Soluble Rocks Research Articles

Responses of cover-collapse sinkholes to groundwater changes: a case study of early warning of soil cave and sinkhole activity on Datansha Island in Guangzhou, China

In karst areas of Quaternary sediments, fissures and solution channels through soluble rocks provide unseen conduits for the vertical movement of surface water into the underlying karst aquifers. This downward flow may also transport overburden material, which can result in the formation of soil caves and ground loss called cover-collapse sinkholes. Because of the concealed development of such soil caves and generally complicated geological conditions, the prediction of soil cave development and sinkhole activity is far from perfect. This study focused on the early warning of soil cave and sinkhole development by monitoring groundwater-level decline. Based on the improved Terzaghi loosening pressure theory and using excess pore water pressure, two types of critical groundwater-level decline are discussed. The first, denoted as ∆0, is the critical groundwater-level decline related to soil cave formation and evolution; the second, denoted as ∆HT, is the critical groundwater-level decline related to soil cave roof collapse. This method of groundwater monitoring for the early warning of soil cave and sinkhole development is currently being applied on Datansha Island in Guangzhou, China.

Mapping and modelling of collapse sinkholes in soluble rock: The Münsterdorf site, northern Germany

Münsterdorf is a small village in the north of Hamburg, located along the northern rim of a salt diapir. The Permian rocks are uplifted and overlying rocks such as the Cretaceous limestone, normally at several kilometers depth, have been pushed close to the surface. In Münsterdorf, the Cretaceous limestone can be found at around 20 m depth, and about 2 km further south, Cretaceous limestones are quarried in a large open-pit mine.Since 2004, collapse sinkholes have formed on a sports field in Münsterdorf, with a frequency of about 1 every two years, about 3–5 m in diameter and 3–5 m deep. The collapse sinkholes do not reach the underlying limestone, but seem to be related to accelerated dissolution in that formation. Above the Cretaceous limestone, Quaternary gravels and glacial tills provide a non-soluble, but permeable and heterogeneous cover of about 20 m thickness.We have mapped the sports field and its vicinity with gravity (GRAV), electrical resistivity imaging (ERI), and ground-penetrating radar (GPR). The ERI profiles indicate a significant change in the surface layer, from thin and irregular in the northern part to thicker and more homogeneous in the southern part of the sports field. GPR profiles confirm this result.We numerically model the evolution of flow and porosity in the Cretaceous limestone to estimate the evolution time of subsurface voids in the limestone, and we discuss the potential cause of the sinkhole formation and its sudden onset in light of the hydraulic boundary conditions.

Baseflow index assessment and master recession curve analysis for karst water management in Kakap Spring, Gunung Sewu

Karst terrain occurs in combination of high solubility rock and well developed secondary porosity. Over the time, groundwater resources have not been well managed including karst aquifers. Karst aquifers formed in a very complex hydrological system. Developed in fracture media and soluble rocks have led karst aquifers into various porosity types and aquifer properties. Karst spring hydrograph is an essential element for water resource management. The form of karst spring hydrograph reflects the aquifer characteristics. The shapes of flood discharge hydrographs represent aquifer responses to recharge and contain information about the interior condition of karst drainage basin. Every year, Gunung Sewu karst area is suffering to severe water scarcity. The development of sub-terrain drainage networks lead into the minimum surface water resources. Kakap Spring is perennial gravity spring that located adjacently to the border of Gunung Sewu and the alluvial formation of Baturetno. Kakap spring play vital role regarding water supply in Giriwoyo sub-district as the spring fulfill most of the water needs in Giriwoyo sub-district. Kakap Spring utilized by the local authorities as the main source for pipeline water and distributed to the households. Water level data series obtained using automatic water level data logger and then correlated with manual discharge measurement to generate stage-discharge rating curve. The stage-discharge rating curve formula for Kakap Spring calculated as y = 14,504e8,9763x with r2 value = 0.8582. From the MRC result, flow regimes formula determined as + 400 (1-0,005t) + 700 (1-0,01t)., indicated that the aquifer dominated by turbulent flow regime. From the MRC formula, the degree of karstification in Kakap Spring classified at eighth scale. The average baseflow index in Kakap Spring calculated using recession curve analysis with the BFI index = 0,7485.

Specialized core bacteria associate with plants adapted to adverse environment with high calcium contents.

