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The mineralogical compositions along with physical, chemical, elemental and mineralogical properties of four pedons occurring along a toposequence in Chhota Urla village (Abhanpur tehsil), Raipur district of Chhattisgarh state were studied. Landform had significant influence on physical, chemical, elemental and mineralogical properties of soils. Sand content decreased from higher topography to lower topography but clay content increased with decrease in elevation. pH of pedons ranged from strongly acid to moderately alkaline and CEC increased from upland to lowland. Quartz being dominant in sand fraction and absence of primary minerals like Ca-feldspar, K-feldspar indicated intense weathering of soils. Silt had quartz as dominant mineral followed by Ca- feldspar and K-feldspar. Kaolin was dominant mineral in clay fractions of pedons l and 2 (PI and P2) with sub-ordinate amount of smectite while smectite was dominant in other two pedons followed by kaolin. Huge amount of smectite which is first weathering product of plagioclase, did not find its parental legacy with underlying geology (sandstone, limestone and shale sequence) indicative of mixed alluvium, eroded from different geological formation and contradicted the occurrence of catenary sequence as reported earlier.

The depletion of the ozone layer due to the greenhouse effect has created great concern that led to several studies on qualities, kinds, distribution and behavior of soil organic carbon (SOC). The first ever comprehensive study of OC status in Indian soils was conducted by Jenny and Raychaudhuri. Difference in sampling methods, exact season of collecting soil samples on different types of landscapes and kinds of vegetation and the methods of soil analyses in the laboratory determine the quality of SOC data. An attempt has been made to estimate the SOC stock in different soil orders as per Soil Taxonomy. The SOC stock for India in terms of each soil order is estimated at 0–30 and 0–150 cm depths since quantitative data reflect the kinds of soil with different amount of OC at different depths. The accumulation of OC in Indian soils, however, is dependent on the rate of decomposition of OC due to higher temperature in the tropics.

Maintenance of soil organic carbon (SOC) stock is important for monitoring soil health, which appears to be fragile in view of the reported climatic changes due to global warming in tropical countries such as India. This requires accurate and reproducible measurement of SOC. The wet-digestion technique following the Walkley-Black (WB) method to determine SOC has been used throughout the world in soil science, agronomy, and environmental science laboratories. WB suggested a universal correction factor to convert organic carbon to calculate exact quantity of organic carbon present in soil assuming 77% recovery of SOC. We understand that such a blanket recommendation may not hold well in different bioclimatic systems and for soils representing various depths. We present corrected Walkley-Black recovery factors (WBRFc) for different bioclimates and soil depths in two food-growing zones in India.

A study was undertaken in the established benchmark (BM) soil series in different agro-ecological sub-regions of Indo-Gangetic Plains (IGPs), India with an objective to assess the urease activity and its kinetics at different soil depths. The urease activity declined with increase in soil depth in all the selected BM soils of IGP. The mean urea hydrolysis in the surface horizon (0–30 cm; 18.2 µg $$ {\text{NH}}_{4}^{ + } $$ /h) was 2.6-folds higher than the sub-surface horizon (121–150 cm; 7.01 µg $$ {\text{NH}}_{4}^{ + } $$ /h). The enzyme velocity (V max ) and enzyme efficiency (K m /V max ) of urease hydrolysis were at par in surface and sub-surface horizons. The average K m value of urease enzyme in surface and sub-surface horizons were 4.53 and 3.96 mM, respectively. The coefficient of variation, K m for surface horizons showed higher variability and low affinity of soil urease towards substrate urea than the sub-surface horizon. Negative Pearson’s correlation coefficient was recorded between urease activity and soil depth (R = −0.86), while significant positive correlation was observed between urease activity with organic carbon (R = 0.81) and nitrogen (R = 0.81).

