The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Mitsuru Tsubo - One of the best experts on this subject based on the ideXlab platform.
-
Soil clay content, rainfall, and toposequence positions determining spatial variation in field water availability as estimated by a water balance model for rainfed lowland rice
Crop and Pasture Science, 2012Co-Authors: Thavone Inthavong, Mitsuru Tsubo, Shu FukaiAbstract:Drought is a major limiting factor for the production of rainfed rice in the Mekong Region. Thus, estimation of the length of growing period (LGP) based on estimation of the development of water deficit is essential for sound planning of agricultural development. A recently developed soil-water balance model was used to quantify the availability of water for rice crops and yield reduction due to water deficit. Field water availability is known to be largely affected by soil type and rainfall pattern, and their separate effects were investigated in this study of a spatial analysis of LGP, using inputs for rainfed lowland rice in Savannakhet province in central Laos. The analysis showed that the start of growing period (SGP) and end of growing period (EGP) were affected largely by geographical variations in rainfall and soil clay content, respectively. Also, the areas having relatively short LGP were generally associated with large yield reduction because of low water availability associated with coarse-textured soils. At local scale, field water availability varied from upper to lower positions of a sloping land (toposequence) in the rainfed lowland ecosystem of the Mekong region, causing variation in yield within the toposequence. Using the level of field water determined around flowering time at different toposequence positions in 45 farms, estimated yield reduction was compared in seven main rice-growing districts of the province. Variability of yield loss, associated with variation in water availability, was larger across the toposequence positions than across districts, showing the importance of local variability in determining yield in rainfed lowland rice. The present approach of a combination of simulation model and GIS is adopted for characterisation of the water environment for rainfed lowland rice in other parts of Laos, as well as in neighbouring Thailand and Cambodia.
-
a water balance model for rainfed lowland rice fields emphasising lateral water movement within a toposequence
Ecological Modelling, 2007Co-Authors: Mitsuru Tsubo, Sakuko Fukai, To Phuc TuongAbstract:In the Mekong region, most rice paddies lie in gently sloping lowlands. An accurate estimate of paddy water availability is crucial for modelling rice (Oryza sativa L.) productivity in such environments. However, modelling of water balance in the sloping lowlands can be difficult due to problems in estimating lateral water movement from high to low positions in the toposequence. This paper describes a semi-empirical model for estimating net lateral water flow along a toposequence of rice fields. Net lateral water flow is separated into three sub-components: (i) lateral seepage through the bunds from field to field; (ii) surface runoff over the bunds from field to field; (iii) water run-on from the catchment above the toposequence. The lateral seepage is estimated using the Dupuit equation for steady unconfined flow. Surface runoff over the bund is calculated as excess water depth above the bund height, while run-on from the catchment is calculated using a rainfall–runoff relationship. The other water balance components used in the model are rainfall (measured), paddy evapotranspiration (ET), and downward water flow (within the field and under the bund). Paddy ET is estimated using the FAO crop ET model. The downward water flow is empirically determined for soil texture groups. Simulation results showed that field water levels computed by the model varied between the bund height (maximum) and the hardpan level (minimum). The daily change in the water level was satisfactorily validated using data collected from a field experiment in a toposequence in Cambodia. The component governing the water balance in the higher toposequence positions was the downward water flow (45% of seasonal rainfall at the top of the toposequence). However, the water balance in the lower positions was affected largely by the net lateral water flow (21% of seasonal rainfall at the bottom of the toposequence). Seasonal ET was 67–69% of seasonal rainfall.
-
A water balance model for rainfed lowland rice fields emphasising lateral water movement within a toposequence
Ecological Modelling, 2007Co-Authors: Mitsuru Tsubo, T.p. Tuong, Shu Fukai, Makara OukAbstract:In the Mekong region, most rice paddies lie in gently sloping lowlands. An accurate estimate of paddy water availability is crucial for modelling rice (Oryza sativa L.) productivity in such environments. However, modelling of water balance in the sloping lowlands can be difficult due to problems in estimating lateral water movement from high to low positions in the toposequence. This paper describes a semi-empirical model for estimating net lateral water flow along a toposequence of rice fields. Net lateral water flow is separated into three sub-components: (i) lateral seepage through the bunds from field to field; (ii) surface runoff over the bunds from field to field; (iii) water run-on from the catchment above the toposequence. The lateral seepage is estimated using the Dupuit equation for steady unconfined flow. Surface runoff over the bund is calculated as excess water depth above the bund height, while run-on from the catchment is calculated using a rainfall-runoff relationship. The other water balance components used in the model are rainfall (measured), paddy evapotranspiration (ET), and downward water flow (within the field and under the bund). Paddy ET is estimated using the FAO crop ET model. The downward water flow is empirically determined for soil texture groups. Simulation results showed that field water levels computed by the model varied between the bund height (maximum) and the hardpan level (minimum). The daily change in the water level was satisfactorily validated using data collected from a field experiment in a toposequence in Cambodia. The component governing the water balance in the higher toposequence positions was the downward water flow (45% of seasonal rainfall at the top of the toposequence). However, the water balance in the lower positions was affected largely by the net lateral water flow (21% of seasonal rainfall at the bottom of the toposequence). Seasonal ET was 67-69% of seasonal rainfall. (C) 2007 Elsevier B.V. All rights reserved.
