Calcaric Fluvisols Research Articles

DETERMINATION OF GREENHOUSE GAS CONCENTRATION IN THE ATMOSPHERE BY EARTH REMOTE SENSING MEANS. CARTOGRAPHIC AND ANALYTICAL ASSESSMENT OF THE GEOSPATIAL DISTRIBUTION OF ITS VALUES

This article covers the issue of improving the methodology of remote determination of the concentration of greenhouse gases in the atmosphere using the Copernicus Program — Sentinel-5P and MOD11A2.061 Terra satellite systems, as well as the cartographic-analytical assessment of its geospatial distribution. The specified methodology provided for remote determination of the concentration of greenhouse gases CH4, CO, and NO2, development of maps of the distribution of the determined concentration on the territory of Ukraine, localization of areas of formation of the intensity of emission and sequestration of greenhouse gases taking into account data on the soil cover, abiotic conditions of the territory and anthropogenic influences, in particular, military activities. A set of maps of the geospatial distribution of CH4, CO, and NO2, greenhouse gas concentrations, the temperature of the Earth’s surface within the warm period (01.05—30.10) during 2019—2022, as well as a map of the geospatial localization of the maximum concentrations of greenhouse gases within the warm period of the research time interval developed according to the results of emissions from soils, landscapes, production facilities, and combat zones. It was determined that for the warm period of the year, on average for 2019—2022, the optimal temperature range within which the intensity of nitrogen dioxide emission on the territory of Ukraine reaches maximum values is from 13 to 19 °C. If the temperature of the Earth’s surface exceeds the value of 20 °C, the volume of emission emissions is significantly reduced. It is shown that soils with different emission and assessment status are widespread in Ukraine during the warm period. In the South and Southwest of the state, soils with the highest emission capacity of methane to the atmosphere prevail, in particular Jc49-1/3a — Calcaric Fluvisols, Lg54-1a — Gleyic Luvisols, Kh31-2a — Haplic Kastanozems, Gh23-3a — Humic Gleysols. In large cities, as well as in the territories of the South-East of Ukraine, where normal chernozems (Ch22-2a) / (normal chernozems) are common, the maximum concentration of NO2 in the atmosphere is formed, which is caused by the influence of the high temperature of the earth’s surface and the localized consequences of Russia’s military aggression. It was revealed that over the past 4 years, there has been a trend of decreasing CO concentration, which indirectly indicates the negative impact of Russia’s military aggression, a decrease in industrial production, and the relocation of production facilities to the west of the country.

Long-term fertilization affects microbial necromass accumulation by regulating nutrient and enzymatic stoichiometry in a calcareous Fluvisol

Microbial necromass accumulation through rhizodeposition plays a critical role in increasing the stable soil organic carbon pool, which is greatly affected by fertilization. However, the legacy effects of long-term fertilization on microbial necromass accumulation remain unclear. Here, we selected a calcareous Fluvisol treated with no fertilizer (Ctrl), P and K fertilizers (PK), N and K fertilizers (NK), and N, P and K fertilizers (NPK) for 34 years and conducted a 12-week microcosm experiment with simulated daily rhizodeposition to disentangle the legacy effects of long-term fertilization on microbial necromass accumulation. We measured soil C, N and P contents and C-, N- and P-acquiring extracellular enzyme activities and analyzed phospholipid fatty acids (PLFAs) and amino sugars to indicate microbial biomass and necromass, respectively. We found that compared with the Ctrl and NK treatments, the PK and NPK treatments significantly decreased the C:N and C:P ratios and the net accumulation of microbial necromass but significantly increased the ratios of C- to N- and C- to P-acquiring enzyme activities and the fungal PLFAs abundance in soils. The net accumulation of microbial necromass was positively correlated with soil nutrient stoichiometry (mainly the C:N and C:P ratios) but negatively correlated with soil enzymatic stoichiometry (mainly the ratios of C- to N- and C- to P-acquiring enzyme activities) and the fungal to bacterial PLFA ratio. Taken together, these results suggest that long-term fertilization has legacy effects on microbial necromass accumulation and that fertilization-induced changes in nutrient and enzymatic stoichiometry regulate microbial necromass accumulation through rhizodeposition in the calcareous Fluvisol.

