Ecological studies on coccoid bacteria in a pine forest soil—II. growth of bacteria introduced into soil

The growth of five typical but phenetically distinct cocci and Arthrobacter strains, isolated from a pine forest soil, has been investigated. Soil reaction was found to have a marked effect on growth and unless naturally acidic soils were made more alkaline they did not support growth, even in the presence of added nutrients. However, in the presence of fungi which could use the added nutrients, e.g. chitin, mycelial fragments etc., bacterial growth was possible and could be correlated with a decrease in acidity, especially around particles of organic matter. Where the pH rose above 7.9, bacterial growth again decreased. All the bacterial strains tested reacted in the same way, suggesting that they occupied similar microenvironments in both the acidic and alkaline soil horizons examined. Some explanations for the occurrence of nonsporing bacteria in soils in which apparently they cannot grow are suggested.     

Studies on glycine-percolated soil IV. Fractionation of bacteria in glycine-percolated soil in “two-layered sucrose solution system”

Bacteria in a soil crumb are thought to have at least two kinds of habitat (1). Bacteria living in “the outer-part”** of a soil crumb are directly exposed to influences of environmental conditions such as supply and exhaustion of nutrients or loss of moisture. Consequently, the number of the viable bacteria fluctuates dramatically with these changes. On the other hand, the bacteria in “the innerpart” of the soil crumb are influenced by environmental conditions to a lesser extent.     

Ecological studies on cocco1d bacteria in a pine forest soil—III. competitive interactions between bacterial strains in soil

Strains of bacteria with differing degrees of overall (phenetic) similarity have been paired and grown together and separately in both acid and alkaline soils from a pine forest. A decrease in yield of an organism when grown in the presence of a second organism was taken as evidence of competition. It was shown that, contrary to expectations, pairs of organisms with different degrees of similarity might have similar competitive interactions. It is postulated that this is because one key property could result in a marked change in competitive ability while not markedly altering the taxonomic relationships of the organisms. The possibility that spatial separation of organisms can result in two or more organisms with identical functions becoming established in soil is discussed.     

Long-term effect of manure and mineral fertilizer application on the distribution of organic nitrogen fractions in soil under a rice–wheat cropping system

A long-term experiment was used to evaluate the effect of integrated nutrient management on the distribution of soil organic N fractions and their contribution to N nutrition of a rice–wheat system. Continuous application of mineral fertilizers, alone or in combination with organic manures for 7 years, led to a marked increase in total N, hydrolysable N (amino acid-N, amino sugar-N, ammonia-N, hydrolysable unknown-N) and non-hydrolysable N compared with their original status in soil. However, continuous rice–wheat cropping without any fertilization resulted in depletion of total N, hydrolysable N and non-hydrolysable N by 21.3, 23.5 and 15.1% over their initial status in surface soil. The effect of press mud (PM) treatment was more pronounced in increasing total and hydrolysable N compared with farmyard manure (FYM) or green manure (GM) treatment. Incorporation of PM, FYM and GM along with mineral fertilizers increased the total N content by 32.8, 18.3 and 5.1% and that of hydrolysable N by 25.7, 19.6 and 9.5%, respectively, over mineral fertilizer treatment. Among the most important fractions, amino sugar-N, amino acid-N and ammonia-N were found to be most the important fractions contributing to grain yield and nitrogen uptake of rice and wheat crops.     

Negligible effect of X-ray μ-CT scanning on archaea and bacteria in an agricultural soil

X-ray Microfocused Computed Tomography (X-ray μ-CT) allows a non-destructive and three-dimensional observation of microbial habitats (i.e. pore space) in soil. A major premise for microbiological studies integrating X-ray μ-CT is that soil microorganisms are not affected by irradiation dose in terms of physiology and composition. However, the compatibility of X-ray μ-CT and soil biological experiments has been evaluated controversially.We performed an incubation experiment with packed microcosms to assess the effect of X-ray μ-CT on native microbial populations with emphasis on soil archaea and bacteria. Before (14 days) and after (1 and 14 days) scanning we analyzed (i) respiration, (ii) enzyme activity, (iii) microbial biomass, (iv) abundance and (v) community structure in scanned and control treatments.None of the microbial parameters exhibited significant differences among scanned and unscanned soil samples at all sampling times with the exception of lower archaeal cell numbers subsequent to X-ray μ-CT. Incubation time was the main factor that induced a significant alteration of microbial soil populations while irradiation had no or only very little effect thereupon. Taken together, three-dimensional in situ data obtained via X-ray μ-CT may well be combined with microbiological analyses in soil.     