Karst topography is formed from the dissolution of soluble rocks, such as limestone and dolomite. In soils of such a landform, excessive contents of exchangeable calcium seriously limit the growth of vegetations. Researches have proved that rhizosphere microorganisms and endophytes help host plants to adapt to various adverse environments. The adaptive capacity of plants that grow in adverse environment with salt, drought, thermal and heavy metal stresses partially or completely comes from symbiotic microorganisms. By using the high-throughput amplicon sequencing, the bacterial community structures in soil with high calcium contents and roots and leaves of Cochlearia henryi that is commonly seen in karst area were analyzed. The bacteria community structures in these three compartments showed obvious differences. This indicates that C. henryi, which is adaptive to high calcium stress, selectively co-exists with specific bacteria. Although the bacteria community structures in these three compartments differed significantly, there were 73 operational taxonomic units (OTUs) shared by karst soils as well as roots and leaves of C. henryi. The phylogenetic diversity of these 73 OTUs differed significantly from that of overall OTUs detected. There were also obvious differences in KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways and abundance values between the 73 OTUs and overall bacterial communities. A large number of OTUs shared by the karst soils, roots and leaves of C. henryi had close genetic relationship with known stress-resistant bacterial strains. Our results showed that the functional bacteria can be predicted by exploring core bacteria, bacteria shared by soils, adaptable plant roots and leaves. This information will potentially accelerate studies on natural microbial communities which can promote the adaptive capacity of host plants to high calcium stress, and will be valuable for finding microbial strains for field application in karst topography.

ANALISIS VEGETASI KAWASAN KARST GOMBONG SELATAN KEBUMEN JAWA TENGAH

Karst area is a well-developed porosity landscape with a specific condition as a result of soluble rock development through a process of karstification. The karst soil has low nutrients, but high calcium and magnesium content. Due to its unique environmental characteristics, karst vegetation differs from other areas. This study aimed to determine the community structure and species composition of vegetation in the karst area of Gombong Selatan and to compare the environmental factors affecting the plant of the karst area. This study was conducted in the border of Watukelir and Pakuran Villages. The method was a survey with sampling quadrat sizes used of 10 x 10 m for trees, 5 x 5 m for saplings, and 2 x 2 m for understorey vegetation. The variables observed were plant species and number of trees, saplings, and understorey. The environmental factors measured were air temperature, humidity, soil pH, and soil moisture. Data were analyzed using Importance Value Index (IVI), Shannon-Wienner Diversity Index (H’), Evenness Index (E), and Similarity Index (IS). The results showed there were 22 species of understoreys, five species of saplings, and seven species of trees. The understoreys were found dominated by Axonopus compressus dan Cyperus rotundus , in the other category, Tectona grandis and Albizia chinensis were dominated saplings and trees. Humidity and soil moisture were suggested the important environmental factors for plant diversity in karst area of Gombong Selatan

The soil organic carbon stock and its influencing factors in a mountainous karst basin in P. R. China

Soil organic carbon represents a major carbon pool in terrestrial ecosystems. Currently, in karst areas, there is considerable uncertainty regarding the estimation of soil organic carbon pools due to limited profile numbers and heterogeneity. Using a grid-based sampling method, 2755 soil profiles consisting of 22,057 soil samples were analyzed to determine the spatial distribution and storage of soil organic carbon (SOC) in the Houzhai River Basin in the Guizhou Province in southwest China. The results suggest that the total SOC storages in the 0–20 and 0–100 cm soil horizons of the Houzhai River Basin are approximately 2.65 × 108 and 5.39 × 108 kg C, respectively. The differences in the soil bulk density between different soil types were considerable. The average soil bulk density of large mud field loam, which ranged from 1.25 to 1.52 g/cm3, was significantly higher than that of the other soil types. The differences in soil organic carbon content were obvious as well. As soil depth increased, the organic carbon content gradually decreased. At a depth of 0–50 cm, the soil organic carbon content significantly decreased. In contrast, soil organic carbon content decreased slowly from 50 to 100 cm, indicating that a depth of 50 cm is the turning point for organic carbon content. The different degrees of soil organic carbon storage in different soil types were mainly caused by differences in organic carbon density. In karst regions, the soil parent material limits the spatial distribution of soil organic carbon, and soluble rock is the base development material. Soil thickness, slope gradient, and rock exposure are the primary factors leading to differences in SOC storage in different soil types. In addition, this study also suggests that increased attention should be paid to rock exposure in the assessment of SOC stocks in karst mountainous areas, such as the Houzhai River Basin.

