SIMULATION OF THE DRIP IRRIGATION MANAGEMENT PRRACTICES AND THEIR EFFECTS ON THE SOIL PROPERTIES BY USING « HYDRUS » MODEL
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Date
2021
Authors
Journal Title
Journal ISSN
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Publisher
HAMOUDI Saaed / El-NESR Mohammad
Abstract
Enhancing the wet characters of the root zone under drip irrigation is one of the
objectives of the irrigation designers and researchers, in the goal to increase production and
yield of agricultural crops.
During drip irrigation, the moisture content of the root zone rises, thus reducing the
capillary forces between the water and the soil particles, so that it makes root extraction easier
to obtain its water needs. Information about temporal evolution of the wetted soil volume can
be helpful in establishing the optimal emitters spacing and the duration of irrigation, for the
volume of soil where the main crop roots are located; it is of great importance in realizing the
full potential of drip irrigation technology.
The mathematical equation that governs water transfer in porous soils with specific
conditions is the Richards’s equation. In this research, numerical simulations were performed
with HYDRUS-2D/3D, this model numerically solves Richards equation, to investigate the
influence of different irrigation management and design strategies on the soil water dynamics,
HYDRUS-2D/3D uses a numerical finite element approach in plan (where the flow region is
divided into a triangular (2D) network. The corners of these elements are taken to be the nodal
points. In addition, HYDRUS was used to simulate the impact of 8 discharges rate
application (1, 2, … 7, 8 L/h) With difference distances between drippers ( 20, 30 ,50cm )
according to a frequency ranging from one to seven days in the climatic conditions of the
study area to predict the water content mode in the root zone of tomato crop. Furthermore, to
validate the program and choose the best strategy for managing drip irrigation, model
accuracy was evaluated against experimental data in the field.
The experimental study was carried out in the private farm in Chlef. The field is
geographically located at coordinate of 1° 27' 20'' E, 36° 13' 60'' N. Soil moisture was
measured using a TDR where several water content readings at different depths in the root
zone were carried out during the growing season of tomato crop.
The first objective was to validate the HYDRUS-2D / 3D for two simultaneouslyworking
surface drippers with sandy-loam texture. Root-mean-square-error (RMSE) was
employed such as statistical analysis to evaluate the performance of the HYDRUS-2D/3D
model and to test the goodness of fit between simulated and observed soil volumetric water
content values. The RMSE value range between 0.0057 and 0.043 m3.m-3. These results
Simulation of the drip irrigation management practices and their effects on the soil properties by using
“HYDRUS” model
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demonstrate the reliability of HYDRUS2D/3D in the simulation of volumetric water content
values (VWC) compared to those measured in the field.
The second objective was to simulate various irrigation strategies using the validated
model to optimize lateral and the vertical leaching water movement.
According to the model studies, emitter discharge rates affects significantly the wetting
pattern shape, with a large discharge rate, the width of an isoline increases, while the depth of
the isoline decreases, while the reverse is true at small flow rates. From the results of studies
on the simulator, it is recommended to use a dripper of 3 L / h with irrigation every three days
and at 50 cm between drippers to obtain a homogeneous distribution of moisture in the wet
area (optimal strategy) while avoiding problems of saturation or lack of moisture in the active
roots area, thus the wet diameter does not exceed 50 cm vertically. This has been proven in
the field by the high yield of tomatoes under this strategy which has recorded 30% rising
compared to other strategies.
Description
Keywords
simulation, drip irrigation, soil properties, HYDRUS 2D/3D Model