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USDA Agricultural Research Service –Lincoln,
Nebraska
Publications from USDA-ARS / UNL Faculty
University of Nebraska - Lincoln Year
Effect of irrigation amounts applied with
subsurface drip irrigation on corn
evapotranspiration, yield, water use
efficiency, and dry matter production in a
semiarid climate
Jose O. Payero∗David D. Tarkalson†Suat Irmak‡
Don Davison∗∗ James L. Petersen††
∗Queensland Government, Department of Primary Industries and Fisheries (QDPI&F),
203 Tor Street, Toowoomba, Queensland 4350, Australia
†USDA-ARS NW Irrigation and Soils Research Lab, 3793 North 3600 East, Kimberly, ID
‡University of Nebraska - Lincoln, sirmak2@unl.edu
∗∗University of Nebraska - Lincoln, ddavison1@unl.edu
††University of Nebraska - Lincoln, jpetersen2@unl.edu
This paper is posted at DigitalCommons@University of Nebraska - Lincoln.
http://digitalcommons.unl.edu/usdaarsfacpub/199
Effect of irrigation amounts applied with subsurface drip
irrigation on corn evapotranspiration, yield, water use
efficiency, and dry matter production in a semiarid climate
Jose
´O. Payero
a,
*, David D. Tarkalson
b
, Suat Irmak
c
, Don Davison
d
, James L. Petersen
d
a
Queensland Government, Department of Primary Industries and Fisheries (QDPI&F), 203 Tor Street, Toowoomba,
Queensland 4350, Australia
b
USDA-ARS NW Irrigation and Soils Research Lab, 3793 North 3600 East, Kimberly, ID 83341, USA
c
Department of Biological Systems Engineering, University of Nebraska-Lincoln, 241 L.W. Chase Hall, Lincoln, NE 68583-0726, USA
d
University of Nebraska-Lincoln, West Central Research and Extension Center, 461 West University Drive, North Platte, NE 69101, USA
agricultural water management xxx (2008) xxx–xxx
article info
Article history:
Received 20 July 2007
Accepted 27 February 2008
Keywords:
Subsurface drip irrigation (SDI)
Corn
Maize
Deficit irrigation
Water stress
Water use efficiency
Evapotranspiration (ET)
Harvest index
Dry matter
Yield response factor (ky)
abstract
Quantifying the local crop response to irrigation is important for establishing adequate
irrigation management strategies. This study evaluated the effect of irrigation applied with
subsurface drip irrigation on field corn (Zea mays L.) evapotranspiration (ETc), yield, water
use efficiencies(WUE = yield/ETc, and IWUE = yield/irrigation), and drymatter production in
the semiarid climate of west central Nebraska. Eight treatments were imposed with irriga-
tion amounts ranging from 53 to 356 mm in 2005 and from 22 to 226 mm in 2006. A soil water
balance approach (based on FAO-56) was used to estimate daily soil water and ETc.
Treatments resulted in seasonal ETc of 580–663 mm and 466–656 mm in 2005 and 2006,
respectively. Yields among treatments differed by as much as 22% in 2005 and 52% in 2006.
In both seasons, irrigation significantly affected yields, which increased with irrigation up to
a point where irrigation became excessive. Distinct relationships were obtained each
season. Yields increased linearly with seasonal ETc (R
2
= 0.89) and ETc/ETp (R
2
= 0.87)
(ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative
reduction in yield to relative reduction in ETc, averaged 1.58 over the two seasons. WUE
increased non-linearly with seasonal ETc and with yield. WUE was more sensitive to
irrigation during the drier 2006 season, compared with 2005. Both seasons, IWUE decreased
sharply with irrigation. Irrigation significantly affected dry matter production and parti-
tioning into the different plant components (grain, cob, and stover). On average, the grain
accounted for the majority of the above-ground plant dry mass (59%), followed by the
stover (33%) and the cob (8%). The dry mass of the plant and that of each plant component
tended to increase with seasonal ETc. The good relationships obtained in the study between
crop performance indicators and seasonal ETc demonstrate that accurate estimates of ETc
on a daily and seasonal basis can be valuable for making tactical in-season irrigation
management decisions and for strategic irrigation planning and management.
Published by Elsevier B.V.
*Corresponding author. Tel.: +61 7 4688 1513; fax: +61 7 4688 1197.
E-mail addresses: jose.payero@dpi.qld.gov.au,jpayero2@hotmail.com (J.O. Payero).
AGWAT-2589; No of Pages 14
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/agwat
0378-3774/$ – see front matter . Published by Elsevier B.V.
doi:10.1016/j.agwat.2008.02.015
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
1. Introduction
Irrigation water supplies are decreasing in many areas of the
US Great Plains due to extended drought periods, decline in
groundwater levels, litigation among states related to surface
water allocations, and diversion of water from irrigation to
environmental and municipal uses (McGuire, 2004; McGuire
and Fischer, 1999; Lingle and Franti, 1998). Water shortages
have heightened the importance of water in agricultural
production in the area and have triggered recent regulations
affecting irrigation water use. Such regulations include
installation of water meters on pumping stations, morator-
iums on drilling new wells, and limitations in groundwater
pumping to fixed multi-year water allocations. Under these
conditions, it is important to know how much yield can be
expected from a given water allocation for each alternative
crop, which is especially important for field corn (Zea mays L.),
the most important irrigated crop in the region.
In the semiarid environment of west central Nebraska,
water allocations that result in crop water stress can have a
significant impact on corn growth, development, and yield.
Knowing how much yield can be expected from a given water
allocation, however, is complicated by the fact that corn yield
is affected not only by the amount of seasonal irrigation, but
also by irrigation timing. Also, yield is affected by other
sources of water available to the crop in addition to irrigation.
These sources include water stored in the soil profile at crop
emergence and effective rainfall occurring during the growing
season. Many researchers have shown how corn grain yield
can be affected by irrigation timing (Jurgens et al., 1978;
NeSmith and Ritchie, 1992; Bryant et al., 1992; Jama and
Ottman, 1993). Most of these studies show that corn yield is
most affected by water stress when it occurs during the
reproductive stages (tasselling, silking, pollination, or grain
filling). In Nebraska, the reproductive growth stages coincide
with the period of peak crop evapotranspitation (ETc)
requirement, making stress during these stages even more
significant.