To Phuc Tuong - One of the best experts on this subject based on the ideXlab platform.
-
a water balance model for rainfed lowland rice fields emphasising lateral water movement within a toposequence
Ecological Modelling, 2007Co-Authors: Mitsuru Tsubo, Sakuko Fukai, To Phuc TuongAbstract:In the Mekong region, most rice paddies lie in gently sloping lowlands. An accurate estimate of paddy water availability is crucial for modelling rice (Oryza sativa L.) productivity in such environments. However, modelling of water balance in the sloping lowlands can be difficult due to problems in estimating lateral water movement from high to low positions in the toposequence. This paper describes a semi-empirical model for estimating net lateral water flow along a toposequence of rice fields. Net lateral water flow is separated into three sub-components: (i) lateral seepage through the bunds from field to field; (ii) surface runoff over the bunds from field to field; (iii) water run-on from the catchment above the toposequence. The lateral seepage is estimated using the Dupuit equation for steady unconfined flow. Surface runoff over the bund is calculated as excess water depth above the bund height, while run-on from the catchment is calculated using a rainfall–runoff relationship. The other water balance components used in the model are rainfall (measured), paddy evapotranspiration (ET), and downward water flow (within the field and under the bund). Paddy ET is estimated using the FAO crop ET model. The downward water flow is empirically determined for soil texture groups. Simulation results showed that field water levels computed by the model varied between the bund height (maximum) and the hardpan level (minimum). The daily change in the water level was satisfactorily validated using data collected from a field experiment in a toposequence in Cambodia. The component governing the water balance in the higher toposequence positions was the downward water flow (45% of seasonal rainfall at the top of the toposequence). However, the water balance in the lower positions was affected largely by the net lateral water flow (21% of seasonal rainfall at the bottom of the toposequence). Seasonal ET was 67–69% of seasonal rainfall.
Makara Ouk - One of the best experts on this subject based on the ideXlab platform.
-
A water balance model for rainfed lowland rice fields emphasising lateral water movement within a toposequence
Ecological Modelling, 2007Co-Authors: Mitsuru Tsubo, T.p. Tuong, Shu Fukai, Makara OukAbstract:In the Mekong region, most rice paddies lie in gently sloping lowlands. An accurate estimate of paddy water availability is crucial for modelling rice (Oryza sativa L.) productivity in such environments. However, modelling of water balance in the sloping lowlands can be difficult due to problems in estimating lateral water movement from high to low positions in the toposequence. This paper describes a semi-empirical model for estimating net lateral water flow along a toposequence of rice fields. Net lateral water flow is separated into three sub-components: (i) lateral seepage through the bunds from field to field; (ii) surface runoff over the bunds from field to field; (iii) water run-on from the catchment above the toposequence. The lateral seepage is estimated using the Dupuit equation for steady unconfined flow. Surface runoff over the bund is calculated as excess water depth above the bund height, while run-on from the catchment is calculated using a rainfall-runoff relationship. The other water balance components used in the model are rainfall (measured), paddy evapotranspiration (ET), and downward water flow (within the field and under the bund). Paddy ET is estimated using the FAO crop ET model. The downward water flow is empirically determined for soil texture groups. Simulation results showed that field water levels computed by the model varied between the bund height (maximum) and the hardpan level (minimum). The daily change in the water level was satisfactorily validated using data collected from a field experiment in a toposequence in Cambodia. The component governing the water balance in the higher toposequence positions was the downward water flow (45% of seasonal rainfall at the top of the toposequence). However, the water balance in the lower positions was affected largely by the net lateral water flow (21% of seasonal rainfall at the bottom of the toposequence). Seasonal ET was 67-69% of seasonal rainfall. (C) 2007 Elsevier B.V. All rights reserved.
