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Laboratory tests for unsaturated soils
\"Testing of unsaturated soils is particularly difficult and time-consuming, and guidance for engineers is minimal. This is the first book to systematically collate the various laboratory tests. It covers general background and theory along with test procedures and the interpretation of test results. Test procedures are broken down into simple stages, and the pitfalls are described. Test data and calculation methods are provided along with several numerical examples. It serves for students and researchers who are new to the field as well as for established professionals\"-- Provided by publisher.
Book
Effects of gypsum, peat moss, and date-palm biochar on arid soil quality and seedling performance of Acacia tortilis in Fujairah
Background
Lower soil quality is one of the biggest challenges that limit farming systems under arid regions. However, little is known about the use of organic components and their synergistic effects to restore arid soil quality. Here, we evaluated the impacts of peat moss, biochar, and gypsum on the seed germination, seedlings growth and nodulation of
Acacia tortilis
considering their separated and combined effects under natural conditions.
Method
Acacia tortilis
seed germination, seedlings growth and nodulation were exposed to the following treatments: (a) gypsum alone, (b) gypsum + peat moss, (c) gypsum + biochar, (d) gypsum + peat moss + biochar with three levels of gypsum applications including 0, 5 and 10%, and one rate of date palm biochar (2%).
Results
Based on the findings, photosynthetic photon flux density (PPFD) values (1255.69 µmol m
− 2
s
− 1
) and temperatures (40.04 °C) were greater in the noontime, while relative humidity values (29.68%) were lower. Soil treated with peat moss alone had a higher pH (7.43), while electrical conductivity (EC; 2.36 mS cm
− 1
), and water holding capacity (WHC; 64.33%) were greater in soils treated with all three agricultural components. The amounts of potassium, magnesium, manganese, iron, lead, chromium, cobalt, and copper were less in the soil treated with the three agricultural materials. Germination percentage (95.55%), seed vigor index (9.67), shoot length (12.33 cm), leaves number/plant (10.66), shoot dry weight (0.1 g), root dry weight (0.03 g), chlorophyll a (0.76 mg g
− 1
), chlorophyll b (0.24 mg g
− 1
), total carotenoids (0.16 mg g
− 1
), ash (5.71%), nodules number/plant (7), and nodule length (6.66 mm) were higher in the soil treated with the three mixtures whereas, root length was highest (16.66 cm) in the mixture of gypsum and biochar.
Conclusion
The results of this study suggest that emphasizing these agricultural materials while farming could potentially and positively optimize arid soil quality and then help in water and nutrients retention.
Journal Article
Impact of Fertilizer on Crop Yield and C:N:P Stoichiometry in Arid and Semi-Arid Soil
Fertilization can significantly affect the quality of crop and soil. To determine the effects of long-term fertilization on crop yield and carbon:nitrogen:phosphorus (C:N:P) stoichiometry in soil, a study was conducted on the terraced fields of the Loess Plateau from 2007 to 2019. Nine fertilization treatments were included: no fertilizer; organic fertilizer (O); organic and nitrogen fertilizers (ON); organic, nitrogen, and phosphorus fertilizers (ONP); organic and phosphorus fertilizers (OP); phosphorus and nitrogen fertilizers; potash and nitrogen fertilizers; potash, nitrogen, and phosphorus fertilizers; and potash and phosphorus fertilizers. Under these treatments except for CK and PK, crop yields initially decreased but later increased. The nutrient content and C:N:P stoichiometry increased in soil depth of 0–20 cm. The soil available nutrients did not change significantly with the duration of fertilization. The O, ON, ONP, and OP had the most evident effect on the enhancement of soil nutrient content, whereas O and ON had the most evident effect on the increase in soil organic carbon (SOC):total phosphorus (TP) and total nitrogen (TN):TP. In soil depth of 0–20 cm, crop yield, SOC:TN, SOC:TN, SOC:TP, and TN:TP significantly correlated with soil nutrients. This study indicated that long-term fertilization can effectively improve crop yield, soil fertility, and soil C:N:P stoichiometry. Meanwhile, the single application of an organic fertilizer or the combination of organic and nitrogen fertilizers can improve the condition of nitrogen limitation in arid and semi-arid areas.
