Soil CaCO3 Content Research Articles

The distribution of organic carbon fractions in a typical loess-paleosol profile and its paleoenvironmental significance.

BackgroundThe loess-paleosol sequence on the Loess Plateau has been considered an important paleoclimatic archive to study global climatic and environmental changes in the Quaternary. So far, little attention has been paid to the characteristics of soil organic carbon fractions in loess-paleosol sequences, which may provide valuable information for exploring the evolution of climate and environment in the Quaternary on the Loess Plateau.MethodsIn order to explore the significance of mineral-associated organic carbon to total organic carbon (MOC/TOC) ratios in the loess-paleosol sequence for reconstructing paleoenvironmental and paleoclimatic evolution in the Quaternary on the Loess Plateau, we selected a typical loess-paleosol profile in Chunhua county, Xianyang city, Shaanxi province, as the research object. The content of total organic carbon (TOC) and MOC/TOC ratio in each loess and paleosol layers of the Chunhua loess-paleosol profile were analyzed, together with the paleoclimatic proxies, such as soil grain size, CaCO3 content and their correlations with organic carbon parameters.ResultsThe main results were as follows: (1) the total content of soil organic carbon and MOC/TOC ratios were generally higher in paleosol layers than in the underlying loess layers of the Chunhua loess-paleosol profile. Compared to total organic carbon content, MOC/TOC ratios changed more obviously in soil layers below a paleosol layer S8; (2) soil clay content and median grain size (Md (ϕ)) were higher in paleosol than in the underlying loess, while CaCO3 content showed an opposite tendency. In the Chunhua profile, the distribution characteristics of the three paleoclimatic proxies showed good indications of paleoclimate changes in the Quaternary; (3) in the Chunhua loess-paleosol profile, MOC/TOC ratios were positively correlated with clay content and median grain size (ϕ), while negatively correlated with CaCO3 content, and the correlations were more significant in soil layers below S8.DiscussionOur results indicated that MOC/TOC ratios in the Chunhua loess-paleosol profile correlated with the cold dry-warm wet paleoclimatic cycle in the Quaternary. The high MOC/TOC ratios in the loess-paleosol profile might reflect warm and humid climate, while lower ratios indicated relatively cold and dry climate. That is because when the climate changed from warm-humid to cold-dry, the vegetation coverage and pedogenesis intensity decreased, which increased soil CaCO3 content and decreased soil clay content and Md (ϕ), leading to decreased MOC/TOC ratios. Compared to TOC, MOC/TOC ratios had greater significance in indicating paleoenvironmental evolution in the Quaternary on the Loess Plateau. Therefore, investigating MOC/TOC ratios in loess-paleosol profile can offer new evidence to reconstructing paleoenvironmental changes, and also provide a basis for predicting responses of soil organic carbon pools to vegetation and climate changes in the future.

Long-term irrigation with zinc smelter effluent affects important soil properties and heavy metal content in food crops and soil in Rajasthan, India

ABSTRACTUse of wastewater for irrigating agricultural crops is on the rise, particularly in the developing countries. The present study was undertaken to assess the long-term effect of irrigation with zinc smelter effluent on important soil properties including heavy metal status. Metal concentration in the edible parts of the crops grown on smelter effluent-irrigated soils was also measured. For this purpose, the agricultural lands which have been receiving the zinc smelter effluent irrigation for about five decades at Debari, Udaipur, India were selected. The adjacent tubewell water-irrigated fields were selected as reference. Long-term irrigation with smelter effluent resulted into significant buildup of ethylenediaminetetraacetic acid extractable Zn (57.7 fold), Cu (4.51 fold), Fe (3.35 fold), Mn (1.77 fold), Ni (1.20 fold), Pb (45.1 fold), and Cd (79.2 fold) in soils over tubewell water-irrigated fields. Total Zn, Cu, Mn, Ni, Pb, and Cd content in effluent-irrigated soils was also increased by 27.0, 1.60, 1.40, 1.30, 26.2, and 167 fold, respectively. Risk assessment indicated a very high to moderate potential ecological risk due to Cd, Pb, and Zn in soils close to the immediate vicinity of the smelter plant. Cadmium and Pb concentrations in edible parts of almost all the crops grown on effluent-irrigated soils were above the safe limit of CODEX commission. On an average, soil pH dropped by 0.31 units due to smelter effluent irrigation. Smelter effluent irrigation resulted into significant increase in soil organic carbon, electrical conductivity, and CaCO3 content. On an average, there was decrease in available N (21.0%) and P (20.8%) content in effluent-irrigated soils over the tubewell water-irrigated ones. An increase in available K (102%) and S (26.0 fold) was recorded in effluent-irrigated soils. Long-term irrigation with zinc smelter effluent resulted into reduced microbial activities in soil as evidenced from the level of microbial biomass carbon and dehydrogenase activity. In view of the buildup of heavy metals and subsequent imbalance in essential plant nutrients in smelter effluent-irrigated soils, appropriate remediation-cum-fertilization strategy needs to be adopted for better soil health and plant nutrition.

