No description available.

published_or_final_version / Comparative Asian Studies / Master / Master of Arts

A field survey was conducted in eight villages in Northeastern Thailand to examine the impact of non-farm employment on rice production during the 1994-95 crop year. This study uses the human ecology approach based on the conceptual framework of Duncan's (1959) ecological complex. This study found that participation in non-farm employment directly affects whether the household will produce rice, but its impacts vary according to the extent of participation. Full-time employment, particularly with the yearlong absence of the male head of household, appears to inhibit rice production because it has the potential to cause a critical farm labor shortage. Part-time employment creates opportunities for farmers to integrate both farm and non-farm production to sustain their households. Women and elders have become the principal labor source for their own farms and waged labor for others. The traditional pattern of exchange labor can hardly be practiced when the demand for hired labor exceeds the supply. Waged laborers receive the same pay regardless of age and gender, and employers have no control over the wage rate. The use of machines is increasing. The supply of threshers exceeds demand, but there is a shortage of power-tillers. / However, non-farm employment does not lead to increased levels of farm investment as hypothesized, because a large proportion of waged income was used for other purposes, including daily consumption and debt repayment. Consequently, there is no significant difference in farm productivity (kg. of paddy/unit area) between households with and without participation in non-farm employment. Out-migration to participate in non-farm employment seems inevitable in the face of population growth and land scarcity, but its impacts on rice production vary according to how farmers adapt to the changing resource base and use of modern farm technology. If possible, farmers tend to continue farm and non-farm employment to distribute their risks. However, it is crucial to retain a balance between the types of employment so that the loss of labor does not lead to poor farm productivity nor to production costs that exceed the farm household's means.

The Mae Tao watershed, northwestern Thailand, has become contaminated with cadmium (Cd) from the zinc mining activities area in the nearby Thanon-Thongchai mountains. Consumption of Cd-contaminated rice has led to documented human health impacts. The aim of this study was to clarify transfer pathways from creek and canal waters to the paddy field soils near Baan Mae Tao Mai village and to determine the relationship between Cd forms in the soil and uptake by rice plants. Soils, irrigation canal sediments and water samples were collected during the dry season and at the onset of the rainy season. Rice samples were collected at harvesting time and samples of soil fertiliser were also obtained. Water samples were filtered, ultrafiltered and analysed by ICP-MS whilst sub-samples of dried, ground soils and sediments were first subjected to micro-wave assisted acid digestion (modified US EPA method 3052). XPRD and SEM-EDX methods were used for mineralogical characterisation and selective chemical extractions have assisted in the characterisation of solid phase Cd associations. Transfer mainly occurred in association with particulate matter during flooding and channel dredging and, in contrast with many other studies, most of the soil Cd was associated with exchangeable and carbonate-bound fractions. Moreover, there was a significant positive relationship between soil total Cd and rice grain Cd (R2=0.715), but a stronger relationship between both the Tessier-exchangeable soil Cd and the BCR-exchangeable soil Cd and rice grain Cd (R2=0.895 and 0.861, respectively). Stable Isotope Exchange (gives isotopically exchangeable Cd - E value) is generally considered to provide a better measure of bioavailability. The results of this study showed that SIE gave values which significantly positive correlated with the Tessier exchangeable fraction. Biochar has a porous structure and acidic functional groups on its surface which give it a high capacity to affect heavy metal adsorption when added to soils. Biochar samples were produced from rice husk (RHC) and miscanthus (MC) since these are cheap and readily available materials in Thailand. Indeed rice husk char is already used for rice seed germination by local farmers. Evaluation of the chemical and physical properties of the chars showed that the lower temperature (350°C) chars had greater proportions of oxygen-containing functional groups than those produced at 700°C. Moreover the low temperature RHC had the greater cation exchange capacity than the MC produced at the same temperature. In abiotic feasibility tests, it was shown that RHC was more effective than MC at lowering soil available Cd. The former reduced the E values for the medium-Cd soils by 4.7% and 16.0% when 1% and 5% RHC, was added, respectively. From pot experiments, in medium-Cd soils, 1% and 5% RHC amendment showed the potential to decrease Cd uptake by rice roots. However, further work involving addition of a greater proportion of biochar with a higher number of replicates is needed to reach more robust conclusions.