Characteristics, detection, and prevention of karst sinkholes: a case study in Laiwu iron ore mine areas, Shandong Province, China

Karst-related sinkholes are globally recognized geohazards that can be triggered by mining activities. Totally, 136 sinkholes have occurred in the Laiwu iron ore mine area of Shandong Province, China. At the surface, the sinkholes are mostly round or oval shaped. Most are ceiling collapse sinkholes, and they have caused road and building damage, destruction of farmland, connection of surface and ground water, and groundwater contamination. Based on analysis of characteristics on karst sinkhole, geological and hydrogeological conditions, the proposed key factors of the karst collapse in the study area include soil characteristics, degree of karst development in soluble rocks, faults, folds, groundwater dynamic conditions, and human engineering and mining activities. A 300-m-long, 40-m-wide, and 25-m-high cavern was identified with high-density electrical resistivity imaging. Complex solutions were proposed to mitigate karst collapse in the iron ore mining area.

Evaluating the susceptibility to anthropogenic sinkholes in Apulian calcarenites, southern Italy

Abstract Sinkholes are the main hazard related to underground voids of both natural and anthropogenic origin. Instabilities developing underground may propagate upwards in a dramatic manner and reach the surface in the form of a sinkhole. The Apulia region in southern Italy is an interesting case study due to the outcropping of soluble rocks throughout the region. These rocks are affected by karst processes and have a high number of anthropogenic cavities. The latter were excavated by humans at different times for a variety of purposes. The worrying recent increase in the number of sinkhole events registered in Apulia led us to collect information on natural and anthropogenic sinkholes in Apulia. We focused on anthropogenic cavities, mostly excavated in Plio-Pleistocene calcarenites, and characterized the rock masses before using two- and three-dimensional parametric numerical analyses to model the instability processes, with the aim of exploring the failure mechanisms that lead to the occurrence of sinkholes. The parametric studies allowed us to carry out a preliminary evaluation of the stability conditions through simple charts designed for use in the field.

Recent advances in karst research: from theory to fieldwork and applications

Abstract Karst landscapes and karst aquifers, which are composed of a variety of soluble rocks such as salt, gypsum, anhydrite, limestone, dolomite and quartzite, are fascinating areas of study. As karst rocks are abundant on the Earth's surface, the fast evolution of karst landscapes and the rapid flow of water through karst aquifers present challenges from a number of different perspectives. This collection of 25 papers deals with different aspects of these challenges, including karst geology, geomorphology and speleogenesis, karst hydrogeology, karst modelling, and karst hazards and management. Together these papers provide a state-of-the-art review of the current challenges and solutions in describing karst from a scientific perspective.

About this title ‐ Advances in Karst Research: Theory, Fieldwork and Applications

Karst landscapes and karst aquifers are composed of a variety of soluble rocks, such as salt, gypsum, anhydrite, limestone, dolomite and quartzite. They are fascinating areas of exploration, study and research. As karst rocks are abundant on the Earth's surface, the fast evolution of karst landscapes and the rapid flow of water through karst aquifers present many challenges from a number of different perspectives. This collection of 25 papers deals with different aspects of these challenges, including karst geology, geomorphology and speleogenesis, karst hydrogeology, karst modelling, and karst hazards and management. Together these papers provide a state-of-the-art review of the current challenges and solutions we face in describing karst from a scientific perspective, while at the same time providing useful data and information for managing karst territories to land planners, developers, and managers of show caves, natural parks and reserves in karst terrains.

Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

Abstract. In November 2010, a large sinkhole opened up in the urban area of Schmalkalden, Germany. To determine the key factors which benefited the development of this collapse structure and therefore the dissolution, we carried out several shear-wave reflection-seismic profiles around the sinkhole. In the seismic sections we see evidence of the Mesozoic tectonic movement in the form of a NW–SE striking, dextral strike-slip fault, known as the Heßleser Fault, which faulted and fractured the subsurface below the town. The strike-slip faulting created a zone of small blocks ( < 100 m in size), around which steep-dipping normal faults, reverse faults and a dense fracture network serve as fluid pathways for the artesian-confined groundwater. The faults also acted as barriers for horizontal groundwater flow perpendicular to the fault planes. Instead groundwater flows along the faults which serve as conduits and forms cavities in the Permian deposits below ca. 60 m depth. Mass movements and the resulting cavities lead to the formation of sinkholes and dissolution-induced depressions. Since the processes are still ongoing, the occurrence of a new sinkhole cannot be ruled out. This case study demonstrates how S-wave seismics can characterize a sinkhole and, together with geological information, can be used to study the processes that result in sinkhole formation, such as a near-surface fault zone located in soluble rocks. The more complex the fault geometry and interaction between faults, the more prone an area is to sinkhole occurrence.

Geophysical observations and structural models of two shallow caves in gypsum/anhydrite-bearing rocks in Germany

Abstract The development of subsurface voids and cavities in soluble rocks is controlled by the hydrological and chemical processes in the host rock. Water (enriched with carbon dioxide) percolates through fractures and bedding partings of the host rock and removes material from the rock surface. As this enlargement is a highly heterogeneous process, only some fractures and bedding partings become significantly enlarged, evolving towards larger voids and caves. The size of the enlarged voids, often reaching the metre scale, can result in mechanically unstable structures, which, when close to the surface, are prone to collapse and thus are a hazard to infrastructure. We explored two caves in the anhydrite host rock of the Permian Zechstein sequences in northern Germany using geophysical measurements: the Kalkberghöhle close to Bad Segeberg (Hamburg region) and the Jettenhöhle close to Osterode (Harz region). Based on the results of gravity and electrical measurements, we were able to identify the cave voids and to characterize the local geological setting. Using these indirect geophysical observations, we deduced a structural model for both cave sites by numerical modelling. Our structural models were successfully calibrated against the Bouguer gravity data.

Leaf trait variations associated with habitat affinity of tropical karst tree species.

Karst hills, that is, jagged topography created by dissolution of limestone and other soluble rocks, are distributed extensively in tropical forest regions, including southern parts of China. They are characterized by a sharp mosaic of water and nutrient availability, from exposed hilltops with poor soil development to valleys with occasional flooding, to which trees show species‐specific distributions. Here we report the relationship of leaf functional traits to habitat preference of tropical karst trees. We described leaf traits of 19 tropical tree species in a seasonal karst rainforest in Guangxi Province, China, 12 species in situ and 13 ex situ in a non‐karst arboretum, which served as a common garden, with six species sampled in both. We examined how the measured leaf traits differed in relation to species’ habitat affinity and evaluated trait consistency between natural habitats vs. the arboretum. Leaf mass per area (LMA) and optical traits (light absorption and reflectance characteristics between 400 and 1,050 nm) showed significant associations with each other and habitats, with hilltop species showing high values of LMA and low values of photochemical reflectance index (PRI). For the six species sampled in both the karst forest and the arboretum, LMA, leaf dry matter content, stomatal density, and vein length per area showed inconsistent within‐species variations, whereas some traits (stomatal pore index and lamina thickness) were similar between the two sites. In conclusion, trees specialized in exposed karst hilltops with little soils are characterized by thick leaves with high tissue density indicative of conservative resources use, and this trait syndrome could potentially be sensed remotely with PRI.

Distribuição e morfologia do sistema radicular de Eucalyptus dunnii em resposta à aplicação de fósforo

use of soluble phosphates and rock phosphates is a normal practice in Eucalyptus fertilization. As the phosphorus fertilizer is located near the plant, phosphorus (P) may interfere with the growth and morphology of the root system. The objective of this work was to evaluate the growth and morphological characteristics of root system of Eucalyptus dunnii using soluble and rock phosphate. Samples were collected in 2013 from an experiment established in 2010 in the city of Otacilio Costa, SC. Samples were collected from four treatments: 1) control without P; 2) fertilization with 60 kg ha-1 of P2O5 in the form of phosphate rock; 3) 75 kg ha-1 of P2O5 in the form of triple superphosphate and; 4) 60 kg ha-1 rock phosphate P2O5 plus 75 kg ha-1 P2O5 soluble phosphate (these doses being chosen because it represents the usual practice in the reforestation of the region). The collection of roots occurred 28 months after planting of the seedlings and application of treatment with a 40 mm in diameter and 100 mm high probe. The soil and root samples were collected at three distances from the shaft (10, 60 and 120 cm) and two layers (0-10 and 10-20 cm). The roots were separated in two diameter classes: 0 to 2 mm and 2 to 5 mm. Dry matter of roots were characterized, root radius, length, volume and root area. Rock phosphate did not stimulate root growth and the soluble phosphate was the source that improved growth and development of fine roots in Eucalyptus dunnii, with the highest concentration of these roots being located near the shaft and in the most superficial layer of soil.