Precipitation and topsoil attributes determine the species diversity and distribution patterns of crustal communities in desert ecosystems

Despite the important role of biological soil crusts in desert ecosystems, the responses of the crustal composition and distribution to changes in both climatic and edaphic factors at different spatial scales are not well understood. The goal of our research was to study the drivers of crustal community diversity at different scales, determine how crustal diversity and distribution patterns are related to abiotic and biotic factors, and identify the characteristics of crustal communities along a precipitation gradient. We investigated the distribution and characteristics of crustal communities based on 457 soil samples that were randomly collected from six desert regions of northern China. These regions represent a precipitation gradient from 450 mm in the east to 80–100 mm in the west. The measured environmental variables included soil moisture, pH, clay and silt content, soil organic carbon (SOC), total N, total P, total K, CaCO3 content, annual and perennial plant cover and crustal variables, including species richness, crustal cover and biomass. An ANOVA analysis, a stepwise regression and a redundancy analysis were used to analyse and interpret the response of biological soil crusts to environmental factors at two spatial scales. Our results showed that the moss distribution and biomass were strongly related to the topsoil moisture content. The highest diversity of cyanobacteria and algae was observed at sites with relatively dry topsoil, and lichen diversity was promoted at sites with fine-textured soils. In addition, the cover and biomass of moss were positively correlated with perennial plant cover and higher topsoil moisture, which was expected because plant cover provides shade for the moss. The cover and biomass of lichens, cyanobacteria and algae were positively correlated with that of annual plants because these plants may create an ideal habitat and provide nutrients. The physiochemical properties of the topsoil greatly influenced the distribution pattern of the crustal communities at the regional scale. The species richness and biomass of the crustal mosses were positively correlated with precipitation, whereas the species richness and biomass of cyanobacteria and algae were negatively correlated with precipitation at the landscape scale. Rainfall largely determined the species richness and cover of the crustal cyanobacteria and mosses, whereas soil properties had a greater impact on the crustal lichens. Future changes to rainfall regimes could result in the conversion of biological soil crusts and further contribute to changes in the structure and functioning of desert ecosystems.

Quantifying in situ and modeling net nitrogen mineralization from soil organic matter in arable cropping systems

