Differential soil acidification caused by parent materials and land-use changes in the Pearl River Delta region

Soil acidification occurs widely across the world, which has been partly attributed to land-use change. However, measureable effect of land-use change as well as parent materials on soil acidification remains poorly understood. Here, a typical area with intensive land-use change in the Pearl River Delta of China was chosen for this study. Topsoil (0–20 cm) and subsoil (20–40 cm) samples (n = 169) under different land uses (paddy fields, vegetable lands and orchards) and parent materials (granite and alluvial sediment) were collected in 2020. Soil pH, exchangeable base cations, exchangeable acidity and pH buffering capacity were measured to evaluate the status of soil acidification. The change of soil pH over the last 15 years was evaluated via comparing with historical data (n = 329) in 2005. The results showed a higher exchangeable acidity and lower pH buffering capacity and exchangeable base cations of soils derived from granite compared with soils derived from alluvial sediment in 2020. In the last 15 years, significant soil acidification under different parent materials was observed under vegetable lands and orchards but not paddy fields. Faster pH decline was found under land-use change from paddy fields compared with the unchanged vegetable lands or orchards. Furthermore, stronger acidification under the same land-use change was observed for soils derived from granite compared with soils derived from alluvial sediment. These results indicate that land-use change induced soil acidification is dependent on parent materials. This study implies that cropping management such as suitable rotation operation may slow soil acidification, and measures including straw returning may ameliorate acidified soils.     

Early pedogenic evolution of constructed Technosols

Purpose  

Constructed soils are Technosols resulting from the deliberate combination of various artefacts. Similarly to natural soils, technogenic parent materials are transformed by pedogenic factors contributing to their evolution. This work was conducted to study the first stages of the pedogenesis of constructed soils.     

Classification of Urban and Industrial Soils in the World Reference Base for Soil Resources (5 pp)

Background, Aim and Scope   Historically, built areas were ignored in soil mapping and in studies of soil formation and behaviour. It is now recognized that these areas, and therefore their soils, are of prime importance to human populations. Another trend is the large increase in reclaimed lands and new uses for old industrial areas. In several countries there are active projects to map such areas, either with locally-developed classification systems or ad-hoc names. Soil classification gives unique and reproducible names to soil individuals, thereby facilitating correlation of soil studies; this should be possible also for urban soils. The World Reference Base for Soil Resources (WRB) is the soil classification system endorsed by the International Union of Soil Science (IUSS). The 2006 edition has important enhancements which allow urban and industrial soils to be described and mapped, most notably a new reference group, the Technosols. Main Features   Urban soils are first defined, followed by the philosophical basis of soil classification in general and the WRB in particular. WRB 2006 added a new Technosols reference soil group for soils whose properties and function are dominated by technical human activity as evidenced by either a substantial presence of artefacts, or a impermeable constructed geomembrane, or technic hard rock. Technosols are one of Ekranic, Linic, Urbic, Spolic or Garbic; further qualifiers are added to show intergrades to other groups as well as specific soil properties. Soils from fill are recognized as Transportic Regosols or Arenosols. Toxic soils are specifically recognized by a qualifier. Results   - Discussion   The limit between Technosols and other groups may be difficult to determine, because of the requirement that the technic nature dominate any subsequent pedogenesis. Conclusions   - Perspectives   The WRB should certainly be used in all urban soil studies to facilitate communication and correlation of results. In the period leading up to the next revision in 2010, the quantitative results from urban soil studies should be used to refine class definitions.     

Contribution of technic materials to the mobile fraction of metals in urban soils in Marrakech (Morocco)