The present study was undertaken with an objective to study the impact of pedo-edaphic environments, cropping systems, land use, and management practices on the MBC. Soil samples were collected from seventeen benchmark soils representing different agro-ecological sub regions of black soil region of India. The pooled comparisons of MBC in different bio-climates indicated significant differences (p

Information on soil hydraulic properties is a prerequisite in irrigation management decisions and crop planning. Such information on soils of the black soil region (BSR) occupying 7.7×107 ha of India is sparse. Soil profile information for 49 representative sites (244 samples) was collected and used for analysis. Ten different functions were evaluated for their efficacy to describe soil water retention characteristics (SWRC) of the BSR soils. Campbell model fitted to measured SWRC data with relatively lower root mean square error (RMSE=0.0214 m3·m−3), higher degree of agreement d=0.9653), and lower absolute error on average (MAE=0.0165 m3·m−3). The next best description was by van Genuchten (VG) function with RMSE (0.0249 m3·m−3), d(0.9489), and MAE (0.0868 m3·m−3). Pedotransfer functions (PTF) were developed to predict field capacity (FC) and permanent wilting point (PWP) using nearest neighbor (kNN) algorithm and artificial neural networks (ANN). Four levels of input information used for po...

Carbon content in soils changes depending on the land use system, type of management practice and time. There is an increasing concern about the soil quality vis-a-vis organic carbon content in soils due to global warming and enhanced CO 2 concentration in the atmosphere. This has led to estimate carbon stock in soils at global and regional levels. The objective of the present study was to evaluate Roth C model to estimate total organic carbon (TOC) changes under four long term fertilizer experimental sites representing sub-humid moist (Sarol and Nabibagh), sub-humid dry (Panjri) and semi-arid (Teligi) climate in India. The plant carbon input rate was calibrated using organic carbon and other soil parameters using Roth C . The results showed that Roth C could simulate changes in TOC in two contrasting eco-sites for surface soil layers. The root mean square error (RMSE) considered as modelling error ranged from 11.50 to 15.01, 4.70 to 11.60, 2.14 to 6.52 and 1.45 to 13.74 in the surface layers of Sarol, Nabibagh, Panjri, and Teligi sites, respectively. The simulation biases expressed by M (relative error) by Student‘ t ’ value for all the treatments at these sites were non-significant with two exceptions. Observed trends in TOC consist of an increase for all the four treatments in the sub-humid site of Sarol and Nabibagh; while manures alone or in combination increase TOC appreciably in Teligi and Panjri. TOC remained, however, almost similar over years for the control (no fertilizer or manure) and NPK treatments in all the four sites. Analysis of Roth C output data showed that this model could be used as a tool to arrive at different threshold values of rainfall to influence decomposition rate modifier and thus to find out rate of organic carbon sequestration in various bioclimatic systems.

There are many reports on soil parameters that have both yield-reducing and yield-favouring potential. However, only a few are available on the index soil properties of fibrous minerals containing soils on crop yields in the semi-arid tropical (SAT) regions. These minerals in soils are mostly palygorskite and sepiolite. In the present study, only the palygorskite mineral in black soils (cracking clay soils), its formation and probable influence on soil quality is addressed. The present study was also undertaken to indicate a possible genesis of palygorskite in Indian black soils with and without soil modifiers (Ca-zeolites and gypsum) supporting both rainfed and irrigated agriculture in SAT environments. Palygorskite is absent in aridic/ gypsic/sodic intergrades of black soils (Haplusterts), which might indicate non-interference of soil modifiers in its formation. Palygorskite is present only in sodic black soils (Calciusterts) in Maharashtra and parts of central and western India that contain no soil modifiers, and are under both rainfed and irrigated agricultural systems. The severe impairment of hydraulic properties of palygorskite containing naturally degraded black soils warrants a new research initiative for soils containing fibrous minerals.

