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Bacterial pathogens in surface waters may threaten human health, especially in developing countries, where untreated surface water is often used for domestic needs. The objective of the long-term multiscale monitoring of Escherichia coli ([E. coli]) concentration in stream water, and that of associated variables (temperature (T), electrical conductance (EC), dissolved oxygen concentration ([DO]) and saturation (DO%), pH (pH), oxidation-reduction potential (ORP), turbidity (Turb), and total suspended sediment concentration ([TSS])), was to identify the drivers of bacterial dissemination across tropical catchments. This data description paper presents three datasets (see “Data availability” section) collected at 31 sampling stations located within the Mekong River and its tributaries in Lao PDR (0.6–25 946 km2) from 2011 to 2021. The 1602 records have been used to describe the hydrological processes driving in-stream E. coli concentration during flood events, to understand the land-use impact on bacterial dissemination on small and large catchment scales, to relate stream water quality and diarrhea outbreaks, and to build numerical models. The database may be further used, e.g., to interpret new variables measured in the monitored catchments, or to map the health risk posed by fecal pathogens.

Mục tiêu nghiên cứu: Xác định tỷ lệ và phân tích các yếu tố liên quan đến tỷ lệ nhẹ cân theo tuổi thai ở sản phụ có chẩn đoán tiền sản giật tại Bệnh viện Từ Dũ trong giai đoạn 2019 – 2021. Phương pháp nghiên cứu: Thiết kế nghiên cứu dọc hồi cứu khảo sát 386 hồ sơ bệnh án của sản phụ được chẩn đoán tiền sản giật. Nghiên cứu sử dụng công cụ INTERGROWTH-21 để khảo sát trẻ sinh nhẹ cân theo tuổi thai ở các trường hợp có tiền sản giật với tiêu chuẩn Z-score < -1 hoặc centile < 10th. Kết quả: Qua khảo sát có 87 trường hợp trẻ sinh ra nhẹ cân so với tuổi thai chiếm 22,5% (KTC 95%: 18,4 - 26,9). Sản phụ được chẩn đoán thai chậm tăng trưởng trên siêu âm tăng nguy cơ nhẹ cân so với tuổi thai gấp 28,1 lần (OR=28,1; KTC95%: 11,4 - 69,1). Sản phụ tăng acid Uric tăng nguy cơ nhẹ cân theo tuổi thai so tuổi thai gấp 2,3 lần (OR=2,3; KTC95%: 1,2 - 4,8). Sản phụ tăng ALT ≥ 50 U/L tăng nguy cơ trẻ nhẹ cân theo tuổi thai gấp 8,1 lần (OR=8,1;KTC95%:1,9 – 33,0). Sản phụ giảm HCT

A field experiment was conducted during the rainy season of 2014, in the steeply sloping agricultural land of northern Laos to determine the factors that cause the generation of surface runoff wate...

Bacterial pathogens in surface waters may threaten human health, especially in developing countries, where untreated surface water is often used for domestic needs. The objective of the long-term multiscale monitoring of Escherichia coli concentration in stream water, and that of associated variables (temperature, electrical conductance, dissolved oxygen concentration and saturation, pH, oxidation-reduction potential, turbidity, and total suspended sediment concentration), was to identify the drivers of bacterial dissemination across tropical catchments. This data description paper presents three datasets (see section Data availability) collected at 31 sampling stations located within the Mekong river and its tributaries in Lao PDR (0.6–25,946 km2) from 2011 to 2021. The 1,602 records have been used to describe the hydrological processes driving in-stream Escherichia coli concentration during flood events, to understand land-use impact on bacterial dissemination on small and large catchment scales, to relate stream water quality and diarrhea outbreaks, and to build numerical models. The database may be further used e.g. to interpret new variables measured in the monitored catchments, or to map the health risk posed by fecal pathogens.

Bacterial pathogens in surface waters may threaten human health, especially in developing countries, where untreated surface water is often used for domestic needs. The objective of the long-term multiscale monitoring of Escherichia coli ([E. coli]) concentration in stream water, and that of associated variables (temperature (T), electrical conductance (EC), dissolved oxygen concentration ([DO]) and saturation (DO%), pH (pH), oxidation-reduction potential (ORP), turbidity (Turb), and total suspended sediment concentration ([TSS])), was to identify the drivers of bacterial dissemination across tropical catchments. This data description paper presents three datasets (see “Data availability” section) collected at 31 sampling stations located within the Mekong River and its tributaries in Lao PDR (0.6–25 946 km2) from 2011 to 2021. The 1602 records have been used to describe the hydrological processes driving in-stream E. coli concentration during flood events, to understand the land-use impact on bacterial dissemination on small and large catchment scales, to relate stream water quality and diarrhea outbreaks, and to build numerical models. The database may be further used, e.g., to interpret new variables measured in the monitored catchments, or to map the health risk posed by fecal pathogens.

