Major Soil Research Articles

SOIL NITROGEN CYCLING AND ENVIRONMENTAL IMPACTS IN THE SUBTROPICAL HILLY REGION OF CHINA: EVIDENCE FROM MEASUREMENTS AND MODELING

<List> <ListItem><ItemContent> ● Soil nitrogen fluxes and influencing factors were reviewed in the subtropical hilly regions. </ItemContent></ListItem> <ListItem><ItemContent> ● Fertilizer application and atmospheric deposition contributed largely to soil nitrogen input. </ItemContent></ListItem> <ListItem><ItemContent> ● High gaseous, runoff and leaching losses of soil nitrogen were measured. </ItemContent></ListItem> <ListItem><ItemContent> ● Soil nitrogen cycles are well modelled with the Catchment Nutrients Management Model. </ItemContent></ListItem></List> The subtropical hilly region of China is a region with intensive crop and livestock production, which has resulted in serious N pollution in soil, water and air. This review summarizes the major soil N cycling processes and their influencing factors in rice paddies and uplands in the subtropical hilly region of China. The major N cycling processes include the N fertilizer application in croplands, atmospheric N deposition, biological N fixation, crop N uptake, ammonia volatilization, N₂O/NO emissions, nitrogen runoff and leaching losses. The catchment nutrients management model for N cycle modeling and its case studies in the subtropical hilly region were also introduced. Finally, N management practices for improving N use efficiency in cropland, as well as catchment scales are summarized.

Soil Characterization and Classification for Agricultural Land Use Planning: A Study of Semi-arid Rajasthan

Based on morphological, physical, physicochemical and chemical characteristics of soil, six representative soil profiles from the Phulera tehsil of Jaipur district of Rajasthan were studied for soil characterization and classification. Results revealed that the soils of the study area were dominantly dark yellowish-brown in colour, with loamy sand texture having a higher content of sand. These soils were poor in organic carbon content (0.8 to 3.5 g kg-1). The soils were moderately alkaline (pH 7.3 to 8.3) in reaction and non-saline (EC 0.02-1.21 dS m-1). The cation exchange capacity (CEC) in most of the profiles was low (3.99 to 8.32 cmol(p+)kg-1) and calcium (Ca2+) and magnesium (Mg2+) dominated the exchange sites on the colloidal complex. All the profiles were placed under Entisol due to the absence of a diagnostic sub-surface horizon. Due to the ustic soil moisture regime, hyperthermic temperature regime, and higher sand content, the soils were classified as sandy, mixed, hyperthermic Typic Ustipsamments. On the basis of major soil constraints and potentials, suitable land use plans has been suggested.

Effect of Land Uses on Soil Erodibility in the Njala Area of Southern Sierra Leone

Soil loss through erosion continues to pose serious challenges to increasing the smallholder agricultural productivity in Sierra Leone. While emphasis on sustainable land use practices continue to gain attention among land users, however, the rate of adoption among smallholder farmers is still very low and hence, in most part of the country soil fertility has been declining at alarming rates. In the Njala area, studies have shown that soil loss ranges from moderate to high. Though soil erosion has been identified as a major soil fertility declining factor, however, the effect of land use practices on the inherent resistance of soil materials to erosion is lacking. This study was therefore conducted to assess the effect of land uses on soil erodibility. The results showed that the soils are coarse sandy loam with high sand content. The dispersion ratios and erosion indices of soils under cassava, plantain, maize and guava were above the minimum thresholds of 15.0 and 10.0 respectively, thus indicating that these soils are highly erodible compared to soils under fallow and sweet potato which have dispersion ratios and erosion indices below the minimum thresholds. Clay content was inversely proportional to and significantly correlated with dispersion ratio and erosion index while the correlations between silt + clay, dispersion ration and erosion index, and silt, silt + clay and dispersion ratio were negative and non-significant. Considering the coarse nature of soils, landscape features and high erodibility indices, these soils would need special soil and water conservation practices to counter further degradation. These may include following, agroforestry, silvi-pasture, controlled and rotational grazing. In addition, awareness of sense of self-responsibility and forest policies and regulations are needed.