Background, Aim and Scope  In urban areas, soils are often dramatically altered by anthropogenic activity and these modifications distinguish these soils (Anthrosols, Technosols) from those in natural systems. In urban environments, they receive considerable pollution from industry, traffic and refuse. Since contaminated soil particles can be easily inhaled or ingested, there is a potential transfer of toxic pollutants to humans. Risk assessment is essentially based on the determination of the total or mobile contents of pollutants in soils using chemical extractions. This approach could be improved by taking into consideration the bioavailable fractions of these toxic elements as measured by biotests. The coarse soil fraction usually neglected in analyses can nevertheless have an effect on the concentration of metals in the soil solution. This coarse fraction is made up of the natural materials and of technic materials constituting anthropogenic soils (plastic, paper, fabric, wood, bones, metallic elements and building materials). These materials have variable capacities to release or adsorb trace elements. Samples representative of different technic fraction components of Marrakech urban soils permit one to quantify their contribution to the enrichment of the soluble metal concentrations. Works are carried out to achieve partial extractions of metals from the three fractions (less than 2 mm, coarse natural and coarse technic) of selected urban soils in order to determine their contribution to the metal contamination of soils. Materials and Methods  Selected soils were collected from 9 sites according to a gradient of increasing anthropogenic influence from suburban to urban zones. Soils were air-dried, homogenized, and sieved (2 mm). The coarse fraction was sorted to separate the different technic materials and natural materials. Water extractions were run, on the natural, coarse fraction, on the complete technic fraction of the 9 soils and on average samples made of technic materials sorted out of 58 topsoils sampled from different sites in the city of Marrakech. Results  Results show that the percentage of the technic fraction increases while approaching the historic city center. It represented about 14% in the most anthropogenically disturbed soils. Along this gradient, soils changed progressively from Anthrosols to Technosols according to the WRB classification of urban and industrial soils. Analyses of metal contents showed that the fine fraction (<2 mm) mainly contributed to the metallic contamination of the water soluble fraction. The natural coarse fraction had the highest contribution to the copper release and was responsible for the release of all water-extractable copper in some soils. Concerning the technic fraction, it has a significant contribution essentially in the most anthropogenically disturbed soils as characterized by an elevated percentage of anthropogenic elements. The water extractable metal contents of average samples of these anthropogenic elements shows that elevated metal concentrations were released by bones, wood, plastic and fabric/paper. Discussion  This study concerns soils in urban areas, which are strongly impacted by human activities. Part of the soils can be classified as Anthrosols, profoundly impacted through the addition of organic materials from household wastes, irrigation, or cultivation. Other soils strongly impacted by human activities are Technosols dominated or strongly influenced by man-made materials. Technosols appear mostly in urban and industrial areas and are more likely to be contaminated than Anthrosols. The composition and heterogeneity of urban soils lead to modifications of the mobility and availability of pollutants depending on successive land-uses and on the composition of technic materials. The fine fraction offers a high transferring surface capacity, leading to a high mobilization of metals. The technic fraction contributes significantly to the metal release in the Technosols. This property can be explained by a reversible adsorption of metals on the organic matter. Conclusions  Results confirm that anthropogenic activity causes a wide spatial diversity of soil quality in the urban and suburban area. It introduces large amounts of technic materials in soils that could have an impact on the metal availability. It therefore acts on the metal bioavailability in the urban Technosols. Recommendations and Perspectives  These results show that it is necessary, in addition to the characterization of the fine particles, to take into account the contribution of the coarse fraction of the Technosols in the evaluation of risks of transfer of metals to the food chain.     

Generation,sink, and emission of greenhouse gases by urban soils at different stages of the floodplain development in Moscow

Purpose

The purpose of this research was to study the generation, sink, and emission of greenhouse gases by soils on technogenic parent materials, created at different stages of the Moskva River floodplain development (1—construction and 2—landscaping of residential areas).

Materials and methods

Field surveys revealed the spatial trends of concentration and emission of the greenhouse gases in following groups of soils: Retisols (RT-ab-ct) and Fluvisols (FL-hu, FL-hi.gl) before land engineering preparation for the construction, Urbic Technosols Transportic (TC-ub-ar.tn and TC-ub-hu.tn) at stage 1 and Urbic Technosols Folic (TC-ub-fo) at stage 2. CO₂ and CH₄ concentration in soils and their emission were determined using subsurface soil air equilibration tubes and the closed chamber method, respectively. Bacterial methane generation rate (MGR) and methane oxidation rate (MOR) were measured by kinetic methods.