Organic Fertilizer Substitution Promoted the Organic Carbon Sequestration in Calcareous Fluvisol: A Study Based on Acid Hydrolysis and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR)

ABSTRACT This study aimed to elucidate the mechanism of substituting organic fertilizer for mineral fertilizer to increase calcareous fluvisol soil organic carbon. Four years of soil culture experiments were conducted, wheat yield, soil nutrients, soil organic carbon (SOC) and SOC fractions were measured and the compositional changes of SOC was analyzed by attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. Treatments included applying no fertilizer (CK), mineral N and P fertilizers (CF) and organic fertilizers to replace 6% (OF6), 12% (OF12), 18% (OF18) and 24% (OF24) of N and P under the same nutrient conditions. The results showed that the OF24 treatment was the best among the treatments employed. Compared with CF, wheat yield, SOC, microbial biomass carbon (MBC), labile fraction 1 (LOC1) and recalcitrant fraction (ROC) of OF24 increased by 10.4%, 24.4%, 66.3%, 43.2% and 30.7%, however, the labile fraction 2 (LOC2) decreased by 16.8%. ATR-FTIR results showed that the relative absorption intensity of OF24 treatment at 1,000 cm−1 band is lower than CK and CF treatment, other bands are higher than CK and CF treatment. Overall, OF24 treatment not only significantly increased wheat yield, but also increased the content of LOC1 and MBC. The increase of MBC can improve the soil microbial environment and promote the decomposition of LOC2, while also accelerate the turnover rate of soil carbon and then show the increase of ROC content and improve the proportion of the recalcitrant carbon pool.

Influence of the Type and Use of Soil on the Distribution of Organic Carbon and Other Soil Properties in a Sustainable and Resilient Agropolitan System

Urban and peri-urban agriculture is one of the strategies that emerged on the path towards agri-food sustainability in cities. This paper aims at improving the knowledge of the soil properties in a peri-urban area and their agricultural potential to support ecosystems with biodiversity worth conserving. The study area was located in the mid-plain of the Segura River (SE Spain). Arable soil layer samples were collected at 68 points to assess the distribution of organic carbon and to study other indicators of soil quality. A Wilcoxon and Kruskal–Wallis test was conducted to compare between the types of soils present in the area (calcaric Fluvisols and calcaric Regosols) and soil uses (industrial, cultivated and abandoned). Statistical analysis indicates that there are significant differences (at the 0.05 significance level) between Fluvisols and Regosols (p value = 3.65 × 10−5). Regarding use, the abandoned Fluvisols presented an average value of 9.33 g kg−1 of OC while the Fluvisols that are currently cultivated have a higher average content of OC (11.35 g kg−1). For soils under industrial use, the average OC content is 5.13 g kg−1. Spatial distribution of organic carbon in these soils depends on the type of soil and the human influence on them, including the use.

The coupling between iron and carbon and iron reducing bacteria control carbon sequestration in paddy soils

The coupling between iron (Fe) and carbon (C) and the activity of Fe reducing bacteria (FeRB) can strongly affect C sequestration in paddy soils. Although the geochemical cycling of C and Fe has been reported at individual sites, a lack of information exists across soil types and regions. In this study, we investigated the coupling of Fe-C and the role of FeRB across five contrasting paddy soils, which account for 60 % of China’s rice cultivation area: Haplic Solonchaks (SCh), Calcaric Fluvisols in Henan (FLc1) and in Tianjin (FLc2), Cumulic Anthrosols (ATc), and Eutric Cambisols (CMe). ATc and CMe were in oxidizing environments and contained significantly higher Fe (III), free Fe oxide (Fed), amorphous Fe oxide (Feo), and organic matter complexed iron oxides (Fep) than SCh, FLc1, and FLc2 which were in reducing environments with higher relative abundance of FeRB. Nonmetric multidimensional scale analysis (NMDS) demonstrated the variability of FeRB in different soil types (r = 0.928, P = 0.001). The higher Fe-soil organic carbon (Fe-SOC) in CMe (2.27 g kg−1; 2.72 g kg−1) and ATc (1.32 g kg−1; 1.6 g kg−1) was likely due to the complexation of Fe (III) and its oxides within SOC and minimal dissimilatory Fe reduction. The existence of the “iron gate” in ATc and CMe also revealed the inhibitory effect of low quantities of Fe (II) on phenol oxidase (PO) enzyme activity and SOC mineralization. According to canonical correspondence analysis (CCA), our study indicates the importance of DOC aromaticity as characterized by UV light absorption at 254 nm (SUV254) (16.6 %), Fed (10.9 %), Feo (9.2 %) to FeRB. Moreover, the structural equation model (SEM) further revealed that SOC and DOC were regulated by PO activity, Fe, and FeRB (χ2 = 7.002, P = 0.536). Our study highlights the importance of soil characteristics on Fe-C coupling in the biogeochemical cycle through interactions among Fe morphology and microorganisms via different oxidation–reduction conditions.