Other studies have linked yields reduction to a reduction in
ETc or transpiration, and some researchers have developed
different yield versus ETc relationships for different growth
stages (Jensen, 1968; Hanks, 1974; Nairizi and Rydzewski, 1977;
Barrett and Skogerboe, 1978; Doorenbos and Kassam, 1979;
Gilley et al., 1980; Schneekloth et al., 1991; Klocke et al., 2004).
Payero et al. (2006b), however, showed that the reported yield
versus ETc relationships for corn are not consistent and vary
with location, which is likely due to differences in rainfall
pattern, soil and crop characteristics, management practices,
and weather conditions.
In Nebraska, research on irrigation has previously focused
on sprinkler and surface systems (Gilley et al., 1980;
Schneekloth et al., 1991; Hergert et al., 1993; Klocke et al.,
2004; Payero et al., 2005, 2006a,b; Schneekloth et al., 2006).
However, due to the current and expected limited water
supplies, interest in subsurface drip irrigation (SDI) systems to
irrigate row crops in Nebraska is growing. Although studies
with SDI-irrigated corn have been conducted in other states
(Ayars et al., 1999; Camp, 1998; Caldwell et al., 1994; Howell
et al., 1997; Lamm et al., 1995; Lamm and Trooien, 2003), local
information on the response of corn growth, yield and other
crop–water dynamics with SDI is very limited. The agronomic
response of the crop to irrigation with SDI is needed to be able
to evaluate the economic and technical feasibility of using SDI
under local conditions and provide scientifically based
practical information to the users on best management
practices for SDI-irrigated corn. The objective of this study
was to evaluate how different seasonal irrigation depths
applied with SDI affected the soil water balance, seasonal
evapotranspiration, yield, water use efficiency, and dry matter
production of corn in the semiarid climate of west central
Nebraska.
2. Materials and methods
2.1. Site description
Field experiments were conducted during the 2005 and 2006
growing seasons. The experiments were located at the
University of Nebraska-Lincoln West Central Research and
Extension Center, in North Platte, Nebraska (41.18N: 100.88W:
861 m above sea level). The climate at North Platte is semiarid,
with average annual precipitation of approximately 508 mm
and reference evapotranspiration of 1403 mm (USDA, 1978).
Table 1 – Seasonal total and monthly irrigation depths (mm) applied to each corn irrigation treatment (T1–T8) during the
2005 and 2006 growing seasons at North Platte, Nebraska
Year Month Treatment
T1 T2 T3 T4 T5 T6 T7 T8
2005 July 53 61 87 87 107 104 105 106
August 0 15 15 66 114 150 188 225
September 0 0 0 0 0 0 13 25
Total 53 76 102 153 221 254 306 356
2006 June 8 4 8 8 8 8 8 8
July 13 62 89 121 124 120 123 176
August 0 0 0 0 39 46 65 41
September 0 0 0 0 13 0 1 0
Total 22 66 97 130 184 173 197 226
agricultural water management xxx (2008) xxx–xxx2
AGWAT-2589; No of Pages 14
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
On average, about 80% of the annual precipitation occurs
during the growing season, which extends from late-April to
mid-October (USDA, 1978). The soil at the experimental site is
a Cozad silt loam (fine-silty, mixed, mesic Fluventic haplustoll).
From measurements obtained from the experimental plots
during this study, it was estimated that the average water
contents at field capacity (FC) and permanent wilting point
(PWP) in the crop root zone were approximately 0.35 and
0.09 m
3
m
3
, respectively.
2.2. Experimental design
The field experiment was conducted using a randomized
complete block design with eight irrigation treatments (T1–T8)
and four replications. Each treatment received a seasonal
irrigation allocation, which ranged from 53 to 356 mm in 2005
and from 22 to 226 mm in 2006 (Table 1). The aim was to
develop well-defined crop response functions to irrigation,
ranging from near dryland to over-irrigated conditions. A
dryland treatment was not included because some irrigation
water was needed to apply nitrogen fertilizer. Irrigations were
scheduled to avoid or minimize water stress and deep
percolation. The target was to keep the percent soil water
depletion in the crop root zone below 50% of the total available
soil water for as much of the season as possible. Another target
was to maintain a soil water depletion of at least 50 mm to
store potential rainfall and avoid deep percolation, which was
especially important for treatments receiving and excessive
allocation. For treatments with a deficient allocation to meet
irrigation requirements for the entire season, the strategy was
to minimize stress during the peak ETc period (in July),
allowing stress later in the season. Once irrigation started, all
treatments were irrigated at the same time until the allocation
for a given treatment ran out. Irrigations were usually applied
two to three times a week. In 2005, irrigations started in mid-
July, since rainfall and stored soil water provided adequate
moisture for crop development earlier in the season. In 2006,
irrigation started in June due to drier soil conditions compared
with 2005.
Each experimental plot was 9 m 37 m, which accom-
modated 12 corn rows. The crop was irrigated with a SDI
system that was installed just prior to planting in 2005, in a
field that was planted to surface-irrigated soybean in 2004.
The SDI laterals were spaced at 1.5 m (every other corn row)
and were installed at a depth of 0.4 m between the two crop
rows. Laterals were 12.5-mil thin-wall dripper lines (Dripnet
PC 1613 F, Netafim USA, Fresno, CA) with inside diameter of
1.6 cm and pressure-compensating emitters spaced every
46 cm. The nominal flow of the emitters was 0.98 L h
1
(applying 1.5 mm h
1
) at a pressure of 69 kPa. Water for the
system was pumped from the Ogallala aquifer and was
filtered using a 152-mm diameter screen filter with a 150-
mesh screen (model 8060F-MN, Netafim USA, Fresno, CA).
