The available soil water capacity (ASWC) is important for studying crop production, agro-ecological zoning, irrigation planning, and land cover changes. Laboratory determined data of ASWC are often not available for m...The available soil water capacity (ASWC) is important for studying crop production, agro-ecological zoning, irrigation planning, and land cover changes. Laboratory determined data of ASWC are often not available for most of soil profiles and the nationwide ASWC largely remains lacking in relevant soil data in China. This work was to estimate ASWC based on physical and chemical properties and analyze the spatial distribution of ASWC in China. The pedo-transfer functions (PTFs), derived from 220 survey data of ASWC, and the empirical data of ASWC based on soil texture were applied to quantify the ASWC. GIS technology was used to develop a spatial file of ASWC in China and the spatial distribution of ASWC was also analyzed. The results showed the value of ASWC ranges from 15 × 10-2 cm3·cm-3 to 22 × 10-2 cm3·cm-3 for most soil types, and few soil types are lower than 15 × 10-2 cm3·cm-3 or higher than 22 × 10-2 cm3·cm-3. The ASWC is different according to the complex soil types and their distribution. It is higher in the east than that in the west, and the values reduce from south to north except the northeastern part of China. The "high" values of ASWC appear in southeast, northeastern mountain regions and Northeast China Plain. The relatively "high" values of ASWC appear in Sichuan basin, Huang-Huai-Hai plain and the east of Inner Mongolia. The relatively "low" values are distributed in the west and the Loess Plateau of China. The "very low" value regions are the northern Tibetan Plateau and the desertified areas in northern China. In some regions, the ASWC changes according to the complex topography and different types of soils. Though there remains precision limitation, the spatial data of ASWC derived from this study are improved on current data files of soil water retention properties for Chinese soils. This study presents basic data and analysis methods for estimation and evaluation of ASWC in China.展开更多
With six packed columns composed of < 1 μm and 5 μm～0.25 mm fractions from an Eum-Orthic An- throsol (Columns 1～6) and one column of the Eum-Orthic Anthrosol (Column 7), K～(+) transport experiments under the c...With six packed columns composed of < 1 μm and 5 μm～0.25 mm fractions from an Eum-Orthic An- throsol (Columns 1～6) and one column of the Eum-Orthic Anthrosol (Column 7), K～(+) transport experiments under the condition of saturated steady water flow were conducted to qualify the effects of soil texture com- position on the retardation factor (R) of K～(+) transport. The results showed that the retardation factor of K～ (+) transport in the tested soil columns greatly increased with increasing clay contents. In an attempt to use pedo-transfer function (PTF) approach in the solute transport study, a preliminary PTF was established through the six packed columns (Columns 1～6) with soil basic data including soil bulk density, volumet- ric water content and clay content to predict the retardation factor, and proved valid by the satisfactory prediction of R in Column 7.展开更多
Parameters of water retention and air capacity are important factors for the evaluation of soil material that will be used for vegetative covers or evapotranspiration (ET) covers of landfills. These values are often m...Parameters of water retention and air capacity are important factors for the evaluation of soil material that will be used for vegetative covers or evapotranspiration (ET) covers of landfills. These values are often measured in the laboratory (usually on disturbed samples), but are also estimated from texture, organic matter content and dry bulk density. The standard basis for the estimation in Germany is the German Soil Classification Handbook (KA5). This estimation implicitly assumes that the data in the KA5 compiled from naturally developed soils are also valid for artificially compacted materials. In the present study, 25 materials were evaluated in the laboratory for the available water capacity, air capacity and permanent wilting point at 85%, 90% and 95% of Proctor density. The data were compared with parameter estimations from the KA5 and the program ROSETTA. Both estimation methods show significant deviations from the measured values;specifically, the change in the available water capacity in compressed samples is not estimated correctly. A possible explanation is a change in pore structure at different compaction levels of build in soil material in comparison with naturally developed soils of different bulk densities.展开更多