First isolation of Leptomyxa (Amoebozoa, Leptomyxida) from endozoic conditions: an interaction between two common soil organisms

We report the first isolation of a widely distributed free-living soil amoeba Leptomyxa (Amoebozoa, Leptomyxida) from endozoic conditions. The amoebae were detected after 14 days following inoculation of the intestine of the earthworm Lumbricus terrestris on an agar plate with Escherichia coli. The earthworm was collected from Calcaric Fluvisol (pH 7) in the Upper Váh region, north-west Slovakia. Observed amoebae were uninucleate, polypodial with typically branched pseudopodia, and morphologically resembled Leptomyxa australiensis. This study enlarges the range of amphizoic tendency in leptomyxid amoebae and indicates their interactions with Oligochaeta.

Influence of ecological and anthropogenic factors on soil transformation in recreational areas of Volgograd (Russia)

In this paper, we studied the soils of recreational areas of Volgograd within three research areas. The survey found that in research area I the soils spatial distribution is mainly represented by the following soil group according to WRB: Urbic Technosols, Urbic Technosols (Mollic) and Gleyic Terric Phaeozem (Mollic, Prototechnic). Buried soils are represented by Gleic Cambisols (Protocalcic). In research area II, among natural soils, the largest areas are occupied by Calcaric Fluvisols (Loamic, Technic, Protovertic), Calcaric Fluvisols (Arenic, Salic), and Gleyic Calcisols (Sodic, Protocalcic, Technic, Salic). The anthropogenic-transformed soils include Urbic Technosols, and Ekranic Technosols are under buildings and road surfaces. In research area III, the natural soils spatial distribution is homogeneous and mainly represented by Gleyic Cambic Calcisols (Protocalcic), Gleyic Cambisols (Protocalcic, Prototechnic), and Calcaric Colluvic Regosols (Arenic, Prototechnic) in the bottoms of small flat-bottom valleys. In irrigation sites occur Urbic Technosols, and on hiking trails – Gleyic Cambisols (Prototechnic). Despite the presence of reclaimed horizons with a high content of phosphorus in the soils (average concentration of 82 mg kg−1), none of the profiles revealed Hortic horizon, but only some of its properties (colour, horizon thickness, zoogenic activity). The thickness of urbic-stratifying layer (Au) varies in a wide range from 10 to 135 cm, and the thickness of reclaimed horizons (A) also varies from 10 to 48 cm. The bulk density in Au horizons is 1.4 g cm−3, in the reclaimed horizons (A) – 1.39 g cm−3. The content of soil carbon in soil surface horizons varies from 0.85% to 4.58% in urbic horizons, and to 1.49% in reclaimed horizons. Chemical analysis of urbic (Au) and reclaimed (A) horizons revealed a low content of easily soluble salts (0.16%) and carbonates (1.5% and 1.7%, respectively).