Irrigation to each treatment was controlled from a manifold
that had eight branches. Each branch had a flow meter (25.4-
mm model 36M251T), equipped with a pulse reed switch
(model 36RD, Netafim USA, Fresno, CA). It also had a 19-mm
electric/manual control valve (model S390-3-0, Dorot Control
Valves Inc., Fresno, CA), a pressure regulator (‘‘Standard’’
model, 0.22–1.26 L s
1
, 62.1 kPa) (Netafim USA, Fresno, CA),
and an air and vacuum relief air vent with shrader valve
(‘‘Guardian’’ model, Netafim USA, Fresno, CA). Irrigations
were controlled manually in 2005, and an automatic con-
troller (model NMC-64; Netafim USA, Fresno, CA) was used in
2006.
2.3. Cultural practices
Corn was planted on May 18 and 11, and matured on
September 23 and 20 in 2005 and 2006, respectively. During
both seasons, corn with a comparative relative maturity of
112 days (hybrid Kaystar KX-8615Bt) was planted at 0.76-m
row spacing and an average seeding rate of 7.6 seeds per m
2
.
Nitrogen (N) was applied with the starter fertilizer and by
fertigatingthroughtheSDIsystemduringthegrowing
season. The N application rate was based on soil analysis.
All treatments received 11 kg N ha
1
as 10-34-0 with
the starter fertilizer. Fertigation with urea ammonium
nitrate consisted of 108 kg N ha
1
applied on 15 July 2005,
and 213 kg N ha
1
applied on 5 July 2006. In 2005, an
estimated 50 kg N ha
1
was supplied by the previous
soybean crop.
A herbicide mixture (93.4 L ha
1
) containing Lumax
1
(3.51 L ha
1
), Banvel
1
(0.58 L ha
1
), Atrazine 90 DF
(1.12 kg ha
1
) and crop oil (1.42 L per 378 L of water) was
applied when the crop was at the V4 stage. Target weeds were
Kochia (Kochia scoparia L.), Common Lambsquaters (Chenopo-
dium album L.), Redroot Pigweed (Amaranthus restroflexus L.),
Field Sandbur (Cenchrus longispinus (Hack.) Fern.), Yellow
Foxtail (Setaria glauca L.) and Puncturevine (Tribulus terrestris
L.). The insecticide Force
1
3G (4.92 kg ha
1
) was applied using
a 18-cm T-band in front of the press wheel at planting time.
Target insects were the Corn Rootworm Beetle (Diabrotica
virgifera LeConte) and the European Corn Borer (Ostrinia
nubilalis (Hu
¨bner)). These applications prevented negative
effects of weeds and insects on corn growth.
2.4. Yield and dry matter measurements
The center three rows (37 m) of each plot were harvested in
early November using a plot combine with a three-row corn
head. The combine had a Harvest Data System (model HM-400,
Juniper Systems Inc. Logan, Utah), which measured the total
mass, water content, and ‘‘test weight’’ of the harvested grain.
The grain yield per plot was calculated both in a ‘‘dry-mass
basis’’ (0% water content) and in a ‘‘wet-mass basis’’ (standard
water content of 15.5%).
Eight plants from each plot were also hand-harvested to
determine dry matter production and its partitioning into the
different plant components (grain, stover, and cob). Plants
were cut at ground level and the ears were separated from the
stover. The stover samples were weighted, chopped using a
tractor-operated plant chopper, and a sub-sample was
collected from each plot and weighted. The sub-samples were
oven-dried at 70 8C until they reached a constant mass (7 days)
and their masses were recorded. The ear samples were placed
in a greenhouse to air-dry to a moisture content of
approximately 15–16%, and then weighted and shelled by
hand. Grain and cob samples were taken, oven-dried at 70 8C
until they reached a constant mass (7 days), and weighted.
agricultural water management xxx (2008) xxx–xxx 3
AGWAT-2589; No of Pages 14
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
From this information, the average dry mass per plant and the
dry mass and percent of total plant dry mass of the grain, cob,
and stover were calculated for each plot.
2.5. Soil water balance and crop evapotranspiration
Daily soil water balance and crop evapotranspiration (ETc)
were estimated with a computer program that was written
in Microsoft Visual Basic
1
. The inputs to the program were
daily weather data, including rainfall, irrigation date and
amounts, initial water content in the soil profile at crop
emergence, and crop- and site-specific information such as
planting date, maturity date, soil parameters, maximum
rooting depth, etc. Similar daily soil water balance models
have previously been used by Robinson and Hubbard (1990),
Swan et al. (1990),andBryant et al. (1992). The computer
program calculated daily ETc and the water balance in the
crop root zone using the procedure described in FAO-56
(Allen et al., 1998). Readers are referred to the original
sources for additional details. This procedure obtains
ETc as the product of the evapotranspiration of a grass-
reference crop (ET
o
)andacropcoefficient(K
c
). ET
o
is
calculated using the weather data as input to the
Penman–Monteith equation and the K
c
is used to adjust
the estimated ET
o
for the reference crop to that of other
crops at different growth stages and growing environments.
In this study, the dual K
c
approach was used, which
separates the two components of ETc, namely evaporation
(E) and transpiration (T). For corn, this procedure linearly
reduces ETc when the soil water depletion in the crop
root zone exceeds 55% (taken from Table 22 in FAO-56) of
total available water. Reducing the ETc rate when the crop
is under water stress is consistent with the findings
of Dwyer and Stewart (1984, 1985),andGavloski et al.
(1992).ThedualK
c
procedure also accounts for the sharp
increases in E due to a wet soil surface following rain or
irrigation events. This procedure, therefore, permitted
calculation of daily ETc under water-limiting conditions,
and when soil water was not limiting (ETp). From the
seasonal ETc and ETp values, the ETc/ETp ratio was
calculated for each treatment.
Weather data were obtained from an automatic weather
station located within 1.5 km from the research site. This
weather station was part of the High Plains Regional Climate
Center (HPRCC) weather network. Daily weather data
were downloaded from the HPRCC web site (http://
www.hprcc.unl.edu/home.html), including daily maximum
and minimum air temperature, relative humidity, wind
speed, rainfall, solar radiation, reference and crop ET for
different crops, including corn. Rainfall data were also
collected manually from rain gauges installed at each of the
four corners of the field.