During a 2005 visit with National Agricultural and Forestry Institute (NAFRI) Director, Dr. Kouang Doungsila issued a challenge to these authors to determine if it was true that crops could not be grown in the extensive uplands of Xiengkhouang Province, Laos PDR. In response, a two-phase series of experiments was proposed and implemented. The Phase I experiment was to bring soil from the Xiengkhouang province uplands to a NAFRI greenhouse near Vientiane to assess possible nutrient requirements using a nutrient omission experiment. Simultaneously, soils were collected and analyzed from seven recognized agricultural regions of Laos. The initial Vientiane greenhouse experiment indicated that maize did grow, but there were multiple issues of extreme soil acidity and clear deficiencies of phosphorus and other nutrients. Phase II of the study included field studies on the site of soil selected for the greenhouse study. Field experiments were carried out for two years at the site with yields of maize exceeding 5500 kg⋅ha−1 in the first year and exceeding 6250 kg⋅ha−1 in a subsequent year. Intense symptoms of nutrient zinc (Zn) deficiency were observed, however. In 2008 another experiment was designed and carried out that included a Zn variable. The results from that experiment confirmed that maize yields nearing 6000 kg⋅ha−1 were indeed possible. Substantial amounts of lime were needed to correct the strong soil acidity, and a series of other nutrients including N, P, K, and Zn were also required. Ongoing issues are where to obtain the extensive amounts of limestone needed as well as an evaluation of the residual effect of the limestone The finely ground, very reactive burnt lime residual effect was, as expected, short-lived. The results clearly demonstrated that, indeed, it was possible for maize to be produced in the extensive uplands of Xiengkhouang province, in answer to Director Khouang’s challenging question.

Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m2) and small catchment (0.6 km2) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to e.g. assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g. contaminants other than fecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.

International audience; Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m2) and small catchment (0.6 km2) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to e.g. assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g. contaminants other than fecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.

Rainfed rice production in Lao PDR is critical to national food security; under traditional transplanting methods farmers are exposed to climate risks at both the onset and the conclusion of the wet season. Production of the annual crop has a high labour requirement especially during transplanting and harvesting. We engaged with smallholder farmers to investigate the feasibility of one form of dry seeding of rice, i.e. mechanised dry drill seeding, which in this paper we refer to as “dry seeding”. We hypothesised that dry seeded rice crops will be established earlier in the wet season and will produce a comparable yield while requiring less water and labour than transplanted rice. Field trials, supported by scenario modelling using the APSIM model, indicated average dry seeded rice yields are comparable to average transplanted yields over the longer term but with reduced risk of crop failure, under both current (1971–2011) and near-future (2021–2040) climates, for two common soil types. Net overall labour savings reduce the cost of rice production under mechanised dry seeding, better positioning households against fluctuations in labour costs and rice prices. Mechanised dry seeding requires different crop management to traditional methods and will not be appropriate for all farmers. Performance of DSR under future climate scenarios is projected to be as good as or better than under current climate conditions.

Rice is the most important agricultural commodity of the Lao People's Democratic Republic (Lao PDR), produced largely using traditional methods with limited inputs of fertilizers and other chemicals. The country has a wide diversity in rice production systems and rice varieties, with over 3000 different varieties recorded. The rich diversity and the production environment and methods are favorable for organic rice production. Investigations were carried out to describe soil fertility conditions, management practices, opportunities and problems associated with organic production methods for rice. Soils used for rice production are mostly of low fertility, with low organic matter and N-availability. In spite of this, virtually no fertilizer inputs are used for upland rice production. Inorganic fertilizer inputs for lowland rice production have increased rapidly over the past decade, but are still below 20 kg ha−1. The most important nutrient sources are rice straw and manure from buffalo and cattle. Chromolaena odorata plays an important role in nutrient cycling in upland rice systems and is sometimes added to lowland fields. In a range of fertility management studies, yield increase ranged from 2 to 89% for manure, straw or rice husk applied at modest rates (3 t ha−1), 32–156% for modest rates of inorganic fertilizer (60 kg N ha−1) and 36–167% for combined application of manure or crop residues with inorganic fertilizer. The response to locally produced commercial organic fertilizer was poor. The most promising inputs and strategies available to optimize yields in organic rice production systems are (1) optimizing use of locally available nutrients, mostly from manure, crop residues and weed biomass, (2) N addition through green manure and legumes growing in rotation and (3) additions of P through guano or rock-phosphate. The Lao PDR is fortunate to have substantial bat guano deposits in limestone caves. Extensive experience is available on straw and husk management for lowland systems and green manure species for upland production systems.

