Effects of Flow Depth on Water Flow and Solute Transport inFurrow Irrigation: Field Data Analysis
Fariborz Abbasi1; Floyd J. Adamsen2; Douglas J. Hunsaker3; Jan Feyen4; Peter Shouse5;
and M. Th. van Genuchten6
Abstract: Because of field-scale heterogeneity in soil hydraulic and solute transport properties, relatively large-scale experiments are
now increasingly believed to be critical to better understand and predict the movement of water and dissolved solutes under field
conditions. In this study, five field experiments were conducted on short blocked-end furrows to assess the effects of irrigation water levelon water flow and solute transport in furrows. Three experiments were carried out, each of the same duration but with different amountsof water and solutes resulting from 6, 10, and 14 cm furrow water depths, designated as low, moderate, and high water levels, respectively.
Two more experiments were performed with the same amounts of applied water and solute and, consequently, different durations, on
furrows with depths of 6 and 10 cm of water. Results show that both the water level and the duration play an important role in transportingand distributing water and solutes in the soil profile. A positive correlation was found between water level and infiltrated amount of wateror solute. Irrigation/solute application amounts increased with decreasing water level. Water and solutes were both distributed almost
vertically 共one-dimensionally兲 for the low water level and short application treatments, while they moved much more two-dimensionallywith low and moderate water depths but longer application times. Irrigation with the 14 cm water level and short application time
improved the distribution of water and solutes within the soil profiles, while also causing relatively less deep percolation of water andsolutes as compared to low and moderate water levels and relatively long duration times.
DOI: 10.1061/共ASCE兲0733-9437共2003兲129:4共237兲
CE Database subject headings: Furrow irrigation; Water levels; Solutes; Water quality; Water depth; Data analysis; Transportphenomena.

Introduction
The transport of agrochemicals in soils is a significant aspect ofboth crop production and groundwater quality control. Solutetransport in soils is affected by many factors including soil physical, chemical, and biological properties, the particular soil conditions at the top and bottom of the profile, and management practices 共Wallach et al. 1991兲. Those factors, particularly in fieldstudies, may vary over time and space. Irrigation is also one of1
Institute for Land and Water Management, Katholieke Univ. Leuven,
Belgium; Vital Decosterstraat 102, 3000-Leuven, Belgium. E-mail:Frabbasi@hotmail.com
2
U.S. Water Conservation Laboratory, USDA-ARS, 4331 E. Broadway Rd., Phoenix, AZ 85040.
3
U.S. Water Conservation Laboratory, USDA-ARS, 4331 E. Broadway Rd., Phoenix, AZ 85040.
4
Institute for Land and Water Management, Katholieke Univ. Leuven,
Belgium; Vital Decosterstraat 102, 3000-Leuven, Belgium. E-mail:jan.feyen@agr.kuleuven.ac.be5
George E. Brown Jr. Salinity Laboratory, USDA-ARS, 450 W. Big
Springs Dr., Riverside, CA 92507.
6
George E. Brown Jr. Salinity Laboratory, USDA-ARS, 450 W. Big
Springs Dr., Riverside, CA 92507.
Note. Discussion open until January 1, 2004. Separate discussions
must be submitted for individual papers. To extend the closing date by
one month, a written request must be filed with the ASCE Managing
Editor. The manuscript for this paper was submitted for review and possible publication on December 17, 2001; approved on November 19,
2002. This paper is part of the Journal of Irrigation and Drainage Engineering, Vol. 129, No. 4, August 1, 2003. ©ASCE, ISSN 0733-9437/
2003/4-237–246/$18.00.