The performance of the computer model was evaluated by
comparing its soil water content outputs with values
measured using the neutron probe method (Evett and Steiner,
1995). Measurements were made at 0.3-m increments to a
depth of 1.8 m three times each season on 7 July, 15 August,
and 23 September 2005, and on 14 June, 11 August, and 21
November 2006. Gravimetric samples were also taken on 7
June 2005 to a depth of 1.0 m.
2.6. Water use efficiencies
Water use efficiency (WUE, kg m
3
) and irrigation water use
efficiency (IWUE, kg m
3
) were calculated as
WUE ¼Y
ETc (1)
IWUE ¼Y
I(2)
where Y= yield (g m
2
), ETc = seasonal crop evapotranspira-
tion (mm), I= seasonal irrigation (mm).
2.7. Statistical analyses
Analysis of variance (ANOVA) and separation of means were
conducted using the GenStat
1
for Windows
1
statistical
software (VSN International Ltd., Hertfordshire, UK). To
evaluate the effect of irrigation treatment, a separate ANOVA
was conducted for each year of the experiment. Year was not
included as a factor in the ANOVA since irrigation amounts for
the different treatments varied with season. Regression
analyses were performed with Microsoft Excel
1
. The root
mean square error (RMSE) was used to evaluate the perfor-
mance of the soil water balance model. The RMSE was
calculated as
RMSE ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
nX
n
i¼1
ðSWmSWeÞ2
v
u
u
t(3)
where n= number of observations, SW
m
= measured soil
water (m
3
m
3
), and SW
e
= estimated soil water (m
3
m
3
).
Because it is an indication of both bias and variance of the
SW
e
values with respect to the SW
m
values, the RMSE provides
an effective measure to evaluate the performance of the
model. Lower RMSE values indicate better agreement between
SW
e
and SW
m
values.
3. Results and discussion
3.1. Weather conditions during the growing seasons
Average values of weather variables during the 2005 and 2006
corn growing seasons at North Platte, Nebraska, are shown in
Table 2. The seasonal average air temperature was the same
(21.8 8C) during both seasons. In 2006, however, temperatures
were hotter in May–July, and cooler in August and September,
compared with 2005. On average, wind speed and relative
humidity were higher in 2005. The average solar radiation,
however, was about 5% higher in 2006.
The cumulative daily rainfall during 2005, 2006 and 1982–
2006 at North Platte are shown in Fig. 1. The two seasons had
similar annual rainfalls of 409 and 403 mm for 2005 and 2006,
respectively. The rainfall during both seasons was just below
the 1982–2006 average of 423 mm. The average rainfall during
the last 25 years (1982–2006) was only 83% of the long-term
average of 508 mm reported in USDA (1978). Although both
agricultural water management xxx (2008) xxx–xxx4
AGWAT-2589; No of Pages 14
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
seasons had similar rainfall, 2005 followed a wetter-than-
normal year (2004), while 2006 followed a year with just-
below-normal rainfall. Therefore, there was a higher chance of
having more water stored in the soil profile at planting in 2005
compared with 2006.
The monthly distribution of rainfall for 2005, 2006, and the
1982–2006 average for rainfall and alfalfa-reference evapotran-
spiration (ETr) at North Platte are shown in Fig. 2. ETr values,
instead of ET
o
, are normallyreported by the HPRCC and areused
here. However, ETc values in this study were calculated based
on ET
o
. At North Platte, ETr is normally much higher than
rainfall, which explains the need for irrigation. The average
annual rainfall for 1982–2006 was 423 mm, while ETr was
1532 mm, therefore, rainfall represented only 27.6% of ETr.
During 2005 and2006 there was almost twice as much rainin
June, which is the wettest month for the area, compared with
the long-termaverage. The total in-seasonrain was very similar
both seasons, with 295 and 282 mm for 2005 and 2006,
respectively. However, in 2005 there was considerably more
rain in May, makingmore water available to the crop at planting
time and early in the season compared with 2006. In 2006, there
was very little rain in May (only 13 mm), which was well below
normal. In 2006,there was more rain in September than in 2005.
That additionalrain in September, however,occurred too late in
the growing season to have a significant impact on cropgrowth
and yield, considering that by 1 September 2006 the corn had
already entered the R5 growth stage (dent) (Hoeft et al., 2000).
During both seasons, rain in July was considerably below
normal. This is significant because Julyhad the peak ETr (Fig. 2),
and the corn had progressed to the reproductive growth stages.
The R1 growth stage (silking) started on 18 July and 11 July in
2005 and 2006, respectively.
3.2. Initial soil water
In 2005, all treatments started with the same soil water profile,
since there was abundant rain in May and irrigation treat-
ments were not applied in the experimental plots in 2004.
Gravimetric soil sampling in early June (Fig. 3) showed a near
uniform soil water content in the top 1 m of soil profile,
although later measurements showed considerable water
depletion deeper in the soil profile. In 2006, however, due to
little rain in May and to the irrigation treatments applied in
2005, there were considerable differences in the initial soil
water profiles among treatments (Fig. 3). The treatments that
were deficit irrigated in 2005 started the 2006 season with little
soil water, especially deep in the profile.
3.3. Performance of the soil water balance model
The computer model provided very good estimates of average
soil water in the crop root zone compared with neutron probe
measurements during both seasons (Fig. 4). On average, the
estimated soil water values tended to follow the 1:1 line when
compared with measured values during both seasons. Also the
measured and estimated values were linearly related with
high R
2
values of 0.90 and 0.85 in 2005 and 2006, respectively.
The RMSEs calculated between the estimated and measured
values were also relatively small with 0.018 and 0.019 m
3
m
3
for 2005 and 2006, respectively.
Fig. 1 – Cumulative rain for 2005, 2006 and 1982–2006 at
North Platte, Nebraska.