Smectitic parent material from the weathering Deccan basalt has been deposited in the lower piedmont plains, valleys and microdepressions during a previous wetter climate. The cracking clay soils (Vertisols) were developed in such alluvium during drier climate of the Holocene period. In India they occur in humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicate an array of soils in a climosequence. The soils show a change in their morphological, physical, chemical and micromorphological properties in the climosequence. Soils of HT climate are dominated by Ca++ ions in their exchange complex throughout depth. However, in the sub-humid climates Mg++ ions tend to dominate in the lower horizons. The sub-humid moist to aridic climatic environments caused a progressive formation of pedogenic calcium carbonates (PC) with the concomitant increase in Na+ ions in soil solution. This facilitated the translocation of Na-clay in the soil profile. This is responsible for the increase in pH, decrease in Ca/Mg ratio of exchange sites with depth and finally in the development of subsoil sodicity. The reduction in mean annual rainfall (MAR) from sub-humid moist to arid climates accelerated the formation of PC and thus the soils of semi-arid and arid climates (SAM, SAD and AD) are more calcareous and sodic than soils of other climates (SHM and SHD). Formation of PC, illuviation of clay and the development of subsoil sodicity are concurrent, contemporary and active pedogenetic processes operating during the climate change of the Holocene period. These processes impaired the hydraulic properties of soils in general, and in soils of drier climates in particular. As a result, cracking pattern, chemical composition and plasmic fabric were more modified in soils of the drier climates. Such modifications in soil properties have a place in the rationale of Vertisol order of the US Soil Taxonomy. The soils of wetter climates (HT, SHM and SHD) are grouped in Typic Haplusterts whereas the soils of drier climates (SAM, SAD and AD) are classified as Aridic Haplusterts, Sodic Haplusterts and Sodic Calciusterts. The present study demonstrates how the intrinsic soil properties of the cracking clay soils in a climosequence may help in inferring the change in climate in a geologic period.

The common GIS-based approach to regional analyses of soil organic carbon (SOC) stocks and changes is to define geographic layers for which unique sets of driving variables are derived, which include land use, climate, and soils. These GIS layers, with their associated attribute data, can then be fed into a range of empirical and dynamic models. Common methodologies for collating and formatting regional data sets on land use, climate, and soils were adopted for the project Assessment of Soil Organic Carbon Stocks and Changes at National Scale (GEFSOC). This permitted the development of a uniform protocol for handling the various input for the dynamic GEFSOC Modelling System. Consistent soil data sets for Amazon-Brazil, the Indo-Gangetic Plains (IGP) of India, Jordan and Kenya, the case study areas considered in the GEFSOC project, were prepared using methodologies developed for the World Soils and Terrain Database (SOTER). The approach involved three main stages: (1) compiling new soil geographic and attribute data in SOTER format; (2) using expert estimates and common sense to fill selected gaps in the measured or primary data; (3) using a scheme of taxonomy-based pedotransfer rules and expert-rules to derive soil parameter estimates for similar soil units with missing soil analytical data. The most appropriate approach varied from country to country, depending largely on the overall accessibility and quality of the primary soil data available in the case study areas. The secondary SOTER data sets discussed here are appropriate for a wide range of environmental applications at national scale. These include agro-ecological zoning, land evaluation, modelling of soil C stocks and changes, and studies of soil vulnerability to pollution. Estimates of national-scale stocks of SOC, calculated using SOTER methods, are presented as a first example of database application. Independent estimates of SOC stocks are needed to evaluate the outcome of the GEFSOC Modelling System for current conditions of land use and climate.

The GEFSOC Project developed a system for estimating soil carbon (C) stocks and changes at the national and sub-national scale. As part of the development of the system, the Century ecosystem model was evaluated for its ability to simulate soil organic C (SOC) changes in environmental conditions in the Indo-Gangetic Plains, India (IGP). Two long-term fertilizer trials (LTFT), with all necessary parameters needed to run Century, were used for this purpose: a jute (Corchorus capsularis L.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) trial at Barrackpore, West Bengal, and a rice-wheat trial at Ludhiana, Punjab. The trials represent two contrasting climates of the IGP, viz. semi-arid, dry with mean annual rainfall (MAR) of 1600 mm. Both trials involved several different treatments with different organic and inorganic fertilizer inputs. In general, the model tended to overestimate treatment effects by approximately 15%. At the semi-arid site, modelled data simulated actual data reasonably well for all treatments, with the control and chemical N + farm yard manure showing the best agreement (RMSE = 7). At the humid site, Century performed less well. This could have been due to a range of factors including site history. During the study, Century was calibrated to simulate crop yields for the two sites considered using data from across the Indian IGP. However, further adjustments may improve model performance at these sites and others in the IGP. The availability of more long-term experimental data sets (especially those involving flooded lowland rice and triple cropping systems from the IGP) for testing and validation is critical to the application of the model's predictive capabilities for this area of the Indian sub-continent.