Results and discussion

In natural soils MOR is caused only by intra-aggregate methanogenesis. The imbalance of methane generation and oxidation was observed in FL-hi.gl. It caused CH₄ accumulation in the profile (7.5 ppm) and its emission to the atmosphere (0.11 mg CH₄ m^?2 h^?1). RT-ab-ct acted as the sink of atmospheric methane. CO₂ emission was 265.1?±?24.0 and 151.9?±?37.2 mg CO₂ m^?2 h^?1 from RT-ab-ct and FL-hi.gl, respectively. In Technosols CH₄ concentration was predominantly low (median was 2.7, 2.9, and 3.0 ppm, in TC-ub-ar.tn, TC-ub-hu.tn, and TC-ub-fo, respectively), but due to the occurrence of peat sediments under technogenic material, it increased to 1–2%. Methane emission was not observed due to functioning of biogeochemical barriers with high MOR. In TC-ub-ar.tn and TC-ub-hu.tn, the barriers were formed at 60-cm depth. In TC-ub-fo, the system of barriers was formed in Folic and Technic horizons (at 10- and 60-cm depth). CO₂ emission was 2 times lower from TC-ub-ar.tn and TC-ub-hu.tn and 1.5 times higher from TC-ub-fo than from natural soils.

Conclusions

Greenhouse gas generation, sink, and emission by natural soils and Technosols in floodplain were estimated. CO₂ and CH₄ content in Technosols varied depending on the properties of parent materials. Technosols at stage 1 did not emit CH₄ due to formation of biogeochemical barriers—soil layers of high CH₄ utilization rates. Urbic Technosols (Folic) at stage 2 performed as a source of significant CO₂ emission.

     

Technosols in the World Reference Base for Soil Resources – history and definitions

ABSTRACT

The World Reference Base for Soil Resources (WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the update 2015 of its third edition. WRB has two levels: first and second. The first level comprises 32 Reference Soil Groups (RSGs), identified using a Key. At the second level, the soil names are constructed by adding a set of qualifiers to the name of the RSG. In the WRB, diagnostic horizons, properties and materials are defined. Diagnostic materials are materials that significantly influence soil-forming processes. Diagnostic properties and horizons have a combination of attributes that mostly reflect results of soil-forming processes.

The RSG Technosols was introduced in the second edition of the WRB in 2006. In the current version of the WRB, two diagnostic materials are defined for Technosols: artefacts and technic hard material. Artefacts are substances that are created or substantially modified by humans or brought to the surface from a depth, where they were not influenced by surface processes. The technic hard material is a (relatively) continuous consolidated material resulting from an industrial process. The Technosols are at the third place in the Key after Histosols and Anthrosols. A soil is a Technosol if it has technic hard material within 5 cm or a geomembrane or a significant amount of artefacts within 100 cm. If a soil has no technic hard material and no geomembrane but a layer with artefacts that has undergone enough soil formation to develop a diagnostic horizon typical for advanced pedogenesis, the soil is excluded from the Technosols. There are specific qualifiers to further characterise the Technosols. They are also important to characterise soils other than Technosols that have artefacts or technic hard material. Human-transported natural soil material does not qualify as Technosol.     

Fertility of Technosols constructed with dam sediments for urban greening and land reclamation

Purpose

Fine sediment accumulates upstream of hydroelectric dams. To ensure that dams can operate properly, part of the sediment has to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening or land restoration is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct multifunctional soils. This agronomic use is only possible if sediment can provide acceptable physical and chemical properties for plant growth.

Materials and methods

Four dredged sediments with contrasted initial agronomic properties and one control soil were mixed or not with green waste compost (40% v/v) and used to construct triplicate 30-cm depth soils in lysimetric containers (1.11?×?0.71 m). The 30 constructed soils were exposed to the in situ conditions and sown with ryegrass (Lolium perenne). The evolution of soil chemical and physical properties and plant development were studied every 6 months for 18 months.

Results and discussion

Above- and below-ground biomass production of the constructed soils contrasted according to the sediment properties and to compost addition. A statistical approach identified eight soil parameters linked to biomass production. Among these parameters, soil structure, quantified from aggregate stability, played a fundamental role. A focus on physical properties confirmed that some sediments were only partially adapted to ryegrass support. Compost addition improved sediment physical properties over time, but caused temporary N deficiency during the first months after installation which limited shoot biomass production. Exogenous plant species developed on the constructed Technosols, especially on the soils where the lack of structure and N deficiency had the strongest effect.

