Variation In Soil pH Research Articles

Soil pH is a major driver of soil diazotrophic community assembly in Qinghai-Tibet alpine meadows

The biological nitrogen input is essential for nutrient enrichment in natural grassland ecosystems. This process is carried out by diazotrophic microbes. However, the patterns and assembly processes of diazotrophic communities in grassland soil are not fully understood, especially in alpine meadows of high-altitude Qinghai-Tibet Plateau (QTP). In this study, the diversity patterns and community assembly processes of soil diazotrophic communities were investigated in QTP alpine meadows. The results showed that different diazotrophic taxa responded differentially to the increase of soil pH, and α-diversity increased linearly with pH values. Diazotrophic community turnover was enhanced by the increased variation in soil pH, moreover, it also showed strong response to mean annual temperature. Null model analysis showed that deterministic processes were most important in shaping the phylogenetic community structure and assembly of diazotrophs. Diazotrophic communities of each sampling site tended to be phylogenetically clustered, while communities at high pH soils (pH 7.00 to 8.00) showed more clustering than those of low pH (pH 5.02 to 7.00). The soil pH is a main driver in structuring soil diazotrophic community assembly by regulating the relative importance of deterministic and stochastic processes in QTP alpine meadows.

Aided phytostabilisation of As- and Cu-contaminated soils using white lupin and combined iron and organic amendments

An aided phytostabilisation strategy consisting of several composite amendments of iron sulphate and organic materials combined with Lupinus albus L. (white lupin) was evaluated for remediation of an As- and Cu-contaminated soil. Iron sulphate was combined with lime, paper mill sludge (PS), olive mill waste compost (OMWC) or holm oak biochar (BC) and applied to a slightly acidic soil with high concentration of As (∼2200 mg kg−1) and Cu (∼150 mg kg−1). White lupin was grown for 48 days in pots containing amended and non-amended soils and the effect of soil treatments on soluble and extractable trace elements, soil fertility and plant growth and composition was evaluated. The addition of the amendments raised soil pH and reduced soluble As (50–93%) and extractable As and Cu (50–89%). Despite the reduction of As- and Cu-extractable fractions, plant As and Cu uptake was not greatly affected by the amendments. Variations in soil pH and P-Olsen seemed to have influenced As dynamics in the treated soils, although they did not provoke its mobilisation with respect to the non-amended soil. Our results suggest that the freshly formed iron oxides resulting from addition of iron sulphate controlled As dynamics in the treated soils, avoiding its mobilisation due to application of organic materials. The combination of iron sulphate with OMWC and BC is shown as appropriate for aided phytostabilisation of metal(loid)s contaminated soils, as it improved soil fertility and plant nutrition while reduced As and Cu mobility.

PH and Soil Additive-Depending Uptake of Various Metals and Metalloids by Helianthus tuberosus from a Uranium Containing Test Field Site

In the recent decades phytoremediation became an emerging technology for the stabilization and rehabilitation of slightly to medium heavy metal contaminated sites, as well of mining sites. In previous own studies the general suitability of Helianthus tuberosus under slightly acidic soil pH and increased heavy metal (HM) concentrations was successfully tested. Phytoremediation was here investigated as a suitable remediation method for the stabilization of a U mining site near Ronneburg in Thuringia/ Germany. In the experiments presented here, the uptake of heavy metals/ radionuclides (HM/R) of H. tuberosus from test field substrate with different soil additives and mineral fertilizers under variation of soil pH was tested in pot and real field experiments. Compost was added in different masses (40 – 120 t/ha), and CaO was added in several experiments. The test field soil without additives (pH 4.65) was applied as control experiment. Good growth yields for tubers and shoot biomass were achieved for the addition of compost and CaO, but also for N-fertilization. The highest metal concentrations were achieved at the test field site for Al with 2.1 g/kg in roots at an N-fertilized soil of pH 4.6, furthermore 2.4 g/kg Fe, 0.66 g/kg Mn, 0.9 mg/kg U, and 1.9 g/kg Mn in shoots (transfer factor 2.8). Good metal transfer factors were also achieved for Zn, Cd and Co. As a conclusion from these results, H. tuberosus is suited as a plant for phytostabilization and phytoextraction at such a site and for the subsequent winning of bioenergy. It was growing successful under the rough soil and climatic conditions at this test field site.