Table 2 – Average weather conditions during the 2005 and 2006 corn growing seasons at North Platte, Nebraska
Year Month T
max
(8C) T
min
(8C) T
avg
(8C) u
2
(m s
1
) Rs (MJ m
2
d
1
) RH (%) VPD (kPa)
2005 May 21.4 7.9 14.6 2.8 17.9 65.7 0.7
June 27.6 14.2 20.9 3.2 22.5 69.5 0.9
July 32.9 16.2 24.5 3.2 24.4 57.0 1.5
August 29.8 15.2 22.5 2.5 19.8 68.3 1.0
September 29.4 12.9 21.2 3.2 18.4 59.5 1.2
Total 29.4 14.3 21.8 3.0 21.2 63.9 1.1
2006 May 30.1 10.8 20.4 2.7 27.1 42.4 1.7
June 30.5 14.7 22.6 2.8 25.7 54.5 1.5
July 32.6 17.6 25.1 2.6 24.2 58.1 1.6
August 29.2 15.6 22.4 2.6 18.3 68.9 1.0
September 23.6 7.2 15.4 2.2 17.0 68.5 0.7
Total 29.6 14.0 21.8 2.6 22.4 59.5 1.3
Grand total 29.5 14.1 21.8 2.8 21.8 61.7 1.2
T
max
= maximum air temperature, T
min
= minimum air temperature, T
avg
= average air temperature, u
2
= wind speed at 2 m height, Rs = solar
radiation, RH = relative humidity, VPD = vapour pressure deficit, only data from corn emergence to maturity were included.
agricultural water management xxx (2008) xxx–xxx 5
AGWAT-2589; No of Pages 14
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
3.4. Effect of irrigation on evapotranspiration
The potential corn evapotranspiration (ETp) (ETp = ETc with
no water stress) from emergence to the R6 growth stage
(physiological maturity or ‘‘black-layer’’) was practically the
same during both seasons, calculated at 663 mm. The
cumulative ETp was linearly related (except early in the
season) to the Fraction of Season
1
(Fs) (Fig. 5). Both seasons,
cumulative ETp followed the same straight line after approxi-
mately Fs 0.25 in 2005 and Fs 0.20 in 2006. Where properly
calibrated, this linear relationship between cumulative ETp
and Fs can potentially be used to extrapolate and predict ETp
during the season and to make in-crop irrigation scheduling
decisions. Payero et al. (2005) reported similar linear relation-
ships for soybean at this site.
During both seasons, ETc increased with irrigation up to a
point where irrigation became excessive (Fig. 6). No increase in
ETc was observed for irrigation amounts above 221 mm (T5) in
2005 and 173 mm (T6) in 2006. There was a steeper increase in
ETc with irrigation during 2006 compared with 2005.
The cumulative crop evapotranspiration (ETc) for each
treatment and the cumulative ETp are shown in Fig. 7. During
both seasons, some of the treatments suffered from water
stress, although water supplies were adequate for all treat-
ments early in the season. In 2005, stress for the driest
treatment started in mid August. In 2006, however, stress for
the driest treatment occurred about a month earlier (in mid
July). Stress created differences in seasonal ETc among
Fig. 2 – Monthly rain for 2005, 2006, and the long-term averages (1982–2006) for rain and alfalfa-reference evapotranspiration
(ETr) at North Platte, Nebraska.
Fig. 3 – Average soil water for all treatments measured from gravimetric samples in June 2005 (error bars are treatment
means Wstandard deviation), and soil water for the different irrigation treatments (T1–T8) measured with the neutron
probe method in June 2006.
1
Fraction of Season is the ratio of cumulative growing degree
days (CGDD) from crop emergence to required CGDD from crop
emergence to maturity.
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Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
treatments. A wider range of seasonal ETc among treatments
resulted in 2006 compared with 2005. The seasonal ETc and
ETc/ETp ratios for the different treatments are shown in
Table 3. In 2005, seasonal ETc for all treatments averaged
630 mm and ranged from 580–663 mm. The ETc/ETp ratio
averaged 0.95 and ranged from 0.87 to 1.00. In 2006, drier soil
conditions resulted in a lower seasonal ETc that averaged
600 mm and ranged from 466 to 656 mm. The ETc/ETp ratio
averaged 0.90 and ranged from 0.70 to 0.99.
3.5. Effect of irrigation on yield and water use efficiencies
Yield, water use efficiency (WUE), and irrigation water use
efficiency (IWUE) for the different treatments are shown in
Table 4, both in ‘‘dry-mass basis’’ and ‘‘wet-mass basis’’.
Irrigation significantly affected yields during both years.
Yields were higher in 2005 compared with 2006, averaging,
in a ‘‘dry-mass basis,’’ 968 and 828 g m
2
in 2005 and 2006,
respectively. In 2005, yields ranged from 844 to 1085 g m
2
,a
yield difference of 241 g m
2
(22%). In 2006, yields ranged from
455 to 957 g m
2
, a yield difference of 502 g m
2
(52%).
Relationships relating yield to seasonal irrigation, ETc, ETc/
ETp are shown in Fig. 8A–C. It also shows the relative yield
decrease with respect to the relative evapotranspiration deficit
(Fig. 8D) as proposed by Doorenbos and Kassam (1979). During
both seasons, yields tended to increase with irrigation up to
the point where irrigation became excessive (Fig. 8A).
Although not quantified, excessive irrigation most likely
reduced the amount of oxygen in the crop root zone and
increased the likelihood of nitrogen leaching, making less of it
available for crop uptake. During both seasons yields peaked
Fig. 4 – Estimated and measured soil water content obtained at North Platte, Nebraska, during the 2005 and 2006 growing
seasons. Each data point represents the average soil water content in the crop root zone to a depth of 1.8 m for each
treatment (T1–T8), including three sampling dates each year. RMSE is the root mean squared error.
Fig. 5 – Relationships between cumulative ETp and Fraction
of season (FS) obtained during the 2005 and 2006 growing
seasons at North Platte, NE. ETp = crop evapotranspiration
(ETc) with no water stress. FS is the ratio of cumulative
growing degree days (CGDD) from crop emergence to
required CGDD from crop emergence to maturity.