Soil-landform relationship and pedogenesis of flood plain soils of Mahananda sub-basin, Bihar

Alluvial flood plain soils are one of the major soil groups in northern Bihar and are highly heterogeneous as a result of the hydromorphic environment in which they are formed. Hence, the present investigation was carried out to understand the soil-landform relationship in Katihar district of Bihar. Five major landforms like old alluvial plains (1.97%), young alluvial plains (35.64%), meander plains (30.85%), flood plains (25.35%) and, char land and point (4.5%) were identified after visual interpretation of Sentinel-2 data in conjunction with survey of India toposheet and digital elevation model (SRT DEM). The detailed soil survey was carried out to understand the variability in the study area and 200 soil profiles were studied in different identified landforms. The soils of active alluvial plain (flood plain, char land and point bar) showed wide range of soil morphological properties with lithological discontinuities. Low chroma and value in soils of meander plain due to poor drainage conditions and high groundwater table showed gleying characteristics. The soils of young alluvial plain and active alluvial plain showed irregular distribution of clay content, cation exchange capacity (CEC) and organic carbon (OC). This study indicates that the soil-landform relationship in alluvial floodplains of Mahananda sub-basin partially followed due to mass movement of sediments from Himalayas, periodic flooding and deposition of alluvium during different fluvial cycles of Mahananda river and its tributaries. This was further confirmed by study on pedogenic indices of different landforms. The study on pedogenic indices in two selected sites (window area) away from the Mahananda river like fine sand/total sand, very fine sand/total sand, sand/silt, silt/clay, index of weathering and CEC/clay in the study area doesn't follow the trend in the flood plain as compared to nearly stable land. This may be due to the effect of shifting of river course and their tributaries in the selected two window areas across the different landforms. To overcome the above mentioned problems in soil-landform relationship in the study area, the identified landforms were further sub-divided based on the local factors like percentage of crop cover and moisture content. In revised landforms soil types present in each landform showed soil-landform relationship. Thus, the knowledge on soils in relation to landforms vis-a-vis soil properties and their pedogenesis is useful in understanding their potentials and problems for sustainable land use planning.

Soil Communities: Who Responds and How Quickly to a Change in Agricultural System?

The use of conservation and sustainable practices could restore the abundance and richness of soil organisms in agroecosystems. Fitting in this context, this study aimed to highlight whether and how different soil living communities reacted to the conversion from an integrated to an organic orchard. The metataxonomic approach for fungi and bacteria and the determination of biological forms of diatoms and microarthropods were applied. Soil analyses were carried out in order to evaluate the effect of soil chemical features on four major soil living communities. Our results showed that the different taxa reacted with different speeds to the management changes. Fungi responded quickly to the changes, suggesting that modification in agricultural practices had a greater impact on fungal communities. Bacteria and microarthropods were more affected by abiotic parameters and less by the management. The diatom composition seemed to be affected by seasonality but the highest H’ (Shannon index) value was measured in the organic system. Fungi, but also diatoms, seemed to be promising for monitoring changes in the soil since they were sensitive to both the soil features and the anthropic impact. Our study showed that soil biodiversity could be affected by the conversion to sustainable management practices from the early years of an orchard onwards. Therefore, better ecological orchard management may strengthen soil sustainability and resilience in historically agricultural regions.

Evaluation of phosphate sorption capacity and external phosphorus requirement of some agricultural soils of the southwestern Ethiopian highlands

&lt;span&gt;One of the most soil fertility management problems for crop production on acidic soils of the Ethiopian highlands is phosphorus fixation. The research was executed to assess the P-sorption capacity and to determine the external P requirement of different acidic soils in the Southwestern highlands of Ethiopia. Phosphorus sorption capacity (Kf) and its relation with selected soil characteristics were assessed for some major agricultural soils in the Ethiopian highlands to answer the questions, ‘What are the amount of P-sorption capacity and external P requirement of Nitisols, Luvisols, Alisols, and Andosols in Ethiopia?’. Twelve surface soil samples (at depth of 0-30 cm) were gathered and the P-sorption capacity was estimated. Phosphorus-sorption data were obtained by equilibrating 1 g of the 12 soil samples with 25 ml of KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt; in 0.01 M CaCl2, having 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 mg P L&lt;sup&gt;-1&lt;/sup&gt; for 24 hours. The data were adjusted to the Freundlich adsorption model and the relationship among P-sorption and soil characteristics was established by correlation analysis. Clay content and exchangeable acidity, organic matter, Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, and Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; oxides have affected phosphorus-sorption at a significance level of (P &amp;lt; 0.05). Alisols had the highest Kf value (413 mg kg&lt;sup&gt;-1&lt;/sup&gt;) but Nitisols had the lowest Kf (280 mg kg&lt;sup&gt;-1&lt;/sup&gt;). The external phosphorus fertilizer requirement of the soils was in the order of 25, 30, 32, and 26 mg P kg&lt;sup&gt;-1&lt;/sup&gt; for Nitisols, Luvisols, Alisols, and Andosols sequentially. The Kf varies among different soil types of the study area. The magnitude of the soil’s Kf was affected by the pH of the soil, soil OM content, and oxides of Fe and Al. Therefore, knowledge of the soils’ P retention capacity is highly crucial to determine the correct rate of P &lt;/span&gt;&lt;span&gt;fertilizer&lt;/span&gt;&lt;span&gt; for crop production.&lt;/span&gt;