Improved assessment and prediction of net nitrogen mineralization (NNM) from soil organic matter in field conditions are essential for a better management of nitrogen (N) in arable cropping systems and an accurate simulation of its seasonal dynamics. The first objective of this study was to quantify accurately NNM rates by combining measurements of soil water and mineral N contents in soil profile, daily weather data and the LIXIM calculation model (Mary et al., 1999). The second objective was to develop a predictive model of in situ NNM rates based on basic soil properties and to evaluate if additional factors related to cropping history, organic matter fractions or microbial biomass could improve the model performance.We selected a set of 65 field experiments representative of arable cropping systems in France which were carried out in bare fallow soils without recent addition of crop residue (minimal delay of 4 months) or organic amendment. In these experiments, soil water and mineral N contents were monitored over the soil profile (0–90 to 0–150 cm depth, 3 to 5 layers) during 100–555 days (median value of 272 days). LIXIM was able to satisfactorily simulate water (EF = 0.58) and mineral N contents (EF = 0.80) in the several layers, allowing to disentangle the two main processes involved in mineral N changes: NNM (occurring in the upper soil layer) and nitrate transfer (through the whole soil profile). The actual NNM rates varied widely between sites from 0.13 to 1.10 kg N ha−1 day−1. The potential NNM rates (Vp), calculated under standard conditions of water and temperature, varied between 0.17 and 1.67 kg N ha−1 nday−1 (nday = “normalized” day at 15 °C and field capacity).A novel model with a multiplicative structure and a sequential approach was developed by including functions explaining the relationship between mineralization rate Vp (predicted variable) and explanatory variables. Soil organic N (SON) was the most correlated variable with Vp (r = 0.51, p < 0.001) and the first variable introduced in the model as a linear function. Non-linear functions of soil clay content, pH, C/N ratio and CaCO3 content were successively introduced, leading to a “soil model” based on five basic soil parameters that allowed explaining 61% of the variance in Vp. Two functions relative to the frequency of rapeseed and legumes in rotations were found to further improve the predictive quality of the soil model, explaining finally 72% of Vp variance (“soil-history model”). Organic matter fractions (particulate or extractible organic matter) did not explain significantly more variance of Vp due to their strong correlations with SON. Microbial biomass explained only 2% additional variance in Vp compared to the “soil-history model”. The predictive error of prediction (RMSEP) varied between 0.22, 0.19 and 0.17 kg N ha−1 nday−1 for the “soil” (n = 65), “soil-history” (n = 65) and “soil-history-biological” (n = 47) models. This multiplicative, non-linear approach performed better than a multiple linear regression approach which explained 10–15% less variance of Vp when using the same explanatory variables.The models based on soil properties and cropping history could be further implemented in multidisciplinary soil-crop models and decision support systems in order to enhance the prediction of N dynamics in soils and improve fertilizer recommendations.

NICKEL, COPPER, ZINC AND CADMIUM FRACTIONATION IN MANGROVE SEDIMENTS, RED SEA, EGYPT

Nickle (Ni), copper (Cu), zinc (Zn) and cadmium (Cd) in eight sediment samples from mangrove area, Red Sea, Egypt were fractionated using diethylenetriamine pentaacetic acid (DTPA) and a sequential extraction procedure (SEP). These sediment samples were collected horizontally from two locations (four samples from each site) based on different layer visual characterizations. Sediments were initially characterised using different analytical and statistical procedures. DTPA-extract table metal percent of the total metal content varies widely from 1.93 : 25.6% for Ni, from 3.86 : 18.2% for Cu from 0.6 to 4.1 for Zn and from 3.36 : 11.2% for Cd depending on soil characteristics. There no consistent trend of metal extracted by DTPA as a function of sediment depths although CdDTPA (%) was increased by increasing sediment depths in site 1 and in site 2. Moreover, metal extracted by DTPA showed no consistent correspondence with any single fraction of SEP. The metal extracted by DTPA showed reasonable correlation with the summation of exchangeable (F1) and carbonate (F2) fractions in both sites. So it may be reasonable to conclude that most ‘available’ metal is (presumably) surface-bound on CaCO3, rather than occluded within CaCO3 or present as a mixed solid-solution (Ca1-xMxCO3). Approximately 84%, 30%, 70% and 95% of the variability in PTPA-extractable-Ni, Cu, Zn and Cd (mg kg-1) values for a whole dataset, respectively were explained by the variation in soil pH, (%) SOM, (%) CaCO3 and total metals content. CdDTPA showed the highest prediction performance while Cu showed the worst case of the regression model in which Cu availability is more likely controlled by either the source of Cu or other conditions rather than sediment properties.

Comparison of different methods to determine wind-erodible fraction of soil with rock fragments under different tillage/management

Rock fragments (the coarse fraction >2mm in soil) widely exist in the surface soils of the agro-pastoral ecotone of northern China (APEC region) where is suffering severe soil degradation induced by wind erosion. The wind-erodible fraction of soil aggregate (<0.84mm dry soil aggregate) (EF) is an important parameter to evaluate soil management systems and estimate wind erosion. Rotary sieve is considered to be a standard device to determine EF. Flat sieves and EF estimation equation used in the Revised Wind Erosion Equation (RWEQ) are two alternatively methods to obtain EF. In this study, 74 soil samples for different soil management/tillage in a typical region of the APEC region were collected to compare rotary sieve, flat sieve and the EF estimation equation for determining EF. The results showed that (1) the EF determining from rotary sieve (EF-r) is closely related to the EF obtaining from flat sieve (EF-f) but the EF-r are generally lower than the EF-f, (2) the EF-r is significantly associated with surface soil rock fragments content for all soil management, (3) the EF-r is not related to soil textural fractions, organic matter and CaCO3 content for tree windbreak, conservation and conventional tillage farmland but is related to that for grassland, (4) the EF estimation equation in the Revised Wind Erosion Equation (RWEQ) cannot be used to predict the measured EF in the APEC region.

