TDR Technique for Estimating the Intensity of Evapotranspiration of Turfgrasses.
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Those parameters are the temperature and the volumetric moisture of soil at the depth of 2.5 cm.Evapotranspiration has the character of a modified logistic function with empirical parameters.It assumes the form ETR(θ (2.5 cm), T (2.5 cm)) = A/(1 + B · e (-C · (θ (2.5 cm) · T (2.5 cm)), where: ETR(θ (2.5 cm), T (2.5 cm)) is evapotranspiration [mm · h(-1)], θ (2.5 cm) is volumetric moisture of soil at the depth of 2.5 cm [m(3) · m(-3)], T (2.5 cm) is soil temperature at the depth of 2.5 cm [°C], and A, B, and C are empirical coefficients calculated individually for each of the grass species [mm · h(1)], and [-], [(m(3) · m(-3) · °C)(-1)].
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PubMed Central - PubMed
Affiliation: Institute of Environmental Protection and Development, Wrocław University of Environmental and Life Sciences, Plac Grunwaldzki 24, 50-363 Wrocław, Poland.
ABSTRACT
The paper presents a method for precise estimation of evapotranspiration of selected turfgrass species. The evapotranspiration functions, whose domains are only two relatively easy to measure parameters, were developed separately for each of the grass species. Those parameters are the temperature and the volumetric moisture of soil at the depth of 2.5 cm. Evapotranspiration has the character of a modified logistic function with empirical parameters. It assumes the form ETR(θ (2.5 cm), T (2.5 cm)) = A/(1 + B · e (-C · (θ (2.5 cm) · T (2.5 cm)), where: ETR(θ (2.5 cm), T (2.5 cm)) is evapotranspiration [mm · h(-1)], θ (2.5 cm) is volumetric moisture of soil at the depth of 2.5 cm [m(3) · m(-3)], T (2.5 cm) is soil temperature at the depth of 2.5 cm [°C], and A, B, and C are empirical coefficients calculated individually for each of the grass species [mm · h(1)], and [-], [(m(3) · m(-3) · °C)(-1)]. The values of evapotranspiration calculated on the basis of the presented function can be used as input data for the design of systems for the automatic control of irrigation systems ensuring optimum moisture conditions in the active layer of lawn swards. No MeSH data available. Related in: MedlinePlus |
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Mentions: Figure 6(a) presents the relation of evapotranspiration, calculated from relation (4), with the time step Δt = 1 day, with the mean diurnal soil temperature at the depth of 2.5 cm. The relation constructed in this way suggests that, with the increase in temperature, the diurnal values of evapotranspiration decrease which is untrue. In the experiment described, the decrease of the diurnal evapotranspiration is due to the fact that, with the passing of time, the volume of water decreases, and not to an increase of the mean temperature (Figure 3). For example, in the case of Niweta, when θidNW on the 11th of June (1st day) was 0.33 m3·m−3, ETRNW = 7.37 mm·day−1. Meanwhile, on the 21st of June (11th day), when θidNW was 0.12 m3·m−3, ETRNW = 0.55 mm·day−1—likewise for the other grasses. Figure 6(b) presents the same type of relationship, the difference being that the values of ETR were calculated with the time step of Δt = 1 h. In this case, there is an increase of evapotranspiration with increase of the mean temperature for a given hour. This regularity results from the fact that the variation of evapotranspiration is caused only by changes of temperature, since moisture varies only slightly during 24 hours. For example, for Poa pratensis L. cult. Niweta on the 13th of June (3rd day) θNW ∈ 〈0.21 m3 · m−3; 0.25 m3 · m−3〉. Further reduction of the time step Δt causes that the values of R2 decrease. For instance, for Δt = 15 min, R2 = 0.47. This is due to the fact that for the short time steps the changes of moisture are smaller than the accuracy of measurement. |
View Article: PubMed Central - PubMed
Affiliation: Institute of Environmental Protection and Development, Wrocław University of Environmental and Life Sciences, Plac Grunwaldzki 24, 50-363 Wrocław, Poland.
No MeSH data available.