Perspectives from the Fritz‐Scheffer Awardee 2020—The mutual interactions between roots and soil structure and how these affect rhizosphere processes#

AbstractRoots growing into soil interact with soil structure in numerous ways. They can grow into the soil matrix and leave elongated macropores after decomposition, that is, biopores. Conversely, the soil may already have a large and connected macropore system through which the roots can expand, and thus reach deeper soil layers. Both, the formation of new biopores or the reuse and occupation of existing macropore systems are expected to affect major soil processes like water and gas flow through the soil profile, as well as water flow toward the root. Despite the increasing research interest in the limitation of root growth by soil structure, as well as the modification of soil structure by roots, the mutual interactions between the two are largely overlooked. This study highlights new methodological developments which enable describing interactions between roots and soil structure with X‐ray computed microtomography. It further shows how roots affect the pore system and can create a massive biopore system in less than a decade. After this, it is evaluated how the mutual interaction of roots and structure determines the physical properties of the rhizosphere. It is outlined that this has implications for major rhizosphere processes. Thus, it is emphasized, that the role of structure needs to be considered in future experiments with plants, in particular if extrapolation of results from laboratory experiment with sieved, homogenized substrates to field conditions with well‐established soil structure is intended. Lastly, in this study, research gaps are outlined remaining in respect to the dynamics of biopore creation and destruction and their consequences for processes in rhizospheres like carbon storage. These reveal the need for novel research approaches that consider the mutual interactions of root growth and soil structure.

Effect of lime on selected soil chemical properties, maize (Zea mays L.) yield and determination of rate and method of its application in Northwestern Ethiopia

Soil acidity is the major soil chemical constraint that limits agricultural productivity in the highlands of Ethiopia receiving high rainfall. This study was conducted to evaluate the effect of different lime rates determined through different lime rate determination methods on selected soil chemical properties and yield of maize (Zea mays L.) on acidic Nitisols of Mecha district, Amhara Region, Ethiopia. The experiment had 10 treatments (0, 0.06, 0.12, 0.18, 1, 2, 3.5, 4, 7 and 14 tons ha−1 lime) that were calculated by three lime rate determination methods and applied through three lime application methods (spot, drill and broadcast). The experiment was arranged in randomized complete block design (RCBD) with four replications. N at the rate of 180 kg ha−1 and P at the rate of138 P2O5 kg ha−1 were applied to all plots. A full dose of P and lime as a treatment were applied at planting; whereas N was applied in split, 1/2 at planting and 1/2 at knee height stage. One composite soil sample before planting from experimental site and again one composite sample from each experimental unit were taken after harvest to analyze soil chemical parameters following appropriate laboratory procedure. Liming showed a positive significant difference on pH-H2O, pH-buffer, cation exchange capacity (CEC) and exchangeable bases but it had an inverse and significant effect on exchangeable acidity (EA). However, it didn't show any significant difference on soil C and N. Grain and above-ground biomass of maize yields had significant differences among treatments. The highest grain and biomass yields (7719 and 18180.6 kg ha−1, respectively) were obtained from application of broad cast method while the lowest (6479 and 15004.6 kg ha−1, respectively) were obtained from control treatment. Drill lime application method provided better efficiency with over 200% cost reduction advantage compared to the broadcast method to ameliorate the same level of acidity. Application of 3.5 tons ha−1 lime in the drilling method is recommendable to ameliorate soil acidity. However, from an economic point of view, application of 0.12 tons ha−1 lime applied in the micro-dosing method is more profitable due to low variable cost.

