Evaluation of soil physical properties as influenced by various green manuring legumes and phosphorus fertilization under rain fed conditions

A field experiment was conducted under rainfed environment of Pothowar region of Pakistan to assess physical properties of soil as influenced by various green manure legumes (sesbania, cluster bean and rice bean) and different P levels (0, 30, 60, 90 kg P2O5/ha). Highest fresh biomass was observed in sesbania (23 t/ha) followed by cluster bean (19 t/ha) and lowest in rice bean (17 t/ha). Maximum crude protein content was found in sesbania (17%) followed by rice bean (10%) and cluster bean (8%). Green manuring crops, on average reduced soil bulk density (5%), enhanced total porosity (8%), and macropores and large mesopores (28%). Maximum reduction (7%) in soil bulk density, and an increase (11%) in total soil porosity and available water (17%) was observed in plots where sesbania was incorporated as green manuring crop. The order of effectiveness in improving bulk density, macro and mesopores was sesbania > cluster bean > rice bean. Sesbania produced greater number of macro and large mesopores about 41% increase over control followed by cluster bean (29%) and rice bean (16%). Phosphorus application showed meager positive impact on various soil physical properties but did not significantly increased porosity or reduced bulk density. Significant differences in volume fraction in pore space suggest that pore space on a volume basis was much higher in sesbania-amended soil than in other treatments.     

Managing crop stubble during fallow period for soil water conservation: field experiment and modelling

In the arid and semi-arid environments where the rainfall is limited and variable, fallow period soil moisture conservation using stubble is one of the ways of increasing the soil moisture required for crop sowing and development. However, the effectiveness of moisture conservation using stubble depends on the paddock management, soil water content, and rainfall characteristics. To assess the effect of stubble rate and amount of rainfall on the soil moisture conservation, a two-season field experiment was conducted using four stubble rates (0, 2, 4, 6 t/ha) and two water supply amounts. The soil water dynamics was also analysed using a validated Agricultural Production System Simulator (APSIM). In the relatively wet summer season with a high initial soil water content, the amount of water stored in the 2, 4, and 6 t/ha stubble rate treatment plots was higher than that of the bare plots by 10.4, 15.9, and 17.8 mm, respectively. However, in the summer season with a relatively high amount of in-season water input and low initial soil water content, the soil water storage was increased by 29.4, 35.6, and 43.0 mm, respectively. Comparing the results of the two seasons, the highest increase was observed for the 2 t/ha stubble rate. The amount of conserved soil moisture was found to be the highest when the soil profile water content at the start of the summer-fallow period is low and the amount of rain during the summer season is high. The good agreement between the measured and APSIM-simulated soil water contents (R ² = 0.812), indicates that the model can be used to assess the soil water dynamics under a fallow condition. The APSIM-simulated soil water balance using the weather data of the past 100 years indicated that in a year with low start-of-fallow period soil water content, a 6 t/ha stubble rate can increase the end-of-fallow period soil moisture by up to 60 %.     

Simulation of Electrical Conduction in Geomaterials by SPICE

Electrical responses of the subsurface can be used to identify geologic strata, locate anomalies, detect and delineate contamination, among many other applications. All these applications depend on the spatial variations of electrical properties in the subsurface and the resulting flow pattern of electric current. Due to the heterogeneity of the subsurface and complex boundary conditions, three-dimensional electric current flow problems are not easy to analyze, in particular when the response is frequency- and/or time-dependent. In this paper, a method of electric circuit analogy is proposed to simulate the electrical responses of geomaterials using the circuit simulator SPICE. The technique will allow simulation of more complex electrical conduction behavior of geomaterials without much extra effort. The excellent agreement between simulated results and analytical solutions developed for surface geophysical techniques establishes the viability of the method. Limitations of the approach and potential solutions to relax these limitations, and other potential applications of the technique in geosciences are also discussed.     

Clay mineral variations in Holocene terrestrial sediments from the Indus Basin

We employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and flood plains since ~ 14 ka, spanning a period of strong climatic change. Assemblages are dominated by smectite and illite, with minor chlorite and kaolinite. Delta sediments integrate clays from across the basin and show increasing smectite input between 13 and 7.5 ka, indicating stronger chemical weathering as the summer monsoon intensified. Changes in clay mineralogy postdate changes in climate by 5–3 ka, reflecting the time needed for new clay minerals to form and be transported to the delta. Samples from the flood plains in Punjab show evidence for increased chemical weathering towards the top of the sections (6–< 4 ka), counter to the trend in the delta, at a time of monsoon weakening. Clay mineral assemblages within sandy flood-plain sediment have higher smectite/(illite + chlorite) values than interbedded mudstones, suggestive of either stronger weathering or more sediment reworking since the Mid Holocene. We show that marine records are not always good proxies for weathering across the entire flood plain. Nonetheless, the delta record likely represents the most reliable record of basin-wide weathering response to climate change.     

