Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand<sup>1</sup>

Al-Khafaf, S.; Wierenga, P. J.; Williams, Brent D.

doi:10.2134/agronj1978.00021962007000060005x

Cited by 75 publications

(23 citation statements)

References 7 publications

(7 reference statements)

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“…It is an important nexus between the water cycle and energy budget and can further impact regional and global climate [2][3][4]. The atmospheric evaporative demand can be evaluated based on potential evapotranspiration [5,6] or evaporimeters [7,8] and is regarded as the upper limit of evaporation [9][10][11]. The evaporative demand of the atmosphere is controlled by radiative and aerodynamic factors, and it can be calculated using meteorological variables, such as radiation, wind speed, air temperature, and humidity [7,10].…”

Section: Introductionmentioning

confidence: 99%

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Liu

Liang

2016

Water

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Pan measurement is a reliable and efficient method for indicating the evaporative demand of the atmosphere. There are several types of pan evaporimeters worldwide, and the estimation of the conversion coefficients (K p ) between them is necessary in hydrologic research. In China, E601B pans were installed at all meteorological stations beginning in 1998. They replaced the 20 cm pans (φ20). To fully use the records from the two pans and obtain long-term pan evaporation, the spatial patterns of K p between φ20 and E601B and the factors that influence K p are investigated based on records from 573 national meteorological stations from 1998 to 2001. In this study, The results show that higher K p values are found in southwestern regions and lower values are found in northeastern regions during the warm seasons (from May to September), while K p values are lower during warm seasons than during cold seasons (from October to April the following year). In addition, net radiation was found to be the dominant climate factor that affects variations in K p , followed by relative humidity and the vapor pressure deficit. This study can improve the benefit of not only the selection of appropriate evaporimeters by meteorological departments, but also of the study of temporal variability and trends in the evaporative demand.

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Section: Introductionmentioning

confidence: 99%

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Liu

Liang

2016

Water

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“…The value of a obtained was 0.623 as in Al-Khafaf et al (1978). Potential evaporation for the period between seeding and plant emergence (bare soil) was estimated by the Penman-Monteith equation (Allen et al, 1994) with zero surface resistance.…”

Section: Is the Time (T) And S(h) Is The Root Water Uptake (1/t)mentioning

confidence: 99%

“…Towards this computation, if irrigation/precipitation is less than 10 mm day -1 , actual evaporation from soil surface (E a ) is computed by a modified Al-Khafaf et al (1978) equation:…”

Section: Is the Time (T) And S(h) Is The Root Water Uptake (1/t)mentioning

confidence: 99%

Evapotranspiration and simulation of soil water movement in small area vegetation