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
with treatment T6, which applied 254 and 173 mm of irrigation
in 2005 and 2006, respectively. Different yield versus irrigation
functions were obtained each season, with a steeper slope
obtained in 2006. When seasonal irrigation was not excessive,
higher yields were obtained with the same amount of
irrigation in 2005 compared with 2006. These results are not
surprising since the relationship between yield and irrigation
is not unique and varies with season and location. On the
other hand, yields were linearly related to seasonal ETc
(Fig. 8B) and to seasonal ETc/ETp (Fig. 8C), and the relation-
ships practically followed the same line during both seasons.
Good linear relationships between relative evapotranspira-
tion deficit and relative yield decrease were observed in 2006
and combining data from the two seasons (2005–2006)
(Fig. 8D). In 2005 the relation was poor probably due to the
limited stress observed that year. The slope of the line in
Fig. 8D represents the yield response factors (ky) as proposed
by Doorenbos and Kassam (1979). The ky = 1.58 was higher
than the 1.25 value reported by Doorenbos and Kassam (1979)
for stress during the total growing period, but close to the 1.50
value reported for stress during the reproductive stages.
WUE values varied considerably with irrigation treatment,
especially during the drier 2006 season (Table 4). Values
tended to be higher in 2005, averaging 1.53 and 1.37 kg m
3
(dry-mass basis) in 2005 and 2006, respectively. Differences in
WUE between the driest and wettest treatment were 12 and
35% in 2005 and 2006, respectively. Irrigation treatments,
however, impacted IWUE much more than WUE. Differences
in IWUE between the driest and wettest treatment were 82 and
80% in 2005 and 2006, respectively. Fig. 9 shows that WUE
increased non-linearly with seasonal ETc and with yield, when
combining data from both seasons. Both of these relationships
are determined by the observed linear relationship between
yield and ETc (Fig. 8B). If the relationship between yield and
ETc is linear (yield = slope ETc intercept), then for
WUE = 0, ETc = (intercept/slope), and yield = 0. The curvilinear
function results from the fact that the intercept 6¼ 0.
Fig. 10 shows IWUE and WUE as functions of irrigation.
IWUE sharply decreased with irrigation, with similar tenden-
cies observed during both seasons. The decreasing tendency of
IWUI with irrigation is expected in areas where the dryland
yield (yield with no irrigation) is positive. However, in
situations when no dryland yield can be obtained without
irrigation, IWUE would be expected to increase with irrigation,
and in situations when the dryland yield is exactly zero (a rare
Fig. 7 – Cumulative corn evapotranspiration (ETc) for each
irrigation treatment (T1–T8) during the 2005 and 2006
growing seasons at North Platte, Nebraska. ETp = ETc with
no water stress.
Fig. 6 – Relationship between irrigation and seasonal crop
evapotranspiration (ETc) for corn obtained at North Platte,
Nebraska, during 2005 and 2006.
Table 3 – Seasonal corn evapotranspiration calculated for
each irrigation treatment during the 2005 and 2006
growing seasons at North Platte, Nebraska
Treatment 2005 (ETp = 663 mm) 2006 (ETp = 663 mm)
ETc (mm) ETc/ETp ETc (mm) ETc/ETp
T1 580 0.87 466 0.70
T2 586 0.88 537 0.81
T3 612 0.92 570 0.86
T4 633 0.96 627 0.95
T5 663 1.00 639 0.96
T6 655 0.99 656 0.99
T7 655 0.99 651 0.98
T8 655 0.99 653 0.99
Average 630 0.95 600 0.90
Minimum 580 0.87 466 0.70
Maximum 663 1.00 656 0.99
ETc = crop evapotranspiration and ETp = ETc with no water stress.
agricultural water management xxx (2008) xxx–xxx8
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
Fig. 8 – Corn yield response to seasonal irrigation, evapotranspiration (ETc) and ETc/ETp obtained during 2005 and 2006 at
North Platte, Nebraska. ETp = ETc with not water stress, Y= yield and Y
m
= maximum yield. Yields were calculated in a dry-
mass basis (0% grain water content). Error bars are treatment means Wstandard deviation.
Table 4 – Corn yield, water use efficiency (WUE), and irrigation water use efficiency (IWUE) for each irrigation treatment
obtained in 2005 and 2006 at North Platte, Nebraska, considering grain yield in both dry-mass and wet-mass basis
Treat Dry-mass basis Wet-mass basis
2005 2006 2005 2006
Yield
(g m
2
)
IWUE
(kg m
3
)
WUE
(kg m
3
)
Yield
(g m
2
)
IWUE
(kg m
3
)
WUE
(kg m
3
)
Yield
(g m
2
)
IWUE
(kg m
3
)
WUE
(kg m
3
)
Yield
(g m
2
)
IWUE
(kg m
3
)
WUE
(kg m
3
)
T1 844 e 15.93 1.46 455 e 21.08 0.98 999 e 18.85 1.72 539 e 24.95 1.16
T2 901 de 11.85 1.54 711 d 10.77 1.32 1066 de 14.03 1.82 842 d 12.74 1.57
T3 932 cd 9.14 1.52 814 c 8.37 1.43 1103 cd 10.81 1.80 963 c 9.90 1.69
T4 935 cd 6.11 1.48 875 cb 6.76 1.40 1106 cd 7.23 1.75 1036 cb 8.00 1.65
T5 1022 ab 4.62 1.54 953 a 5.17 1.49 1209 ab 5.47 1.82 1128 a 6.12 1.76
T6 1085 a 4.27 1.66 957 a 5.52 1.46 1284 a 5.06 1.96 1133 a 6.53 1.73
T7 984 bc 3.21 1.50 927 ab 4.70 1.42 1164 bc 3.80 1.78 1097 ab 5.56 1.68
T8 1040 ab 2.92 1.59 933 ab 4.13 1.43 1231 ab 3.46 1.88 1104 ab 4.88 1.69
Average 968 7.26 1.53 828 8.31 1.37 1145 8.59 1.82 980 9.84 1.62
Minimum 844 2.92 1.46 455 4.13 0.98 999 3.46 1.72 539 4.88 1.16
Maximum 1085 15.93 1.66 957 21.08 1.49 1284 18.85 1.96 1133 24.95 1.76
Difference 241 13.01 0.20 502 16.95 0.51 285 15.39 0.24 594 20.06 0.61
Difference (%) 22% 82% 12% 52% 80% 35% 22% 82% 12% 52% 80% 35%
S.E.M. 26 29 26 29
WUE = yield/[seasonal crop evapotranspiration], IWUE = yield/irrigation. The ‘‘dry-mass basis’’ and ‘‘wet-mass basis’’ yields were calculated at
0 and 15.5% grain water contents, respectively. Yields with the same letters are not significantly different at the 5% significance level.
