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Accueil du site → Doctorat → Royaume-Uni → 1993 → Evaporation from sandy soils beneath crops in the semi-arid zone : a study of the use of microlysimeters and numerical simulation

University of Reading (1993)

Evaporation from sandy soils beneath crops in the semi-arid zone : a study of the use of microlysimeters and numerical simulation

Daamen, Carl Christopher

Titre : Evaporation from sandy soils beneath crops in the semi-arid zone : a study of the use of microlysimeters and numerical simulation.

Auteur : Daamen, Carl Christopher.

Université de soutenance : University of Reading

Grade : Doctor of Philosophy (Ph.D.) : 1993

Résumé
Direct evaporation from the soil surface is a major component of crop water balance in the semi-arid zone often accounting for half of seasonal rainfall. This loss of water has been reduced by appropriate crop management in some environments. However, evaporation from soil is often not measured independently in water balance studies and the dominant processes are not well understood. This study considers the measurements and the prediction of evaporation from sandy soils in the semi-arid zone, and the influence of crop management on this flux. A full description of a numerical simulation model (SWEAT) is given. SWEAT simulates heat and water (liquid and vapour) movement in the soil and throught a sparse crop canopy. The required inputs are soil hydraulic properties and hourly weather data. A sparse crop canopy is simulated using a new approach which allows the interaction of heat and water fluxes from the soil and the crop. Use of the microlysimeter method is examined to determine the appropriate dimensions and usable lifetime for microlysimeters in this environment. A new method for continuous measurement of evaporation from microlysimeters allowed diurnal patterns in the evaporation rate to be recorded. These rates indicated that potential evaporation is often not maintained throughout the first day following rain. Thus shading of the soil surface was not very effective in the reduction of evaporation from soil on a daily basis. These diurnal patters in evaporation were accurately simulated by SWEAT. Evaporation from soil in two different crop management systems is compared during the 1991 season in Niger. In July and August, rain totalled 333 mm and the average evaporation from soil was estimated to be 100 mm. Leaf area index only reached 0.85, but two-fold or larger differences in both leaf area index and total dry matter occurred between the systems during the season

Annonce : EThOS (UK)

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