Yves Bergeron - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal evolution of paludification associated with autogenic and allogenic factors in the black spruce moss boreal forest of quebec canada
Quaternary Research, 2019Co-Authors: Eloise Le Stumboivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three Toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along Toposequences allowed us to understand the spatiotemporal dynamics of paludification and its impacts on the vegetation dynamics over the Holocene.
-
Spatiotemporal evolution of paludification associated with autogenic and allogenic factors in the black spruce–moss boreal forest of Québec, Canada
Quaternary Research, 2019Co-Authors: Éloïse Le Stum-boivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three Toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along Toposequences allowed us to understand the spatiotemporal dynamics of paludification and its impacts on the vegetation dynamics over the Holocene.
T.p. Tuong - One of the best experts on this subject based on the ideXlab platform.
-
The effect of toposequence position on soil properties, hydrology, and yield of rainfed lowland rice in Southeast Asia
Field Crops Research, 2008Co-Authors: A.a. Boling, T.p. Tuong, H. Suganda, Y. Konboon, Dome Harnpichitvitaya, Bas A. M. Bouman, D.t. FrancoAbstract:Abstract A large proportion of rainfed lowland rice in Southeast Asia is grown in gently sloping areas along Toposequences with differences in elevation of a few meters. These small differences in elevation can lead to differentiation in soil properties and hydrological conditions, which in turn may affect crop performance and yield. It may be appropriate to replace blanket crop management recommendations in rainfed areas with toposequence-specific management recommendations. However, thorough statistical analyses of the relationships between toposequence position and field and crop conditions are lacking. In this paper, we statistically analysed the effect of toposequence position on soil properties, hydrological conditions, yield, and yield increase due to weed control and/or fertilizer management in rainfed areas in four villages in Indonesia and Thailand each in 2000–2002. Differences were substantial in field hydrology (average depth of ponded surface water and of groundwater, number of days without ponded surface water), exchangeable K, organic C, and clay content depending on toposequence position. There were also differences in other soil properties, including N, P, CEC, pH, sand, silt, bulk density, yield, and the magnitude of yield increase due to intensive weed control and/or recommended fertilizer application, but these effects were not consistent across countries, seasons, and years. The hypothesis that toposequence position would be a useful recommendation domain for weed control and fertilizer recommendations was not supported by our statistical results. The reasons why toposequence position has an inconsistent statistical effect could be (1) that the variability of the field conditions is larger among villages than among toposequence positions, and/or (2) that farmers already respond to differences in field conditions in their prevalent management practices, thus masking the effects of toposequence-specific variation on yield. Our findings suggest that despite the large toposequence effects on soil nutrient and water availability, weed and fertilizer management recommendations should be field-specific and time-specific rather than toposequence-specific.
-
A water balance model for rainfed lowland rice fields emphasising lateral water movement within a toposequence
Ecological Modelling, 2007Co-Authors: Mitsuru Tsubo, T.p. Tuong, Shu Fukai, Makara OukAbstract:In the Mekong region, most rice paddies lie in gently sloping lowlands. An accurate estimate of paddy water availability is crucial for modelling rice (Oryza sativa L.) productivity in such environments. However, modelling of water balance in the sloping lowlands can be difficult due to problems in estimating lateral water movement from high to low positions in the toposequence. This paper describes a semi-empirical model for estimating net lateral water flow along a toposequence of rice fields. Net lateral water flow is separated into three sub-components: (i) lateral seepage through the bunds from field to field; (ii) surface runoff over the bunds from field to field; (iii) water run-on from the catchment above the toposequence. The lateral seepage is estimated using the Dupuit equation for steady unconfined flow. Surface runoff over the bund is calculated as excess water depth above the bund height, while run-on from the catchment is calculated using a rainfall-runoff relationship. The other water balance components used in the model are rainfall (measured), paddy evapotranspiration (ET), and downward water flow (within the field and under the bund). Paddy ET is estimated using the FAO crop ET model. The downward water flow is empirically determined for soil texture groups. Simulation results showed that field water levels computed by the model varied between the bund height (maximum) and the hardpan level (minimum). The daily change in the water level was satisfactorily validated using data collected from a field experiment in a toposequence in Cambodia. The component governing the water balance in the higher toposequence positions was the downward water flow (45% of seasonal rainfall at the top of the toposequence). However, the water balance in the lower positions was affected largely by the net lateral water flow (21% of seasonal rainfall at the bottom of the toposequence). Seasonal ET was 67-69% of seasonal rainfall. (C) 2007 Elsevier B.V. All rights reserved.