Paraskevas¹,

Georgiou²,

Ilias³

et al. 2013

International Agrophysics

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A b s t r a c t. In Greece, crops are frequently cultivated in small isolated areas in close proximity to roads and bare soils and therefore evapotranspiration is affected by local advection. Under these circumstances, oasis effect conditions are present and evapotranspiration is higher than what is expected. In this paper, the evapotranspiration and soil water dynamics of a cotton crop cultivated in small areas under the oasis effect is studied. To this end, two isolated free-drainage lysimeters cultivated with cotton in the year 2007 were used. Soil moisture of the soil profile of both the lysimeters was monitored with two capacitance water content probes. The soil water balance method was used to estimate crop evapotranspiration and corresponding crop coefficients in one of the two lysimeters. These coefficients were 75% larger than the FAO-56 crop coefficients at the mid-season stage. The FAO-56 and the derived crop coefficients were used for the simulation of the water dynamics in the second lysimeter by the SWBACROS model. The derived crop coefficients for these conditions produced much better results than the FAO-56 crop coefficients. The results were improved when crop coefficient value equal to 2.5 was used for the mid-season stage.K e y w o r d s: modelling soil water flow, evapotranspiration, oasis-effect, crop coefficients INTRODUCTIONCrop evapotranspiration (ET c ) can be calculated under standard or non-standard conditions and various management practices. Standard conditions refer to crops grown in large fields under non-limiting agronomic and soil conditions. Non-standard conditions and various management practices refer to management and environmental conditions that deviate from standard conditions such as salt toxicity, pests, diseases, surface mulches, small areas vegetation etc. (Allen et al., 1998).Frequently, fields in Greece are very small (<1 000 m 2 )representing typical non-standard conditions. Under these circumstances, the crops are growing under conditions of the oasis effect resulting in very high evapotranspiration values. Increased evapotranspiration is also observed at the upwind series of crops resulting in lower yields since these series obtain the same amount of water as the interior series. Therefore, the overall yield is reduced because of the non-satisfactory yield of the upwind series. The climatic definition of the 'oasis effect' or 'cold island effect' refers to the phenomenon of a cooling effect caused by vegetation (Givoni, 1991;Potchter et al., 2008). According to Oke (1987) this cooling effect is due to the fact that the energy required for evaporation (Q E ) is more than that supplied by radiation (Q*). It has been observed that the ratio Q E /Q* can be as large as 2.5 over an irrigated field of cotton (Lemon et al., 1957). Kai et al. (1997) also explained the cooling effect by the difference of the energy balance between oasis and the surrounding area. The oasis effect phenomenon is observed in different climates and urban or rural conditions (Oke, 1987;Potchter e...

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“…Possibly, for this reason van Genuchten and Gupta () and Al‐Khafaf et al . () considered a logistic curve with smooth derivatives (Hopmans and Bristow, ; Raats, ).…”

Section: Loss Functionmentioning

confidence: 99%

“…Intuitively, the discontinuous behaviour of the dET/dh function is unphysical. Possibly, for this reason van Genuchten and Gupta (1993) and Al-Khafaf et al (1978) considered a logistic curve with smooth derivatives (Hopmans and Bristow, 2002;Raats, 2007). Another point is derived from the work by Metselaar and De Jong van Lier (2007).…”

Section: Loss Functionmentioning

confidence: 99%

On stochastic modelling of groundwater uptake in semi‐arid water‐limited systems: root density and seasonality effects

Vervoort

Zee

2012

Ecohydrology

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In recent ecohydrological modelling, a common basis has been found in methodology and axiomas, such as the minimalist, systems analysis approach and a piecewise linear root zone water loss function. In this paper, we consider the loss function for root zones in contact with ground water through capillary upflow and including deep root systems. The basic assumption of a piecewise linear behaviour is not well supported, and we highlight how this generates a series of new research questions, related to important knowledge gaps at the interface of physics, plant physiology and ecology. We develop analytical solutions for the probability density functions for soil saturation and evapotranspiration for simple ecohydrological box models that are based on different vegetation groundwater feedbacks, for which numerical results have been presented earlier. In the case of intermediate groundwater levels and wetter climates, a feedback model that regulates groundwater uptake in response to root zone wetness regulates the transpiration most realistically. In semi‐arid regions, root zone salinization may occur as a result of groundwater quality and ineffective root zone leaching. How to combine the adverse effects of drought and osmotic stress in models is subject to debate, and several alternatives are presented. Seasonality is another unexplored area, and we highlight how this affects root zone salinization. Finally, a further feedback between upper root zone density and transpiration regulation in the loss function highlights dependence of deep rooted vegetation on groundwater. Experimental data are needed as the availability at this time is limiting further development of models. Copyright © 2012 John Wiley & Sons, Ltd.

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Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand¹

Cited by 75 publications

References 7 publications

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Evapotranspiration and simulation of soil water movement in small area vegetation

On stochastic modelling of groundwater uptake in semi‐arid water‐limited systems: root density and seasonality effects

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Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand1

Cited by 75 publications

References 7 publications

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Spatial Patterns and Influence Factors of Conversion Coefficients between Two Typical Pan Evaporimeters in China

Evapotranspiration and simulation of soil water movement in small area vegetation

On stochastic modelling of groundwater uptake in semi‐arid water‐limited systems: root density and seasonality effects

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Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand¹