Article

Wetting front advance patterns and water losses by deep percolation under the root zone as influenced by pulsed drip irrigation

Department of Natural Resources Management & Agricultural Engineering, Agricultural University of Athens, 11855 Athens, Greece
Agricultural Water Management 01/2007; DOI: 10.1016/j.agwat.2007.02.005

ABSTRACT The increased use of trickle irrigation is seen as a way to improve the sustainability of irrigation systems around the world. However, soil hydraulic properties, trickle discharge rate and irrigation frequency are often not adequately incorporated in the design and management of trickle irrigation systems. The influence of the before-mentioned factors on the wetting front advance and on the water losses by deep percolation under the root zone was studied for surface trickle irrigation. For this purpose a cylindrical flow model incorporating evaporation from the soil surface and water extraction by roots was used. The results show that, for both types of soils used in this study and for the two discharge rates, the vertical component of the wetting front was greater for the pulse than for the continuous irrigation for a time equal to irrigation duration. However, this difference was practically eliminated for a longer time.

0 Bookmarks
 · 
111 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Se evaluó el efecto de un régimen simulado de lluvia sobre el crecimiento y establecimiento de plántulas de los pastos navajita azul (Bouteloua gracilis) y boer (Eragrostis curvula var. conferta) bajo condiciones de invernadero. Un grupo de plántulas se mantuvo bajo condiciones de humedad adecuada mediante riegos a capacidad de campo, mientras que otro grupo de plántulas se mantuvo bajo un régimen simulado de lluvia que se derivó de los registros de una estación climática cercana al lugar de colecta de la semilla. Cada 3 d se midió el número de hojas, de vástagos secundarios y la altura de cada plántula, y al final (37 d) se determinó el porcentaje de establecimiento de plántulas, los pesos secos de vástago y raíz, y las relaciones raíz/vástago. Las plántulas de B. gracilis desarrollaron más vástagos secundarios y mayor altura bajo el régimen de capacidad de campo que en el régimen simulado de lluvia (P ≤ 0.05). Contrariamente, las plántulas de E. curvula crecidas bajo el régimen simulado de lluvia desarrollaron mayor cantidad de vástagos y de hojas que sus contrapartes crecidas bajo capacidad de campo y que B. gracilis bajo las dos condiciones de riego. Ambos pastos mostraron 90 % de establecimiento bajo condiciones de capacidad campo, pero bajo el régimen simulado de lluvia esta variable disminuyó en 10 % en el pasto boer. El esquema de evaluación aquí propuesto puede ser una herramienta confiable para analizar el establecimiento y desarrollo de plántulas de pastos bajo condiciones de invernadero y estrés hídrico. Palabras clave: Bouteloua gracilis, Eragrostis curvula, estrés hídrico, capacidad de campo, invernadero.
    Revista fitotecnia mexicana publ. por la Sociedad Mexicana de Fitogenética 01/2012; 35(4):299-308. · 0.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study was carried out to determine the effects of discharge rate, irrigation duration and inter-emitter distances on the wetting front advance patterns and on deep percolation under surface trickle irrigation. For this purpose a cylindrical flow model incorporating evaporation and water extraction by roots, was used in order to optimize the use of irrigation water. The mathematical model was applied to two different soil types: loamy sand and silt. Two irrigation depths (18 and 30 mm), two spaces between the emitters (80 and 60 cm) and two discharge rates (2 and 4 l h−1) were used. The initial condition for the two involved soils was that of uniform initial moisture content.From the analysis of the different numerical experiments, it is concluded that for the same irrigation depth, the same dripper spacing and the same soil (for time t ≤ ti) the vertical component of the wetted zone is greater for a smaller discharge rate than for a higher one. It was noticed that there was a faster overlapping of the wetted bulbs in the fine-grained soil and that deep percolation seems to be lower in the fine-grained soil than in the coarse-grained. Deep percolation increases as applied irrigation depth increases. Copyright © 2009 John Wiley & Sons, Ltd.La présente étude a été consacrée à la détermination des effets du débits des goutteurs, des durées d'irrigation et des écartements