Effect of SDBS–Tween 80 mixed surfactants on the distribution of polycyclic aromatic hydrocarbons in soil–water system

Purpose

Enhancing desorption of hydrophobic organic contaminants from soils is a promising approach for the effective remediation of soils contaminated with organic compounds. The desorption efficiency of chemical reagent, such as surfactant, should be evaluated. In this study, the effect of mixed anionic–nonionic surfactants sodium dodecylbenzene sulfonate (SDBS)–Tween 80 on the distribution of polycyclic aromatic hydrocarbons in soil–water system was evaluated.

Materials and methods

Batch desorption experiments were employed to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and surfactants in soil–water system. PAHs and SDBS were determined by high-performance liquid chromatography, Tween 80 by spectrophotometry, and total organic carbon with a carbon analyzer.

Results and discussion

Sorption of PAHs to soil was increased at low surfactant concentration due to the effective partition phase on soil formed by sorbed surfactants. The mixture of anionic and nonionic surfactants decreased the sorption of surfactants to soil, increasing the effective surfactant concentration in solution and thus decreasing the sorption of PAHs on soil. Anionic–nonionic mixed surfactant showed better performance on desorption of PAHs from soil than single surfactant. The greatest desorption efficiency was achieved with low proportions of SDBS (SDBS/Tween80?=?1:9).

Conclusions

SDBS–Tween 80 mixed surfactant showed the highest desorption rate with low proportion of SDBS, which indicated that the addition of relative low amount of anionic surfactant could significantly promote the desorption efficiency of PAHs by nonionic surfactants. Results obtained from this study did provide useful information in surfactant-enhanced remediation of soil and subsurface contaminated by hydrophobic organic compounds.     

Studies on the ecology of actinomycetes in soil— VII. Actinomycetes in a coastal sand belt

Distribution of actinomyeetes in beach and dune sand at two sites was studied. At one site. dunes were eroding while at the other accretion of sand and dune development occurred. Actinomycetes occurred in low numbers in beach sand hul increased sharply when dunes were colonized by Ammophila arenaria (L) Link or Agropyron junceiforme (A & D Löve) A & D Löve. Micromonospora strains predominated in beach sand but Streptomyces was the predominant genus in dunes.Salinity tolerance of isolates was not clearly related to their source but tolerance of dune isolates was generally greater than those from the beach. Tolerance of Streptomyces strains varied but all Micromonospora isolates were intolerant of salinities above that of sea water.Evidence for increased growth of actinomycetes in the root region of A. arenaria and A. junceiforme was obtained but there was little qualitative difference between those in the root region and root-free sand. In laboratory experiments actinomycetes colonized old. dead Ammophila roots more readily than young ones and arose carly in succession on the former. Young, living roots stimulated bacteria and fungi but not actinomyeetcs. It was concluded that most activity of actinomycetes in the Ammophila root region occurred on old root tissue and it was suggested that this might be true of other plants.     

Studies on soil fumigation—I: Effects on ammonium,nitrate and phosphate in soil and on the growth,nutrition and yield of wheat

Fumigation of field soil with chloropicrin alone or followed by methyl bromide, each at 220Kg·ha^?1, released 20–30 parts/10⁶ NH⁺₄-N which persisted for 75 days; such fumigation also doubled the amount of bicarbonate-extractable phosphate 28 days after fumigation. Soil fumigation increased both the vegetative and grain yields as well as increasing the content of N in the grain and the content of K and Cl in the tops at ear emergence. Root growth and the phosphate uptake activity of the roots were increased by soil fumigation.     

Monitoring the combined action of controlled‐release fertilizers and a soil conditioner in soil

Abstract

The combined action of a soil conditioner and a controlled‐release fertilizer was followed by conducting soil column leaching and tomato growth experiments. The change in soil water‐holding capacitiy and the release of potassium sulfate (K₂SO₄) from conventional and controlled‐release forms was evaluated using leaching experiments in soil columns. Tomato growth was followed by the comparison of biomass yields on a dry matter basis with experiments where different combinations of controlled‐release or conventional fertilizer rates and soil conditioner applications. It was demonstrated that the combined usage of controlled‐release fertilizers and soil conditioners increased tomato yield and enhanced the nutritional status of the tomato plants in comparison to conventional fertilizer materials.     