Conclusions

All sediments were suitable for plant growth over the 18 months of the study. A few soil properties emerged as markers of the fertility of sediment-made Technosols. Among them, the soil structure was one of the most determining parameters. It can be assessed by measuring aggregate stability, macroporosity, the crustability index, and bulk density, while available nutrients (N, P, K) and pH seem sufficient to assess chemical fertility. The balance between the properties of the sediment-made Technosols and the needs of the plants seems to be an essential lever for the establishment of functional soil-plant systems for urban greening or for ecological restoration.

     

Technosol genesis: identification of organo-mineral associations in a young Technosol derived from coking plant waste materials

Background, aim and scope  

Technosols form a new soil group in the World Reference Base for Soil Resources (WRB) (FAO, World Soil Resour Rep 132:145, 2006) mainly characterised by anthropogenic parent material of organic and mineral nature and which origin can be either natural or technogenic. The increasing number of sites affected by technogenic materials and their impact on the environment as growing media for plants or as source of pollutants requires an understanding of their functioning and evolution. Among the parameters describing soil functions, the structure is a key property, encompassing physical, chemical and biological soil processes, which is not yet usually studied in Technosols. The presence of high levels of complex technogenic materials and pollutants (polycyclic aromatic hydrocarbons [PAHs] and trace elements) is likely to determine aggregation and induce a specific soil structure. This work was undertaken to test this hypothesis and assess whether technogenic material would contribute to the formation of water-stable aggregates in Technosols.     

利用Technosols改善铜矿土壤的物理化学特性

Mine tailing soils created from the copper extraction in Touro Mine (Northwest Spain) are very degraded both physically and chemically. Three plots in this mine tailing were amended with Technosols in different proportions in each one to know if this mixture improved the physico-chemical characteristics of the mine soil and contaminated it with heavy metals. The Technosols were made of organic wastes, including mussel residues, wood fragments, sewage sludges and paper mill ashes. An unamended area was used as a control soil. Pseudototal and diethylenetriaminepentaacetic acid (DTPA)-extractable contents of Al, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in soil samples. The untreated soil had significant limitations for vegetation growth. All the Technosols improved the properties of the mine soil by increasing organic carbon and pH value, but they added Ni, Pb or Zn to the soil. It is advisable to check whether the heavy metal concentrations of the wastes are hazardous or not before adding to soils. It is also necessary to study the effect of these wastes over time and in more areas to conclude if they are actually favourable to restore degraded mine soils.     

山西平朔露天矿区复垦农用地表层土壤质量差异对比

以复垦农用地为研究对象,以原地貌未受损农用地和排土场未复垦地作为对照,共选择18个样地,对比研究复垦农用地、未复垦地及原地貌未受损农用地的土壤容重、田间持水量、pH值、有机质、全氮、全钾、有效磷、速效钾的差异,揭示复垦农用地土壤重构的过程及变异的规律。结果表明：（1）复垦农用地土壤容重、田间持水量、pH值、全钾、有效磷、速效钾的均值都略高于未受损农用地;而复垦农用地有机质、全氮的均值都略低于未受损农用地。（2）复垦农用地和未受损农用地在0-10cm的土壤容重及pH值均略低于10～20cm土层;0～10cm的土壤肥力指标均值略高于10～20em土层。（3）在0～10cm土层,复垦耕地和复垦林地的相关土壤理化性质要优于未受损耕地;在10—20cm,复垦林地土壤理化性质基本上优于未受损耕地。（4）复垦13年的耕地土壤容重、速效钾与未受损耕地差异不显著;复垦22年林地的单个土壤理化指标基本上优于复垦19年林地,复垦19年林地的单个土壤理化指标基本上优于未受损林地。     

Characterization of organic matter fractions in the top layer of soils under different land uses in Central‐Eastern Europe

