- BB
Tác giả: Graham, S.L.; Người hướng dẫn: -; Người tham gia: Srinivasan, M.S.; Faulkner, N.; Carrick, S. (2018) - This study investigated, for a heterogeneous stony soil, four methods of soil hydraulic parameterization: (i) use of a pedotransfer function with a four‐layer soil profile based on detailed soil physical and textural description; (ii) use of a pedotransfer function with a single‐layer soil description; (iii) inverse estimation from soil moisture data; and (iv) inverse estimation from lysimeter drainage. Soil drainage, volumetric water content, and evapotranspiration were each modeled using HYDRUS‐1D for an irrigated pasture in New Zealand during the time period 1 July 2011 to 15 Mar. 2014. The first 15 mo were used for model spin‐up and inverse parameter estimation, while the remainder of the study period was used as a validation period, during which model results were compared agai...
|
- BB
Tác giả: Torrentó, C.; Người hướng dẫn: -; Người tham gia: Prasuhn, V.; Spiess, E.; Ponsin, V.; Melsbach, A. (2018) - Conditions for preferential flow were promoted by applying heavy simulated rainfall shortly after pesticide application. In some of the experiments, preferential flow was also artificially simulated by injecting the solutes through a narrow tube below the root zone. With depth injection, preferential leaching of atrazine occurred shortly after application in both soil types, whereas with surface application, it occurred only in the moraine soil. Thereafter, atrazine transport was mainly through the porous soil matrix, although contributions of preferential flow were also observed. For all the application approaches and soil types, after 900 d, <3% of the applied amount of atrazine was recovered in the drainage water. Only uranine realistically illustrated the early atrazine breakthr...
|
- BB
Tác giả: Teuling, A.J.; Người hướng dẫn: -; Người tham gia: - (2018) - In spite of the large number of studies on the role of forests in affecting local and global water and energy cycles, conflicting reports on even the sign of the change in evapotranspiration over forest compared with non‐forest land cover can be found depending on the type of data used. Whereas studies based on closure of the water balance suggest higher evapotranspiration over forests, studies based on turbulent exchange and/or energy balance closure suggest generally higher latent heat flux over non‐forest sites. In this study, this forest evapotranspiration paradox was investigated using data from four long‐term lysimeter stations in western Europe with contrasting land cover conditions. The results were consistent with evapotranspiration estimates from catchment‐scale water bala...
|
- BB
Tác giả: Doležal, F.; Người hướng dẫn: -; Người tham gia: Hernandez-Gomis, R.; Matula, S.; Gulamov, M.; Miháliková, M.; Khodjaev, S. (2018) - We selected 585 rainless days with regular records for the analysis of daily differences. On most days, the lysimeter‐measured actual evapotranspiration, ETa, was smaller than the Penman–Monteith FAO 56 reference crop evapotranspiration, ET0. The FAO 56 procedure was found to be a reasonable estimator of the unstressed evapotranspiration in a moderately stressed environment. The ETa/ET0 ratio and the canopy surface resistance, rs, depend on the soil water content and suction measured at 5 cm. These graphs break down into horizontal unstressed parts and declining (for ETa/ET0) or inclining (for rs) water‐stressed parts. The ratio ETa/ET0 is about 85% and rs is about 250 s m−1 when the grass is not under water stress. The annual curve of the unstressed crop coefficient has a sine shap...
|
- BB
Tác giả: Shao, M.; Người hướng dẫn: -; Người tham gia: Wang, Y.; Xia, Y.; Jia, X. (2018) - The Loess Plateau (LP) of China is a good representative area for critical zone (CZ) science studies. The LP is famous for its deep loess. In most areas, the thickness of the loess profile is deeper than 100 m, and two‐thirds of the area is arid and semiarid. With the Grain‐for‐Green project, the vegetation of the plateau has recovered gradually. However, with the increase in vegetative coverage, especially the planted vegetation, the water content of the soil profile has decreased and the soil is much drier. In this review, particular emphasis is paid to the dry conditions of deep soil, drought, regional restoration of vegetation, and effective management of soil moisture. We reviewed the progress of research on dried soil layers (DSLs) that resulted from soil drought in the past d...
|
- BB
Tác giả: Singh, G.; Người hướng dẫn: -; Người tham gia: Kaur, G.; Williard, K.; Schoonover, J.; Kang, J. (2018) - A number of contaminants including agrochemicals (fertilizers, pesticides), heavy metals, trace elements, and pathogenic microbes along with pharmaceuticals and hormones used in animal production move through the soil and are responsible for degradation of groundwater quality. Therefore, it is essential to sample soil solution for better understanding of movement and environmental fate of various contaminants in soils. We review different soil solution extraction samplers. The soil solution samplers discussed here are: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate. We have reviewed 304 journal articles representing a wide array of scientific disciplines. A brief history of soil solution monitoring and termi...
|
- BB
Tác giả: Wang, Z.; Người hướng dẫn: -; Người tham gia: Luo, C.; Sauer, T.J.; Helmers, M.J.; Horton, R. (2018) - Crop canopy CO2 exchange rate (CER) includes crop photosynthesis and soil/plant respiration. A portable canopy chamber is effective in determining crop CER values at a relatively small spatial (m2) scale. The objectives of this study were to use a canopy chamber to measure CO2 fluxes in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chamber measurements were performed for 18 and 15 d in 2013 and 2014, respectively. The canopy chamber measures instantaneous CER fluxes, and daily and daytime cumulative CO2 values were calculated from the instantaneous CER. The chamber CER results were compared with nearby eddy covariance (EC) flux tower measurements at a variety of time scales, i.e., instantaneous, daily, and daytime cumulative (multiple months). The daily and daytime cumula...
|
- BB
Tác giả: Zhu, W.; Người hướng dẫn: -; Người tham gia: Li, H.; Qu, H.; Wang, Y.; Misselbrook, T.; Li, X.; Jiang, R. (2018) - The soil water storage (SWS) decreased significantly during the early stage of the maize growing season, especially in 2014. The root depth and crop height were 20 cm deeper and 100 cm higher, respectively, in 2014 than in 2013 at the early stage. These results suggest that in the early stage of the maize growing season, pre‐seeding SWS can alleviate crop water stress effectively via deep roots. Model simulation showed that the plow pan layer (at a depth of 20–40 cm), with high soil bulk density and a lower soil water retention curve, significantly reduced infiltration. High evapotranspiration and low precipitation result in a temporary dry layer during the early stage, highlighting the plow pan as the sensitive layer for water stress during the drought period. Effective management ...
|
- BB
Tác giả: Berezniak, A.; Người hướng dẫn: -; Người tham gia: Ben-Gal, A.; Mishael, Y.; Nachshon, U. (2018) - Drip irrigation is a useful method for the application of low‐quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier dev...
|
- BB
Tác giả: Cai, C.; Người hướng dẫn: -; Người tham gia: Vanderborght, J.; Couvreur, V.; Mboh, C.M.; Vereecken, H. (2018) - These models were implemented in HYDRUS‐1D, and soil hydraulic parameters were optimized by inverse modeling using soil water content and potential measurements and observations of root distributions of winter wheat (Triticum aestivum L.) in horizontally installed rhizotubes. Soil moisture was equally well predicted by the three models, and the soil hydraulic parameters optimized by the models with compensation were comparable. The obtained RWU parameters of the Feddes–Jarvis model were consistent with data reported in the literature, although the pressure heads h3l and h3h for lower and higher transpirations rates, respectively, could not be uniquely identified. Response surfaces of the objective function showed that the root‐related parameters of the Couvreur model could be identi...
|