Spatial variation in the solute transport attributes of adjacent Typic Haplusteps, Mollic Ustifluvents, and Lithic Ustipsamments

Spatial variation in water flow and solute transport are important considerations when assessing field-scale remediation options, and for managing water and chemicals during agricultural production. Here, we evaluated the relationship between laboratory-measured solute transport variables pore-water velocity (v), dispersivity (λ), and retardation coefficient (R) and land use, soil type, and other independently measured soil properties in adjacent Typic Haplusteps, Mollic Ustifluvents, and Lithic Ustipsamments. We also characterized the spatial variation in v, R, coefficient of hydrodynamic dispersion (D), and λ. We obtained 100 geo-referenced, undisturbed soil columns (8.4cm diameter and of varying length) from the topsoil at sites with varying land uses, topographies, and soil types, and synchronized disturbed soil samples to analyze the basic soil properties. We conducted miscible displacement tests on all 100 columns, and predicted the retardation coefficient (R) and D using the computer program CXTFIT, and measured v. All four variables, except R, had strongly right-skewed and kurtotic distributions, and were highly variable. Log λ (logarithm to base 10) was significantly correlated with land use, with the mean of λ being significantly greater in grasslands, followed by orchards and croplands. By contrast, v was significantly correlated with soil type, with the mean being significantly greater in Lithic Ustipsamments. Log v (logarithm to base 10) was also significantly correlated with the soil CaCO3 content, log organic matter content, pH, cation exchange capacity, and log electrical conductivity, whereas neither v nor λ was correlated with soil texture measures. An analysis of the spatial structure of solute transport variables using semivariograms showed that R and λ had considerably high nugget effect. Log-transformed semivariograms performed well using ordinary point kriging for v and D. However, λ and R exhibited a very weak spatial dependency that could not be interpolated using ordinary kriging at the current sampling resolution. Therefore, this should be considered when designing future sampling programs to analyze spatial structure of R and λ.

Effect of soil characteristics on plant distribution in coastal ecosystems of SW Iberian Peninsula sand spits

Some studies report particular soil conditions occurring on barrier islands and sand spits that contrast with those found on the mainland. The effects of soil characteristics on the distribution of plants established on a sand spit in the SW Iberian Peninsula were evaluated in order to elucidate the mechanisms that drive plant communities in this type of coastal ecosystem, furthering the knowledge regarding plant–soil interactions in this type of coastal ecosystem in comparison with the mainland. Effects of soil characteristics on plant species distribution, abundance, richness, and diversity were analyzed by multivariate analyses and correlation tests, and biotic interactions were also examined. Results revealed that soil pH, electrical conductivity, CaCO3 content, sand mobility (dunes), and flooding (marshes) played an important role in shaping plant communities, while biotic interactions became important only in advanced successional stages. Particularly, CaCO3 content determined general soil basicity in the spit, which favored the establishment of calcicolous species that were absent in the acidic dunes of the nearby mainland, and could reinforce positive biotic interactions in these dunes. In salt marshes, predominantly sandy soils favored the development of upper marsh communities, also favoring positive interactions in some areas, as well as the development of notable dune–marsh ecotones, compared to the muddy marshes that prevail on the mainland.

Evidences for Bioprecipitation of Pedogenic Calcite by Calcifying Bacteria from Three Different Soils of L'Aquila Basin (Abruzzi, Central Italy)

To provide further evidences on the role of bacterial soil species in the development of calcium carbonate deposits in soil, we isolated 36 heterotrophic bacterial strains from three soils of L'Aquila basin characterized by different CaCO3 content and tested their ability to precipitate CaCO3 when cultured on a Ca-rich medium. We found that the majority (63.89%) of these isolates could precipitate CaCO3 minerals at 27°C. The aptitude to calcification (time and crystal amount) of each calcifying strains, morphology (SEM) and mineralogy of the formed bioliths were also investigated. X-ray diffraction confirmed the production of calcite. Crystal formation was not observed in the controls. Organic matter, total N and assimilable P, cation exchange capacity and exchangeable Ca2+, Mg2+, K+, Na+, pH, total and active calcium carbonate content, electric conductivity, skeleton, sand, silt and clay fractions of each soil sample were determined and related with its microbiological parameters. We found that the CaCO3 content of soil was significatively related, in particular, to the percentage of calcifying bacterial strains (r = 0.95) and to the heterotrophic bacterial density (r = 0.98), which was found significatively related also with Ca2+ content of soil (r = −0.97) and its CEC (r = −0.97).