the main factors affecting the fate and transport of agrochemicals
in soils in arid and semiarid regions 共Yaron et al. 1985兲. Predominant irrigation methods used in those regions include drip, sprinkler, and furrow irrigation. Water flow and solute transport undersprinkler irrigation most closely approximate one-dimensional
flow. By contrast, flow and solute transport under furrow and drip
irrigation are usually two- and three-dimensional, respectively.
Our understanding of how different irrigation methods affect solute transport is still relatively poor.
The number of comprehensive solute transport studies at thefield scale is still quite limited, in part because of often excessive
demands in terms of time and available resources. Additional
complications arise because of difficulties in controlling spatial
and temporal variabilities in the soil hydraulic and transport parameters, and the presence of preferential flow, which has beenreported in both well-structured and unstructured soils 共Blake
et al. 1973; Kanchanasut et al. 1978; Rice et al. 1991兲. Troiano
et al. 共1993兲 found that under furrow irrigation the herbicide atrazine and other chemicals leached more rapidly than under sprinkler and trickle irrigation. Izadi et al. 共1993, 1996兲 conducted afield solute experiment on furrows and used several onedimensional piston flow models to predict bromide movement in
the soil profile. They found that while piston flow theory generally described the bromide position well during the first irrigation,
the tracer was transported somewhat faster than predicted by piston flow. They attributed this discrepancy to the preferential flow.
Goderya et al. 共1996兲 used the water quality models TDNIT
共Bogardi and Bardossy 1984兲 and EPIC 共USDA 1990a,b兲 for 13year simulations of nitrogen transport in a furrow-irrigated fieldunder continuous cultivation of corn. They found that the

JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003 / 237

Table 1. Soil Texture, Textural Fractions, and Soil Bulk Density Measured at Different Depths of Experimental Field
Textural fractions 共%兲

Depth
共cm兲

0–20
20– 40
40– 6060– 8080–100
100–140
140–180
180–220
220–260

Sand

74.29
75.04
76.73
72.34
71.16
69.57
70.32
75.30
74.65

Standard
deviation
2.17
1.74
3.97
5.53
7.69
7.37
2.01
7.21
4.73

Silt

9.36
9.31
8.27
11.94
12.67
14.51
14.18
10.75
12.00

Clay
Standard
deviation
2.10
1.66
1.73
2.85
4.80
5.29
3.47
4.74
3.68

two models predicted deep water percolation, plant transpiration,soil evaporation, and nitrate leaching satisfactorily, but that the
TDNIT model underestimated mineralization and denitrification.
Wang et al. 共1997兲 used the CHAIN-2D model 共Simunek and van
Genuchten 1994兲 to investigate the effect of different irrigation
methods and spatial variability in the saturated hydraulic conductivity (K s ) on solute transport in the soil. They found that sprinkler irrigation required the least amount of time to infiltrate aprescribed amount of water or chemical, followed by furrow anddrip irrigation. Furrow irrigation appeared to leach the tracer
more efficiently than either drip or sprinkler irrigation. They also
showed that spatial variability in K s had no significant effect on
the solute distribution in the profile. Recent laboratory studies by
Wildenschild et al. 共2001兲 showed that the flow rate had a significant influence on both the soil water retention curve and K s of asandy soil, while the effect was not readily apparent for a finertextured loam soil. Results by Vanderborght et al. 共1997兲 using
small soil columns also showed that soil type and flow rate canhave an important impact on water flow and solute mixing in asoil. Significant effects of the flow regime on field-scale solutetransport were also found by Bowman and Rice 共1986兲 during
intermittent flood irrigation and Jaynes et al. 共1988兲 during continuous flood irrigation.
A closely related aspect of irrigation is the effect of water level
on infiltration rate and ensuing soil water distributions in the soil
profile. Previous studies have shown that the effect of water level
on infiltration in borders is relatively minimal 共Philip 1958; Parlange 1972兲 but that with furrows it has a first-order effect on thesurface area over which infiltration occurs 共Fangmeier and Ramsey 1978; Souza 1981; Wallender and Rayej 1990兲.
The main objective of this study was to monitor twodimensional field-scale water flow and solute transport, and to
more precisely evaluate the effect of water level on transport anddistributions of water and bromide in a field with blocked-end
furrows under variable conditions.

Materials and Methods
Field Experiments
Field experiments were conducted at the Maricopa Agricultural
Center 共MAC兲, 45 km southwest of Phoenix, in February 2001 on
a Casa Grande sandy loam 共fine-loamy, mixed, hyperthermic
Typic Natrargids兲 with about 0.5% organic matter and 3–5%
CaCO3 . Soil texture and textural fractions were determined using
the hydrometry method and wet soil particle size distribution

16.35
15.65
15.00
15.72
16.17
15.92
15.50
13.95
13.35

Standard
deviation
1.45
2.49
3.08
3.85
3.18
3.69
1.24
2.47
1.06

Textureclass

Sandy loam
Sandy loam
Sandy loam
Sandy loam
Sandy loam
Sandy loam
Sandy loam
Sandy loam
Sandy loam