The colonization of host-root and soil by Rhizobia—I. Species and strain differences in the field

Growing-season populations of rhizobia associated with annual host-plant roots and nearby soil were examined in a field soil showing a nodulation problem in the second year after establishment. Rhizobium lupini reached higher populations at a faster rate than R. trifolii. A sharp drop in the population of R. trifolii associated with subterranean clover roots early in the growing season was followed by a recovery to high numbers. No such phenomenon occurred with R. lupini. The numbers of rhizobia under patches of non-nodulated plants in second-year stands were very low, usually <5/g soil, whereas the numbers under healthy plants in problem stands were similar to those under established stands. Differences in the colonization of both root and soil by R. trifolii in the first year were reflected in the second-year nodulation.     

Ergebnisse zur bodenverlagerung durch bearbeitungserosion in der jungmoränenlandschaft Nordostdeutschlands: Investigations of soil movement by tillage as a type of soil erosion in the young moraine soil landscape of Northeast Germany

Soil translocation by soil tillage can have a considerable importance on arable land. These results were published in the international literature. The aim of the experiments is to quantify the translocation of soil due to tillage with different typical tools. A mouldboard plough and a disc harrow were tested in field experiments on a slope (4° inclination) with sandy soil. The average movement of soil particles of the top soil was determined about the changed tracer concentration. The tracer coloured gravels were most suitable of all tested tracer. The comparison of the tools showed more soil translocation caused by mouldboard plough (145?kg) than by disc harrow (12?kg). The transport was also different: plough 0.50?m and disc harrow 0.11?m average distance.     

Influence of vegetation on low-molecular-weight carboxylic acids in soil solution—a review

Low-molecular-weight (LMW) carboxylic acids found in soils and soil solutions comprise mainly aliphatic mono-, di- and tricarboxylic acids and substituted benzoic and cinnamic acids. This review compiles current information on the content of LMW carboxylic acids in soil solutions collected by centrifugation and in lysimeters, and soil extracts in relation to type of vegetation, soil type and soil depth. Contents of LMW carboxylic acids are highest in soil solution from the upper soil layers where carbon in LMW carboxylic acids constitutes up to 10% of DOC. The concentrations of aliphatic LMW di-/tricarboxylic acids (oxalic, malonic, malic, succinic, tartaric and citric acid) are usually in the range 0–50 μM with the higher concentrations in soil solutions from meadow, permanent pasture and forest soils as compared to ley and cultivated soils. In contrast, the concentrations of aliphatic LMW monocarboxylic acids (formic, acetic, propionic, butyric, valeric and lactic acid) are commonly in the range 0–1 mM with high concentrations found in soil solutions from both cultivated and forested soils. Especially insence cedar (Calocedrus decurrens (Torr.) Florin), ponderosa pine (Pinus ponderosa Dougl.), Douglas fir (Pseudotsuga menziesii Franco) and Norway spruce (Picea abies (L.) Karst.) seem to cause higher contents of LMW carboxylic acids in soils and soil solutions as compared to other tree species. Soil solution concentrations of substituted benzoic and cinnamic acids are submicromolar for all vegetations, whereas similar amounts in the range 0–800 μmol kg⁻¹ of aliphatic LMW carboxylic acids and substituted benzoic and cinnamic acids are extractable from mineral soils with alkaline and dilute acid extractants. Seasonal variations are observed in soil solutions isolated by centrifugation and soil extracts with highest concentrations in 2–4 months in a period from mid spring to early summer, minimum concentrations around early autumn, and increasing concentrations during autumn.     

Strategies to mitigate the adverse effect of drought stress on crop plants—influences of soil bacteria: A review

Drought stress affects plant growth and causes significant issues in meeting global demand for food crops and fodder. Drought can cause physiological, physicochemical, and morphological changes in plants, which negatively affects plant growth and productivity. To combat this under the increasing global threat of water shortage and rapid population expansion, it is crucial to develop strategies to meet global food demands. Plant growth-promoting rhizobacteria (PGPR) may provide a safe solution to enhancing crop yields through various mechanisms. These soil bacteria can provide drought tolerance to crop plants, allowing them to survive and thrive in water-scarce conditions. Productions of phytohormones, free radical-scavenging enzymes, and stress-combating enzymes that can increase tolerance to drought-induced stress are key features of plant-associated microbial communities. This review summarizes the beneficial properties of microbes that help plants tolerate water scarcity and highlights the bacterial mechanisms that enhance drought tolerance in plants.     

