Effect of exo-polysaccharides producing bacterial inoculation on growth of roots of wheat (Triticum aestivum L.) plants grown in a salt-affected soil

Effect of soil salinity on physico-chemical and biological properties renders the salt-affected soils unsuitable for soil microbial processes and growth of the crop plants. Soil aggregation around roots of the plants is a function of the bacterial exo-polysaccharides (EPS), however, such a role of the EPS-producing bacteria in the saline environments has rarely been investigated. Pot experiments were conducted to observe the effects of inoculating six strains of EPS-producing bacteria on growth of primary (seminal) roots and its relationship with saccharides, cations (Ca²⁺, Na⁺, K⁺) contents and mass of rhizosheath soils of roots of the wheat plants grown in a salt-affected soil. A strong positive relationship of RS with different root growth parameters indicated that an integrated influence of various biotic and abiotic RS factors would have controlled and promoted growth of roots of the inoculated wheat plants. The increase in root growth in turn could help inoculated wheat plants to withstand the negative effects of soil salinity through an enhanced soil water uptake, a restricted Na⁺ influx in the plants and the accelerated soil microbial process involved in cycling and availability of the soil nutrients to the plants. It was concluded that inoculation of the EPS-producing would be a valuable tool for amelioration and increasing crop productivity of the salt-affected soils.     

Grain size and geochemical partitioning of heavy metals in sediments of the Damodar River – a tributary of the lower Ganga, India

 The distribution of Si, Al, Fe, Mn, Cu, Zn, Ni and Cr in different grain-size fractions and geochemical association of Fe, Mn, Cu and Zn with <63-μm size fraction of bed sediments of Damodar River has been studied. In general, concentrations of heavy metals tend to increase as the size fractions get finer. However at two sites, near mining areas, the coarser particles show similar or even higher heavy metal concentrations than finer ones. The higher residence time and/or presence of coarser particles from mining wastes are possibly responsible for higher metal content in the coarser size fractions. The chemical fractionation study shows that lithogenic is the major chemical phase for heavy metals. Fe and Mn are the major elements of the lithogenic lattice, constituting 34–63% and 22–59%, respectively, of total concentrations. Fe-Mn oxide and organic bound fractions are significant phases in the non-lithogenic fraction. The carbonate fraction is less significant for heavy metal scavenging in the present environment and shows the following order of abundance Zn>Cu>Mn>Fe. The exchangeable fraction of the Damodar sediments contains very low amounts of heavy metals suggesting poor bioavailability of metals. Received: 18 August 1998 · Accepted: 1 December 1998     

Engineering properties of sabkha soils in the benghazi plain and construction problems

This paper describes the geological, geotechnical and chemical properties of some Sabkha (lagoonal) soils in the Benghazi plain. Several buildings constructed on such soils show tilting and cracks. The cause of this trouble has been traced to the special characteristics of Sabkha soils. It is suggested that improved mix design and dense concrete should be used so as to make concrete in the foundation impermeable.     

Stability of remanent magnetization of some dykes from Mysore State,India

Summary The magnetic properties of some dykes from Mysore State, India, have been studied in detail. The rocks were found to have aQ _n ratio varying from 1.5 to 11.6, a remanent coercive force varying from 100 to 250 Oersteds, Curie temperature varying from 250 to 480°C and were found to have lamellae of ilmenite oriented in (111) plane of magnetite. The stable natural remanent magnetization of the rock seems to be of TRM origin with titanomagnetite and low grade titanomaghemite being the main carrier of remanent magnetization.N.G.R.I. Contribution No. 70-215.     

Weathering and Geochemical Processes Controlling Solute Acquisition in Ganga Headwater–Bhagirathi River, Garhwal Himalaya, India

Water and suspended sediment samples were collected along a longitudinal transect of the Bhagirathi – a headwater stream of the river Ganga, during the premonsoon and postmonsoon seasons, in order to assess the solute acquisition processes and sediment transfer in a high elevation river basin. Study results show that surface waters were dominated by HCO₃ and SO₄ in anionic abundance and Ca in cationic concentrations. A high concentration of sulphate in the source region indicates oxidative weathering of sulphide bearing minerals in the drainage basin. The combination of high concentrations of calcium, bicarbonate and sulphate in river water suggests that coupled reaction involving sulphide oxidation and carbonate dissolution are mainly controlling the solute acquisition processes in the drainage basin. The sediment transfer reveals that glacial weathering and erosion is the major influence on sediment production and transfer. The seasonal and spatial variation in ionic concentration, in general, is related to discharge and lithology. The sediment mineralogy and water mineral equilibrium indicate that water composition is in equilibrium with kaolinite. The river Bhagirathi annually delivers 0.74 M.tons of dissolved and 7.88 M.tons of suspended load to the river Ganga at Devprayag. The chemical and physical denudation rate of the Bhagirathi is 95 and 1010 tons/km²/yr, higher than the Indian and global average.     

Sediment transfer in the glaciofluvial environment — a Himalayan perspective

The Alaknanda river, a major Himalayan proglacial stream, and its tributaries have been studied to evaluate sediment sources, production mechanisms, and transport pathways in the Alaknanda river basin. The study is based on a single-time sampling of the river and its tributaries and gives an insight into the suspended load pattern of the river from its source to its confluence with the other major Himalayan proglacial stream, the Bhagirathi. It is tentatively concluded that the suspended load of the Alaknanda is primarily due to natural processes and events and does not reflect the effects of human intervention.     

Polar wandering path for India during the Precambrian

Summary The recent radiometric dating on some Precambrian formations of India and the available paleomagnetic data have enhanced the possibility of deducing the Polar wander path for India during the remote past. The data indicate that India was in the northern hemisphere during the Precambrian times. This inference has also been substantiated by the paleoclimatic evidences.