Earlier hypothesis on the factors and processes of natural degradation in Vertisols and also their evaluation for crops on the basis of only hydraulic properties was developed on limited soils by the Division of Soil Resource Studies (DSRS) of the National Bureau of Soil Survey and Land Use Planning (NBSS & LUP), Nagpur, India. In order to validate the above similar soils occurring in major states of the Peninsular India and also to document the extent of modification by gypsum and Ca-zeolites therein, the present study on twenty-six benchmark Vertisols representing a climosequence from sub-humid moist to arid dry climate was undertaken. The results of the present study validates the hypothesis that formation of pedogenic calcium carbonate (PC) at the expense of non-pedogenic calcium carbonate (NPC) is the prime chemical reaction for the natural chemical degradation realized in terms of impairment of hydraulic properties of soils mediated through the development of subsoil sodicity. Presence of gypsum and Ca-zeolites, on the other hand, prevented the rise of pH, decrease in Ca/Mg ratio of exchange sites and improved the hydraulic properties amidst an exchangeable sodium percentage (ESP) > 15. The improvement in saturated hydraulic conductivity (sHC) (> 10 mm h − 1 ) of zeolitic sodic soils does commensurate fairly well with the performance of rainy season crops. Thus characterization of sodic soils in terms of sHC − 1 (weighted mean in 0–100 cm depth of soil) instead of any ESP or sodium adsorption ratio (SAR) emerges as a robust criterion that stands for a universal acceptance for the better use and management of such naturally degraded soils, not only in the Indian semi-arid tropics, but also in similar climatic and geologic areas elsewhere.

In the northwestern part of the Indo-Gangetic Plains (IGP), India, non-sodic and moderately sodic soils occur on microhigh (MH) and highly sodic soils on microlow (ML) positions under a semi-arid climate. The main soil-forming processes have been clay illuviation, deposition of pedogenic calcium carbonate and concomitant development of sodicity. The microlows are repeatedly flooded with surface water during brief high-intensity showers, so the soils are subject to cycles of wetting and drying. This provides a steady supply of alkalis by hydrolysis of feldspars, leading to precipitation of calcium carbonate at high pH and development of subsoil sodicity. This impairs the hydraulic conductivity of soils and eventually leads to the development of Natrustalfs with exchangeable sodium percentages increasing rapidly up the profile. The semi-arid climate and topography interact to facilitate greater penetration of bicarbonate-rich water in microlow than microhigh positions. Thin sections show deformational pedofeatures such as cross and reticulate striation of plasmic fabric, disruption of clay pedofeatures and carbonate nodules and elongation of voids as a result of tectonic activity during the Holocene. In view of the persistent build up of stresses in the IGP in general, and the study area in particular, it seems that the neotectonics have caused the microtopographical variations (0.5–1 m) that control the formation of sodic soils.

Although the major soils of India (alluvial, ferruginous and black soils), endowed with fine-grained micas, are known as natural K suppliers to plants, crop response to K fertilizer treatment has been anomalous. The silt and clay fractions of 14 benchmark soils were subjected to repeated batch type Ba–K exchange to study the rate of K release. The significant positive correlation between cumulative K release in 25 extractions and X-ray intensity ratio of peak heights of the 001 and 002 basal reflections of mica in the silt ( r =0.629 at 1% level) and clay ( r =0.729 at 1% level) suggested that although the fine-grained muscovite and biotite co-exist in soils, the rate of K release and crop response to K are related primarily to the presence of biotite only while muscovite remains as an inert source of K in soils justifying the crop response to K fertilizers. Soil micas under a scanning electron microscope (SEM) indicated that biotite particles were generally thick, showing layer separation with bending at edges due to the formation of vermiculite around their rims. The muscovites, on the other hand, were characterized by very minor layer separation at their edges. To resolve the issue of layer separation of micas through the release of K during the formation of soils, experimental studies of repeated Ba–K exchange were conducted with specimen muscovite and biotite and also on the mixture of the two micas. Experimental studies indicated that at ambient temperature and pressure, muscovite released negligible amount of K from its exposed surfaces and the weathering of muscovite was inhibited in the presence of biotite. This confirmed the observation that when muscovite and biotite co-exist, muscovite hardly weathers in soil environments. Hence, its enrichment in soils does not enhance the supply of K. Therefore, weathering products like di- and trioctahedral vermiculite and smectite are generally the products of the weathering of biotite mica. The X-ray intensity ratio of 001 and 002 basal reflections of mica has been found to be an effective diagnostic parameter to find out the quality of mica and therefore to judge the K releasing potential of soils. However, actual quantification of fine-grained biotites of soils appears to be mandatory for the precise determination of K reserves in soils in order to predict release of K for sustainable K management.