In the Lao People’s Democratic Republic (PDR), increasing food security remains a challenge since smallholder agricultural systems, which are the main source of food production, are under serious threat due to poor soil fertility and climate variability. This study was undertaken in Lao PDR to investigate the impacts of organic and clay-based soil amendments on maize yield, total nutrient uptake, and soil properties. Structured field experiments were established over two consecutive years (2011 and 2012) with maize as the test crop at the Veunkham and Naphok sites. Ten treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (applied at a rate of 10 t ha−1), bentonite clay (10 t ha−1), compost (4 t ha−1), clay-manure compost (10 t ha−1), rice husk biochar compost (10 t ha−1), and their combinations. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in maize grain yields, total nutrient uptake, and soil...

Soils used for cropping of rainfed lowland rice are frequently rather poor, and nutrient limitation is known to be a major constraint for grain yields. However, actual fertilizer use by most rainfed rice farmers is still very low even if input-responsive rice varieties are widely adopted. To address this contradiction, this study, conducted in central and southern Laos, intended to test existing fertilizer recommendations in farmers’ fields and under their crop management, to evaluate the effect of topographic field position on fertilizer response, and to conduct an economic evaluation of fertilizer use based on farmers’ input and output prices. Trials were conducted for two seasons in three different agroecological environments (rainfed rice in lower fields and in middle/upper fields, and irrigated rice in lower fields). Tested were five different fertilizer treatments in four farmers’ fields per site and season. Commercial organic fertilizer increased yields but resulted in negative economic returns in almost all cases because of its unfavorable nutrient/price ratio. In lower fields, farmyard manure and inorganic fertilizer gave good yield responses and positive economic returns but the average value/cost ratios of 1.3–1.6 were at the lowest level required for widespread adoption of fertilizer use. Water limitation reduced attainable yields in middle/upper fields and in this environment good fertilizer response was observed only for farmyard manure and half the recommended rate of inorganic fertilizer. The actual benefit of fertilizer use depended strongly on the input/output price ratios at each site. Thus, site-specific fertilizer management options, including economic parameters, are required to make fertilizer use in rainfed lowland rice more profitable. The necessary information for such guidelines is available but needs to be prepared in the form of decision tools to help farmers choose the optimal nutrient management option for their agroecological and socioeconomic production environment.

Lowland rice in Laos as in some other SE Asian countries is grown mostly under rainfed conditions in wet season (WS), but some crops are grown under irrigated conditions in dry season (DS). In Laos, the rice breeding program is concentrating on development of photoperiod insensitive varieties which can be grown in both WS and DS, nevertheless most selection is conducted in WS. In order to determine consistency of genotypic performance between WS and DS, 23 advanced breeding lines and varieties were grown in both seasons for 2–3 years at four locations in the country. All experiments in DS showed significant genotypic variation for grain yield, while genotypic variation was smaller and often not significant in each experiment in WS. The heritability was also higher in DS than in WS. Significant genotype-by-environment interaction was found, and some of this interaction was due to long duration genotypes being affected by extreme temperature conditions in DS particularly at a high altitude location in Northern Laos. Cluster analyses indicate that the genotypic discrimination was large in experiments with intermediate yield levels (mean yield of 2.9–3.8 t/ha). It is concluded that the use of DS trials should be increased to improve the efficiency of selection for widely adapted varieties in the lowland rice breeding program in Laos and other countries of similar growing conditions.