The objective of this study was to investigate differences in organic matter fractions, such as dissolved organic carbon and humic substances, in soils under different land uses. Soil samples were collected from the upper layer of arable lands and grasslands. Humic substances (HS) were chemically fractionated into fulvic acids (FA), humic acids (HA) and humins (HUM), and based on the separated fractions, the humification index (HI) and the degree of HS transformation (DT) were calculated. Dissolved organic carbon (DOC) was determined by cold (CWE) and hot water (HWE) extractions. Regardless of land use, the results indicated significant differences in soil organic carbon (SOC) and HS composition, with HA and HUM as the dominant fractions. Total SOC was higher in grassland (median = 17.51 g kg^?1) than arable soils (median = 9.98 g kg^?1); the HI and DT indices did not differ significantly between land uses (HI = 0.3–10.3 and DT = 0.2–6.2 for grasslands, p > 0.05; HI = 0.3–3.9 and DT = 0.2–20.1 for arable lands, p > 0.05). This indicates the relatively high stability of organic carbon and efficient humification processes in both land uses. Additionally, in arable soils lower CWE‐C (0.75 g kg^?1) and higher HWE‐C (2.59 g kg^?1) than in grasslands (CWE‐C = 1.13 g kg^?1, HWE‐C = 1.60 g kg^?1) can be related to farming practice and application of soil amendments. The results showed that both labile and humified organic matter are better protected in grassland soils and are consequently less vulnerable to mineralization.     

Rapid Changes in Soil Nematodes in the First Years after Technosol Construction for the Remediation of an Industrial Wasteland

Technosol construction is an emergent technology that uses an assemblage of technogenic materials for the ecological reclamation of derelict land and waste recycling. Knowledge about the colonisation of Technosols by soil biota is limited, despite the latter’s central role in ecosystem functioning. In this four-year field (2008 to 2011) study, we characterized the development over time of the diversity and the abundance of soil nematodes in two types of Technosols in North-Eastern France. We also studied the nematode community structure, abundance of taxa and functional groups in both Technosol profiles in the third year of the study. Samples were collected from the top soil layer (0–20 cm) each year in the spring (April), on a one ha. field experiment that had spatially divided in 24 sampling areas. For soil profiles, three samples were collected in three horizons within six pits (three pits per Technosol). Nematodes were extracted from soil and identified at the family or genus level and then classified into functional feeding guilds. In the first year, the community was dominated by opportunistic bacterial feeders. The taxonomic and functional nematode diversity increased with time, with a dominance of non-opportunistic bacterial feeders after four years, but also the significant presence of fungal feeders, omnivorous and carnivorous, as well as plant parasites and insect parasites. No significant difference was observed between the two Technosols. Each layer showed distinct communities, with nematode diversity and abundance decreasing with depth. Abundance and diversity, coupled with the analysis of several indexes, commonly used for nematodes, including Maturity index (MI), Enrichment index (EI), Structure index (SI) and Nematode channel ratio (NCR), lead to the conclusion that the high organic matter content, particularly in the upper horizon of both Technosols, guaranteed nematode colonization and progressive diversification, and is likely to be the key for successful biodiversity reclamation.     

Characterization of Degraded Soils in the Humid Ethiopian Highlands

Hardpan is a major cause of land degradation that affects agricultural productivity in developing countries. However, relatively, little is known about the interaction of land degradation and hardpans. The objective of this study was, therefore, to investigate soil degradation and the formation of hardpans in crop/livestock‐mixed rainfed agriculture systems and to assess how changes in soil properties are related to the conversion of land from forest to agriculture. Two watersheds (Anjeni and Debre Mewi) were selected in the humid Ethiopian highlands. For both watersheds, 0–45 cm soil penetration resistance (SPR, n  = 180) and soil physical properties (particle size, soil organic matter, pH, base ions, cation exchange capacity, silica content, bulk density and moisture content) were determined at 15 cm depth increments for three land uses: cultivated, pasture and forest. SPR of agricultural fields was significantly greater than that of forest lands. Dense layers with a critical SPR threshold of ≥2000 kPa were observed in the cultivated and pasture lands starting at a depth of 15–30 cm but did not occur in the undisturbed forest land. Compared with the original forest soils, agricultural fields were lower in organic matter, cation exchange capacity, and exchangeable base cations; more acidic; had a higher bulk density and more fine particles (clay and silt); and contained less soluble silica. Overall, our findings suggest that soil physical and chemical properties in agricultural lands are deteriorated, causing disintegration of soil aggregates, resulting in greater sediment concentration in infiltration water that clogged up macro‐pores, thereby disconnecting deep flow paths found in original forest soils. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of fly ash,apatite and rice straw derived-biochar in varying combinations for in situ remediation of soils contaminated with multiple heavy metals

ABSTRACT

In

-situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam.     