The quality of water and sediments of street runoff in Amman,Jordan

Metallic content (Cr, Fe, Mn, Cu, Ni, Pb and Cd) of street sediments and street runoff in addition to major inorganic constituents (Ca, Mg, Na, K, HCO₃, Cl, NO₃ and SO₄) of street runoff were determined under semi‐arid conditions. Two sites in the vicinity of Amman during the pluvial year 1998–1999 were chosen for this investigation. A higher quantity of ionic contents was found at site 2 in comparison to site 1 except for iron, which was significantly higher at site 1. This finding was attributed to higher anthropogenic activity and lower rainfall at site 2, which indicates better water quality of street runoff from residential sites than the city centre. The average concentrations of Pb, Cu and Cd in Amman street runoff compared with the highest levels recorded at humid sites of the world as a result the prevailing semi‐arid conditions in the areas investigated. The highest concentrations of all constituents were detected during the first month of sampling, which might be the result of low rainfall, and a long dry period of atmospheric deposition preceding rainfall events. However, high levels of both lead and copper were recorded (below that of iron) which might be attributed to traffic pollution. In contrast, a significant variation between the average concentrations for Cu, Ni and Cr was found in sediments from the two sites. Moreover, a significant difference was detected only for Cu and Mn at each site overtime. The overall pattern of the results suggests that all heavy metal concentrations for street runoff showed a significant variation over time at site 1 whereas only a significant variation was found for Ni at site 2, which can be explained as the result of higher rainfall at site 1 than at site 2. Copyright © 2001 John Wiley & Sons, Ltd.     

Stepwise,earthquake-driven coastal subsidence in the Ganges–Brahmaputra Delta (Sundarbans) since the eighth century deduced from submerged in situ kiln and mangrove remnants

Natural Hazards - This study reconstructs the coastal subsidence over the past 1300&nbsp;years in a mangrove region along the coast of the Ganges–Brahmaputra Delta, an area not affected...     

The Indigenous Aetas of Bataan,Philippines: Extraordinary genetic origins,modern history and land rights

The Aeta Magbukún of Bataan in Luzon, the Philippines remain one of the least known and documented Indigenous tribes. They retain primarily subsistence hunter‐gathering strategies to supply their basic needs. They also strive for recognition of their ancestral connection with, and rights to inhabit their ancestral forest domains, which is threatened by the expansion of agriculture and urban development by non‐Aetas, primarily the majority Tagalog population. The Aeta continue to endure dispossession, poverty and political discrimination through decades of protracted land rights processes. This review explores the potential use of recent genetic evidence in anthropology and human geography to legitimize the Aeta's status as Indigenous people and contradict the perspective of some governments in the Asia Pacific region who question the existence of Indigenous peoples generally, often from fear of land tenure and associated political repercussions. The acquisition and use of genetic research on Indigenous populations is both socially and politically contested through fear of the potential to jeopardize sovereignty claims and lead to biologically‐based discrimination. However, the full implications of the potential use of genetic research to legitimize Indigenous status, as described within this research, has yet to be thoroughly explored. By exploring both the genetic and anthropological evidence using a case study of the Indigenous Aeta, this paper provides a unique approach to building a case for Indigenous rights, occupation, use of ancestral lands, self‐determination, and ultimately, recognition as Indigenous people.     

Desertification in the Arab Region: analysis of current status and trends

The total area of the Arab Region is about 14·2 million km², 90% of it lies within arid, semi-arid and dry sub-humid areas. The area is characterized by harsh environment, fragile ecosystems and limited water resources and arable lands. Throughout its long history these lands were the main source of grain and animal production.By the end of this century and in spite of the national, regional and international efforts to combat desertification and mitigate the effect of drought and desiccation, desertification is still one of the major environmental problems in the Arab Region. The rapid increase in population by some 3% annually, considered among the highest worldwide, along with the changing of consumption patterns and life styles, resulting in increasing food demand, have hastened land degradation in this arid environment.Land degradation in the Arab Region due to misuse is widespread and is proceeding at accelerating rates. Failures of resource management policies are aggravated by overgrazing, overexploitation of water and land resources, overcultivation of marginal lands, deforestation, and the use of inappropriate technologies.This paper attempts to provide:

• A synthesis and analysis of the status of desertification in the Arab Region.

• Identification of the major causes and trends of land degradation.

• Highlighting the limitations and constraints on combating desertification in the Arab Region.

Rock mass characterization for the underground cavern design of Khiritharn pumped storage scheme

A general approach to rock engineering designing aspects adopted at the Khiritharn Pumped Storage Scheme is described. The scheme involves excavation of three large caverns and tunnels in jointed sandstone within a suture zone in Southeast Thailand. Geological condition and engineering properties of the sandstone were investigated. Strength and modulus properties of the intact rock were determined from laboratory tests and properties of rock mass were empirically estimated for the design analysis in the de.nite study stage on the basis of three rock mass classi.cation systems namely the Rock Mass Rating (RMR), Geological Strength Index (GSI) and a Japanese system (EPDC). While the GSI gives strength and modulus of deformation values slightly higher than the RMR classi.cation, the EPDC gives a lower value of modulus of deformation but comparable rock mass strength value for the level of con.ning pressures at the depth of the cavern excavation. The results of stress analysis and loosening wedge analysis for the cavern excavations suggest favorable excavation condition.