Phytoremediation of secondary saline soil by halophytes with the enhancement of γ-polyglutamic acid

Soil salinization has severely affected the quality of tillage land in China, and most greenhouse soils in Shanghai suburb suffer from secondary salinization with high salinity levels dominated by Ca2+, Mg2+ and NO3−. In this work, a sandy loam soil (Calcaric Fluvisols) contaminated by the above ions was selected as research object, and the binding conditions and abilities of γ-polyglutamic acid (γ-PGA) to water-soluble Ca2+ and Mg2+ in the soil were examined, and then pot experiments were conducted to remove Ca2+, Mg2+ and NO3− by two halophytes (Sedum aizoon L., Sesbania cannabina Pers.) integrated with γ-PGA application. The results showed that under the conditions of adding 1000 mg L−1γ-PGA (pH 7) and 25 °C, the binding efficiencies of Ca2+ and Mg2+ were 51.59% and 68.03%, respectively. Compared with Sesbania cannabina Pers., Sedum aizoon L. displayed better remediation performance for the soil with γ-PGA application in pot experiments, and the removal efficiencies of Ca2+, Mg2+ and NO3− reached 93.25%, 94.78% and 84.26% after applying 1000 mg L−1γ-PGA for 56 d, respectively. Moreover, γ-PGA application could mitigate salt stress and promote plant growth, and activate antioxidant defense systems. Compared with the control, 1000 mg L−1γ-PGA application significantly increased plant height and fresh weight of Sedum aizoon L., and the removal efficiencies of Ca2+, Mg2+ and NO3− increased by 45.48%, 82.62% and 69.91%, respectively. In the future, more in-depth mechanism of joint effect and field-scale investigation need to be further studied.

Soil structure as a significant indirect factor affecting crop yields

Soil structure as a significant indirect factor affecting crop yields

Soil Distribution in Nepal

Soil is the important natural recourse for living things of the world and regulates its ecosystem. Soil types are depending on physiographic and climatic factors. The study discussed soil types of Nepal prepared by Land Resource Mapping Project (LRMP) based on world reference base developed by Food and Agriculture Organization of the United States (FAO) and Soil and Terrain (SOTER) soil type of Nepal by ISRIC-World soil Information based on universal soil classification system developed by United State Department of Agriculture (USDA) using Geographic information system (GIS). According to LRMP the soil types of Nepal are as follow: Dystrochrepts Haplumbrepts Haplustalfs, Dystrochrepts Haplustalfs Rhodustalfs, Haplumbrepts Dystrochrepts Cryumbrepts, Udipsamments Dystrochrepts Rhodustalfs, Glaciated Mountain, Haplaquents Haplaqepts Eutrocrepts, Udorthents Ustorthents Haplaquents, Dystrochrepts Halpumbrepts Haplustalfs-calcarious Materials, Rhodustalfs Dystrochrepts Haplustalfs, Dystrochrepts Eutrochrepts Argiudolls, Dystrochrepts Hapludalfs Haplustalfs-Calcarious Materials, Haplaquents Psammaquents Ustorthents, Haplaquents Eutrocrepts Heplaquents-calcareous Materials and Haplaquepts Dystrochrepts Haplaquents covering four soil order i.e. Entisols, Inseptisols. Mollisols and Alfisols. According the SOTER map, the soil types are as follow: Gelic LEPTOSOLS, Eutric CAMBISOLS, Eutric REGOSOLS, Humic CAMBISOLS, Chromic CAMBISOLS, Dystric REGOSOLS, Eutric GLEYSOLS Calcaric, PHAEOZEMS, Gleyic CAMBISOLS, Haplic PHAEOZEMS, Calcaric FLUVISOLS and other are glacier, ice, rock croup, lake and water. These types of soils are controlled by physiography and climatic factors. The SOTER soil types are more familiar than LRMP soil map although in LRMP soil map is useful to understand the soil characteristics and soil forming processes of Nepal. The soil degradation mitigation and adaptive strategies should consider the soil diversity types and its controlling factors such as physiography and climate.

Impact of Sustainable Land Management Practices on Soil Properties: Example of Organic and Integrated Agricultural Management

Maintaining good soil quality is crucial for the sustainability of agriculture. This study aimed to evaluate the effectiveness of the visual soil assessment (VSA) method by testing it on two soil types and two agricultural management practices (AMP) (organic and integrated) that are considered to protect soil quality. We selected two farms with plots on two river terraces with different soil properties. The test was based on the modified method Annual Crops Visual Quality Assessment developed by the Food and Agriculture Organization of the United Nations and supported by a standardized soil physical and chemical analysis. This study showed that the assessed score is highly dependent on the type of farming practice and how soils are managed. The soil type also plays an important role. The results for Calcaric Fluvisol showed that the effects of selected agricultural management practices on the visual assessment of soil quality could be almost undetectable. The time of assessment also plays a significant role in VSA scoring. Different crops and agricultural activities with significant impacts on the soil occur throughout the year (especially in vegetable production). It was observed that a higher score for the soil cover indicator had a beneficial effect on the total VSA rating.