The high altitude ferruginous Alfisols associated spatially with shrink–swell soils on the Deccan basalt plateau and dissected table lands in the Western Ghats of India were analysed for their morphological, chemical and mineralogical properties with a view to comprehend their formation and persistence in the tropical humid climate prevailing since the early Tertiary. The study indicates that despite their acidic pH the soils have high bases and their clay fractions are dominated by interstratified smectite-kaolin. The persistence of these non-kaolinitic and/or non-oxidic Alfisols has been possible due to the presence of base-rich zeolites of amygdoloidal basalt. It suggests that for an open system such as soil, the existence of steady state is a more meaningful concept than thermodynamic equilibrium. The knowledge gained on the role of zeolites in soils provides a check on the reasoning of models on the formation of soils in tropical humid climate. The study also indicates that the supply of bases from zeolites can prevent the soils from losing their productivity even in intense leaching environment.

Soil organic carbon (SOC) and rainfall are generally positively related, whereas a negative relationship between soil inorganic carbon (SIC) and rainfall with some exception is observed. Land use pattern in black soil region (BSR) of the semi-arid tropical (SAT) India, consists of 80% under agriculture, followed by forest, horticulture, wasteland and permanent fallow. For sustainable agriculture on these soils, there is a concern about their low OC status, which warrants fresh initiatives to enhance their OC status by suitable management interventions. In the BSR region, cotton, soybean and cereal-based systems dominate but it is not yet clear as to which cropping system in the SAT black soils is most suitable for higher OC sequestration. Many short-term experiments on cotton or cereal-based systems clearly suggest that cotton or cereal-based cropping systems including leguminous crops perform better in terms of SOC sequestration whereas soybean–legume combination do not add any substantial amount of OC. In sub-humid bioclimatic zones (1053–1209 mm mean annual rainfall), soybean is grown successfully with wheat or fallowing, and SOC concentration is maintained at 0.75% in the 0.30 m soil layer under integrated nutrient management. In view of enhancement and maintenance of OC in many shortterm experiments conducted in various agro-climate zones of SAT, it is realized that OC accumulation in soils of the semi-arid ecosystem with suitable cropping and management practices could be substantial especially in cotton–pigeon pea rotation, and thus the discussed crop rotations in each major bio-climatic zone stand for wide acceptance by the SAT farmers.

Soils in the semi-arid tropics (SAT) are subject to chemical degradation mostly due to climatic reasons which make the pedo-environment hostile to form calcium carbonate. This triggers an overall deterioration of soil properties affecting its physical and chemical parameters. Such soils require management interventions which may include chemical and other phytoremediation process. The present paper details this process of degradation in light of resilience of these soils of SAT.