S.E.M. = standard errors of means.
agricultural water management xxx (2008) xxx–xxx 9
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
coincidence), IWUE would be constant with irrigation,
assuming no over-irrigation. Fig. 10 also shows that WUE
varied little with irrigation in 2005, but tended to be well
related to irrigation in 2006. In 2006, WUE increased with
irrigation up to the point where additional irrigation did not
produce additional yield, in a similar fashion as the relation-
ship between irrigation and yield (Fig. 8A). These results show
that IWUE and WUE had an opposite behavior with irrigation.
Some researchers and the general public often refer to
‘‘increasing water use efficiency’’ in general terms as a
desirable objective. In some cases they are referring to WUE
and in others to IWUE or other measures of water use
efficiency such as yield/(total water) (total water = rain + irri-
gation + soil water). These results show that these terms
should not be interchanged and care should be taken to define
exactly what it is that they want to increase. The feasibility of
increasing either the WUE or IWUE is a decision that needs to
be based not only on the biophysical response of the crop but
also on economic factors. Often the objective of producers is
not to increase yields but to increase profits. If water is the
factor limiting production, increasing IWUE (which means
decreasing WUE) could be desirable. In instances where water
is not the limiting factor, irrigation to produce maximum yield,
which will tend to increase WUE but to decrease IWUE could be
the most profitable option. Determining the level of irrigation
needed to optimize profits can be complex and depends on
both biophysical and economic factors (English et al., 2002;
Martin et al., 1989; Norton et al., 2000).
3.6. Effect of irrigation on dry matter production
The dry matter productions for the entire corn plant and for
the different plant components (grain, cob, and stover)
obtained during the two seasons are shown in Table 5. Data
Fig. 9 – Corn water use efficiency (yield/ETc) as a function of seasonal crop evapotranspiration (ETc) and yield obtained
during 2005 and 2006 at North Platte, Nebraska. Functions were extrapolated beyond observed values to fit the values
dictated by the observed yield versus ETc linear function. Yields were calculated in a dry-mass basis (0% grain water
content).
Fig. 10 – Corn water use efficiency (WUE = yield/ETc) and irrigation water use efficiency (IWUE = yield/irrigation) as a
function of seasonal irrigation obtained during 2005 and 2006 at North Platte, Nebraska. ETc = crop evapotranspiration.
Yields to determine WUE and IWUE were calculated in a dry-mass basis (0% grain water content).
agricultural water management xxx (2008) xxx–xxx10
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
Fig. 11 – Relationships between corn seasonal evapotranspiration (ETc) and the dry mass of the plant, grain, cob, and stover
obtained with different irrigation treatments during 2005 and 2006 at North Platte, NE. Differences in dry mass of plant,
grain and cob among treatments were statistically significant at the 5% significance level for both seasons, while those of
the stover were not.
Table 5 – Corn dry matter production obtained during 2005 and 2006 with different irrigation treatments at North Platte,
Nebraska
Year, treatment Dry mass (g plant
1
) % Of plant dry mass
Plant Grain Cob Stover %Grain %Cob %Stover
2005, T1 248 bc 146 bc 22 a 80 a 58.8 ab 9.0 a 32.2 b
T2 244 c 137 c 21 a 86 a 56.2 d 8.6 bc 35.2 a
T3 258 bc 149 bc 22 a 87 a 57.6 bcd 8.6 b 33.7 ab
T4 264 bc 155 bc 23 a 86 a 58.7 ab 8.6 b 32.6 b
T5 281 ab 163 ab 24 a 95 a 57.9 abc 8.5 bc 33.6 ab
T6 307 a 175 a 26 a 106 a 57.0 cd 8.4 bc 34.6 a
T7 262 bc 155 bc 22 a 84 a 59.3 a 8.6 bc 32.1 b
T8 284 ab 162 ab 24 a 98 a 57.2 cd 8.3 c 34.4 a
Average (2005) 268.5 155.3 23.01 90.2 57.9 8.58 33.6
2006, T1 143 a 74 a 10 a 59 a 52.2 a 6.9 a 41.0 c
T2 221 b 131 b 17 b 73 a 59.4 b 7.7 a 32.9 b
T3 240 b 147 b 19 b 74 a 61.2 bc 7.8 a 31.0 ab
T4 246 b 152 b 19 b 75 a 61.6 c 7.6 a 30.8 a
T5 248 b 152 b 18 b 79 a 61.0 bc 7.3 a 31.8 ab
T6 247 b 152 b 18 b 76 a 61.7 c 7.4 a 30.9 a
T7 254 b 157 b 19 b 78 a 61.7 c 7.5 a 30.7 a
T8 262 b 162 b 20 b 80 a 61.8 c 7.5 a 30.7 a
Average (2006) 232.7 140.8 17.5 74.4 60.1 7.5 32.5
Average (2005–2006) 250.6 148.1 20.2 82.3 59.0 8.0 33.0
Means with the same letters within a season were not significantly different at the 5% significance level.
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
are presented as dry mass per plant and as a percentage of
total plant dry mass (%Grain, %Cob, and %Stover). On average
for all treatments, dry matter production (dry mass) for the
plant and for each of the plant components was higher in 2005
than in 2006. In a percentage basis, however, the %Grain was
higher, while the %Cob and %Stover were lower in 2006. In
2005, irrigation treatments significantly affected all dry matter
variables, except for the dry mass of the cob and the stover. In
2006, all variables were significantly affected by irrigation
treatments, except for the dry mass of the stover and the
%Cob.