Pressure calcimeter as a simple method for measuring the CaCO3 content of soil and comparison with Scheibler calcimeter

A pressure calcimeter was made as an alternative to Scheibler calcimeter which is the conventional method of soil CaCO3 content analyses. Since the measurement of CaCO3 content of soil with Scheibler calcimeter is a slow and labor intensive method, the accuracy and presicion of the results are based on labor experience. The pressure calcimeter gives fast and accurate results by eliminating these disadvantages. The measurement of CaCO3 by pressure calcimeter, as in Scheibler, is done by measuring pressure of CO2 gas produced from reaction of soil with HCl. The gas pressure, formed by the chemical reaction in a gasproof chamber was measured by a digital manometer on the cap. The results were converted to % CaCO3 by calculations. Excellent correlation (R2=0,998) was obtained in calibration carried out with pure CaCO3. 46 soil samples contain CaCO3 between % 1–30 were analysed by Scheibler calcimeter and the results were compared with pressure calcimeter. It can be concluded that pressure calcimeter has given satisfactory results and can be used as an alternative to conventional Scheibler calcimeter in soil CaCO3 content analysis.

Improvement of hard saline–sodic soils using polymeric aluminum ferric sulfate (PAFS)

Highly dispersed hard saline–sodic soils are important agricultural land reserves in the world. These soils are difficult to be ameliorated by conventional amendments because of poor soil properties. The objectives of this study are to screen a highly efficient inorganic polymer soil amendment using laboratory experiments and to evaluate its effectiveness in soil improvements and grain yield promotion under paddy field conditions using field experiments. Compared with control soils cultivated with rice for one year without PAFS treatment, the pH of the 0–8cm and 8–16cm layers of PAFS-treated soil decreased from 10.70 and 10.75 to 8.94 and 9.99, respectively, soil CaCO3 contents decreased by 29.49% and 16.19%, respectively, and contents of silt-plus-clay particles decreased by 46.06% and 14.55%, respectively. Soil saturated hydraulic conductivity increased from 0.05mmd−1 to 40.01mmd−1 and soil bulk density decreased from 1.55gcm−3 to 1.29gcm−3 in the 0–8cm soil layer. Soil exchangeable Na+, exchangeable sodium percentage (ESP), and salinity (ECe) in the 0–8cm soil layer were reduced by 61.92%, 63.23%, and 45.61%, respectively; in the 8–16cm soil layer, the corresponding values decreased by 34.91%, 34.57%, and 37.47%, respectively. Rice yields with PAFS application in the first year of cultivation were as high as 4.66tha−1. By contrast, rice yields without PAFS application were only 0.83tha−1 in plots cultivated with rice for one year and 1.55tha−1 in plots cultivated with rice for two years. Therefore, PAFS is effective for amending hard sodic soils.

Physiological responses to soil lime in wild grapevine (Vitis vinifera ssp. sylvestris)

Lime-induced chlorosis is a widespread nutritional disorder affecting grapevines cultivated in calcareous soils. A greenhouse experiment was conducted to investigate the response of Vitis vinifera ssp. sylvestris to soil lime by evaluating the effects of a range of soil CaCO3 contents (0–60%) on plant growth, nutrient content (iron, potassium, nitrogen and phosphorus) and photosynthetic performance (gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments). The highest soil CaCO3 concentration induced nutrient imbalances and significantly inhibited photosynthetic function, causing a reduction in carbon gain and consequently, a drastic growth reduction and high mortality. However, all the plants survived external CaCO3 contents of up to 40%, and reduction in growth at 20% CaCO3 was slightly lower than that recorded in several previously studied lime-tolerant varieties of grapevine. Plants grown at 20% CaCO3 maintained net photosynthesis values of around 6μmolm−2s−1, a similar chlorophyll content to that of the control plants and dawn Fv/Fm values close to the optimal values for unstressed plants. Up to the 40% CaCO3 treatment, the study species was capable of maintaining Fe uptake by the roots and translocation to leaves, while controlling the nutritional status of N and P. Our study indicates that the studied population of V. vinifera ssp. sylvestris could provide a source of genetic diversity for lime tolerance improvement in grapevine.

Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

In calcareous soils, phosphorus (P) retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA) required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % CaCO3 for 15 days. Freundlich adsorption isotherms (P = aC b/a) were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1) were calculated. It was observed that P adsorption in soil increased with CaCO3. Moreover, at all the levels of CaCO3, P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil CaCO3 contents and quantity of fertilizer to other similar textured soils needs confirmation.

A multiscale analysis of herbaceous species richness in a Mediterranean ecosystem

Aims Studies of species distribution patterns traditionally have been conducted at a single scale, often overlooking species-environ- ment relationships operating at finer or coarser scales. Testing diversity-related hypotheses at multiple scales requires a robust sampling design that is nested across scales. Our chief motivation in this study was to quantify the contributions of different predictors of herbaceous species richness at a range of local scales. Methods Here, we develop a hierarchically nested sampling design that is balanced across scales, in order to study the role of several envi- ronmental factors in determining herbaceous species distribution at various scales simultaneously. We focus on the impact of woody vegetation, a relatively unexplored factor, as well as that of soil and topography. Light detection and ranging (LiDAR) imaging enabled precise characterization of the 3D structure of the woody veg- etation, while acoustic spectrophotometry allowed a particularly high-resolution mapping of soil CaCO3 and organic matter contents. Important Findings We found that woody vegetation was the dominant explanatory variable at all three scales (10, 100 and 1 000 m 2 ), accounting for more than 60% of the total explained variance. In addition, we found that the species richness-environment relationship was scale dependent. Many studies that explicitly address the issue of scale do so by comparing local and regional scales. Our results show that efforts to conserve plant communities should take into account scale dependence when analyzing species richness-envi- ronment relationships, even at much finer resolutions than local vs. regional. In addition, conserving heterogeneity in woody veg- etation structure at multiple scales is a key to conserving diverse herbaceous communities.

Assessment of soil characteristics in orchard

The research field was at Siófok, in Hungary, which is situated in the South East side of Lake Balaton. The physical characteristic of the soil is sandy loam and loam and the peach orchard is irrigated. The detailed goals were mapping and analyzing of physical properties of the soil in water management point of view, mapping the acidity and CaCO3content of soil for precision liming, measurement of humus the element content. Sites with different physical characteristics (from sandy loam to loamy clay) could be distinguished. The reason for this is that besides the possible increase of clayminerals, the increasing rate of colloidal humus content contributes to larger soil plasticity. Statistics also proved positive and strong correlation (r=0.822) between the soil plasticity and humus content. In the case of pH, only a small part of the orchard is has to be limed, since most of the orchard has neutral pH, which is advantageous for nuts and stone fruits. It has to be mentioned, that the CaCO3 supply is also appropriate for the stone fruits. Based on the results hyperspectral imagery can be a good solution for detecting calciferous soils, although these measurements are still need validation.