The Jettencave, Southern Harz Mountains, Germany: Geophysical observations and a structural model of a shallow cave in gypsum/anhydrite-bearing rocks

Gypsum and anhydrite are soluble rocks, where fissures and bedding partings can be enlarged with time by the dissolution of the mineral species through water. The selective enlargement results in sub-surface voids acting as preferential flow path for the drainage of the rock. With time, larger cavities develop, and a network of cave passages can evolve. If the enlarged cave voids are not too deep under the surface, geophysical measurements can be used to detect, identify and trace these structures. We have used gravity measurements (GRAV), electrical resistivity imaging (ERI), self-potential measurements (SP), electrical conductivity measurements (EC), and ground-penetrating radar (GPR) above the cave Jettenhöhle, a cave located in the southern Harz Mountains in Germany. The Jettencave is developed in the Hauptanhydrit formation of the Permian Zechstein sequence, characterised by large breakdown rooms and an exposed water table. The overburden of the cave is only around 10–15m, and dolomitic rocks are located in close vicinity. We present results from our geophysical surveys in vicinity of the cave. We are able to identify the cave geometry from GRAV, ERI, and GPR measurements, which distinguish the local lithology of the Permian Zechstein rocks in the area. From the ERI and EC measurements, we derive information on the void volume in the soluble rocks. We finally present a three-dimensional structural model of the Jettencave and its surroundings, based on our geophysical results and the hydrological interpretation.

Small-scale modelling of cementation by descending silica-bearing fluids: Explanation of the origin of arenitic caves in South American tepuis

Geoscientific research was performed on South American table mountains (tepuis) and in their sandstone cave systems. To explain speleogenesis in these poorly soluble rocks, two theories were introduced: a) arenization theory implying selective weathering of quartz along grain boundaries and releasing of sand grains, b) selective lithification theory implying cementation by descending silica-bearing fluid flow. The latter theory presumes that the descending fluid flow becomes unstable on the interface between two layers with different porosity and splits to separate flow channels (so-called “finger flow”). The arenites outside these channels remain uncemented.To verify the latter theory, small-scale modelling was performed, using layered sands and sodium-silicate solution. Fine to medium sand was used (0.08–0.5mm), along with a coarse sand fraction (0.5–1.5mm). The sands were layered and compacted in a transparent plastic boxes. Three liters of sodium-silicate solution (so-called water glass) were left to drip for several hours to the top of the sediment. The fine-grained layers were perfectly laterally impregnated, whereas the descending fluid flows split to “fingers” in the coarse-grained layers due their higher hydraulic conductivity. This small-scale laboratory simulation mimics the real diagenesis by descending silica-bearing fluids and matches the real phenomena observed on the tepuis. The resulting cemented constructions closely mimic many geomorphological features observed on tepuis and inside their caves, e.g. “finger-flow” pillars, overhangs, imperfectly formed (aborted) pillars in forms of hummocks hanging from ceilings, locally also thicker central pillars that originated by merging of smaller fluid-flow channels. The modelling showed that selective lithification theory can explain most of the geomorphological aspects related to the speleogenesis in tepuis.

Quantitative groundwater estimation of Izhora Plateau, Russian Federation using thermodynamic and kinetic methods for carbonate rock interaction in identified karst terrain