Taxonomic and functional characterization of microbial communities in Technosols constructed for remediation of a contaminated industrial wasteland

Purpose

The construction of Technosols is an emergent technology based on the assemblage of technogenic materials for ecological reclamation of polluted land and waste recycling. Although this technology is in expansion, knowledge about the microbial communities in Technosols is limited, despite their central role in ecosystem functioning. In this 2-year study, the diversity and the abundance of total and functional microbial communities were characterized in two types of Technosols constructed to reclaim contaminated sites.

Materials and methods

The structure of the microbial community was analyzed by automated ribosomal intergenic spacer analysis fingerprinting in both types of Technosols, and the taxonomic diversity was further assessed by 16S rRNA clone library sequencing. Real-time PCR was used to quantify the abundance of the total bacterial and crenarchaeal community and of the functional guilds involved in N-cycling.

Results and discussion

16S rRNA sequencing showed that Proteobacteria was the main phylum in the Technosols (50?C80?%). The other significant phyla identified were Bacteroidetes, Firmicutes, Choloroflexi, and Actinobacteria. Real-time PCR quantification of the abundance of ammonia oxidizers, nitrate reducing, and denitrifying microbial communities involved in nitrogen cycling revealed that bacterial ammonia oxidizers were more abundant than crenarchaeal ammonia oxidizers. A high spatial variability of the microbial community, which decreased with time, was also observed.

Conclusions

At the phyla and class levels, the composition of the microbial community in constructed Technosols was similar to ??natural?? soils. Both the total bacteria and microbial guilds involved in N-cycling were abundant, but in contrast to most natural soils, bacteria and not crenarchaea were the numerically dominant ammonia oxidizers in both types of Technosols. The decrease with time of the variability in microbial community structure support early pedogenic evolution of recently constructed Technosols.     

Effects of compost type and storage conditions on climbing bean on Technosols of Tantalum mining sites in Western Rwanda

Little is known about the effects of compost application to reclaim artisanal mining sites for agriculture in Central Africa. A field experiment was therefore conducted to examine the effects of locally available organic household waste composted under traditional (pit under leaf shade) versus improved management (pit under double plastic sheeting) and mixed with either Tithonia diversifolia biomass or Minjingu Phosphate Rock (13–15% P) on climbing bean sown on degraded Technosols (former Tantalum mining sites) and un‐mined control soils (Cambisols). Both soil types were derived from pegmatite. After 6 months of composting, nutrient concentrations in traditional compost were 0.27–0.32% N, 0.06–0.08% P, and 0.20–0.22% K. Comparative values in amended compost were 1.02–1.65% N, 0.10–0.31% P, and 0.41–1.13% K. In farmyard+solid waste, composted under traditional system, dry matter was 65.4%, pH 6.7, and C : N ratio 13.0, as opposed to 81.5% DM, a pH of 8.6, and a C : N ratio of 8.6 in farmyard+solid waste+Minjingu phosphate under improved compost, and 68.3% dry matter, a pH of 8.4, and a C : N ratio of 7.4 for Tithonia +farmyard+solid waste under improved conditions. Compared to bean (Phaseolus vulgaris L.) grain yields of 0.28 (mined soil) and 0.11 (unmined soil) without amendments, the application (on a dry matter basis) of 5 t compost ha⁻¹ led to yields of 3.54 t DM ha⁻¹ for improved compost Tithonia +farmyard+solid waste on mined soil versus 2.26 t DM ha⁻¹ (P < 5%) for the same treatment at the un‐mined sites. The yield obtained for farmyard+solid waste+Minjingu phosphate composted under improved conditions averaged 3.06 t DM ha⁻¹ at mined sites compared with 2.85 t DM ha⁻¹ at un‐mined sites (P > 5%). All amendments were more effective in enhancing bean yields on Technosols with significant positive effects with improved compost than on Cambisols.     