祁连山西水林区土壤阳离子交换量及盐基离子的剖面分布

Soil cation exchange capacity(CEC) has been used as an indictor of soil fertility and buffering capacity.The exchangeable base cation content and saturation percentage reflects the bioavailability and movement of soil nutrients.This study was conducted to determine the distribution of CEC and exchangeable base cations in the profiles of four typical soils in the Xi-Shui Forest Zone of the Qilian Mountains.The soil types were brown calcic(BC) soil,grey cinnamon(GC) soil,chestnut soil(CH) soil,and alpine meadow(AM) soil.Three separate profiles(replications) were selected for each soil type.The profiles were divided into A,B,and C horizons and then sampled,making a total of 36 soil samples.Soil CEC as well as exchangable K+,Na+,Ca2+,Mg2+ were determined in the laboratory.Differences in the cation exchange capacity among soil types and horizons were analyzed by analysis of variance and multiple comparisons.Correlation analysis was also conducted to determine the relationships between soil cation exchange properties and soil physico-chemical properties such as soil organic carbon,total N,pH,CaCO3,available P,available K,clay(0.002 mm) content,silt(0.002—0.02 mm) content and sand(0.02—2 mm) content.The results indicated that CEC in the profiles ranged from 4.80 to 48.10 cmol/kg and the total exchangeable base(TEB) content ranged from 4.67 to 21.34 cmol/kg.Both the CEC and the TEB content decreased as soil depth increased.The GC soil had the highest CEC and TEB content followed by the AM soil,the CH soil,and then the BC soil.Averaged across the four soil types,exchangeable Ca2+ comprised 71.6% of the TEB content,exchangeable Mg2+ comprised 22.9% of the TEB content,exchangeable K+ comprised 3.3% of the TEB content,and exchangeable Na+ comprised 2.2% of the TEB content.For the BC,GC,and CH soils,the exchangeable Mg2+ and Na+ content tended to be greater in the upper part of the soil profile whereas the exchangeable Ca2+ and K+ content tended to be greater in the lower part of the soil profile.For the AM soil,the exchangeable Ca2+ content tended to be greater in the upper part of the soil profile,the exchangeable Mg2+ and Na+ content tended to be greater in the middle part of the soil profile,and the exchangeable K+ content tended to be greater in the lower part of the profile.The relative order of the exchangeable cations and the saturation percentage in different soil types varied among the horizons.Soil organic matter was the major factor contributing to CEC.Soil CEC increased as the silt content increased,but decreased as the sand and CaCO3 contents increased.The base saturation percentage(BSP) ranged from 44.4 to 97.2% among the four soil types.The BSP increased as soil depth increased because the recovery of base saturation due to biological factors is weaker than the effect of eluviation.Correlation analysis indicated that soil exchangeable Na+ content and saturation percentage were positively correlated with exchangeable Mg2+(P0.01).The saturation percentage of exchangeable Na+ and Mg2+ were positively correlated with the soil CaCO3 content(P0.01).Furthermore,there were highly significant positive correlations between pH and BSP,available P and CEC,and available K and exchangeable K+(P0.01).

Effects of soil stoichiometry of the CaCO3/available phosphorus ratio on plant density in Artemisia ordosica communities

In soil, CaCO3 can reduce the availability of phosphorus in arid and semi-arid regions, thereby influencing plant growth. However, the effects of soil stoichiometry of the CaCO3/available phosphorus ratio (CaCO3/AP ratio) on plant density are unknown. In this study, we examined 4 Artemisia ordosica communities located in arid and semi-arid regions, and performed a pot experiment with an orthogonal design to examine the relationships between the soil CaCO3/AP ratio and plant density. The results showed that the soil stoichiometry of the CaCO3/AP ratio had a greater effect on growth of A. ordosica than either CaCO3 or AP as single factor. The influence of the soil CaCO3/AP ratio on density of A. ordosica was related to the climatic zone and the types and/or amplitudes of increases in the soil CaCO3/AP ratio. When the soil CaCO3/AP ratio was within the same amplitude and was less than 2.5, the A. ordosica density increased in the semi-arid region, whereas the density decreased with increasing soil CaCO3/AP ratios in the arid region. In the semi-arid region, when the soil CaCO3/AP ratio was within the same amplitude and the increase in the soil CaCO3 content was greater than the increase in soil AP, the A. ordosica density increased with increasing soil CaCO3/AP ratios. This means that the relationship between the soil CaCO3/AP ratio and the A. ordosica density remained the same. In the arid region, an increase in the soil CaCO3/AP ratio as a result of increased soil CaCO3 content and decreased soil AP resulted in increased density of A. ordosica. Therefore, the relationship between soil CaCO3/AP ratios and density of A. ordosica was altered by these changes in soil chemistry. Thus, the soil stoichiometry of the CaCO3/AP ratio is an important factor affecting the density of A. ordosica in arid and semi-arid regions.