Application of XAFS and XRD methods for describing the copper and zinc adsorption characteristics in hydromorphic soils.

Modeling metal sorption in soils is of great importance to predict the fate of heavy metals and to assess the actual risk driven from pollution. The present study focuses on adsorption of HM ions on two types of hydromorphic soils, including calcaric fluvisols loamic and calcaric fluvic arenosols. The individual and competitive adsorption behaviors of Cu and Zn on soils and soil constituents are evaluated comprehensively. It is established that the sorption processes were best described with the Langmuir model. The results suggest that the calcaric fluvic arenosols are more vulnerable to heavy metal input compared to fluvisols loamic. In all cases, Cu had a higher range of values of the adsorption process parameters relative to Zn. The Zn is likely to be the most critical environmental factor in such soils since it exhibited a decreased sorption under competitive conditions. The retention mechanisms of HM in hydromorphic soils are considered. Based on theoretical calculations of ion activity in soil solutions using solubility diagrams of Cu and Zn compounds, the possibility of precipitation of Cu hydroxide and Zn carbonate in the studied soils is shown. Direct physical methods of nondestructive testing (XAFS and XRD) are applied to experimentally prove the formation of these HM compounds on the surface of montmorillonite, the dominant mineral in hydromorphic soils, and calcite. Thus, the combination of both physicochemical methods and direct physical methods can provide a large amount of real information about the mechanisms of HM retain with solid phases.

Mechanisms of copper immobilization in Fluvisol after the carbon sorbent applying

Biochar is widely used sorbent for soil remediation but the mechanism of its effect on immobilization of metals and particular processes of metal transformation are still unclear. We designed an incubation experiment to investigate the impact of wood biochar to copper (Cu) contamination in Calcaric Fluvisols Loamic. The efficiency of biochar implementation for reduction of Cu mobility in soil has been studied using combined method of heavy metal fractioning (Minkina et al., 2013). It was shown that the use of sorbent into polluted soil results in the change of fraction-group composition of metal compounds, fixation of Cu due to reduction of weakly bound forms and increase of the part of residual and metal fractions strongly bound with organic matter. Decrease of pollutant mobility occurs along an increase of the dose of a sorbent. The greater effect was observed after use of biochar in the concentration 2.5 %. Thus, the present study demonstrates the possible remediation of soil contaminated by heavy metals using biochar and provides a particular strategy for remediation of soils contaminated with Cu.

Long-term effect of integrated fertilization on maize yield and soil fertility in a calcaric fluvisol

ABSTRACT In an 8-year study, the influence of integrated fertilization (combination of organic and inorganic fertilizers) on maize (Zea mays L.) yield and nutrition, with respect to nitrogen, phosphorus and potassium, at the different growth stages, was investigated in Quzhou County of the North China Plain. Three treatments were chosen for this study: inorganic fertilizers without organic fertilizers (IF), inorganic fertilizers plus low organic fertilizers (LOF) and inorganic fertilizers plus high organic fertilizers (HOF). The results showed that integrated fertilization significantly improved maize grain yield; the magnitude of increase in maize grain yield with HOF and LOF was 1.52 and 0.74 t ha−1, respectively, over the IF (9.20 t ha−1). The total plant biomass and uptake of nitrogen, phosphorus and potassium in maize plants across growing stages were significantly improved with integrated fertilization. The integrated supply of nutrients was also beneficial in improving soil organic carbon, total nitrogen, available phosphorus and exchangeable potassium over the years. The result suggests that nutrient management practices for maize cultivation in the North China Plain should preferably include the integrated use of organic and inorganic fertilizers (3.75 t ha−1 organic fertilizers supplemented with 125 kg N ha−1) to increase soil fertility and maize yield.