Journal Article
HONO Emissions from Soil Bacteria as a Major Source of Atmospheric Reactive Nitrogen
Abiotic release of nitrous acid (HONO) in equilibrium with soil nitrite (NO 2 - ) was suggested as an important contributor to the missing source of atmospheric HONO and hydroxyl radicals (OH). The role of total soil-derived HONO in the biogeochemical and atmospheric nitrogen cycles, however, has remained unknown. In laboratory experiments, we found that for nonacidic soils from arid and arable areas, reactive nitrogen emitted as HONO is comparable with emissions of nitric oxide (NO). We show that ammonia-oxidizing bacteria can directly release HONO in quantities larger than expected from the acid-base and Henry's law equilibria of the aqueous phase in soil. This component of the nitrogen cycle constitutes an additional loss term for fixed nitrogen in soils and a source for reactive nitrogen in the atmosphere.
Journal Article
In Silico Prediction of Secondary Metabolites and Biosynthetic Gene Clusters Analysis of Streptomyces thinghirensis HM3 Isolated from Arid Soil
Natural products produced by microorganisms are considered an important resource of bioactive secondary metabolites, such as anticancer, antifungal, antibiotic, and immunosuppressive molecules. Streptomyces are the richest source of bioactive natural products via possessing a wide number of secondary metabolite biosynthetic gene clusters (SM-BGCs). Based on rapid development in sequencing technologies with advances in genome mining, exploring the newly isolated Streptomyces species for possible new secondary metabolites is mandatory to find novel natural products. The isolated Streptomyces thinghirensis strain HM3 from arid and sandy texture soil in Qassim, SA, exerted inhibition activity against tested animal pathogenic Gram-positive bacteria and pathogenic fungal species. In this study, we report the draft genome of S. thinghirensis strain HM3, which consists of 7,139,324 base pairs (bp), with an average G+C content of 71.49%, predicting 7949 open reading frames, 12 rRNA operons (5S, 16S, 23S) and 60 tRNAs. An in silico analysis of strain HM3 genome by the antiSMASH and PRISM 4 online software for SM-BGCs predicted 16 clusters, including four terpene, one lantipeptide, one siderophore, two polyketide synthase (PKS), two non-ribosomal peptide synthetase (NRPS) cluster)/NRPS-like fragment, two RiPP/RiPP-like (ribosomally synthesised and post-translationally modified peptide product), two butyrolactone, one CDPS (tRNA-dependent cyclodipeptide synthases), and one other (cluster containing a secondary metabolite-related protein that does not fit into any other category) BGC. The presented BGCs inside the genome, along with antibacterial and antifungal activity, indicate that HM3 may represent an invaluable source for new secondary metabolites.
Journal Article
Characterization and low-cost treatment of an industrial arid soil polluted with lead sulfide in northern Chile
Lead (Pb) dust exposure can have detrimental environmental and human health effects. Improperly enclosed stockpiles of Pb concentrates can cause dust emissions, subsequent pollution of the soil and environmental risk. The aim of this work was to study Pb form, distribution and immobilization (by using eggshell and seashell) in an industrial arid soil near a storage area of Pb mineral concentrates in northern Chile. High amounts of sulfur (S; 9900 mg kg
−1
) and Pb (6530 mg kg
−1
) were found in the polluted soil. The energy-dispersive X-ray spectroscopy analysis revealed a lead sulfide (PbS: galena). Metallic Pb particles, which were between 41 and 46 µm, were identified in the soil. After eggshell and seashell (20%) were applied, the soil pH increased from 6.0 to 7.84 and 8.07, respectively. In the studied soil, the leaching test showed a 59 mg L
−1
average Pb extractable concentration. After 240 days, extractable Pb by toxicity characteristics leaching procedure decreased to 4.79 mg L
−1
(93.3%) with the application of seashell at 20% compared with a decrease of 33.33 mg L
−1
(53.6%) using eggshell. Pb in the polluted soil was mainly found in the exchangeable fraction (66%), followed by the reducible (24%), residual (7%) and oxidizable (6%) fractions. According to the risk assessment code, the contaminated soil before treatment was classified as very high risk. Adding eggshell (20%) and seashell (20%) decreased the exchangeable fractions to 39 and 35%, respectively. Applying these liming materials achieved Pb immobilization in the soil, but the soil remained in the high environmental risk category. We conclude that the application of seashell waste, resulting from high aquaculture activity, opens an interesting window to the treatment of contaminated arid soils.
Journal Article
A Multiscale, Hierarchical Model of Pulse Dynamics in Arid-Land Ecosystems
Ecological processes in arid lands are often described by the pulse-reserve paradigm, in which rain events drive biological activity until moisture is depleted, leaving a reserve. This paradigm is frequently applied to processes stimulated by one or a few precipitation events within a growing season. Here we expand the original framework in time and space and include other pulses that interact with rainfall. This new hierarchical pulse-dynamics framework integrates space and time through pulse-driven exchanges, interactions, transitions, and transfers that occur across individual to multiple pulses extending from micro to watershed scales. Climate change will likely alter the size, frequency, and intensity of precipitation pulses in the future, and arid-land ecosystems are known to be highly sensitive to climate variability. Thus, a more comprehensive understanding of arid-land pulse dynamics is needed to determine how these ecosystems will respond to, and be shaped by, increased climate variability.