施肥による土壌酸性化ならびに中和に関する研究(第1報) : 土壌と肥料との化学的反応ならびに硝酸化成による土壌pHの変化

施肥による土壌酸性化ならびに中和に関する研究(第1報) : 土壌と肥料との化学的反応ならびに硝酸化成による土壌pHの変化

The use of constructed wetlands for the treatment and reuse of urban wastewater for the irrigation of two warm-season turfgrass species under Mediterranean climatic conditions.

Constructed wetlands (CWs) represent low-cost technology for the treatment and reuse of wastewater in urban areas. This study aimed to evaluate the pollutant removal efficiency of a CW system and to assess the effects of irrigation using treated urban wastewater on soil and on two warm-season turf species. The research was carried out in Sicily (Italy) on a pilot-scale horizontal subsurface flow system which was fed with treated urban wastewater following secondary treatment from an activated-sludge wastewater treatment plant. The pilot system was located in an open urban park and comprised two separate parallel planted units. Experimental fields of Cynodon dactylon (L.) Pers. and Paspalum vaginatum Sw. were set up close to the system and irrigated with both treated wastewater (TWW) and freshwater (FW). Irrigation with TWW did not result in a significant variation in soil pH and soil salinity in the topsoil. The turf species tolerated high sodium levels in the soil due to TWW irrigation. Savings in FW and mineral fertilizers were deemed significant. The results highlight the fact that use of CW systems for the treatment and reuse of wastewater can represent a sustainable way to obtain alternative water resources for turfgrass irrigation in urban areas.

Reducing sampling intensity in order to investigate spatial variability of soil pH, organic matter and available phosphorus using co-kriging techniques. A case study of acid soils in Eastern Croatia

ABSTRACTSoil pH, hydrolytic acidity (HA), organic matter (OM) and plant available phosphorus (AP) are factors controlling the environmental-friendly soil management in agroecosystems. These parameters are highly variable in space. The objective of this work is to study spatial variability of pH, HA, OM and AP using several interpolation methods in Eastern Croatia. A total of 1004 (0–30 cm) soil samples were collected, and several univariate and multivariate interpolation performances were tested. The results showed that soils of the study area had high HA and AP, while pH and OM were low. The variogram analysis revealed different spatial structures among studied soil properties and demonstrate a need for variable-rate management. Soil pH and OM had lower spatial variability compared to AP and HA. Ordinary kriging was the most accurate method to estimate the studied variables. The incorporation of auxiliary variables increased the precision of the estimations for HA. Soil AP and OM showed different results for spatial prediction obtained by co-kriging. Overall, the incorporation of pH as auxiliary variable increased the prediction of the models. However, more co-variates should be incorporated in further models, in order to identify with more precision areas that need to be restored.

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.

Sub-basin scale spatial variability of soil properties in Central Iran

Scientific information on the spatial variability of soil properties is essential for making sustainable soil and environmental management decisions. The spatial variation of soil electrical conductivity (EC), pH, carbonates, gypsum, gravel, clay, silt and sand in the Gavkhooni sub-basin, Central Iran was studied employing conventional statistics, geostatistics and a geographical information system (ArcGIS). By the method of random sampling within blocks, the study area was divided into 100 blocks of 6×6 km2 and in each block surface, samples (0–10 cm) were taken randomly. The EC content showed strong variation (CV>100%), pH and carbonates exhibited weak variation (CV<10%) and the other properties showed moderate variation. Soil parameters such as gravel, silt and gypsum were best fitted by a Gaussian model, sand and carbonates fitted best with a Spherical model and the remaining soil parameters were fitted to the Exponential model. Based on the models, the spatial correlation (range) of the soil properties greatly changed from 5.6 (sand) to 74.5 km (EC). Soil pH, EC, carbonates and clay had strong spatial dependence whereas the other properties had moderate spatial dependence. The spatial distribution maps were prepared using ordinary kriging interpolation. Comparison of the results using statistical methods indicated that kriging technique had satisfactory accuracy in characterizing the spatial variability.

