriel Olufemi Dayo-Olagbende ◽  
◽  
Solomon Alaba Adejoro ◽  
Babatunde Sunday Ewulo ◽  
Moses Adeyemi Awodun ◽  
...  
Keyword(s):  
Soil Microorganisms ◽  
Soil Microbes ◽  
Microbial Respiration ◽  
Reduction Reaction ◽  
Soil Microbial ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Anoxic Environments ◽  
Oxidation Reduction Reaction ◽  
Oxygen Requirements

Soil microbes are important in various processes that lead to soil fertility, nutrient availability and plant nutrition. These soil microbial organisms are themselves affected by the environment where they occur. Microbes could either be aerobic or anaerobic depending on their oxygen requirements. Oxidation-reduction reaction is a common reaction in anoxic environments and microbes tend to respond to it in different ways. This study therefore sets out to investigate the effect of oxidation-reduction potentials of the soil on activities of soil microorganisms. Results from this study show that highly reduced soils favors bacteria population more than fungi. It was concluded that the survival of fungi is best supported under oxidized and moderately reduced soils, but their existence can be negatively affected when soils become highly reduced. Bacteria that are aerobic thrive best under oxidized and moderately reduced soil. In these conditions, the highest microbial respiration in the soil was also measured.

DEGRADATION OF MELANOIDINS BY SOIL MICROORGANISMS UNDER LABORATORY CONDITIONS

1987 ◽  
Vol 67 (2) ◽  
pp. 409-414 ◽  
Author(s):  
KARL C. IVARSON ◽  
LAURE M. BENZING-PURDIE
Keyword(s):  
Amino Acids ◽  
Key Words ◽  
Soil Microorganisms ◽  
Soil Microbes ◽  
C:N Ratio ◽  
Soil Suspension ◽  
Penicillium Species ◽  
Laboratory Conditions

Synthetic melanoidins, unlabeled and U–14C labeled, mixed with sand, inoculated with a soil suspension and incubated in Warburg vessels for 30 d, decomposed slowly. Reactants (amino acids, sugars and NH4 salts) involved in melanoidin formation had no influence on rate of degradation, nor did the pH at which the melanoidins were synthesized. However, temperature of synthesis affected the rate; an increase led to a decrease in biodegradability paralleled by both increase in C:N ratio and unsaturation. At lower temperatures species of Penicillium, Cladosporium and Paecilomyces were the dominant fungi degrading the polymers, while at higher temperatures only Penicillium species were present. Key words: Melanoidins, decomposition by soil microbes

Responses of soil microorganisms to volatile exudates from germinating pea seeds

1985 ◽  
Vol 63 (6) ◽  
pp. 1040-1045 ◽  
Author(s):  
J. M. Norton ◽  
G. E. Harman
Keyword(s):  
Soil Microorganisms ◽  
Sclerotium Rolfsii ◽  
Hyphal Growth ◽  
Soil Microbial Activity ◽  
Soil Microflora ◽  
Natural Soil ◽  
Soil Microbial ◽  
Aged Seed ◽  
Seed Rot ◽  
Pea Seeds

Responses of soil microorganisms to volatile exudates from germinating pea seeds of differing quality were determined. Germination of sclerotia of Rhizoctonia solani and Sclerotium rolfsii and subsequent hyphal growth were stimulated by exposure to volatiles from aged but not nonaged pea seeds. Hyphae grew preferentially toward aged seeds. In natural soil, bacterial and fungal populations showed significant increases after exposure to volatiles from aged seed. For example, Fusarium spp. and Pseudomonas spp. showed increases of 79 and 2200%, respectively, over their original population levels after a 48-h exposure to volatiles. Conversely, Pythium populations and associated seed-rotting potential of soil decreased in natural soils exposed to volatiles. In autoclaved soils infested with P. ultimum (PHP4), Pythium populations increased dramatically after exposure to volatiles from aged pea seeds. In soils infested with either soil fungi or bacteria in addition to P. ultimum, Pythium levels remained constant or decreased, respectively, with time of exposure. Exposure to the volatiles from aged pea seeds stimulated soil microbial activity. These results suggest that Pythium germlings, when unable to reach a host, are subjected to microbial antagonism in the presence of the native soil microflora. A decrease in cucumber seed rot coincided with decreases in Pythium numbers.