Chernozemic soils of Canada: Genesis, distribution, and classification

Pennock, D., Bedard-Haughn, A. and Viaud, V. 2011. Chernozemic soils of Canada: Genesis, distribution, and classification. Can. J. Soil Sci. 91: 719–747. Chernozemic soils in Canada have a characteristic biomantle that fully expresses the effect of organisms on soil formation. Additions of large amounts of below-ground biomass from grasses are transformed into complex organic compounds through the activities of meso- and macro-fauna, microbial degradation and combustion by fires. Degradation is regulated by (a) climatic influences on plant inputs and microbial activity, (b) the chemical and biochemical nature of the residues, (c) encapsulation of organic matter within aggregates by soil micro-faunal activities and freeze–thaw processes and (d) protection against decomposition by Ca2+and clay minerals. These organic compounds are mixed with the mineral matrix through the action of organisms from mites to badgers. Regional differences in the regulators cause differences in soil organic carbon (SOC) storage and the colour value of the surface Chernozemic A horizon. The storage of SOC is lowest in the Brown soil zone (≈60 to 80 Mg ha−1) and greatest in the Black soil zone (≈120 to 150 Mg ha−1); this corresponds to a decrease in the annual water deficit from ≈200 mm (Brown) to 70 to 100 mm (Black). Where soil CaCO3contents are high either through initial concentration in the parent material or by the precipitation of secondary CaCO3, substantially higher SOC storage than the regional norms can result. A repetitive catenary pattern occurs throughout the region. The primary controls on this pattern are hydrological – a lateral component to water flow in hillslopes leads to more developed horizonation downslope, and discharge surrounding wetlands causes precipitation of secondary carbonate minerals and more soluble salts in a fringe surrounding the wetlands. Chernozemic landscapes have been highly altered by humans through their conversion to agricultural production. Loss of the dense root network of the native grasslands causes a substantial decrease in SOC. This loss of carbon and reduction in A horizon thickness is accelerated by erosion; the effects of tillage erosion are now recognized as being ubiquitous through the agricultural region. The substantial amounts of SOC storage and our ability to increase storage through altered management practices make these soils a particular focus of interest in a future made more uncertain by the possibility of human-induced climatic change.

Effects of whey on the colonization and sporulation of arbuscular mycorhizal fungus, Glomus intraradices , in lentil ( Lens orientalis )

The aim of this study is to research the effect of 2 different doses of whey [50 ml kg-1(W50) and 100 ml kg-1(W100)], an important organic waste, on colonization and sporulation of arbuscular mycorhizal fungus (AMF) Glomus intraradices’(G.i.) inoculated to lentil plant and the effects of changing P ratio in the soil and plant as a result of whey application, changing salt, pH and CaCO3 values on AMF colonization and sporulation. It is found that macro and micro nutrient elements have increased significantly compared to control plants when G.i. and whey are used alone and together. In the studies on whey’s effect on the colonization and sporulation of fungal symbiont, it is found that low dose of whey (W50) increases G. i.‘s colonization and sporulation. Therefore regression analysis found that the effects of P contents in the plant and soil on AMF, especially on colonization are statistically significant and positive in some applications (G.i + W50, G.i + W100), but the effects of soil pH, saltiness and CaCO3 content on both the colonization and sporulation are statistically insignificant.

Combined Effects on Nitrogen Fertilization and Soil of CaCO3 Contents on Corn Performance in Al-Marj Soil, Libya

A two-year field trial was conducted at Al-Marj Research Center, northeast Libya, during the summers of 1996 and 1997 to examine the effect of nitrogen (N) fertilizers on corn (Zea mays L.) growth in a Libyan soil (fine mixed thermic, Typic Haploxerolls) amended with different calcium carbonate (CaCO3) levels. Two N fertilizer sources (urea and diammonium phosphate, or DAP) were used at three application rates (0, 80, and 160 kg N/ha). The CaCO3 treatments were 1%, 6%, and 12% based on the soil weight of a 15 cm furrow slice. A basal phosphorus (P) dose of 46 kg P2O5/ha as triple superphosphate was applied to all experimental plots before planting. The experimental plots were arranged in a randomized split-split plot design with three replications. The parameters measured included corn grain weight, plant dry-matter content, leaf contents of N, P, potassium (K), calcium (Ca), and magnesium (Mg). The plant dry matter and corn-grain yield were significantly decreased by CaCO3, but were significantly increased by N fertilizer rates. Average grain yield dropped from 8 to 3 Mg/ha at 1% and 12% soil CaCO3 content, respectively. Generally, the N source did not have a significant effect on dry matter or on grain yield. The negative effect of CaCO3 on yield was associated with concomitant significant reduction in leaf N, P, K, and Mg contents, and an increase in Ca content. However, the leaf levels of these nutrients were considered sufficient for corn growth. Therefore, the reduction of leaf-N by CaCO3 in fertilized soils might have been the major cause of corn dry-matter and grain-yield reductions.