The Pedospheric Variation of DTPA-Extractable Zn, Fe, Mn, Cu and Other Physicochemical Characteristics in Major Soil Orders in Existing Land Use Systems of Punjab, India

The agricultural production in Punjab has increased manifold that aggravated the deficiencies of micronutrients in soils and plants. The availability of soil micronutrients in different soil orders depends upon the soil mineralogy, topography, climatic conditions and cropping sequences. Hence, to study the pedospheric variations of DTPA-extractable micronutrients, viz., zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu), in three prominent soil orders of Punjab, a total of 144 depth-wise soil samples were collected from four major land-use systems (cultivated, horticulture, forest and pasture lands). The DTPA extractable micronutrients varied from 1.74–2.81, 1.83–2.82 and 1.81–2.80 for Zn; 5.3–6.8, 5.6–6.9, 4.3–6.3 for Fe; 5.1–7.8, 5.5–7.9, 5.4–7.5 for Mn; and 0.84–1.40, 0.93–1.68, 0.87–1.65 for Cu in soil orders Aridisol, Entisol and Inceptisol, respectively. The average content of DTPA-extractable micronutrients was highest under soil order Entisol followed by Inceptisol and Aridisol. The content of micronutrients showed a declining trend with increase in soil depth in all orders. Among different soil properties, the pH and EC showed significantly negative correlation, however, OC had non-significant correlation with DTPA-extractable micronutrients in soils. Therefore, it is concluded that parent material, land use systems and soil depth affected the distribution of DTPA extractable micronutrients in different soil orders.

Interaction of phosphatase with soil nanoclays: Kinetics, thermodynamics and activities

Nanoclay-enzyme complexes prepared form pure nanoclays isolated from ores or mines are the recent area of attention for their potential agriculture and biotechnological uses. The activity of nanoclay-enzyme complexes depends on both enzyme and nanoclay properties. However pure nanoclay seldom exists in natural soil conditions rather mixed with other soil clays specifically poorly ordered aluminosilicate. Thus, nanoclays isolated from three major soils (Vertisol, Alfisol, and Inceptisol) with or without poorly ordered aluminosilicates were used to comprehend phosphatase reaction occurring in the heterogeneous soil environment by preparing nanoclay-phosphatase complexes. Adsorption isotherms along with catalytic kinetics of organic phosphorus (P) hydrolysis by acid and alkaline phosphatases were studied. The adsorption of acid and alkaline phosphatases on nanoclay was rapid, thus its kinetics could not be ascertained. The adsorptions of acid and alkaline phosphatases were best described by the Freundlich equation (R2 = 0.82–0.99). Selected thermodynamic parameters i.e., changes in Gibbs free energy, entropy and enthalpy were calculated to interpret the energetics of the reactions. Results suggest that phosphatase adsorption to nanoclays was spontaneous, based on energetics. The process of acid and alkaline phosphatase adsorption were exothermic and enthalpy driven. The acid phosphatase is chemisorbed while alkaline phosphatase is physisorbed to the nanoclay surface. The presence of poorly ordered aluminosilicates in nanoclays increased the affinity of acid phosphatase for the substrate while the reverse was true for alkaline phosphatase. Immobilized acid phosphatase showed lower catalytic efficiency whereas alkaline phosphatase, when immobilized, resulted in significantly greater catalytic efficiency than the free enzyme. Therefore, the results of the present experiment emphasize the need to study soil nanoclay-enzyme complexes using nanocalys that coexist with other soil clays specifically poorly ordered aluminosilicates than pure nanoclays extracted from ores and mines. This knowledge could be used for regulating P availability and help alleviating P deficiency in the soils studied in the present investigation.