Soil bulk
density 共g cm⫺3兲

1.49
1.56
1.50
1.41
1.46
1.51
1.38
—
—

Standard
deviation
0.08
0.06
0.09
0.12
0.07
0.11
0.02
—
—

analysis 共Table 1兲. We also took soil bulk densities using a Madera soil sampler up to 180 cm deep at different locations in andoutside the experimental plots 共Table 1兲. The experimental field
was fallow for two years before the experiments started and bromide had never been applied to the field. The static ground waterlevel in the area ranged from 45 to 90 m.
Five experiments were carried out on bare soil with short
blocked-end level furrows using depths of 6, 10, and 14 cm ofwater, designated as low, moderate, and high water levels, respectively. Short blocked-end level furrows were used to enable thewater levels to remain constant and uniform along the relatively
short length of the furrow. The selected water levels, 6, 10, and 14
cm, are representative of water levels common in cutback, freedraining, and blocked-end furrow irrigation regimes, respectively.
More or less the same depths 共4, 10, and 16 cm兲 were previously
used by Vogel and Hopmans 共1992兲 to simulate the effects ofdifferent water levels on infiltration using a two-dimensional numerical model. Furthermore, bromide was dissolved in irrigationwater and just applied during the second phase of the first irrigation event. This was because of higher reported solute leaching
during fertigation 共application of fertilizers with irrigation water兲
compared with conventional fertilizer application methods. Earlier efforts revealed that fertigation could potentially increase
deep leaching of agricultural chemicals 共Bowman and Rice 1986;
Jaynes et al. 1988, 1992; among others兲. Therefore, in this study
we applied the solutes as late as possible to decrease leaching of
the solutes beyond our measurement depths.
Two series of experiments were carried out 共Fig. 1兲. We first
performed the same duration 共SD兲 experiments involving thethree flow depths applied to two successive irrigation events, tendays apart. The first irrigation took place in two phases. In thefirst phase, water was applied for 60 min to wet the profile. Water
was then removed from the furrow and measured using an electricscale. During the second phase, water amended with CaBr2 wasapplied for 30 min. Water in the furrow was again removed andthe amount determined. The second irrigation utilized the same
depths of unamended water employed during the first irrigationand lasted 90 min. As for the first irrigation, water stored in the
furrow was pumped out and measured at the end of the experiment.
The second series of experiments involved similar amounts ofapplied water and solutes 共SWS兲. The amount of water applied
was the same as that infiltrated for the 14-cm depth treatment of
the SD experiments. Water levels of 6 and 10 cm were used. The
first irrigation was carried out in two steps, similarly as for the SD
scenarios, with unamended water being applied first followed by

238 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003

Fig. 1. Plane view of furrow irrigation experiments conducted at Maricopa Agricultural Center 共MAC兲 in Phoenix 共not to scale兲

bromide amended water, except that the irrigation times were
adjusted for each of the water levels such that the desired amountof water infiltrated. The second irrigation event again used unamended water applied with the same water levels as for the firstirrigation, but with times adjusted so that again the same amountof water infiltrated during the second irrigation for the 14 cm
depth as for the first set of experiments.
For all experiments, plots were made up of three furrows
spaced at 100 cm intervals, common in the experimental area forrow crops. The center furrow of each plot was a nonwheel furrow,
which was monitored, with a wheel track furrow on each side of
the monitored furrow. The blocked portion of the furrows was
300 cm in length. The remainder of this section lists measurements that we made for all of our experiments.
A set of neutron probe access tubes was established on eachmonitored furrow, which included five neutron probe access tubes
each 330 cm in length installed at different locations perpendicular to the axis of the monitored furrows 共Fig. 2兲. All five of theneutron tubes within a plot were a minimum of 50 cm apart, toavoid influence of adjacent tubes. Soil removed during the process of installing the neutron access tubes was saved for analysis.
After installing the neutron access tubes, both the monitored andguard furrows were manually rebuilt.
A site-calibrated neutron probe 共Campbell Pacific Nuclear
503, Martinez, California兲 was used to measure the soil watercontents at each tube at soil depths of 20, 40, 60, 80, 100, 140,
180, 220, and 260 cm. Soil water content readings were taken