Soil microbial biomass and diversity respond to tillage and sulphur fertilizers

2001 ◽  
Vol 81 (5) ◽  
pp. 577-589 ◽  
Author(s):  
N. Z. Lupwayi ◽  
M. A. Monreal ◽  
G. W. Clayton ◽  
C. A. Grant ◽  
A. M. Johnston ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Microbial Diversity ◽  
Soil Microorganisms ◽  
Soil Microbial Biomass ◽  
Conventional Tillage ◽  
Bulk Soil ◽  
Zero Tillage ◽  
Negative Effects ◽  
Tillage Systems ◽  
Soil Microbial

There is little information on the effects of S management strategies on soil microorganisms under zero tillage systems o n the North American Prairies. Experiments were conducted to examine the effects of tillage and source and placement of S on soil microbial biomass (substrate induced respiration) and functional diversity (substrate utilization patterns) in a canola-wheat rotation under conventional and zero tillage systems at three sites in Gray Luvisolic and Black Chernozemic soils. Conventional tillage significantly reduced microbial biomass and diversity on an acidic and C-poor Luvisolic soil, but it had mostly no significant effects on the near-neutral, C-rich Luvisolic and Chernozemic soils, which underlines the importance of soil C in maintaining a healthy soil. Sulphur had no significant effects on soil microbial biomass, and its effects on microbial diversity were more frequent on the near-neutral Luvisol, which was more S-deficient, than on the acidic Luvisol or the Chernozem. Significant S effects on microbial diversity were observed both in the bulk soil (negative effects, compared with the control) and rhizosphere (positive effects) of the acidic Luvisol, but all significant effects (positive) were observed in root rhizospheres in the other soils. Sulphur by tillage interactions on acidic Luvisolic soil indicated that the negative effects of S in bulk soil occurred mostly under zero tillage, presumably because the fertilizer is concentrated in a smaller volume of soil than under conventional tillage. Sulphate S effects, either negative or positive, on microbial diversity were usually greater than elemental S effects. Therefore, S application can have direct, deleterious effects on soil microorganisms or indirect, beneficial effects through crop growth, the latter presumably due to increased root exudation in the rhizosphere of healthy crops. Key Words: Biolog, conservation tillage, microbial biodiversity, rhizosphere, soil biological quality, S fertilizer type and placement

Soil microbial biomass—Interpretation and consideration for soil monitoring

Soil Research ◽  
2011 ◽  
Vol 49 (4) ◽  
pp. 287 ◽  
Author(s):  
V. Gonzalez-Quiñones ◽  
E. A. Stockdale ◽  
N. C. Banning ◽  
F. C. Hoyle ◽  
Y. Sawada ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Soil Microorganisms ◽  
Soil Microbial Biomass ◽  
Biological Function ◽  
Anthropogenic Change ◽  
Soil Monitoring ◽  
Soil Microbial ◽  
Quality Assessments ◽  
The Impact

Since 1970, measurement of the soil microbial biomass (SMB) has been widely adopted as a relatively simple means of assessing the impact of environmental and anthropogenic change on soil microorganisms. The SMB is living and dynamic, and its activity is responsible for the regulation of organic matter transformations and associated energy and nutrient cycling in soil. At a gross level, an increase in SMB is considered beneficial, while a decline in SMB may be considered detrimental if this leads to a decline in biological function. However, absolute SMB values are more difficult to interpret. Target or reference values of SMB are needed for soil quality assessments and to allow ameliorative action to be taken at an appropriate time. However, critical values have not yet been successfully identified for SMB. This paper provides a conceptual framework which outlines how SMB values could be interpreted and measured, with examples provided within an Australian context.

Effects of potassium azide on soil microbial populations and soil enzymatic activities

1975 ◽  
Vol 21 (4) ◽  
pp. 565-570 ◽  
Author(s):  
W. D. Kelley ◽  
R. Rodriguez-Kabana
Keyword(s):  
Soil Enzyme ◽  
Soil Microflora ◽  
Microbial Populations ◽  
Bacterial Populations ◽  
Soil Microbial ◽  
Fungal Populations ◽  
Potassium Azide ◽  
Time Changes ◽  
Bacteria And Fungi ◽  
Microbial Numbers

Preplant applications of potassium azide (KN3) to pine nursery beds were evaluated for effect on the soil microflora and on soil enzyme activity where either plastic-sealing or water-sealing techniques were used. Two weeks after incorporation of azide (0–224 kg/ha), soil samplings revealed reduced populations of bacteria and fungi and a corresponding decline in invertase and amylase activities. These effects were proportionate to the amount of azide used and were more pronounced in plastic-sealed plots. Phosphatase activity was little affected. Five weeks after azide application, bacterial populations were higher in treated plots than in controls. Greater numbers of bacteria were recorded from plastic-sealed plots and highest populations coincided with plots receiving the highest rates of azide, regardless of the sealing technique. Fungal populations at this sampling were generally less in treated plots than in the controls, but were higher under plastic seal. At this time, changes in invertase and amylase activities did not correspond to increased microbial numbers. Sixteen weeks after applications of KN3, bacterial populations in treated plots did not differ significantly from controls, but remained higher in plastic-sealed than water-sealed plots. Fungal populations under plastic seal had changed little and remained significantly lower in treated water-sealed plots than in controls. The earlier recorded reduction in invertase and amylase activities was still evident at the final sampling.

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