Characterizing spatial variability of soil properties in alluvial soils of India using geostatistics and geographical information system

ABSTRACTAlluvial soils constitute significant portion of cultivated land in India and it contributes towards food grain production predominantly. The objectives of this study were to assess the spatial variability of soil pH, organic carbon (OC), available (mineralizable) nitrogen (N), available phosphorus (P), available potassium (K) and available zinc (Zn) of alluvial floodplain soils of Kadwa block, Katihar district, Bihar, India. A total of 85 soil samples, representative of the plough layer (0–25 cm depth from surface) were randomly collected from the study area. The values of soil pH, OC, N, P, K and Zn varied from4.4 to 8.4, 0.20% to 1.20%, 141 to 474, 2.2 to 68.2, 107 to 903 kg ha–1 and 0.22 to 1.10 mg kg–1, respectively. The coefficient of variation value was highest for available P (94.3%) and lowest for soil pH (11.3%). Spherical model was found to be the best fit for N, P and Zn contents, while exponential model was the best fit for OC, and Gaussian model was the best-fit model for pH and K. The nugget/sill ratio indicates that except pH and available K all other soil properties were moderately spatially dependent (25–57%). Soil properties exhibited different distribution pattern. It was observed that the use of geostatistical method could accurately generate the spatial variability maps of soil nutrients in alluvial soils.

Dryland forest management alters fungal community composition and decouples assembly of root- and soil-associated fungal communities

Land management practices considerably influence ecosystem processes and functioning, particularly in dryland ecosystems where nutrient and water limitations have direct (via effects on productivity) and indirect (via effects on soil biota) effects on ecosystem properties. Fungi in soils and associated with roots play critical roles in soil nutrient cycling and plant nutrient acquisition, but their responses to land management practices in dryland ecosystems remain equivocal. Here we evaluate the responses of fungal communities in roots and soils associated with a Eucalyptus saligna plantation after six years of forest management practices (irrigation and fertilisation) and in two different microenvironments within treated plots, in the presence and absence of understorey grasses. We observed that the richness and evenness of fungal communities were higher in soil than in root samples, but these two parameters did not vary among any of the management treatments. Effects of fertilisation and irrigation on fungal community composition were observed and appeared to be related to variation in soil pH, moisture, and nitrogen availability. Both fertilisation and irrigation decreased the ratios of ectomycorrhizal fungi to total fungi and increased the frequencies of saprotrophic and/or plant pathogenic fungi. We observed that some OTUs were shared between soil and root-associated fungal communities but that fertilisation was associated with lower frequencies of shared OTUs, suggesting a decoupling of these communities. In the absence of grasses, where only tree roots were present, we observed fewer tight relationships between fungal occurrence in root and soil samples. Our findings highlight the importance of forest management practices for fungal community assembly processes in dryland ecosystems, which may have consequences for the predictability of fungal community dynamics and nutrient cycling.

Assessment of spatial variability of soil properties using geospatial techniques for farm level nutrient management

Crop productivity under rainfed farming systems in India is low due to poor water and nutrient management. The available small scale information of soil nutrients is inadequate to effectively manage individual farms held by small and marginal farmers. Large scale spatial variability assessment using grid sampling method is a feasible option to identify critical nutrient deficiency zones. The present study was conducted in a part of semi-arid tropical Deccan plateau region, India, to assess the spatial variability of soil pH, organic carbon (OC), soil available nitrogen (N), phosphorus (P), potassium (K) and sulphur (S). A total of 1508 composite samples (0–15cm) were collected by adopting 325×325m grid interval (one sample for 10ha area) and they were analysed for soil fertility parameters. Coefficient of variation (CV) indicated that OC, N, P, K and S were high in heterogeneity (CV>35%). Moreover, pH, P, K and S were non-normally distributed and log transformation produced normalised dataset. The semivariogram parameters (nugget to sill ratio, range and slope) indicated that the spatial distribution of soil properties were inconsistent. The spatial variability of parameters were mapped by ordinary kriging using exponential (pH and OC) and spherical (N, P, K and S) models selected based on root mean square error (RMSE) and r2 values. Multi-nutrient deficiencies were observed in most parts of the study area and N was acutely deficient. Farm level nutrient availability status was derived from spatial variability maps and critical nutrient deficiency zones were identified. Nutrient management recommendations based on soil test results were delivered to farmers for adopting need based variable rate of fertilizer application. The generated maps can serve as an effective tool for farm managers and policy makers in site specific nutrient management.