before each irrigation 共initial water contents兲 and immediately
after pumping water out of the furrows. Those readings were
followed by hourly measurements for 6 h after each irrigation andthen every 3 h for the next 18 h. Readings were taken 3– 4 times
per day for 3 days and then 1–2 times per day until the next
irrigation, or for 20 days following the second irrigation. Two to
three neutron readings were taken for each soil increment depth
and averaged in order to improve the precision of the neutron
scatter methodology. Water contents of the surface layer 共0–30
cm兲 were also measured using a site calibrated Time Domain
Reflectometry 共TDR兲, model 6050 XI 共Soil Moisture Inc., Santa
Barbara, California兲. The TDR probes with two-rod wave-guides
were installed vertically 15 cm away from the neutron probe access tubes. The TDR and neutron probe readings were taken at thesame times as indicated above for the neutron probe readings.
The geometry of the experimental furrows was determinedusing a profilometer before each irrigation event at two locations
along the furrows in order to calculate the volume of water
needed to fill the furrow section, and to infer geometry parameters
required for the subsurface water flow and solute transport models.
Water and bromide solutions were supplied from 250 L barrels
equipped with valves. Water depths were kept constant during theirrigation by adjusting the water level to the desired height determined from staff gauges placed at the bottom of the furrow and
70 cm away from the head of the furrow. The barrels that supplied
water and the bromide for the monitored furrows were weighed

Fig. 2. Location of neutron probe access tubes and soil sampling points on experimental furrow cross section, 共a兲 front view and 共b兲 perspective
view 共not to scale兲
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Table 2. Infiltrated Amounts of Water and Bromide at Different Plots During Two Successive Irrigation Events
Irrigation number 1

SDc

SWSd

Irrigation number 2Experiment

Watera共1 m⫺1兲

Bromideb
共g m⫺1兲

Application
time 共min兲

Water
共1 m⫺1兲

Application
time 共min兲

Plot 1 共6-cm兲
Plot 2 共10-cm兲
Plot 3 共14-cm兲
Plot 4 共6-cm兲
Plot 5 共10-cm兲

31.63
50.72
98.83
99.42
98.42

70.67
90.17
218.17218.33218.3390共30兲e90共30兲
90共30兲
337共92兲
123共48兲

18.95
32.57
39.53
39.58
40.58

90
90
90
208
92

a

Water applied in two phases.
Grams bromide per 1 m furrow length.
cSame duration 共SD兲 experiments.
dSame applied water and bromide 共SWS兲 experiments.
e
Total irrigation and bromide application times, respectively.
bevery 5 min during the irrigations. For each experiment, the volume of water or bromide solution needed to fill the furrows andbring the water level to a desired depth, was estimated using themeasured furrow geometries and prepared in 50 L barrels for eachfurrow separately. The volume of water pumped from the furrow
at the end of each experiment was compared to the estimatedvalues based on the furrow geometries. In case of differences, theinfiltrated amounts of water and bromide were later adjusted. The
bromide concentration was 10 g L⫺1 for all experiments.
Soil samples were taken manually with a 2.5 cm auger up to
180 cm depth, corresponding in location and depth to the neutronprobe access tubes prior to the experiments 共soil saved from theneutron access tube installation兲, as initial values; 5 days after the
first irrigation; 6 and 20 days after the second irrigation. The
second, third, and fourth soil samples were taken at 225, 150, and75 cm away from the head of furrows, respectively. The second
and third soil samples from the first two SD experiments weretaken up to 140 cm depth. In addition, holes from the soil samples
were refilled after each soil sampling. The soil samples were also
used for gravimetric soil water content measurements. Soilsamples for Br analysis were air dried and crushed to pass a 2 mmsieve. Soil extractions 共1:1 weight:volume兲 were made and kept at
7°C until analyzed. Bromide concentrations were determinedusing a QuikChem AE Automated Ion Analyzer.
In the event of rain, the plots were covered with plastic sheets
to avoid receiving rain water. The experimental plots were kept
weed free manually. Furthermore, the SD and SWS experiments
started on January 30 and February 26, 2001, respectively, andeach lasted 30 days. Replications were not applied because of theexperimental intensity used in this research and consequently theexcessive demands in terms of time and adequate financial
sources and labor.

