poster - International Conference of Agricultural Engineering

numerical models which require detailed information about soil physicochemical properties
[Li et al., 2003, 2004; Elmaloglou & Malamos, 2006]. Traditional used procedures to monitor
water flow into soil are in situ extraction of soil solution using suction samplers or extracting
soil samples taken from the field and laboratory columns. An alternative for soil solution
samplers is the Time Domain Reflectometry (TDR) technique that infers the concentration
from the in situ measured bulk soil electrical conductivity [Vanclooster et al., 1993; Ward et
al., 1994]. Analytical models also provide a rapid means of determining the wetting front
position [Thorburn et al., 2003; Cook et al., 2003]. These models are based on the
assumption of a point source and certain forms for the soil physical properties [Revol et al.,
1997a,b]. The main problem with these models is that the spatial arrangement and
distribution of these wetting volumes is not known. These wetting volumes must be
detectable with a high spatial resolution.
According to our knowledge, no reports are available on using the image analysis technique
to assess soil flow patterns. The objectives of this study are to assess the feasibility of using
image analysis technique to determine soil wetting area and depth; and to develop an image
processing technique to derive soil wetting front map. This potential approach to characterize
flow patterns allows an objective comparison of soil infiltration patterns in the field. Using
spatial imaging processing techniques for soil wetting pattern monitoring may open a new
avenue for precision irrigation farming.
2. Materials and Methods
2.1. Experimental Set-up and Soil Image Acquisition
The procedure for using image analysis in estimating soil wetting front map under trickle
irrigation is accomplished by placing the soil column inside an illumination chamber shown in
Figure (1). Digital images were acquired sequentially every 30 sec. The digital color image
with a full resolution of 22721704 pixels was acquired for the soil column by using the
experimental set-up and image acquisition unit shown in Figure (1). The schematic diagram
shown in Figure (1) outlines the different components of the experimental set-up used to
estimate the soil wetting front map. The system consists of two (irrigation and imaging) units.
The irrigation unit consists of a main line (cast-iron pipe) 24.5 mm diameter, which have two
pressure regulators to regulate the supply pressure at 100 kPa during the experimental
period. Three Bourdon gages (range 0-250 kPa accuracy 0.1 kPa) and water meter were
used to approximate the desired pressure and discharge, respectively. Three valves were
constructed: at the outlet of the reservoir tank and at the entrance of recycling line (PE pipe
diameter 1.9 cm) to control the pressure at the main line, meanwhile the third valve mounted
on the main line before the water meter. Lateral line constructed one COER 100 emitter has
nominal discharge of 4 l/h. mounted on PE lateral lines (14.5 mm inside diameter). A plastic
cylinder (127 liters) was used to store irrigation water. At the main pipe inlet a screen filter
100 mesh was deployed only with mixed water, a pump with discharge of 1.2 – 6.0 m 3 /h, and
pressure head of 200 - 320 kPa was used. On the other hand, the imaging unit consists of a
digital color camera, PowerShot A580 model (Canon Corporation, USA). Illumination source
composed of two 50W halogen lamps to illuminate the camera's field of view. Illumination
chamber made from a white nylon box to equally disperse and distribute the light around the
soil column and a computer to record images acquired by the camera.
The lamps were placed on each side of the illumination chamber at approximately 0.5-m
distance and 45° angles. The placement of the lamps was adjusted to make sure that no
reflections were visible to the camera. The camera was placed on a tripod at the same level
as the soil column, at approximately 1.5-m height and 1-m distance. The camera was
connected to a laptop computer via the USB port. The software Canon Photo Record (Canon
Corporation, USA) was used to remotely control the camera and capturing the digital images.
Using this software, the images taken by the camera are directly transferred to the hard disk