Soil fungal communities in tea plantation after 10 years of chemical vs . integrated fertilization

Addition of livestock manures and plant residues is a feasible practice to largely mitigate soil-degradative trends by the soil-dwelling fungi. However, long-term impacts of these fertilization regimes on the fungal community are poorly documented in tea (Camellia sinensis (L.) Kuntze) plantations in subtropical areas. In this study, MiSeq sequencing approach was used to estimate the diversity and composition of fungal communities in soils treated with 10 yr of non-fertilization control (CK), chemical fertilizers only (CF), and integrated use of chicken manure and legume straw with chemical fertilizers (IF), respectively. We found that different fertilization treatments produced little effect on the richness and diversity of soil fungi compared to those of the controls. In addition, Ascomycota, Basidiomycota, Zygomycota, Glomeromycota, and Chytridiomycota were the five most abundant phyla in soils under different fertilization treatments. Moreover, IF resulted in the prevalence of the genera Fusarium, unclassified Microascaceae, and unclassified Ascomycota, which accounted for 30.04%, 18.77%, and 6.92% of the total fungi, respectively. Additionally, the relative abundance of the phylum Ascomycota was positively correlated with pH, total N (TN), soil organic C (SOC), soil moisture (SM) and silt (SI) contents; however, these soil physicochemical properties were negatively correlated with the relative abundance of the phylum Basidiomycota. Together, these results suggest that the changes of the fungal community structure at the genus and phylum level under IF treatment could be the result of their responses to variations of soil pH, SM, TN, SOC, and SI contents.

Spatial variability of soil pH and electrical conductivity in the Jammu district of Jammu and Kashmir

A study was conducted to assess the spatial variability of pH and EC of Jammu district soils and generate their prediction maps. The Jammu district of Jammu and Kashmir covers an area of 2336 sq. km. and falls in the sub-tropical zone of the state. The district has two very distinct regions, the southern irrigated plains and northern rainfed foothills. Soil samples were collected from the entire Jammu district following the stratified random manner. A semi-variance analysis was conducted to estimate nugget, sill and range for quantifying the spatial dependence for both pH and EC. The process of digitization and generation of maps was carried out with ArcGIS 9.2 software following ordinary kriging. Soil pH varied widely across the Jammu district ranging from as low as 4.67 to as high as 9.08 with a mean value of 7.07. The coefficient of variation (CV) was 9.85%. Nugget to sill ratio was 0.396 (39.6%), indicating moderate spatial variability. The range of spatial dependence was 32.3 km. Electrical Conductivity (EC) ranged from 0.021 to 1.523 dS m−1 with a mean value of 0.225 dS m−1. The EC had a high variability with a CV (coefficient of variation) value of 79.94%. It's range of spatial dependence was 32.93 km. EC also exhibited a moderate spatial variability with a nugget to sill ratio of 0.478 (47.8%). Both pH and EC increased towards the southern plains of the district. Topography and associated land use/land cover played a major role in the distribution of pH and EC.

Variation in soil properties under different land use types managed by smallholder farmers along the toposequence in southern Ethiopia

Understanding soil properties under different land use types along toposequences is vital in determining the types of soil management practices that could be implemented by smallholder farmers for improving the soil health as well as soil productivity. It is also important in addressing the issues of agricultural sustainability. With the objectives of investigating variation in soil properties under different land use types managed by smallholder farmers along the toposequences, three land use types: agroforestry land (AG), cultivated land (CL) and grazing land (GL) under three slope categories (upper, middle and lower slope) were selected in southern Ethiopia, Deko watershed. A total of 108 composite soil samples [3 treatments (land use types)−3 replications−3 slope categories (upper, middle and lower)−4 soil depth layers: 0–20cm, 20–40cm, 40–60cm and >60cm] were collected for laboratory analyses. In addition, undisturbed soil samples were taken using core sampler from each soil depth for the determination of soil bulk density. To infer the biological properties of the soils naked eye soil macro-fauna (NEMF) was counted. The results showed that among the soil properties sand (p<0.001), clay (p=0.002), soil bulk density (p<0.001), soil reactio (pH, p<0.001), Electrical conductivity (EC, p<0.001), Soil organic carbon (SOC %, p<0.001), Total nitrogen (TN %, p=0.001) and NEMF (p<0.001) have shown a significant variation among the land use types while sand (p=0.027), silt (p=0.001), clay (p<0.001), SOC (p<0.001) and TN (p=0.002) exhibiting significant variation among the slope categories. Similarly, variation of soil bulk density (p<0.001), soil pH (p<0.001), SOC (p<0.001), TN (p=0.002) and NNEMF (p<0.001) were also statistically significant along the soil depth. Clay was the dominant soil textural fraction showing an increasing trend along the toposequence. Agroforestry land use type has the higher SOC, TN, pH values and EC while cultivated land use type having relatively low amount of SOC, TN, pH and EC. The lower values on cultivated land use types were due to the effects of continuous tillage practices by the smallholder farmers in the area. Slope had minimum effect on soil pH, EC, soil bulk density and the number of observable macro-faunas in the area. Moreover, SOC and TN were increased down the slope on the cultivated land use types of the area. The role of erosion is magnificent in removing SOC and TN from upper slope to lower slope as the area is more vulnerable to erosion due rugged topography. Thus, applying soil and water conservation measures on cultivated land use types play a vital role in minimizing the removal of soils down the slope.