Results and Discussion
Infiltrated Water and Bromide
In the SD experiments, a positive correlation was found between
infiltrated water/bromide and applied water levels 关Table 2 andFig. 3. Effect of water level on cumulative amount of infiltrated water and irrigation application time at various plots. 共a兲 Same duration 共SD兲experiments and 共b兲 same applied water and solute 共SWS兲 experiments.
240 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003

the wetted perimeter for furrows were previously also reported by
Fangmeier and Ramsey 共1978兲 and Samani et al. 共1985兲.

Water and Bromide Recovery

Fig. 4. Network of rectangular elements for estimating water andbromide recovery rates. Symbols represent locations of measured soil
water contents and bromide concentrations.

Fig. 3共a兲兴. The infiltrated amounts of water 共IW兲 and bromide
increased with increasing irrigation depth during the two irrigation events. The infiltration rate during the first irrigation wasconsiderably higher than during the second one because of lower
initial soil water contents in the soil profile before the first irrigation as compared to the second one, and because of soil consolidation and surface sealing resulting from the first irrigation.
Similarly, in the SWS experiments there was a correlation between irrigation/bromide application time and water level. Irrigation and bromide application times increased, particularly during
the first irrigation, with decreasing water level in the furrows关Table 2 and Fig. 3共b兲兴. Application times for the second SWS
irrigation with 6 and 10 cm water levels were nearly the same
共Table 2兲. This likely was due mostly to spatial and temporal
共from one irrigation to another兲 variability in the soil hydraulicproperties. We conclude from both series of the experiments
共Table 2 and Fig. 3兲 that different water levels affected theamounts of infiltrated water/bromide and the irrigation/bromide
application time. Regression coefficients (R 2 ) of linear relationships between the different variables 共water levels and infiltrated
water/bromide; water levels and water/bromide application times兲
ranged from 0.76 –0.98. However, high obtained regression coefficients might be due to limited data points in making the linear
regressions. Linear relationships between the infiltration rate andFor purposes of estimating water and bromide recovery rates, thesoil profiles at each plot were subdivided into a network of rectangular elements 共22–30 rectangles depending upon the soil sampling depth, each having 20 cm by 25 cm兲 and volume of waterand mass of bromide were determined for each rectangle 共Fig. 4兲.
The mass of water/bromide in each profile was estimated by summation of water/bromide masses in the small rectangles. Neutronprobe and TDR readings taken immediately before and after eachirrigation event were used for estimating water recovery rates
whereas measured bromide concentrations and gravimetric soil
water contents collected during three different soil sampling
events and soil bulk densities 共Table 1兲 were used for calculating
bromide recovery rates for each plot.
Water and bromide recovery rates for different plots during thedifferent irrigation and soil sampling events are given in Table 3.
Relatively higher water recovery rates were obtained during thesecond irrigation. This may have been caused by the fact that theneutron probe and TDR slightly underestimated water contents
during relatively dry conditions 共including initial water content
values taken before the first irrigation兲.
Relatively high bromide recovery rates 共Table 3兲 were obtained at the first and second soil sampling times, but much lower
rates for the third soil sampling, except for Plot 4, mostly due toleaching below the soil sampling depths. Another reason for the
low recovery of the third soil sampling could be lateral solutetransport. However, the same depths of water or bromide solution
were applied to the adjacent furrows during the irrigation. The
low solute recovery for Plot 1 and Plot 5 during the third soil
sampling 共Table 3兲 could be caused by leaching beyond the maximum sampling depth of 180 cm.

Soil Water Contents
Soil water contour maps 共Figs. 5 and 6兲 were made using the
SURFER code 共Golden Software, Golden, Colo., 1999兲. Kriging
with linear variogram was selected as the gridding method since
this approach is one of the most flexible and useful methods available for almost any type of data sets 共Golden Software 1999兲.
Water contents of the 0–30 cm layer beneath the furrow bottom,
taken immediately after each irrigation event, were similar for all
the plots 关Figs. 5共a兲 and 6共a兲兴. The maximum measured watercontent of the surface layer beneath the furrow bottom was about
0.35 cm3 cm⫺3, orTable 3. Water and Bromide Recovery Rates for Different Experimental Plots During Various Irrigation and Soil Sampling Events 共in %兲
Water recovery
irrigation event