Journal Article
Quantitative assessment of pedodiversity and soil erosion within a karst sinkhole in the dry steppe subzone
A detailed study of the soil cover of a sinkhole (300 m
2
) in the dry steppe landscape of the Bogdinsk–Baskunchak Natural Reserve in Astrakhan oblast has been performed, and the factors of its differentiation have been analyzed. The indices of pedodiversity have been calculated and compared for karst sinkholes in the dry steppe and northern taiga landscapes. Quantitative parameters of the lateral migration of solid soil substances on the slopes of the sinkhole have been determined. The rate of soil erosion decreases from the slope of southern aspect to the slopes of western, northern, and eastern aspects. On the average, it is estimated at 0.4 mm/yr. The average rate of accumulation of solid substances on the lower parts of the slopes and in the bottom of the sinkhole reaches 0.74 mm/yr. A comparative analysis of the soil properties attests to their dependence on the particular position of a given soil within the sinkhole. Downward the slopes of the sinkhole, full-profile brown arid soils (Cambic Calcisols) are replaced by sierozem-like soils (Haplic Calcisols), light-humus poorly developed soils (Luvisols), lithozems (Leptosols), and stratified soils (stratozems, or Colluvic Regosols). The soils within the upper ring-shape soil microzone are more diverse and contrasting with respect to their morphological, physical, chemical, and physicochemical properties. The degree of soil contrasts decreases down the slopes of the sinkhole towards its bottom. The studied sinkhole is characterized by considerable pedodiversity. Quantitative parameters of pedodiversity for the sinkhole in the dry steppe zone are higher than those form the sinkholes in the northern taiga zone.
Journal Article
Plant-associated microbiomes in arid lands: diversity, ecology and biotechnological potential
Background Aridification is a worldwide serious threat directly affecting agriculture and crop production. In arid and desert areas, it has been found that microbial diversity is huge, built of microorganisms able to cope with the environmental harsh conditions by developing adaptation strategies. Plants growing in arid lands or regions facing prolonged abiotic stresses such as water limitation and salt accumulation have also developed specific physiological and molecular stress responses allowing them to thrive under normally unfavorable conditions. Scope Under such extreme selection pressures, special root-associated bacterial assemblages, endowed with capabilities of plant growth promotion (PGP) and extremophile traits, are selected by the plants. In this review, we provide a general overview on the microbial diversity in arid lands and deserts versus specific microbial assemblages associated with plants. The ecological drivers that shape this diversity, how plant-associated microbiomes are selected, and their biotechnological potential are discussed. Conclusions Selection and recruitment of the plant associated bacterial assemblages is mediated by the combination of the bio-pedo-agroclimatic conditions and the plant species or varieties. Diversity and functional redundancy of these associated PGPR makes them very active in supporting plant improvement, health and resistance to drought, salt and related stresses. Implementing proper biotechnological applications of the arid and desertadapted PGPR constitute the challenge to be raised.
Journal Article
Fertilization enhancing carbon sequestration as carbonate in arid cropland: assessments of long-term experiments in northern China
AIMS: Soil inorganic carbon (SIC), primarily calcium carbonate, is a major reservoir of carbon in arid lands. This study was designed to test the hypothesis that carbonate might be enhanced in arid cropland, in association with soil fertility improvement via organic amendments. METHODS: We obtained two sets (65 each) of archived soil samples collected in the early and late 2000’s from three long-term experiment sites under wheat-corn cropping with various fertilization treatments in northern China. Soil organic (SOC), SIC and their Stable ¹³C compositions were determined over the range 0–100 cm. RESULTS: All sites showed an overall increase of SIC content in soil profiles over time. Particularly, fertilizations led to large SIC accumulation with a range of 101–202 g C m⁻² y⁻¹ in the 0–100 cm. Accumulation of pedogenic carbonate under fertilization varied from 60 to 179 g C m⁻² y⁻¹ in the 0–100 cm. Organic amendments significantly enhanced carbonate accumulation, in particular in the subsoil. CONCLUSIONS: More carbon was sequestrated in the form of carbonate than as SOC in the arid cropland in northern China. Increasing SOC stock through long-term straw incorporation and manure application in the arid and semi-arid regions also enhanced carbonate accumulation in soil profiles.
Journal Article