The Global Environment Facility co-financed Soil Organic Carbon (GEFSOC) Project developed a comprehensive modelling system for predicting soil organic carbon (SOC) stocks and changes over time. This research is an effort to predict SOC stocks and changes for the Indian, Indo-Gangetic Plains (IGP), an area with a predominantly rice (Oryza sativa)–wheat (Triticum aestivum) cropping system, using the GEFSOC Modelling System and to compare output with stocks generated using mapping approaches based on soil survey data. The GEFSOC Modelling System predicts an estimated SOC stock for the IGP, India of 1.27, 1.32 and 1.27 Pg for 1990, 2000 and 2030, respectively, in the top 20 cm of soil. The SOC stock using a mapping approach based on soil survey data was 0.66 and 0.88 Pg for 1980 and 2000, respectively. The SOC stock estimated using the GEFSOC Modelling System is higher than the stock estimated using the mapping approach. This is due to the fact that while the GEFSOC System accounts for variation in crop input data (crop management), the soil mapping approach only considers regional variation in soil texture and wetness. The trend of overall change in the modelled SOC stock estimates shows that the IGP, India may have reached an equilibrium following 30–40 years of the Green Revolution. This can be seen in the SOC stock change rates. Various different estimation methods show SOC stocks of 0.57–1.44 Pg C for the study area. The trend of overall change in C stock assessed from the soil survey data indicates that the soils of the IGP, India may store a projected 1.1 Pg of C in 2030.

The GEFSOC soil carbon modelling system was built to provide interdisciplinary teams of scientists, natural resource managers and policy analysts (who have the appropriate computing skills) with the necessary tools to conduct regional-scale soil carbon (C) inventories. It allows users to assess the effects of land use change on soil organic C (SOC) stocks, soil fertility and the potential for soil C sequestration. The tool was developed in conjunction with case-studies of land use and management impacts on SOC in Brazil, Jordan, Kenya and India, which represent a diversity of land use and land management patterns and are countries where sustaining soil organic matter and fertility for food security is an on-going problem. The tool was designed to run using two common desktop computers, connected via a local area network. It utilizes open-source software that is freely available. All new software and user interfaces developed for the tool are available in an open source environment allowing users to examine system details, suggest improvements or write additional modules to interface with the system. The tool incorporates three widely used models for estimating soil C dynamics: (1) the Century ecosystem model; (2) the RothC soil C decomposition model; and (3) the Intergovernmental Panel on Climate Change (IPCC) method for assessing soil C at regional scales. The tool interacts with a Soil and Terrain Digital Database (SOTER) built for the specific country or region the user intends to model. A demonstration of the tool and results from an assessment of land use change in a sample region of North America are presented.

Calcium-rich zeolites control naturally occurring chemical degradation in the black soils (Vertisols and their intergrades). With the help of modern tools such as remote sensing, geographic information system, soil database, geological information, topography and other related datasets, an attempt was made to update the distribution of zeolitic soils in India. To ascertain the presence of Ca-rich zeolites in soils, mineralogical information was generated using X-ray diffraction techniques for the selected soils from the Indo-Gangetic Plains and the black soil region (BSR). The zeolitic soils are mostly confined in the pediments (sloping regions of the upland) of the Deccan plateau in BSR, although a few are also found along the valley floor. The IGP, on the other hand, hosts the zeolitic black soils along the drainage channels in the valley floor where the basaltic alluvium deposited the smectite and clay-rich sediments. The study indicates Ca-rich zeolitic soils in India to occupy an area of ~2.8 m ha, of which BSR and IGP constitute ~92% and ~8% respectively. The zeolites are mostly concentrated in the drier tracts of the country and help in maintaining soil health against natural soil degradation. While the occurrence of Ca-rich black soils in BSR was known, those in the IGP are new findings. With the help of the available information, we have generated state-of-art information approximation map on the distribution of Ca-rich zeolites in Indian soils.

Performance of DNDC model was evaluated using a long term fertilizer experiment (LTFE) datasets at Akola, Maharashtra. The LTFE site represents a semi-arid climate with a mean annual rainfall of 793 mm. Sorghum and wheat crops were cultivated for nine years (1988–1997). The model was parameterized using crop data from black soil region and used to estimate the total organic carbon (TOC) under different nutrient management treatments. It underestimates the total organic carbon in all the treatments in two different ways such as for control (T1) and 50% NPK (T2), it performs less than the measured values in the beginning of the experiment, while for 100% NPK+FYM (T13) and only FYM (T14) treatments the underestimation is found at the end of the experiment. Modelled data analysis using statistical parameters showed 50% NPK treatment was satisfactory. An effort is made to find out the relative performance of three models namely RothC, Century and DNDC using the same LTFE site. By far, RothC model was found to be near to the values of measured TOC as compared to other.