Physicochemical properties of three typical purple soils with different parent materials and land uses in Sichuan Basin, China

Mainly located in the Sichuan Basin, known as the ‘Land of Plenty’, purple soils (developed from purple sandstone and shale) have been long noted as highly productive in spite of their rocky texture. However, information on the physicochemical properties (including mineral properties) of purple soils remained obscure for the scientific community. For example, it is not clear what causes the purple color of the soils. In this study, eight soil profiles of the Jiufeng (JF, acidic), Shibao (SB, neutral), and Yanting (YT, calcareous) areas, representing the three most widely distributed purple soils in Sichuan Basin, were individually sampled under both cropland and forestland, and then analyzed using common chemical analysis and conventional X-ray diffraction to clarify the effects of clay mineral and anthropogenic influences on the typical soils. The results show that considerable variability of soil pH and cation-exchange capacity (CEC) exists between soil types (p < 0.05). Organic matter, total nitrogen, and CEC of forestland are higher than those of farmland, while farmland has a higher content of Olsen-P, indicating significant farming effects on nutrient status. Acidic and neutral purple soils had higher total P contents than calcareous soils while calcareous soils had higher TN, clay, and CaCO3 contents. OM, TN, TP, and Olsen-P decreased with soil depth both in farmland and forestland soil profiles. Vertical distribution of organic-bound Fe-oxides (Fep) and clay particles also shows the anthropogenic interference on farmland. Illite, chlorite, kaolinite, goethite, and trace amounts of an illite–chlorite mixing layer in clay fractions were identified for typical purple soils. Hematite was observed in the coarser fractions of the calcareous pedons, confirming that the purple soil color was mainly derived from the parent rocks. Understanding of the physicochemical properties and mineral species of soil profiles can shed light on the sustainable uses of typical purple soils in subtropical area.

Reuse of urban-treated wastewater from a pilot-scale horizontal subsurface flow system in Sicily (Italy) for irrigation of Bermudagrass (Cynodon dactylon (L.) Pers.) turf under Mediterranean climatic conditions

Constructed wetlands (CW) are one of the most important biological technology for the treatment and reuse of wastewaters. The aim of this study was to evaluate the reuse of treated wastewater (TWW) from CW for irrigation of Bermudagrass turf (Cynodon dactylon (L.) Pers.) and assess the effects of TWW on the biometric and qualitative parameters of the turfgrass and on chemical–physical soil properties. The research was carried out in Sicily (Italy) in a pilot-scale horizontal subsurface flow system which was fed with urban TWW following secondary treatment from an activate sludge wastewater treatment plant. The pilot-system included three separate parallel units. The outflow TWW flowed downhill into three storage tanks which were connected to sprinkler systems. Bermudagrass plots were irrigated with freshwater (FW) and with TWW from planted units and unplanted unit. The TWW quality did not affect the visual turf quality and colour. The above-ground biomass yield of Bermudagrass was on average 1.31 kg m−2 in the TWW-irrigated plots. There was not a significant variation of soil pH, but an increase in organic matter content and salinity were recorded in TWW-irrigated plots. The results confirm that TWW provides an additional water source and fertilisers where the supply of FW is limited.