Estimation of the plant-available water capacity(PAWC)of soils at a regional scale helps in adopting better land use planning,developing suitable irrigation schedules for crops,and optimizing the use of scarce water r...Estimation of the plant-available water capacity(PAWC)of soils at a regional scale helps in adopting better land use planning,developing suitable irrigation schedules for crops,and optimizing the use of scarce water resources.In the current study,72 soil profiles were sampled from the Barossa region of South Australia to estimate pedo-transfer functions deduced from easily estimated soil properties.These functions were then used to estimate the fixed(10 and 33 kPa)and dynamic pressure head(h_(fc))water contents at field capacity(FC)for minimum drainage flux(0.01 and 0.001 cm d^(-1)),which serves as the upper boundary for plant-available water in soils.The estimated residual water content was corrected for subsoil constraints,especially the exchangeable sodium percentage(ESP).The results showed that the mean values of h_(fc)in sand-dominated light and medium textured soils(i.e.,sand,loamy sand,sandy loam,and loam)varied in a narrow range(15.8-18.2 kPa),whereas those in the clay-dominated heavy textured soils(i.e.,clay loam)showed a wide range(11.3-49.3 kPa).There were large differences in PAWC for dynamic FC(PAWC_(fc))and fixed FC at 10 kPa(PAWC10),33 kPa(PAWC33),and a mix of 10and 33 kPa(PAWC_(10,33))pressure heads depending on soil texture.Normally,the difference between PAWC at 10 kPa and h_(fc)(ΔPAWC_(10))was positive,whereas that between 33 kPa and h_(fc)(ΔPAWC_(33))was negative across all sites.Nevertheless,the estimation of PAWC assuming a fixed FC at 10 and 33 kPa pressures(i.e.,PAWC_(10,33))for sandy,clay,and silty soils reduced the difference between fixed and dynamic pressure PAWCs to<10% across the region.The estimation of PAWC was improved by incorporating the impact of subsoil constraints,such as high ESP,which was more pronounced for clay and silty soils.These findings demonstrate the inherent inconsistencies between static pressure and flux-based dynamic FC estimations in soils.Soil heterogeneity,intra-texture variability,subsoil constraints,and swell-shrink clays can have great impacts on the water retention capacity in response to dynamic and fixed pressure FC values.展开更多
基金National Natural Science Foundation of China No.43071093
文摘The available soil water capacity (ASWC) is important for studying crop production, agro-ecological zoning, irrigation planning, and land cover changes. Laboratory determined data of ASWC are often not available for most of soil profiles and the nationwide ASWC largely remains lacking in relevant soil data in China. This work was to estimate ASWC based on physical and chemical properties and analyze the spatial distribution of ASWC in China. The pedo-transfer functions (PTFs), derived from 220 survey data of ASWC, and the empirical data of ASWC based on soil texture were applied to quantify the ASWC. GIS technology was used to develop a spatial file of ASWC in China and the spatial distribution of ASWC was also analyzed. The results showed the value of ASWC ranges from 15 × 10-2 cm3·cm-3 to 22 × 10-2 cm3·cm-3 for most soil types, and few soil types are lower than 15 × 10-2 cm3·cm-3 or higher than 22 × 10-2 cm3·cm-3. The ASWC is different according to the complex soil types and their distribution. It is higher in the east than that in the west, and the values reduce from south to north except the northeastern part of China. The "high" values of ASWC appear in southeast, northeastern mountain regions and Northeast China Plain. The relatively "high" values of ASWC appear in Sichuan basin, Huang-Huai-Hai plain and the east of Inner Mongolia. The relatively "low" values are distributed in the west and the Loess Plateau of China. The "very low" value regions are the northern Tibetan Plateau and the desertified areas in northern China. In some regions, the ASWC changes according to the complex topography and different types of soils. Though there remains precision limitation, the spatial data of ASWC derived from this study are improved on current data files of soil water retention properties for Chinese soils. This study presents basic data and analysis methods for estimation and evaluation of ASWC in China.