Characterisation of clay mineralogy of the major soils in the Northern region of Sri Lanka

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Regional soil moisture prediction system based on Long Short-Term Memory network

In the context of climate change, drought has been recognised as one of the most severe threats for agricultural production since absence of water is one of the most limiting factors for the growth of plants. In this study, a regional system for soil moisture prediction based on ERA5 climate reanalysis dataset, an open-source meteorological dataset issued by Copernicus Climate Change Service, was developed. It consisted of the relevant meteorological parameters for Serbia, during the period 2011–2020. Daily values of maximum and minimum air temperature, precipitation and vapour pressure deficit were used as features, and they were fed to recurrent neural network in order to predict volumetric soil moisture for three days ahead. A Long Short-Term Memory (LSTM) network was designed and trained at a regional scale using the data from the 2011–2016 period, at 28 locations that cover four major soil types. Validation was done on 2017–2018 data and LSTM was compared with a statistical forecasting technique and a classical machine learning approach. Evaluation was done with error measures commonly used in literature. The resulting network yielded the lowest errors and proved to have good generalisation properties. The system was tested from September 2019 to April 2020 using short-range weather forecasts of Yr service. It will present the cornerstone of the irrigation scheduling service in AgroSense.rs, the Serbian national platform for digital agriculture.

Efficacy of Cicer arietinum L. & Vigna mungo L. in remediation of Hexavalent Chromium

Hexavalent Chromium is a major soil pollutant; thus, its remediation from soil deserves due attention. Phytoremediation is an area of active current research which is eco-friendly and economic. Use of leguminous plants for phytoremediation will improve soil quality, fertility and nutrient balance and would help in restoration of natural soil ecosystem. The present study focuses on the use of two commonly growing legumes; Cicer arietinum (RP1) and Vigna mungo (RP2) to explore their remediation potential towards Cr(VI) with concentration ranging from 100-900 mg kg−1 with the growth up to three weeks and were assessed for remediation potential and toxicity parameters. Higher percentage of decrease in root and shoot length was observed in RP2 as compared to RP1. Chlorophyll content was also found to be decreasing with increasing Cr stress in both the species. RP2 recorded higher BCF than RP1. Highest bioaccumulation factor 4.32 was observed in RP2 at 400 mg kg−1 concentration. Translocation factor >1 was observed in both the plants with highest as 1.67 at 600 mg kg−1 in RP2 and 1.93 at 400 mg kg−1 in RP1. Remediation percentage of 72.25% in RP2 at 600 mg kg−1 and 73.13% at 400 mg kg−1 in RP1 was observed. Both the plants showed high tolerance and remediation potential towards Cr(VI) therefore has a great phytoremediation prospect, however, RP2 can be preferred over RP1.

Differences of bacterial communities in different biological soil crusts around thermal power plant and their influencing factors.

To understand the effects of heavy metal pollution derived from atmospheric dust fall on bacterial community structure under different types of biological soil crusts near mining area, we measured the diversity, community composition, and relative abundance of bacteria communities in three different developmental stages of biological soil crusts (BSCs), including algae (ZB), mixed (HB), and moss (TB) crusts, and control (CK, bare soil) around a typical thermal power plant in Ningdong Energy Industrial Base, using the high-throughput sequencing technique. Environmental factors affecting the bacterial community structure were further investigated. The results showed that there were significant differences in physicochemical properties and heavy metal contents among different BSCs. The BSCs were heavily polluted due to the enrichment of heavy metals from atmospheric dust fall. Among the top ten dominant bacterial phyla, Gemmatimonadetes and Cyanobacteria were significantly distinct among different BSCs. Bacterial α diversity decreased in an order of CK&gt;TB&gt;HB&gt;ZB. The NMDS ordination plots indicated that there were significant differences in the bacteria community composition of the three kinds of BSCs and the CK. The correlation analysis showed that the succession of BSCs significantly affected bacterial community composition in BSCs. Bacterial diversity and composition were closely related to pH, nutrients, and heavy metal contents. The relative abundance of Actinomycetes and Chloroflexi was positively correlated with pH, but negatively correlated with total N, total P, and the contents of heavy metal Pb, Zn, Cd. Results of the redundancy analysis showed that organic carbon, pH, total N, and total P were the major soil factors affecting bacterial α diversity, relative abundance of some dominant phyla, whereas heavy metal contents of Zn, Cd, Pb were the major heavy metals affecting structure of bacterial community which inhibited or stimulated the abundance and diversity of bacterial communities. We concluded that pH, heavy metals, and nutrients were the key factors affecting soil bacteria community composition. The succession of BSCs would improve their physicochemical properties and significantly impacted bacterial community composition. Long term heavy metals enrichment would affect bacterial diversity and community composition of BSCs.