Spatial variation in soil pH controls off-season N2O emission in an agricultural soil

Experiments with soils have provided ample evidence that soil pH controls the N2O/(N2O + N2) ratio of denitrification, which increases with decreasing pH, most probably because low pH interferes with the expression of N2O reductase in denitrifying bacteria. In contrast, the N2O/NO3- product ratio of nitrification appears to be unaffected by soil pH within the range relevant for agricultural soils (pH 5.5–7.0). We hypothesized that local pH variations in cultivated soil may control in situ N2O emissions during periods of active denitrification. To test this hypothesis, we identified three plots with slightly different soil pH (5.4–5.9) within an agricultural field under spring ploughed cereal cropping, and placed four frames within each plot for measuring N2O emissions throughout autumn and spring. Soil samples were taken from each frame after the experiment to characterize the kinetics of NO, N2O and N2 production by anoxic incubation. The data were used to calculate an N2O index, IN2O, which is an inverse measure of the capacity of the denitrifying community to effectively express N2O reductase under anoxia and hence a proxy for the soil’s propensity to emit N2O under denitrifying conditions. N2O emissions were greatest during spring thaw, intermediate in autumn and low in late spring. Emissions during autumn and spring thaw were inversely related to soil pH, supporting the hypothesis that soil pH influences N2O emissions when denitrification is the main source of N2O. During these periods, emissions were positively correlated with IN2O, further substantiating the idea that soil pH affects denitrification product ratios in situ. Total organic carbon and nitrate content were negatively correlated with soil pH, thus co-varying with N2O emissions. However, the relationship of N2O emission to TOC and nitrate appeared weaker than to pH. Off-season emissions dominate N2O budgets in many regions. If the pH relationship holds at greater scales, careful soil pH management by precision liming could be a viable tool to reduce N2O emissions.

Spatial scaling of soil salinity indices along a temporal coastal reclamation area transect in China using wavelet analysis

ABSTRACTHigh spatial variability of soil salinity in coastal reclamation regions makes it difficult to obtain accurate scale-dependent information. The objectives of this study were to describe the spatial patterns of saline-sodic soil properties (using soil pH, electrical conductivity (EC1:5) and sodium ion content (SIC) as indicators) and to gain knowledge of the scaling relationships between those variables. The soil pH, EC1:5 and SIC data were measured at intervals of 285 m along a 13,965-m temporal transect in a coastal region of China. The spatial variability of soil pH was weak but it was strong for soil EC1:5 and SIC at the measurement scale. There was a significant positive correlation between soil EC1:5 and SIC, while correlations between soil pH and either EC1:5 or SIC were weak and negative. For each saline-sodic soil parameter, the variability changed with the decomposition scales. The high-variance area at the larger scales (≥570 m) occupied less than 10% of the total area in the local wavelet spectrum, which meant that the spatial variations of the salinity indicators were insignificant at these scales. For local wavelet coherency, at a scale of 1500–2800 m and a sampling distance of 0–4500 m, the covariance was statistically significant between any two of the saline-sodic soil parameters.

Effects of pH and polycyclic aromatic hydrocarbon pollution on thaumarchaeotal community in agricultural soils

Purpose Thaumarchaeota is an ecologically relevant archaeal phylum which may significantly contribute to global nitrogen cycling. Thaumarchaeotal abundance, composition, and activity can be changed by soil pH and pollutants such as toxic metals. This study aims to examine the responses of thaumarchaeotal community to soil pH variation and polycyclic aromatic hydrocarbon (PAH) pollution which may co-occur in agricultural soils.

Spatial variability and geostatistics application for mapping of soil properties and nutrients in intensively cultivated village of Veeranam Command Area, Tamil Nadu

Knowledge of spatial variability in soil fertility is important for site specific nutrient management. In the current study, the spatial variations of soil pH, organic carbon, N, P, K, Fe, Cu, Mn and Zn were evaluated in Orathur village (Typic Haplusterts) of Veeranam command area of Cuddalore district, Tamil Nadu. Global positioning system (GPS) guided surface soil sampling (0-15 cm) were done over an area of about 100 hectares in a 100 x 100 m grid. Wide ranges of variation were noted for different soil physico-chemical properties as well as nutrient status in the study area. The pH of soils ranged from 6.70 to 8.30, organic carbon ( %) varied from 0.49 and 0.88, available nitrogen (kg ha) from 173.60 to 235.20, available phosphorus (kg ha) content varied from 4.90 to 17.10, available potassium varied between 180.00 to 330.0 kg ha, while available S content varied from 3.10 to 21.30 ppm. The available Fe and Mn varied from 3.26 to 20.16 ppm and 0.94 to 8.26 ppm. The variation of soil nutrient contents across the study area was found to be related to the fertilizer use pattern among farmers. The evaluated physico-chemical and nutrient status data of the area were used to develop variability maps with the aim of generating site –specific nutrient management strategies.