基金Project (No. 49901009) supported by the National Natural Science Foundation of China.
文摘With six packed columns composed of < 1 μm and 5 μm～0.25 mm fractions from an Eum-Orthic An- throsol (Columns 1～6) and one column of the Eum-Orthic Anthrosol (Column 7), K～(+) transport experiments under the condition of saturated steady water flow were conducted to qualify the effects of soil texture com- position on the retardation factor (R) of K～(+) transport. The results showed that the retardation factor of K～ (+) transport in the tested soil columns greatly increased with increasing clay contents. In an attempt to use pedo-transfer function (PTF) approach in the solute transport study, a preliminary PTF was established through the six packed columns (Columns 1～6) with soil basic data including soil bulk density, volumet- ric water content and clay content to predict the retardation factor, and proved valid by the satisfactory prediction of R in Column 7.
文摘Parameters of water retention and air capacity are important factors for the evaluation of soil material that will be used for vegetative covers or evapotranspiration (ET) covers of landfills. These values are often measured in the laboratory (usually on disturbed samples), but are also estimated from texture, organic matter content and dry bulk density. The standard basis for the estimation in Germany is the German Soil Classification Handbook (KA5). This estimation implicitly assumes that the data in the KA5 compiled from naturally developed soils are also valid for artificially compacted materials. In the present study, 25 materials were evaluated in the laboratory for the available water capacity, air capacity and permanent wilting point at 85%, 90% and 95% of Proctor density. The data were compared with parameter estimations from the KA5 and the program ROSETTA. Both estimation methods show significant deviations from the measured values;specifically, the change in the available water capacity in compressed samples is not estimated correctly. A possible explanation is a change in pore structure at different compaction levels of build in soil material in comparison with naturally developed soils of different bulk densities.
文摘Estimation of the plant-available water capacity(PAWC)of soils at a regional scale helps in adopting better land use planning,developing suitable irrigation schedules for crops,and optimizing the use of scarce water resources.In the current study,72 soil profiles were sampled from the Barossa region of South Australia to estimate pedo-transfer functions deduced from easily estimated soil properties.These functions were then used to estimate the fixed(10 and 33 kPa)and dynamic pressure head(h_(fc))water contents at field capacity(FC)for minimum drainage flux(0.01 and 0.001 cm d^(-1)),which serves as the upper boundary for plant-available water in soils.The estimated residual water content was corrected for subsoil constraints,especially the exchangeable sodium percentage(ESP).The results showed that the mean values of h_(fc)in sand-dominated light and medium textured soils(i.e.,sand,loamy sand,sandy loam,and loam)varied in a narrow range(15.8-18.2 kPa),whereas those in the clay-dominated heavy textured soils(i.e.,clay loam)showed a wide range(11.3-49.3 kPa).There were large differences in PAWC for dynamic FC(PAWC_(fc))and fixed FC at 10 kPa(PAWC10),33 kPa(PAWC33),and a mix of 10and 33 kPa(PAWC_(10,33))pressure heads depending on soil texture.Normally,the difference between PAWC at 10 kPa and h_(fc)(ΔPAWC_(10))was positive,whereas that between 33 kPa and h_(fc)(ΔPAWC_(33))was negative across all sites.Nevertheless,the estimation of PAWC assuming a fixed FC at 10 and 33 kPa pressures(i.e.,PAWC_(10,33))for sandy,clay,and silty soils reduced the difference between fixed and dynamic pressure PAWCs to<10% across the region.The estimation of PAWC was improved by incorporating the impact of subsoil constraints,such as high ESP,which was more pronounced for clay and silty soils.These findings demonstrate the inherent inconsistencies between static pressure and flux-based dynamic FC estimations in soils.Soil heterogeneity,intra-texture variability,subsoil constraints,and swell-shrink clays can have great impacts on the water retention capacity in response to dynamic and fixed pressure FC values.
