No description available.

Originally presented as the author's thesis, Wageningen. / Includes bibliographical references (p. 112-117).

Proefschrift--Rijksuniversiteit. / "Stellingen" (1 leaf) inserted. Bibliography: p. [154]-159.

Proefschrift--Rijksuniversiteit. / "Stellingen" (1 leaf) inserted. Bibliography: p. [154]-159.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 37-38).

[Various reprints] / Lacks title page and contents / 3 v. : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, 1948

No description available.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 73-75).

It has been established that the impact of arsenic in irrigated agriculture has become a major environmental concern in Bangladesh. However, to date there is still a limited understanding of arsenic in Bangladeshi paddy soils at a landscape level. Besides, there is no data available for soil arsenic on its geographical distribution, geomorphic variations, and biogeochemical relationships across the landscape. In the present study, paddy (n = 1209) and adjacent nonpaddy (n = 235) soil samples across 10 different physiographic regions, comprising the Holocene floodplains and Pleistocene terraces, were collected, and analysed for arsenic and a suite of 16 other elements. The collected paddy soils were from fields irrigated with groundwater (n = 904) and surface waters (n = 281). Additionally, the soils could be categorised into 6 inundation land types. A set of 30 paddy soil samples from 6 physiographic regions were also studied using the diffusive gradients in thin-films (DGT) to assess the porewater dynamics of arsenic, and other geochemical elements in the soils. The paddy soils had generally 60 percent more arsenic than the matching non-paddy soils, perhaps due to the use of arsenic contaminated groundwater for paddy irrigation. Compared to the groundwater irrigated paddy soils, the surface water irrigated paddy soils had lower arsenic concentrations, but higher concentrations of most of the other elements. Within the topologically different inundation land types, the concentrations of arsenic and other elements, including the toxic metals, were found to be elevated in more deeply and prolonged flooded low-lying soils. The soils in the different physiographic regions had variability in arsenic concentrations as well as in their indigenous biogeochemical characteristics. The inherent concentrations and variability in arsenic and most other elements, including nutrients, were greater in the Holocene floodplain soils compared to the Pleistocene terrace soils. Paddy soils in Bangladesh have a high potential for arsenic resupply from soil solid phase to soil solution phase. In the physiographically different soils across the landscape, there is less difference in nutrient/ toxin bioavailability in the paddy soils than might be predicted based solely on the total concentrations in the soils. Therefore, distinctions of soils based just on total concentrations are perhaps misleading, particularly, when elements mobility under reducing paddy environment is concerned. While the bioavailable/ phytoavailable fractions of the elements in soils are of major concern with respect to the uptake by the growing plants, it is of utmost importance to consider the labile concentrations of elements in soil solution rather than the soil total concentrations. The present study substantiates that arsenic is simply associated with less well weathered/ leached soils and sediments, suggesting that it was either due to the geological newness of Holocene sediments or differences between the sources of sediments that gave rise to the arsenic problems in soils of Bangladesh. The inherent biogeochemical variability along with the complexity of the nature and properties of the soils at local and regional levels across the landscape of the dynamic sedimentary depositional environment in Bangladesh should be considered, in any future research on arsenic in the soil-water-crop systems in Bangladesh environment.

A study of the soils and soil capability classification for forestry of the Mission Tree Farm Licence No. 26 was carried out. The soil survey and soil chemical analyses were done in cooperation with the British Columbia Department of Agriculture, Soils Division, Kelowna, B. C. The purposes of the study were: to characterize the soils found in Compartment One, to determine the forest capability of these soils, to recommend management practices for these soils for forestry purposes, and to compare soil mapping at scales of 1:12,000, 1:15,840, 1:31,680, and 1:63,360. Fourteen soil series were recognized and used as criteria for the mapping units in this area. Ten soil series were established, described, and chemically characterized. Although the soil series could be morphologically recognized in the field, the chemical analyses exhibited very little characteristic differences among the series. Vegetation could not be used consistently as criteria for differentiating among the various mapping units. Landform was the chief aid in establishing the extent of the soil mapping units. Each soil series was rated for capability to produce commercial forest growth. The major tree species involved were western hemlock, Douglas-fir, and western red cedar. The soils were evaluated for forest management practices including, reforestation, road building, erodibility, logging practices, and species adaptation to specific soils. Four scales of mapping were compared and discussed in relation to their uses for specific purposes. For an area such as Compartment One on which good forest management is being practiced, mapping at the scale of 1:15,840 was ideal. / Land and Food Systems, Faculty of / Graduate