de goutteurs, sur l'avancement du front d'humectation, l'efficience de l'irrigation et les pertes d'eau par percolation profonde. Dans ce but, un modèle mathématique de l'écoulement axisymétrique de l'eau, qui prend en compte l'évaporation et l'extraction racinaire, a été utilisé pour optimiser l'usage de l'eau d'irrigation. Ce modèle a été appliqué à deux différents types de sol: sablo-limoneux et silt. Deux doses d'irrigation (18 et 30 mm), deux écartements entre les rampes de goutteurs et les goutteurs 80 et 60 cm et deux débits pour chacun 2 et 4 l h−1 ont été appliqués. La condition initiale pour les deux sols impliqués dans cette étude est une teneur en eau initiale uniforme.A partir de l'analyse de différents essais numériques, il a été conclu que pour la même dose d'irrigation, le même sol et le même écartement, pour les temps plus petits ou égaux à la durée d'irrigation, la composante verticale du front d'humectation est plus grande pour le plus petit débit (Q = 2 l h−1). Pour un temps égal à la période d'arrosage (temps total de chaque simulation) la percolation profonde est plus petite sur sol fin et augmente tant que la dose d'irrigation augmente. Aussi pour le même débit de goutteurs, la même dose et le même sol, en diminuant l'écartement des goutteurs et par conséquence en diminuant la durée d'irrigation nous constatons une augmentation de l'efficience d'irrigation. Copyright © 2008 John Wiley & Sons, Ltd.
    Irrigation and Drainage 01/2009; 59(3):254 - 263. · 0.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The HYDRUS-2D model was experimentally verified for water and salinity distribution during the profile establishment stage (33 days) of almond under pulsed and continuous drip irrigation. The model simulated values of water content obtained at different lateral distances (0, 20, 40, 60, 100 cm) from a dripper at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140 and 160 cm soil depths at different times (5, 12, 19, 26 and 33 days of profile establishment) were compared with neutron probe measured values under both irrigation scenarios. The model closely predicted water content distribution at all distances, times and soil depths as RMSE values ranged between 0.017 and 0.049. The measured mean soil water salinity (ECsw) at 25 cm from the dripper at 30, 60, 90 and 150 cm soil depth also matched well with the predicted values. A correlation of 0.97 in pulsed and 0.98 in continuous drip systems with measured values indicated the model closely predicted total salts in the root zone. Thus, HYDRUS-2D successfully simulated the change in soil water content and soil water salinity in both the wetting pattern and in the flow domain. The initial mean ECsw below the dripper in pulsed (5.25 dSm−1) and continuous (6.07 dSm−1) irrigations decreased to 1.31 and 1.36 dSm−1, respectively, showing a respective 75.1 and 77.6% decrease in the initial salinity. The power function [y = ax −b ] best described the mathematical relationship between salt removal from the soil profile as a function of irrigation time under both irrigation scenarios. Contrary to other studies, higher leaching fraction (6.4–43.1%) was recorded in pulsed than continuous (1.1–35.1%) irrigation with the same amount of applied water which was brought about by the variation in initial soil water content and time of irrigation application. It was pertinent to note that a small (0.012) increase in mean antecedent water content (θ i ) brought about 8.25–9.06% increase in the leaching fraction during the profile establishment irrespective of the emitter geometry, discharge rate, and irrigation scenario. Under similar θ i , water applied at a higher discharge rate (3.876 Lh−1) has resulted in slightly higher leaching fraction than at a low discharge rate (1.91 Lh−1) under pulsing only owing to the variation in time of irrigation application. The influence of pulsing on soil water content, salinity distribution, and drainage flux vanished completely when irrigation was applied daily on the basis of crop evapotranspiration (ETc) with a suitable leaching fraction. Therefore, antecedent soil water content and scheduling or duration of water application play a significant role in the design of drip irrigation systems for light textured soils. These factors are the major driving force to move water and solutes within the soil profile and may influence the off-site impacts such as drainage flux and pollution of the groundwater.
    Irrigation Science 05/2011; 30(4):315-333. · 2.29 Impact Factor