Combining data for both seasons, crop yield (dry-mass
basis, g m
2
) was linearly related to the plant dry mass
(g plant
1
)(R
2
= 0.93) as
yield ¼4:09 ðplant dry massÞ127:57 (4)
A linear relationship for corn was also reported by Howell
et al. (1997). This is not surprising because on average for
both seasons, the grain accounted for about 59% of the plant
dry mass, the stover for about 33%, and the cob for about 8%.
The proportion of grain dry mass to total above-ground plant
drymassisusuallyknownastheharvestindex(HI),whichis
avaluecommonlyusedincropmodeling(Stockle and
Campbell, 1985; Bryant et al., 1992). Stockle and Campbell
(1985) indicated that the HI was a function of crop water
stress and estimated it using empirical linear functions of a
stress coefficient. Similarly, Bryant et al. (1992) estimated the
HI by multiplying the ETc/ETp ratio by a potential HI values.
They assumed a potential HI value for corn of 0.50 (50%),
which was much lower than the values obtained in this
study. Traore et al. (2000) found that HI was affected by water
stress only when the stress occurred at anthesis. Under non-
stress conditions they obtained HI values as high as 0.59
(59%), which were similar to the values obtained in this
study for the fully irrigated treatments. The maximum HI
obtained in this study was approximately 0.62 (61.77% for
treatment T8 in 2006). For plants stressed at or after
tasseling, however, they obtained HI values as low as 0.28
(28%).
The relationships between corn dry matter production and
seasonal ETc, in terms of dry mass and in a percentage basis,
are shown in Figs. 11 and 12, respectively. The dry mass of the
whole plant and for each of its components increased with
seasonal ETc during both seasons, although better relation-
ships were obtained in 2006 due to the wider range in seasonal
ETc among treatments. In a percentage basis, %Grain was
poorly related to seasonal ETc in 2005, but a very good
Fig. 12 – Relationships between corn seasonal evapotranspiration (ETc) and the % of dry mass partitioned into grain (%Grain),
cob (%Cob) and stover (%Stover) obtained with different irrigation treatments during 2005 and 2006 at North Platte, NE.
Except for %Cob in 2006, differences among treatments in all variables were statistically significant at the 5% significance
level.
agricultural water management xxx (2008) xxx–xxx12
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evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
relationship was obtained in 2006. In 2006, %Grain increased
with seasonal ETc and then tended to level off for seasonal ETc
above about 580 mm. The %Cob was well related to seasonal
ETc during both seasons. In 2005, it decreased with ETc for ETc
above about 580 mm. The same tendency was observed in
2006, but %Cob increased with ETc when ETc was below about
580 mm. The %Stover was very well related and decreased
with seasonal ETc in 2006 for those treatments with seasonal
ETc of less than about 580 mm. Since in 2005 all treatments
had seasonal ETc of 580 mm or higher, the %Stover was
relatively constant with seasonal ETc.
4. Conclusions
This study evaluated the effect of different seasonal irrigation
depths on corn evapotranspiration, yield, water use effi-
ciency, and dry matter production in the semiarid climate of
west central Nebraska during 2005 and 2006. During both
seasons, some of the irrigation treatments resulted in crop
stress, which reduced seasonal ETc. In 2005, seasonal ETc for
all treatments averaged 630 mm and ranged from 580 to
663 mm. In 2006, drier growing conditions resulted in a lower
seasonal ETc that averaged 600 mm and ranged from 466 to
656 mm.
The differences in seasonal ETc among treatments sig-
nificantly affected crop yields. In 2005, yields (dry-mass basis)
averaged 968 g m
2
and ranged from 844 to 1085 g m
2
(a
difference of 22%). In 2006, yields averaged 828 g m
2
and
ranged from 455 to 957 g m
2
(a difference of 52%). During both
seasons, irrigation significantly affected yields, which
increased with irrigation up to the point where irrigation
became excessive. Different yield versus irrigation functions
were obtained each season, with a steeper slope obtained in
2006. Yields increased linearly with seasonal ETc (R
2
= 0.89)
and ETc/ETp (R
2
= 0.87), with similar relationships observed
both seasons. The average yield response factor (ky) (Door-
enbos and Kassam, 1979), which indicates the effect of water
stress on reducing crop yield, averaged 1.58 over the 2 years.
This value was higher than the 1.25 value reported by
Doorenbos and Kassam (1979) for stress during the total
growing period, but close to the 1.50 value reported for stress
during the reproductive stages.
Combining the data for both seasons, WUE increased non-
linearly with seasonal ETc and with yield. IWUE sharply
decreased with increasing irrigation amount, with similar
trends observed during both seasons, while WUE tended to
increase as irrigation amount increased.
On average for all treatments, the dry mass for the plant
and for each of the plant components (grain, cob, and stover)
was higher in 2005 than in 2006. In a percentage basis,
however, the %Grain was higher, while the %Cob and
%Stover were lower in 2006. In 2005, irrigation treatments
significantly affected all dry matter variables, except for the
dry mass of the cob and the stover. In 2006, all variables
were significantly affected by irrigation treatments, except
for the dry mass of the stover and the %Cob. The grain
accounted for the majority of the above-ground plant dry
mass (59%), followed by the stover (33%) and the cob
(8%). The good relationships obtained in the study between
seasonal ETc and crop performance indicators (such as
yield, WUE, IWUE, and dry matter) demonstrate that
accurate estimates of ETc in a daily and seasonal basis
can be valuable for making tactical in-crop irrigation
management decisions and for long-term and pre-season
strategic irrigation planning.
Acknowledgements
The University of Nebraska Agricultural Research Division,
Lincoln, NE 68583, Journal Serial No. 15126. Partial funding for
this project was provided by the U.S. Department of the
Interior, Bureau of Reclamation. Names of commercial
products are solely provided as information to the reader
and do not imply an endorsement or recommendation by the
authors or their organizations.
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agricultural water management xxx (2008) xxx–xxx14
AGWAT-2589; No of Pages 14
Please cite this article in press as: Payero, J.O. et al., Effect of irrigation amounts applied with subsurface drip irrigation on corn
evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate, Agric. Water Manage. (2008),
doi:10.1016/j.agwat.2008.02.015