Annual Burning Enhances Biomass Production and Nutrient Cycling in Degraded Imperata Grasslands

The invasive species Imperata cylindrica is a dominant grass covering a large part of degraded lands of India. Imperata is managed through traditional annual burning, a practice that is prevalent throughout tropical grasslands. A field experiment was conducted to quantify the effects of burning on aboveground and belowground biomass production and soil organic carbon (SOC), total nitrogen (TN), available phosphorus (Ave P), potassium (K⁺), calcium (Ca⁺), and magnesium (Mg⁺) concentrations in 0‐ to 15‐cm soil depth under Imperata grassland. The burnt site had 44% and 14% higher aboveground and belowground biomass over the un‐burnt control plots after 300 days of the fire event. The concentrations of SOC, TN, and Ave P increased soon after the fire but decreased regressively with time after the fire in both micro and macro soil aggregate size fractions. In contrast, concentrations of K⁺, Ca⁺, and Mg⁺ increased up to 30 days after the fire in both soil aggregate fractions. Burning did not significantly alter the stoichiometric ratios (C : N, C : P, and N : P) in macro aggregates. However, burning significantly reduced the C : N, C : P, and N : P ratios in micro aggregates during the first 0–30 days. Fire increased nutrient stocks (kg ha⁻¹) by 20–35% in the burnt site in comparison to an un‐burnt control site. It is concluded that the conventional practice of annual burning increases soil nutrients in surface soils and supports higher biomass production in Imperata‐covered degraded lands. Copyright © 2017 John Wiley & Sons, Ltd.     

开垦年限对干旱区土壤理化性质及剖面无机碳的影响

为阐明开垦年限对土壤理化性质及无机碳的影响,进一步了解干旱区土地开垦进程中的土壤质量变化规律和碳吸收与存储过程,以开垦年限分明的典型区—新疆三工河流域阜北农场为研究区,调查、分析了不同开垦年限(已开垦0,1,3,5,15,30,50a)剖面土壤的pH值、盐分、无机碳含量与储量的分布特征、变化规律及开垦年限对它们的影响。结果表明:(1)已开垦土地的土壤pH值随土层深度的增加而升高;随开垦年限的延长,0—60cm(耕作层)的土壤pH值显著降低(P0.05),60—140,140—200cm土壤pH值则升高。不同开垦年限的土壤盐分在剖面上呈"S"型分布,研究区土壤盐分为表聚型;随着开垦年限的延长,土壤盐分聚集层逐渐下移,各剖面平均含盐量减少。开垦历史的延长,有助于排盐排碱。(2)不同开垦年限的土壤无机碳含量与储量:0—60cm显著低于60—140cm,60—140cm显著低于140—200cm(P0.05)。随着土层深度的增加,土壤无机碳储量占全碳的比例增大。随着开垦年限的延长,0—60cm耕作层土壤无机碳含量、储量呈"减少—增加—减少"的变化趋势,无机碳储量占全碳的比例减少。与原始荒地相比,开垦50a时,0—60cm耕作层的土壤无机碳储量减少了55%;0—200cm土壤无机碳储量增加了11.74kg/m~2,无机碳储量所占全碳的比例降低了1.28%。(3)开垦年限的延长对土壤pH、盐分及无机碳的显著影响深度不同,分别集中于0—60cm耕作层,0—140cm及整个研究深度范围内。     

高潜水位平原区采煤塌陷地复垦土壤形态发育评价

土壤的形态特征含有丰富的环境信息,是环境变化与生态重建的重要依据,可以推断土壤发育的强弱。矿山复垦土壤为人造新土壤,可能构造出不同的土壤形态,复垦土壤形态特征的研究对复垦土壤生产力的提高和复垦技术的革新具有重要意义。该文以高潜水位平原区采煤塌陷地复垦土壤为研究对象,探讨定量评价复垦土壤形态发育状况。研究采用实地调查和室内分析相结合的方法,依据中国土壤系统分类用土壤剖面描述标准,构建了复垦土壤形态发育评价体系,进行土壤形态定量评价。结果表明,形态发育指数HI(土层发育指数)和WPDI(土壤权重剖面发育指数)能够较好的反映复垦土壤与当地原状土壤的发育程度差异:复垦土壤土层发育指数HI和土壤权重剖面发育指数WPDI平均值分别为0.57、0.56,而当地原状土壤HI和WPDI的平均值为0.68、0.69,表明复垦土壤形态发育程度相对较弱;HI曲线形状异于原状土壤,表层HI高于其他土层,不同复垦方式的WPDI显示的发育程度序列为:充填复垦(外源土)>挖深垫浅>挖深垫浅(泥浆泵)>充填复垦(粉煤灰、煤矸石等);随复垦时间的延长,复垦土壤发育程度呈现增长趋势。