Karst formations are often responsible for the decay of building foundations and road infrastructure. Three conditions are required for the development of karst: porous or fractured rock subject to water filtration, water dissolving rock, and conditions for water exchange (saturated ions prompting water outflow and inflow of new aggressive water for soluble rock). Individual estimation of rock masses which dissolve in an aeration zone and in an unconfined aquifer is an advanced feature for developing karst protection. This article describes modified algorithms of thermodynamic and kinetic calculations for the interactions of groundwater and carbonate rock based on investigations conducted on the karst terrain of the Izhora Plateau, located in the northwest of the Russian Federation. The upper part of the Izhora Plateau consists of Ordovician carbonate rocks (limestone), in which karst has developed. Karst sinkholes emerge on the Izhora Plateau in quantities of 100–300 each year. Groundwater and infiltration waters were sampled to determine chemical composition in different locations of the Izhora Plateau. An estimation of the groundwater reserves for the territory of the Izhora Plateau (2200 km2; size from North to South is 55 km; East to West 40 km) has never been carried out employing carbonate rock interactions through thermodynamic and kinetic methods. Chemical composition of groundwater and infiltration water is a base for thermodynamic calculations and kinetic calculations of interactions between groundwater and infiltration water with rocks and CO2. The result of complex heterogeneous investigations determined that 53% or 1.42 × 108 kg year−1 of carbonate rock in the tested area dissolved in the aeration zone. In the aquifer, the upper part formed an unsaturated layer, which dissolves carbonate rocks. This layer dissolves 47% or 1.24 × 108 kg year−1 of rock. In this work, we also present original methods for arriving at these calculations. These investigations can help in organizing efforts to reduce the quantity of new karst sinkholes.

Understanding and preserving caves and karst landscapes

ABSTRACT Beginning in 1903 with the creation of Wind Cave National Park, ten National Park Service units have been created because of the caves they contained. Since the establishment of the National Park Service in 1916, over 5,360 caves are known to exist within at least 99 park units. These caves are found in different types of rocks and were formed by several different mechanisms. The most prolific landscapes that have formed caves are those in soluble rocks such as limestone. Known as karst landscapes, at least 114 park units contain some amount of karst. In the early days, cave parks were developed for their commercial and recreational values. Little was known of the processes that created caves or the many resources that encompassed these entire landscapes. With the help of cave and karst enthusiasts and researchers, and the advent of cave and karst resource managers, the National Park Service has made great strides in understanding these resources. This has led to increased educational opportunities and better management decisions that will enhance long-term preservation of these resources.

CHANGING NONCOHESIVE SOIL GRANULOMETRIC COMPOSITION THAT PRECEDES KARST-PIPING SINKHOLE FORMATION

In covered karst areas, there are precursory signs of a preparing sinkhole formation. These signs are features of the overburden structure. In particular, they include suffosion decompaction zones of noncohesive soils over fissures and cavities in soluble rocks. The existence of such zones in a geological cross-section can be considered as a precursor of a karst-piping sinkhole formation. This paper presents a detailed description of this phenomenon studied using a laboratory physical modeling and in the natural conditions. The authors consider the principles of search and identification of suffosion decompaction zones on the basis of analyzing the spatial distribution of granulometric composition parameters of noncohesive soils in the lower part of the overburden.

Brief In Vitro Analysis on Improvement of Available Phosphorous In Low Soluble Eppawala Rock Phosphate

Rock Phosphate (RP) is any naturally occurring geological material that contains one or more phosphate minerals suitable for commercial use. There is a major RP deposit in Eppawala, Sri Lanka and this RP identify as Eppawala Rock Phosphate (ERP). Large proportion of soluble inorganic phosphate added to soil is rapidly fixed as insoluble forms soon after application. Development of an economical and environmentally friendly alternative for successful soil P management is major concern in crop production and Phosphate Solubilizing Microorganism (PSM) attracted attention in this regard. This study was conducted to identify the Phosphorus solubilizing bacteria. Soil samples were collected from different Agricultural crop lands. Soil were Spread cultured in NBRIP medium after a serial dilution. The bacterial colonies that produced clear zone of activity were considered as potential phosphate solubilizes. They were sub-cultured for the further purification. The experiment has been carried out adding 28% P2O5 containing Eppawala Rock Phosphate with NBRIP medium. Bacterial growth in 660 wave length by using shimadzu UV spectrophotometer, P solubilization, and pH were measured respectively 1, 3, 5 and 7 days after inoculation. Clear zone producing bacteria in phosphate enriched medium has been selected as P solubilizing bacteria with time period all bacterial strains has shown improvement of solubilized P in the culture media. Among them PSB-7 strain has shown a vigorous growth and maximum P Solubilization 237.61 ppm in vitro during experiment. Despite of environment unfriendly chemical solubilization methods of naturally existing Rock Phosphate this biological solubilization generate maximum amount of plant available phosphorous.