Understanding uncertainty of model-reanalysis soil moisture within Greater Horn of Africa (1982–2014)

Lack of in situ soil moisture over Greater Horn of Africa (GHA) has inhibited evaluation of uncertainty and suitability of land surface model (LSM) and/or satellite-derived soil moisture over the region. This has led to a low utilization of LSM-derived soil moisture in agricultural drought-related studies as reflected by the lower number of soil moisture based studies despite the region being dependent on rain-fed subsistence agriculture. This study evaluated the uncertainty of soil moisture products from the following LSM; MERRA-2, ERA5, GLDAS (NOAH, CLM, and VIC), FLDAS NOAH, and CPC. Generalized three-cornered hat analysis of this suite of soil moisture products showed high magnitudes of uncertainties associated with areas of high rainfall while low magnitudes of uncertainties were associated with low rainfall areas. Further, areas of Ethiopian highlands with complex topographical characteristics had almost twice the magnitude of uncertainties compared to the relatively flat region of East Africa (Kenya, Uganda, and Tanzania). MERRA2 and ERA5 had consistently lower magnitudes of uncertainty while CPC had consistently higher magnitudes of uncertainty. The uncertainties are attributed to quality of the forcing precipitation, difference in model physical dynamics, and topographical changes. From the Taylor diagram analyses, the magnitude of spatial variability (amplitudes) contributed higher uncertainty than spatial patterns (phase). Finally, interannual variability analyses showed higher uncertainties across the considered soil moisture products during wet season than dry season over Ethiopia highlands while Sudan, south Sudan, East Africa, Eastern Ethiopia and Somalia had the reverse. The results of this study are important as they contribute to the knowledge of uncertainty levels and suitability of the major LSM-derived soil moisture over GHA.

Spatio-temporal mapping and analysis of soil salinity: an integrated approach through electromagnetic induction (EMI), multivariate and geostatistical techniques

The information on salt load in soil is needed to enable suitable soil, crop and water management practices for crop production in salt affected land. An investigation was conducted to test the hypothesis that an integrated approach of electromagnetic induction (EMI), multivariate and geostatistical techniques can provide rapid and reliable information on soil salinity (ECe) at spatio-temporal scale. EMI survey and the analyzed data indicated that ECe better correlates with horizontal mode (EMH) of apparent soil electrical conductivity (R 2=0.83) than the vertical (EMV). Principal component (PCA) and Pearson correlation analysis revealed that Na+1, Ca2++Mg2+ and Cl−1 are the major soil chemical properties affecting apparent soil electrical conductivity. The spatial map of soil salinity based on EMH showed close proximity with the area represented by ECe observations. Study indicated that EMI methodology can be effectively used to predict, map and identify salinity zones for devising strategies for reclamation of saline soils.

Relationship between orchardgrass (Dactylis glomerata) dominance and the soil chemical characteristics of nonallophanic Andosol under cutting and cattle grazing

AbstractSoil acidity affects botanical compositions and pasture production, but the relationship between orchardgrass persistence and the soil nutrients in acidic soils with different management methods is understudied in production fields. Here, using exchangeable acidity (y1) as an indicator of exchangeable aluminum (Al), we conducted a survey to investigate the relationship between orchardgrass dominance and the soil characteristics in sown pastures under different management practices. The botanical composition and soil chemical conditions were investigated in six orchardgrass–tall fescue mixed pastures (two cutting meadows and four cattle grazing pastures) from June 18 to July 17, 2018. Six‐ and three‐line transects were fixed in each meadow or pasture, respectively, and five measurement locations were set along each transect at 10‐m intervals. Each location had three square plots (20 × 20 cm) for the vegetation survey and three consecutive soil sampling plots (4‐cm diameter) adjacent to the middle square plot. The dominant plant species in each plot was recorded, and soil samples were collected at 0‐ to 5‐cm depth to measure y1 and major soil nutrients. The y1 ranged from 3.55 to 25.83 in the cutting meadows, which was wider than in the grazing pastures (1.85–16.29). In the cutting meadows, the dominance frequency of orchardgrass increased with the rise in y1, whereas that of tall fescue decreased in cutting meadows. No significant relationship was found between dominance frequencies and y1 in the grazing pastures. Although concentration of some soil nutrients varied with y1, these nutrients were not related to the dominance frequencies of orchardgrass for either management strategy. These results suggest that orchardgrass declines are prevented at high exchangeable Al sites by the non‐establishment of less Al‐tolerant plant species under cutting conditions.