SD

SWS

Bromide recovery
soil sampling event

Experiment

Number 1

Number 2

Number 1a

Number 2b

Number 3c

Plot 1 共6 cm兲
Plot 2 共10 cm兲
Plot 3 共14 cm兲
Plot 4 共6 cm兲
Plot 5 共10 cm兲

88.4
88.4
92.6
90.0
99.3

97.3
90.4
91.0
101.6
102.6

96.8
93.2
85.2
78.2
81.4

96.1
80.02
79.9
70.4
73.4

63.2
70.8
71.1
96.2
66.1

a

Five days after the first irrigation.
Six days after the second irrigation.
cTwenty days after the second irrigation 共30 days from start兲.
b

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Fig. 5. Measured soil water contents 共volumetric %兲 in different plots: 共a兲 immediately; 共b兲 6 h; 共c兲 1 day; 共d兲 5 days; and 共e兲 10 days after firstirrigation.

242 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003

Fig. 6. Measured soil water contents 共volumetric %兲 in different plots: 共a兲 immediately; 共b兲 6 h; 共c兲 1 day; 共d兲 5 days; and 共e兲 10 days after thesecond irrigation

JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003 / 243

85% of the saturated water content, ␪ s ⫽0.407 cm3 cm⫺3 , as measured in the laboratory. This is consistent with the fact that fieldmeasured ␪ s values are generally lower than porosity because ofentrapped or dissolved air 共e.g., Klute 1986兲.
Water in the SD experiments 共6 and 10 cm WL兲 moved predominantly downward and not laterally to areas under the furrow
ridge. Water contents there remained almost unchanged. Lateralflow in the present study was limited because of the relatively
coarse-textured makeup of the soil 共being sandy loam with over
70% sand兲. For the SWS experiments, however, water moved
both vertically and horizontally, thus creating more favorable
two-dimensional wetting patterns in the root zone shortly after
each irrigation event. Wetting fronts from neighboring furrows in
the SD plots 共6 cm WL in particular兲 never reached the top of the
furrows while they met each other in the SWS plots during or
shortly after each irrigation. This may reflect the smaller amountsof water applied to the 6 and 10 cm SD plots as compared to the
SWS experiments.
As expected, most of the changes in water contents of the SD
plots occurred during the infiltration phase. Water contents, especially below depths of 100 cm, remained relatively unchanged,
also during redistribution 共Figs. 5 and 6兲, likely because of relatively small amounts of water applied and low pressure gradientin the soil profile. This is also true for the second irrigation. By
contrast, more pronounced changes were observed in the SWS
plots during both infiltration and redistribution. In those plotschanges below depths of 140 cm were relatively large. For instance, water contents at the bottom of Plot 5 increased fromabout 10% 关as the initial value; see Fig. 5共a兲兴 to about 19% 关10days after the second irrigation, Fig. 6共e兲兴. This means that deep
percolation in the SWS plots was substantially larger than that in
the SD plots.
During the redistribution phase, water contents in the plots
decreased with time in the surface layers 关Figs. 5共c, d, and e兲 and6共c, d, and e兲兴, in part due to the evaporation from the soil surface
and partly because of downward water redistribution within thesoil profile. This caused the water contents of the different plots tobe very similar in the surface layers almost ten days after eachirrigation event 关Figs. 5共e兲 and 6共e兲兴. Water distributions in allplots 共SD and SWS兲 during the second irrigation were almost thesame as during the first one. Even after the second irrigation,water contents of the SD plots below a depth of 140 cm remained
similar to the initial values taken before the first irrigation. Differences in water contents in the lower portions of the different
plots were mostly a consequence of having different initial conditions.

Bromide Concentration
Bromide contour maps 共Fig. 7兲 were made with the same method
as indicated in the previous section. Peak bromide concentrations
are clearly noticeable in the surface layers beneath the furrow
bottom during the first soil sampling five days after the first irrigation. Subsequent upward fluxes caused by evaporation from thesoil surface apparently moved bromide upward in the soil. Peakbromide concentrations during the second and third soil samplings were substantially lower as the second irrigation event
leached and redistributed the solutes within the soil profile bymeans of advective transport and likely some dispersion. Higher
solute concentrations were observed for the SWS experiments,
particularly during the second and third samplings; this becauseof longer solute/water application times for the SWS plots ascompared to the SD plots.

