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Publications (5)0 Total impact

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    ABSTRACT: Crop coefficients and water balance in an irrigated cornfield during the 2004 growing period (Apr. 27 to Oct. 12) in the upper Yellow River basin in Inner Mongolia, China, were analyzed using the dual crop coefficient approach recommended by the FAO, in which crop transpiration and soil evaporation were evaluated based on the crop coefficients and the reference evapotranspiration determined from meteorological conditions. During the initial stage when ground cover by corn plants was approximately less than 10%, the mean crop coefficient was 0.50 and soil evaporation accounted for 84% of evapotranspiration. In the crop development, mid-season and late season stages when most of the ground surface was covered with corn plants, the mean crop coefficients were 0.63, 1.18 and 0.99, respectively, and soil evaporation accounted for only 10-20% of evapotranspiration. During the entire growing period, cumulative crop transpiration and soil evaporation were 389.1 mm and 126.0 mm, respectively, and corresponded to 75.5% and 24.5% of the cumulative evapotranspiration estimated by this approach (515.1 mm), which almost equated with the measurement made by the Bowen ratio method (512.3 mm). Cumulative precipitation was 294.6 mm and about 150 mm of water was irrigated at the end of the crop development stage. These results suggest that approximately 30% of the rainwater and the irrigation water was lost by soil evaporation and about 70 mm of water was supplied to the root zone by capillary rise from the shallow water table (-1 m to -2 m).
    No preview · Article · Jan 2007 · Journal of Agricultural Meteorology
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    ABSTRACT: The bucket with a bottom hole (BBH) model of soil hydrology was improved to incorporate bioprocesses such as surface rainfall interception and macropore flow into it by introducing three model parameters or two composite parameters. The improved model (BBH-B model) was applied to the estimation of evapotranspiration (ET) from a cornfield in the upper Yellow River. The results obtained are summarized as follows.(a) Estimates of the cumulative ET during periods of about one month were made using the BBH-B model with fair accuracy if the model parameters could be evaluated appropriately.(b) ET had a large spatial variation within the cornfield.(c) The major zone of water use by corn moved downward through the soil as the growing season progressed. The ratio of root water uptake in depths between 40 cm and 100 cm to ET increased from about one-forth in June, when LAI increased quickly, to about one-half in September, when the corn maturred.(d) The surface conditions, such as the fraction of crop cover, exerted a large influence on the partition of rainwater at the surface of the cornfield.
    No preview · Article · Jan 2007 · Journal of Agricultural Meteorology
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    ABSTRACT: The bucket with a bottom hole (BBH) model of soil hydrology was improved to incorporate bioprocesses such as interception and macropore flow into it by adding three model parameters, which is called the BBH-B model. This model was applied to the estimation of evapotranspiration (ET) from a cornfield in the upper Yellow River basin, China, with the results as follows: Estimates of the cumulative ET for periods of about one month were made using the BBH-B model with fair accuracy, if the three additional parameters were determined appropriately. It was also found that ET had a large spatial variation within the cornfield.
    Preview · Article · Jan 2006
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    ABSTRACT: An irrigation experiment was conducted at an experimental cornfield established in the Yellow River basin, Inner Mongolia, China, in order to investigate the potential for a saving of irrigation water in this region. The root zone was divided into two layers; the first layer 40 cm thick and the second layer 60 cm thick, and the irrigation requirement, Wa (mm), was assumed to be expressed asWa=(max[W1FC - W1, 0]+ max[W2FC - W2, 0]) (1+ α)where Wi is the amount of water contained in the ith layer (mm)(i=1,2), WiFC is the "dynamic field capacity" of the layer (mm), and α indicates a leaching part for salinity control and uniform distribution of water in the root zone. The dynamic field capacity WiFC is defined as the value of Wi when a balance of forces is made on an element of the water at the bottom surface of the ith layer, and is evaluated using the two-layer BBH model. This critical point is not static but dynamic in nature and depends on the depth of water table and the potential water extract by plant roots.The mean value of α for the experimental cornfield was evaluated to be 0.75 from the irrigation practiced as usual in 2004. It is apparent that this value was too large to be optimum and over-irrigation occurred, because the groundwater level rose up to within the root zone just after the irrigation and the lower part of the zone was almost saturated for a long time.
    No preview · Article · Jan 2005 · JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

  • No preview · Article · Jan 2004 · Suimon mizu shigen gakkaishi Journal of Japan society of hydrology & water resources