Integrating Knowledge for River Basin Management: Progress in Thailand

Resource /Energy Economics and Policy,

Morphology and genesis of Gray Podzolic soils in Thailand

Nine Gray Podzolic soils from different physiographic regions of Thailand were studied to determine their characteristics and genesis in relation to their parent materials, land form, pedogenic environment, classification and management. The clay was characterized by X-ray diffraction and standard chemical and physical analyses were performed. Mineralogy of the light ana heavy minerals from the fine sand to coarse silt fractions was determined by randomized grain counts. Micromorphological study was made of thin sections from selected horizons in each profile. Field and laboratory study showed that Gray Podzolic soils formed under distinctly different climatic zones and vegetation have quite similar characteristics. They occupy similar low terraces with nearly level topography and are associated closely with Low Humic Gley soils. Parent materials and topography are the two most important factors influencing the genesis of these soils. Mineral assemblages in the profiles indicate the parent materials were preweathered sediments from acidic rocks. They are quartz rich, with very few if any weatherable minerals, ubiquitous heavy minerals and with dominantly kaolinitic clay. The few lower stability minerals found in several profiles can be traced to some rocks rich in those minerals in the catchment areas. Climatic variations between the soils are not consistent with the weathering stages found and differences in soil age are not enough to account for mineralogical variation through differential in situ, weathering. Therefore, differences in composition and preweathering of parent materials most logically account for the presence of minor amounts of relatively unweathered feldspar and hornblende in some of these soils. Soil development has resulted in a loosely bound, clay poor, s-matrix with low degree of orientation in the upper horizons, and illuvial B horizons with more oriented plasma, illuviated cutans and vughs in the lower part of the profiles. Pedoplasmation activity by termites and other soil dwellers is partially responsible for the high porosity and mixing of the soil materials and, possibly, for the addition of lime. Plinthite formation in the lower part of some profiles relates directly to iron mobility and accumulation associated with fluctuations of the water table. Cation exchange capacities of the soils were low and the base saturation was generally less than 20% in the lower horizons. These characteristics reflect the low organic matter, sandy texture, kao- linitic clay and high porosity of these soils and strong leaching of bases under the humid climate. Depletion of bases and organic matter has been accelerated by the clearing of forest for shifting cultivation. Eight of the profiles were classified as Ultisols in Paleustult and Paleudult suborders; four of these with plinthite layers were grouped in plinthitic great groups. One profile with low clay content and higher, fluctuating base saturation was placed in the Ustropept great group. The CEC of less than 24 me /100 g clay placed all nine soils in ustoxic, orthoxic or oxic subgroups. Leached Ferruginous Tropical soils of Africa and Australian Lateritic Podzolic soils are similar to Gray Podzolic soils in this study except that they have higher base saturations. In northeastern Thailand, Gray Podzolic soils have been shown to have both high and low base saturations. The higher base saturation may be due to lime accumulation by termites and low buffering capacity of the sandy soils. Characteristics of Gray Podzolic soils indicate serious problems in their management under cultivation. The nutrient level in these soils is very deficient for most crops. In the northeast, where the rainfall is less reliable, development has been most difficult. With the present crops and level of management, response to fertilization and irrigation is very poor. Multiple improvements in other essentials of production is badly needed. Improvements are taking place, but sustained efforts on all aspects of the problem are required for effective and lasting progress

State of weathering of some upland soils in the Alsea Basin, Oregon

Mineralogical analysis of 3 upland soil profiles over Tyee parent rock from the Alsea Basin Area, Oregon showed clear differences among the 4 soil series represented. Soils from the area of higher precipitation (over 80 inches, approximately) had no montmorillonite, lower base saturation and cation exchange capacity, but no lower or only slightly lower amounts of weatherable minerals than soils from the area of lower precipitation. Only the profiles in the lower precipitation area had significant ped coatings of oriented clay. Shallow, yellowish soils, in both precipitation zones were much fresher mineralogically than the corresponding deep, red soils. The most strongly weathered profiles had contents of weatherable minerals too high for Latosols or Oxisols. The change with depth in the red soils suggested that these soils had not formed entirely from rock in place. Fragments of clay skins in the red soils suggested that these soils had developed, with mixing, from older soils. Pyroclastic materials and local mixing are believed responsible for the higher contents of weatherable minerals in the surface horizons of the profiles. The soils were classified in the 1938 Yearbook system as well as in the Seventh Approximation

Satellite downlink scheduling problem: A case study

The synthetic aperture radar (SAR) technology enables satellites to efficiently acquire high quality images of the Earth surface. This generates significant communication traffic from the satellite to the ground stations, and, thus, image downlinking often becomes the bottleneck in the efficiency of the whole system. In this paper we address the downlink scheduling problem for Canada's Earth observing SAR satellite, RADARSAT-2. Being an applied problem, downlink scheduling is characterised with a number of constraints that make it difficult not only to optimise the schedule but even to produce a feasible solution. We propose a fast schedule generation procedure that abstracts the problem specific constraints and provides a simple interface to optimisation algorithms. By comparing empirically several standard meta-heuristics applied to the problem, we select the most suitable one and show that it is clearly superior to the approach currently in use.Comment: 23 page

Parallel machine scheduling with time windows

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