Rice is a major source of food for more than 2.7 billion people and planted on nearly 130 million hectares in which 10% is subjected to low temperature problems. Dry season (DS) rice cropping has been expanding in the high altitude lands in Asia and the low temperature is one of constraints to rice production. This study aims to quantify the potential for growing irrigated rice in DS, particularly in high altitude areas in northern Lao PDR where temperatures are low and pose problems for seedling establishment. Research focused on identifying sowing times to avoid the detrimental effects of low temperature, the optimal seedling age for transplanting, the potential of plastic covers and half burnt paddy husk layer to protect nursery seedbeds from low temperature and varieties suitable for this environment. Studies were conducted over 5 years and were examined at six locations. In two locations, where temperature was favorable for rice production throughout the DS, time of sowing was not critical. In higher altitude areas in northern Lao PDR, however, low temperature caused establishment problems in nurseries. In these areas, mid-November sowing before the onset of winter reduced the low temperature effects on seedling establishment while sowing in mid winter (December and January) increased the risk of failure. There were no significant effects of seedling age (25-, 35- and 45-day old) for transplanting on yield for DS rice. Using clear plastic to cover the nursery increased minimum temperatures on average by about 4 degrees C, which improved seedling growth and resulted in higher grain yield. The mean minimum temperature of 12 degrees C for 30 days after seeding is critical and temperature below 12 degrees C resulted in high risk of crop failure due to poor germination, poor seedling growth or insufficient seedlings. Rice needs to be sown at times where the mean minimum temperature exceeds 12 degrees C or plastic covers are required to protect seedlings. The current popular varieties did not show significant tolerance to extreme cold temperature. (c) 2007 Published by Elsevier B.V.

In the Mekong region, most paddies in rainfed lowland rice (Oryza sativa L.) lie in a sequence on gentle sloping land, and grain yield (GY) often depends on the toposequence position. There is, however, lack of information on toposequential effects on field water supply in rainfed lowland rice and how that influences GY. A total of eight field experiments were carried out on sandy, coarse-textured soils in Southern Laos (Champassak Province and Savannakhet Province) over three wet seasons (2000-2002). Components of the water balance, including downward and lateral water movement (D and L, respectively), were quantified at three different positions along toposequences (top, middle and bottom). GY, days-to-flower (DTF) and rainfall were measured, and the water productivity (WP) was determined. In most experiments, standing water disappeared first in the top position and gradually in lower positions. This was associated with the observation that when there was standing water in the field, the higher position had larger D in both the provinces and also larger L in Champassak Province. However, in one experiment, water loss appeared later in the higher position, as the result of lower L, apparently due to some water inputs other than rainfall occurring at this position. Despite larger D plus L at the top position, seasonal sum of D and L were not much affected by the toposequence position, as the daily rate of D plus L became minimal when the standing water was lost earlier in the top position. Lower GY was associated with earlier disappearance of standing water from the field. Relatively low GY was expected in the top toposequence position. This was clearly shown in the toposequence of Phonthong, Champassak Province, as the timing of standing water disappearance relative to flowering was earlier in the top position. Variation in GY across the toposequence positions was coupled with the WP variation, and both GY and WP tended to decline with increased DTF. Therefore, variation in productivity of rainfed lowland rice across toposequence positions depends mainly on the field water status around flowering time. (c) 2005 Elsevier B.V. All rights reserved.

The rate of fertiliser application to rainfed lowland rice is commonly low while selection in breeding programs is conducted under well-fertilised conditions. The appropriateness of applying fertiliser in a rainfed lowland rice breeding program at a rate above the average farmers' rate was examined in Laos. Experiments were conducted at three locations in 2 years using 72-60 genotypes most of which were typical materials used in the Lao breeding program. The fertiliser rates were nil and 60N : 13P : 16K kg ha(-1). The effect of fertiliser application was significant in most experiments, but the response to fertiliser depended on location, There was often significant genotype-by-environment interaction for grain yield in individual experiments. There was also significant correlation for grain yield between fertilised and non-fertilised conditions, with coefficients of determination (R-2) of 0.45 and 0.54 in the 2 years, for combined results of three locations. Combined analyses of grain yield from three locations indicate that for either year the variance component for the genotype-by-fertiliser interaction was smaller than for genotype. The coefficient of variation for grain yield was often smaller under fertilised compared with non-fertilised conditions. These findings as well as the rapidly increasing use of fertiliser justify the level of fertiliser currently applied in the Lao breeding program, The significant genotype-by-location interaction requires that for an effective breeding program, locations be selected to represent farmers' fields. (C) 2000 Elsevier Science B.V. All rights reserved.