Overall, average solute fronts during the first soil sampling
five days after the first irrigation reached depths of about 60 and
80 cm in the SD and SWS plots, respectively. However, solutes in
the SWS plots were transported much deeper 共to about 150 cm兲,presumably because of preferential flow 关Fig. 7共a兲兴. The effects ofpreferential flow were observed during the second and third soil
sampling times in all the experimental plots 关Figs. 7共b and c兲兴.
The second irrigation event caused the average solute fronts tomove about 140 cm in all the plots except the 6 cm SD plot.
However, soil samples with relatively high bromide concentrations were even obtained at 180 cm depth in some of the plots
during both the second and third soil samplings. While preferential flow and spatial variability in the soil hydraulic and soluteproperties made it difficult to find a general relation between solute front and water level in the furrows, mean solute fronts in the
SWS plots were clearly much deeper than those in the SD plots.
Solute concentrations at relatively deep depths 共140 cm anddeeper兲 in the SD plots remained lower than those in the SWS
plots throughout the sampling period. Bromide in the SD plots
was transported primarily in the vertical direction 共onedimensional兲, leading to relatively high concentrations below the
furrow. By contrast, it was distributed much more evenly throughout the root zone in plots subject to the SWS treatments.
Applying fertilizers with irrigation water 共fertigation兲 using
relatively low water levels and short duration times such as thoseused for the SD experiments may hence be a concern from thepoint of view of fertilizer management. Under these conditions
fertilizers may remain beneath the furrow bottom rather thanbeing taken up by plant roots, and later leached beyond the rootzone through subsequent irrigations during the growing season.
This is particularly true at the beginning of the growing season
before plant roots are fully developed. The concern is also valid
when fertilizers are applied in solid form on the soil surface. In
this case the fertilizers will remain insoluble since the soil surface
will remain dry, particularly in the case of short-duration irrigations at relatively low water levels. Those fertilizers may later belost through volatilization or other environmental processes.

Summary
Several field experiments were carried out on short blocked-end
furrows and run for two successive irrigation events in a sandy
loam soil. The effects of different water levels were evaluated onwater flow and solute transport in the soil profile. We found apositive correlation between the cumulative amount of infiltrated
water/solute and water level in the furrows. Infiltrated water/
solute increased with increasing water level. Higher water levels
required less time for prescribed amounts of water/chemical toinfiltrate. Results also indicate that irrigation with higher waterlevels and relatively short application times leads to more uniform
water and solute distributions in the profile, and to less deep percolation of water and solutes as compared to irrigations withlower water levels and long durations. Irrigation with low andmoderate water levels and relatively short application times could
not provide water to all of the root zone and the surface layers.
The ridges of the furrows in particular remained dry. Althoughirrigation with low and moderate water levels and long application times resulted in better water and solute distributions within
the soil profile, they also caused water and solutes to move deeper
into the profile. Irrigation with a 14 cm water level and relatively
short duration 共90 min兲 provided sufficient water for soil moisture
to become more or less evenly distributed throughout the root
zone, including near the top of the furrows.

244 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JULY/AUGUST 2003

Fig. 7. Measured bromide concentrations 共g/L兲 in different plots: 共a兲 5 days after first irrigation; 共b兲 6 days after second irrigation; and 共c兲 20 days
after second irrigation 共30 days from the beginning兲

From an irrigation management perspective in blocked-end
furrow irrigated fields, it is recommended to use higher waterlevels and shorter durations to produce relatively uniform water
distributions, while lower water levels with longer application
times may be preferred for irrigations using low quality water.
Furthermore, a good irrigation management practice may be to
apply lower water levels and relatively short durations for fertilizers, during the second and third growing stage. Finally, we canconclude that water level and irrigation/solute application timeplayed an important role in this study, however results lack statistical strength since no replications were used in order to reacha solid conclusion. Results of similar experiments on long realistic furrows will be given in the subsequent papers to investigate
the effects of water level and application time under runningwater on subsurface water flow and solute distributions.

Acknowledgments
The first writer is very grateful to J. Jobes and J. Fargerlund at
U.S. Salinity Laboratory, Riverside, Calif. and C. Arterberry, D.
Powers, and C. Van Meeteren at U.S. Water Conservation Laboratory, Phoenix, for their help during the field experiments andsubsequent laboratory analyses. Thanks to Robert Roth, Directorof Maricopa Agriculture Center, and his colleagues for their collaboration during the field experiments and initial laboratory
analysis.

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