Soil texture and straw type modulate the chemical structure of residues during four-year decomposition by regulating bacterial and fungal communities

The changes of chemical structure and decomposer community during straw degradation have been inconsistent in previous reports, showing either convergence or divergence of chemical structures or microbial communities among different straw types. Hence the strength of their relationship remains unclear. Here, we directly measured the chemical structures and bacterial and fungal communities of wheat (Triticum aestivum L.) and maize (Zea mays L.) residues after four-year decomposition in three Calcaric Fluvisols that varied in soil textures. Separation of the chemical structures among the six soil-straw combinations (two straw types × three soil textures) were generally coupled with trends in the communities of bacterial and fungal decomposers, but the nature of their coupling differed. In the sand soil, soil texture was the central feature that shaped bacterial and fungal communities for both straw types, driving in turn the convergence of chemical structures of both decomposing straws. In contrast, in the sandy loam and silty clay soils, straw type was the primary regulator of the colonizing bacterial and fungal communities, which resulted in the divergence of chemical structures according to straw type.

Response of chemical and microbial properties to short-term biochar amendment in different agricultural soils

The objective of this study was to assess the effect of biochar soil amendment (BSA) on chemical and microbial properties in different agricultural soils in Vojvodina Prov?ince. Short-term pot experiment consisted of five biochar application doses (0, 0.5, 1, 2, and 3%) and five contrasting soil types (Mollic Gleysol, Eutric Cambisol, Calcaric Fluvisol, Gleyic Chernozem, and Haplic Chernozem), planted with sunflower (Helianthus annuus L.) and winter wheat (Triticum aestivum L.). The examined chemical and microbial properties were significantly influenced by soil type and interaction of experimental factors. Significant influence of biochar on the contents of calcium carbonate (CaCO3), total nitrogen (N), total carbon (C), soil organic carbon (SOC), humus and potassium (K) of the tested soils was observed. Biochar also significantly affected the number of azotobacters (AZB), fungi (FNG), actino?mycetes (ACT) and copiotrophic bacteria (CB). The effect of BSA varied depending on the applied dose, with higher values of the examined chemical and microbial parameters at higher doses of application. Further studies on using biochar in soils with low fertility will be neces?sary to establish its efficiency as an enhancer for agricultural production in Serbia.

Relationship between the chemical structure of straw and composition of main microbial groups during the decomposition of wheat and maize straws as affected by soil texture

Field decomposition of wheat and maize straws was monitored for 20 months using litterbag method in Calcaric Fluvisol soils with three different textures (sand, sandy loam, and silty clay). Residual straw samples were collected at 0 or after 4, 6, 10, and 20 months of decomposition. The chemical structure of straw was analyzed by solid-state 13C nuclear magnetic resonance (13C-NMR) spectroscopy, and the composition of main microbial groups was evaluated by phospholipid fatty acid analysis. Regardless of the straw type and soil texture, the straw biomass and C loss increased steadily in the first 10 months and then leveled off in the following 10 months; both the chemical structure of straw and the composition of main microbial groups differed during incubation. During the first 4 months of wheat straw degradation, the decrease in di-O-alkyl and O-alkyl C and the increase in alkyl and N-alkyl/methoxyl C contents were related to the enrichment of fungi (18:1ω9c) and Gram-negative bacteria (18:1ω7c and 16:1ω7c), while the degradation of maize straw was associated with the decrease in the fungal (18:1ω9c) abundance and the increase in the abundance of Gram-negative (18:1ω7c and 16:1ω7c) and Gram-positive (a15:0) bacteria. During the 6–10-month period, the decrease in di-O-alkyl and O-alkyl C and the increase in alkyl, aryl, and carboxyl/amide C contents were related to the enrichment of arbuscular mycorrhizal fungi (AMF) (16:1ω5c) and Gram-negative (cy19:0ω8c) bacteria and the decrease in fungal (18:2ω6,9c) abundance, with AMF playing an important role in the degradation of both straw types. The altered chemical structure of wheat and maize straws had opposite links with fungal abundance during the first 4 months, while alterations occurring during the 6–10-month period mainly depended on the variation in the AMF abundance.