Global importance of total organic carbon (TOC) in soil is due to its role in the global carbon cycle and, thus, the part it plays in influencing the atmospheric levels of greenhouse gases (GHGs). It is also of local importance as it determines ecosystem and agro-ecosystem function, influencing various soil parameters. The objective of the present study was to evaluate RothC model (26.3) to estimate TOC changes under two long term fertilizer experimental (LTFE) sites representing humid (Mohanpur) and semi-arid (Akola) climate in India. Five treatments each at the LTFE sites of Mohanpur representing alluvial soils (Alfisol) of the Indo-Gangetic Plains (IGP) and of Akola dominated by black soils (Vertisols) in the Black Soil Region (BSR) were selected. Mohanpur site was modelled for 3 layers (0–13, 13–23, and 23–39 cm) while Akola for surface layer (0–15 cm) only. The root mean square error (RMSE), considered as modelling error, ranged from 3.34 to 17.85%, 6.87 to 14.22% and 6.66 to 24.34% in the 3 soil layers of Mohanpur site respectively. For Akola, RMSE ranges from 1.79 to 13.28. The simulation biases expressed by M (relative error) for all treatments at these sites were non-significant. In Mohanpur, observed trends in TOC show marginal increase in control (T1) and 100% NPK (T2) while the increase was nearly 17 to 35% when organic amendments were applied along with inorganics during 1999 to 2010. For the same period in Akola, control (T1), 50% NPK (T2), and 100% NPK (T4) recorded decrease in TOC while 26 to 29% increase was registered without inorganics and with the combination of inorganics and organics respectively. The calculation of modelled TOC stock to find out effect of global warming indicated that treating the entire soil pedon as a homogenous unit will overestimate effects of global warming in accelerating decomposition of soil carbon.

From a significant positive correlation between linear extensibility (LE) and the smectite content in the soil control section (SCS) of 8 soils (2 red soils, Alfisols, and 6 black soils, Vertisols, and their intergrades), the present study indicates an excellent compatibility between the marked shrink–swell characteristics and the smectitic mineralogy. The initiation of vertic properties at LE of 6 in shrink–swell soils corresponded to a minimum threshold value of 20% smectite. In order to highlight the inherent relationship between vertic properties and the swelling minerals, the mineralogy class for shrink–swell soils in US Soil Taxonomy should be only smectitic.

The terrestrial biosphere is an important global carbon (C) sink, with the potential to drive large positive climate feedbacks. Thus a better understanding of interactions between land use change, climate change and the terrestrial biosphere is crucial in planning future land management options. Climate change has the potential to alter terrestrial C storage since changes in temperature, precipitation and carbon dioxide (CO 2 ) concentrations could affect net primary production (NPP), C inputs to soil, and soil C decomposition rates. Climate change could also act as a driver for land use change, thus further altering terrestrial C fluxes. The net balance of these different effects varies considerably between regions and hence the case studies presented in this paper (the GEFSOC project countries Kenya, Jordan, Brazil, and India) provide a unique opportunity to study climate impacts on terrestrial C storage. This paper first presents predicted changes in climate for the four case study countries from a coupled climate-C cycle Global Circulation Model (HadCM3LC), followed by predicted changes in vegetation type, NPP and soil C storage. These very coarse assessments provide an initial estimate of large-scale effects. A more detailed study of climate impacts on soil C storage in the Brazilian Amazon is provided as an example application of the GEFSOC system. Interestingly in the four cases studied here precipitation seems to control the sign of the soil C changes under climate change with wetter conditions resulting in higher soil C stocks and drier conditions in lower soil C stocks, presumably because increased NPP in wetter conditions here will override any increase in respiration. In contrast, globally, it seems to be temperature that controls changes in C stocks under climate change. Even if there is a slight increase in precipitation globally, a decrease in C stocks is predicted—in other words, the regional response to precipitation differs from the global response. The reason for this may be that whilst temperature increases under climate change were predicted everywhere, the nature of precipitation changes varies greatly between regions.