Application of the “standard cell” concept in research on soil formation

The concept of the “standard cell” of a rock, which compares numbers of cations associated with 160 oxygen ions (Barth, 1948) can be applied to the solid material of soils and saprolites as a means of tracing changes in element content at different depths in soil profiles weathered from igneous rocks. The “standard cells” can be derived readily from total silicate analyses of rock and soil materials and can be expressed as chemical formulae or in tables to facilitate comparisons. Standard cells for several layers from each of three profiles from southeast Queensland illustrate the type of information obtained. Standard cells of solum and weathered rock layers of a profile previously studied by mineralogical techniques permit a comparison of inferences about weathering which have been drawn by the two approaches.     

The effects of biocidal treatments on metabolism in soil—I. Fumigation with chloroform

This series of five papers is a study of how biocidal treatments influence metabolism in soil, directed particularly towards the flush of decomposition caused by fumigation, and designed to see if the size of this flush can be used as a measure of the soil biomass.Chloroform fumigation caused an immediate increase in the amounts of ammonium and organic C extracted from a soil by 1 N K₂SO₄. When the CHCl₃-treated soil was then inoculated with fresh soil and incubated for 10 days. it consumed 2·8 times more O₂, evolved 2·2 times more CO₂ and mineralised 7·3 times more N than an unfumigated soil. Extractable organic C decreased by about 40% when the fumigated soil was incubated for 10 days. A second fumigation given immediately after the first produced no further increase in the flush, but some recovery occurred if the soil was incubated between fumigations. However, this recovery was slow and incomplete; a second fumigation given 53 days after the first gave a flush only one-seventh the size of the first. Glucose (or ryegrass) added to the soil and allowed to decompose before fumigation increased the size of the flush. After a 52-day incubation, 29% of the C originally added as ¹⁴C labelled glucose remained in the soil; fumigation on the 52nd day increased the evolution of labelled CO₂ during the subsequent 10-day period by a factor of 8. Fumigation of a soil that had already been sterilized by 2·5 Mrads of gamma radiation increased the flush slightly; the amount of O₂ consumed in 10 days increased from 123 to 137 mg/100 g soil. It is proposed that the flush of decomposition following CHCl₃ fumigation is caused by the decomposition of killed organisms by the survivors (or by organisms added in the inoculum) and that organisms are more rapidly and completely attacked after exposure to CHCl₃ than after irradiation. On this hypothesis. 10% of the glucose C originally added to the soil was located in the soil biomass after 52 days.     

Effect of vegetation changes on soil erosion on the loess plateau

Vegetation is one of the key factors affecting soil erosion on the Loess Plateau. The effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from long-term field runoff plots established on the eastern slope of the Ziwuling secondary forest region, China and a field survey. The results showed that before the secondary vegetation restoration period （before about 1866-1872）, soil erosion in the Ziwuling region of the Loess Plateau was similar to the current erosion conditions in neighboring regions, where the soil erosion rate now is 8 000 to 10 000 t km^-2 year^-1. After the secondary vegetation restoration, soil erosion was very low; influences of rainfall and slope gradient on soil erosion were small; the vegetation effect on soil erosion was predominant; shallow gully and gully erosion ceased; and sediment deposition occurred in shallow gully and gully channels. In modern times when human activities destroyed secondary forests, soil erosion increased markedly, and erosion rates in the deforested lands reached 10 000 to 24000 t km^-2 year^-1, which was 797 to 1682 times greater than those in the forested land prior to deforestation. Rainfall intensity and landform greatly affected the soil erosion process after deforestation. These results showed that accelerated erosion caused by vegetation destruction played a key role in soil degradation and eco-environmental deterioration in deforested regions.     

Estimation of soil pollution by the main ecotoxicants in the Vorob’evy Gory nature park

Soils of the Vorob’evy Gory nature park (Moscow) are characterized by a high content of technogenic ecotoxicants. Dangerous levels of pollution are fixed on ∼60% of soil cover for benzopyrene, ∼40% of soil cover for heavy metals, and ∼6% of soil cover for mineral oils. Besides the total high aerogenic load, the local sources of soil pollution in cities are highways; increased concentrations of heavy metals are also registered near unauthorized dumps. Benzopyrene and mineral oils are characterized by high migratory ability in soils and can form secondary auras of pollution in accumulative landscape facies.