High soil redox potential contributes to iron deficiency in drip-irrigated rice grown in calcareous Fluvisol

Drip-irrigated rice (Oryza sativa L.) is susceptible to iron (Fe) deficiency. The major possible cause of Fe deficiency is the changes in the water regime, which mainly affects the redox potential (E<sub>h</sub>) of the soil dictating the solubility of Fe. However, how high soil E<sub>h</sub> affects soil available Fe and rice Fe uptake is unclear. In this paper, we investigated the effect of soil E<sub>h</sub> on rice Fe uptake under different water management strategies (drip irrigation (DI), flood irrigation (FI) and forced aeration of soil in flooding irrigation (FIO)). The results showed that the diethylenetriaminepentaacetic acid (DTPA)-extractable Fe and Fe<sup>(II)</sup> concentration in the soil, Fe concentration and chlorophyll contents of leaves and biomass of rice in FIO were greater than those in DI but significantly less than those in FI. The Fe uptake of the plant in DI was the lowest, but which in FI was the highest. Overall, FIO resulted in a significant reduction in Fe uptake of rice, but greater than that in DI. We concluded that both the decreased soil water content and the increased soil E<sub>h</sub> were important factors that caused Fe deficiency of drip-irrigated rice.

Urban growth (1956-2012) and soil sealing in the metropolitan area of Valencia (Eastern Spain)

The aim of this study is to understand the urban growth dynamics from the mid-1950s to 2012 in the Metropolitan Area of Valencia, eastern Spain, and its impact on soils. The study area is a very interesting example of the many changes in land use and land cover in the landscape of Mediterranean alluvial plains. The analysis of urban growth was based on photo interpretation of aerial photographs and GIS based methodology. At a detailed scale (1:10,000), results show that there has been a highly dynamic process produced by the extent of land developed as urban area. In 1956 only 3,441 hectares (9.3% of the overall study area) were occupied by urban use. In 2012 the total sealed surface was 10,523 hectares, around 30% of the studied area. The increase in built-up areas for the whole period was 206%, representing an average annual rate of 126 ha/yr. In the Metropolitan Area of Valencia much of the land converted to urban use was once highly productive agricultural soils. Around 5,763 ha of soil types with very high and high land capability, mainly Calcaric Fluvisols, were sealed throughout the study period.

Chemical nature of soil organic carbon under different long-term fertilization regimes is coupled with changes in the bacterial community composition in a Calcaric Fluvisol

Fertilization is an important factor influencing the chemical structure of soil organic carbon (SOC) and soil microbial communities; however, whether any connection exists between the two under different fertilization regimes remains unclear. Soils from a 27-year field experiment were used to explore potential associations between SOC functional groups and specific bacterial taxa, using quantitative multiple cross-polarization magic-angle spinning 13C nuclear magnetic resonance and 16S rRNA gene sequencing. Treatments included balanced fertilization with organic materials (OM) and with nitrogen (N), phosphorus (P), and potassium (K) mineral fertilizers (NPK); unbalanced fertilization without one of the major elements (NP, PK, or NK); and an unamended control. These treatments were divided into four distinct groups, namely OM, NPK, NP plus PK, and NK plus control, according to their bacterial community composition and SOC chemical structure. Soil total P, available P, and SOC contents were the major determinants of bacterial community composition after long-term fertilization. Compared to NPK, the OM treatment generated a higher aromatic C–O and OCH3 and lower alkyl C and OCH abundance, which were associated with the enhanced abundance of members of the Acidobacteria subgroups 6 and 5, Cytophagaceae, Chitinophagaceae, and Bacillus sp.; NP plus PK treatments resulted in a higher OCH and lower aromatic C–C abundance, which showed a close association with the enrichment of unclassified Chloracidobacteria, Syntrophobacteraceae, and Anaerolineae and depletion of Bacillales; and NK plus control treatments resulted in a higher abundance of aromatic C–C, which was associated with the enhanced abundance of Bacillales. Our results indicate that different fertilization regimes changed the SOC chemical structure and bacterial community composition in different patterns. The results also suggest that fertilization-induced variations in SOC chemical structure were strongly associated with shifts in specific microbial taxa which, in turn, may be affected by changes in soil properties.