A large number of rainfed lowland rice genotypes were grown under two fertiliser conditions to identify whether a genotype's ability to extract more nutrients or to use absorbed nutrients more efficiently to produce grain yield was more important in determining genotypic variation in grain yield. From the yield responses of lines to fertiliser application, 16 contrasting lines were selected, and dry matter and nutrient (N, P and K) contents were determined for grain and straw separately for crops grown under non-fertilised and fertilised (60-13-16 N-P-K kg ha(-1)) conditions at three locations in Laos. There were significant effects of both genotype and genotype-by-fertiliser interaction for grain yield, which were closely associated with total N and P content at maturity. There was, however, also significant genotypic variation in nutrient-use efficiency (grain yield per unit nutrient absorbed), and this also contributed to the genotypic variation for grain yield. There was a large effect of genotype and a smaller effect of genotype-by-location interaction for nitrogen-use efficiency for grain yield. Nitrogen-use efficiency was negatively correlated with grain N concentration at two of the three locations. Both N- and P-use efficiency were consistent across fertiliser levels, and hence are likely to be used as selection criteria. The work also indicates that genotypes with high harvest index (HI) are likely to perform well in different fertility conditions. (C) 2000 Elsevier Science B.V. All rights reserved.

The paper presents the design of PID controllers for a two-link SCARA robot based on internal model control (IMC) technique. For the model of the two-link SCARA robot which includes an integrator, IMC filter must be selected properly so that the designed IMC controllers can be approximated as PID controllers by using Maclaurin approximation. The simulation results verify the applicability and satisfied performance of the proposed control system.

Lowland rice in Lao PDR is predominantly grown under drought-prone, rainfed conditions in the wet season. We utilised a farmer participatory variety selection (PVS) approach in combination with multi-location yield trials (MLTs) conducted in high- and low-toposequence positions to test advanced breeding lines with the aim of improving the efficiency of the rice-breeding program and encouraging rapid adoption of improved lines. Upper position fields were utilised to screen for traits for unfavourable environments, including drought resistance, while lower fields were used to target yield potential. Yield was, on average, 13% lower in upper than lower (2.85 t/ha) field positions, and varieties adapted to high-toposequence position were identified. Farmer preference was not associated well with grain yield performance, with a significant positive relationship (r = 0.34*, n = 23) identified only in the Vientiane (VTN) low-toposequence trial; rather, the famers tended to choose lines they believed were best adapted to their own farm. Although a significant relationship existed for both farmer preference (r = 0.42*, n = 23) and grain yield (r = 0.50*, n = 23) in high and low toposequences across all provinces in 2010, this relationship was not significant in VTN, where the high position was low-yielding (1.2 t/ha). By utilising farmer preference information in combination with traditional MLT data, only lines agronomically acceptable to farmers were progressed into a seed-multiplication system for country-wide, farmer yield testing. Thus, the PVS-MLT approach has provided efficient delivery of highly acceptable lines to farmers, which directly contributes to improved efficiency of the rice-breeding program.

Early attempts to apply N models and decision aids for maize were not successful when predictions far exceeded field-determined N requirements. One hypothesis for the overprediction was that residual nitrate could be accumulating in the dry off-season and that maize rooted sufficiently deeply to use this nitrate. However, there was a lack of information on the content of subsoil nitrate and the distribution of maize roots with depth. Field experiments were conducted in sites of the Lop Buri (Lb) and Pak Chong (Pc) soil series, which are two of the most representative soils of the maize-producing region of Thailand. Subsoil nitrate-N (NO3 j -N) was measured before and after maize was grown; NO3 j -N status was assessed after heavy rains occurred and maize root distributions were measured. Subsoil NO3 j -N levels at the two sites increased with increasing N rate. Before maize was planted maximum levels of NO3 j -N were found at the 20- to 40-cm and 0- to 20-cm depths of Lb and Pc soils, respectively. Subsoil NO3 j -N declined at both sites after maize was more than 40 days old. Nitrate-N status was not significantly different between different depths; however, the maximum NO3 j -N levels in Lb and Pc soils were found at 40- to 60- and 20- to 40-cm depths, respectively. At 40 days after emergence, maize roots were more voluminous in the 49- to 62- and 43- to 50-cm depths for the Lb and Pc sites, respectively; roots clearly grew into the soil zones where NO3 j -N was high. It is probable that N availability from subsoil NO3 j -N diminished the fertilizer N requirement of maize. These results support the hypothesis that failure to include subsoil NO3 j -N concentrations in the decision aids led to the overprediction of N fertilizer needs, which had been predicted solely from surface NO3 j -N levels. In retrospect, a comparison of soil taxonomic classifications would have suggested the possible importance of including subsoil nitrate in the decision aids. (Soil Science 2007;172:861‐875)