Spatial Distribution of Available Trace Metals in Four Typical Mediterranean Soils: The Caia Irrigation Perimeter Case Study

There is a small sample of edaphic geochemistry studies over large geographic areas, especially studies that consider major reference soil groups (RSG) that evaluate both native concentrations of elements and anthropogenically contaminated soils in agricultural settings, considering the long-term effect of agricultural practices on landscape sustainability. In this study, four RSGs were analyzed for the available trace elements Ni, Cr, Cd, Pb, Cu, Mn, and Zn, including other edaphic properties from 2002 to 2012. The main objectives were to assess the range of concentrations of the selected elements in the four typical Mediterranean soils, Cambisols, Luvisols, Calcisols, and Fluvisols, with heavy anthropogenic input (HAI) and compare them to minimal anthropogenic input (MAI). For MAI, the background levels of Pb, Ni, Cd, and Cr were highest in Calcisols, differing from those of Cambisols, Luvisols, and Fluvisols (p &lt; 0.01), Cu is highest both in Calcisols and Luvisols while Mn is higher in Cambisols and Fluvisols (p &lt; 0.05). The background concentration of Zn was the same in all RSGs (p &gt; 0.05). For HAI, the reference levels of Pb, Ni, Cd, Mn, and Cr were highest in the Calcisols, and Cu was high in all RSGs except Fluvisols, while Zn presented the lowest concentrations in the Luvisol RSG, with all these results considering a confidence interval of 95%. Predictive maps for the sampled elements, as well as the edaphic bioavailability, are provided. This environmental impact assessment suggests that the land use is departing from sustainable ecosystem service development and that territorial management practices, with conservation goals in mind, should be adopted.

Experimental Investigations on Black Cotton Soil Stabilized with Sand and Cement

Abstract: Has our Lands getting increasing of population and the reduction of available land, more and more construction of building sand other civil engineering structures has to be carried out on weak or soft soil. Owing to such soil of poor shear strength and high swelling &amp; shrinkage, a great diversity of ground improvement techniques such as soil stabilization and reinforcement are employed to improve mechanical behavior ofsoil, thereby enhancing the reliability of construction. Black cotton soil is one of the major soil with this we are going to improve the soil by using sand and cement in deposits of India. The disappointments of asphalt in from of hurl dejection splitting and unevenness are brought about by the occasional dampness variety in subgrade soil. So, in this we using the various type of tests like plastic limit, liquid limit, California bearing ratio test, freewell index and specific gravity.Instead of cutting out and replacing the unstable soil,soil adjustment isthe only alternative asitsaveslot of time and ofmoneytoo.Theexhibithigh swelling and shrinking when exposed to changes in moisture content and hence have been found to be most troublesome from engineering considerations. Keyword: Black cotton soil, stabilization, CBR, sand and cement, sub- grade, Montmorinolite kaolinite, hydrated cations, Liquid Limit, Plastic Limit, Free swell index, Specific gravity.

Soil microbial communities are driven by the declining availability of cations and phosphorus during ecosystem retrogression

Development of soil microbial communities is driven by local abiotic and biotic conditions, yet our current understanding of their ecology is limited to studies in modified or young and relatively fertile ecosystems. In nutrient-impoverished soils, microbial communities may be predominantly structured by availability of key elements such as phosphorus (P) or nitrogen, regardless of the taxa (bacteria, archaea or fungi). Here, we determined if shifts in bacterial communities and biomass occurred along a long-term soil chronosequence in south-western Australia, and whether such shifts were related to changes in soil nutrient availability along the retrogressive phase of this chronosequence. We quantified shifts in the biomass and abundance of major soil microbial groups using phospholipid fatty acids and quantitative polymerase chain reaction. We found that declining soil P availability limited microbial growth and community structure. Common cations, notably magnesium, showed strong relationships with the abundance of most bacterial and archaeal taxa. In the oldest most severely impoverished soils, the fungal to bacteria ratio was higher than in the young soils, indicating fungi are better adapted to such environments. Finally, archaeal copy numbers decreased more strongly than bacterial copy numbers with increasing nutrient-impoverishment of soils. The study enhances our understanding of the ecology of soil bacteria, archaea, and fungi during ecosystem development and retrogression.