Soil & Tillage Research 234 (2023) 105849

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Soil & Tillage Research
journal homepage: www.elsevier.com/locate/still

Evaluating soil water dynamics under a no-tillage system with residual
plastic film mulching in an arid region of western China using HYDRUS-2DQi Hu a, Xianyue Li a, c, d, *, Jirí Šimůnek b, Haibin Shi a, d, Ning Chen a, Yuehong Zhang a,
Maoxin Xin a, Fanfan Song aaCollege of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Huhhot 010018, China
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA
Collaborative Innovation Center for Integrated Management of Water Resources and Water Environment in the Inner Mongolia Reaches of the Yellow River, Huhhot
010018, ChinadResearch and Development of Efficient Water-Saving Technology and Equipment and Research Engineering Center of Soil and Water Environment Effect in Arid Area of
Inner Mongolia Autonomous Region, Huhhot 010018, Chinabc

A R T I C L E I N F O

A B S T R A C T

Keywords:
No-tillage
Residual plastic film mulching from an earlier
year
Irrigation depth
Soil water dynamic
HYDRUS-2D

No-tillage (NT) with residual plastic film mulching from an earlier year (NTR) is considered an excellent agri­
cultural strategy in arid regions, recommended to reduce not only soil disturbance but also plastic film residues.
However, the soil water dynamic in the root zone under this management is more complex due to variations insoil properties and upper boundary conditions. Soil compaction and a disintegrated fraction (DF) of the residual
plastic film increase in NTR years. Soil water movement under NTR is not fully understood. It is also necessary to
determine a suitable number of NTR years and optimize irrigation to increase water use efficiency (WUE) andmaintain sustainable agricultural development. Therefore, the HYDRUS-2D model was calibrated and validated
using experimental data from 2019 to 2021 collected in the corn field with conventional tillage (CTN), NT with a
new plastic film (NTN), and NTR. The soil water contents (SWC), cumulative water fluxes (CWF), and soil waterbalances under CTNH, NTNH, and NTRH with the high (subscript H) irrigation depth of 315 mm (the local
recommendation) were evaluated using both measured and simulated data. The results for NTRH, NTRM (amedium irrigation depth of 252 mm, 80% of local recommendation), and NTRL (a low irrigation depth of 189
mm, 60% of local recommendation) scenarios were compared, and a suitable number of NTR years was deter­
mined. The results of numerical simulations agreed with observations, with the mean relative error range for thecalibration and validation periods between 4.9% and 5.4%. The larger number of experimental NTR years, thelarger the SWC differences for all irrigation depths, tillage practices, and mulching due to larger soil compaction
under NT and a higher DF of the residual plastic film. The largest SWC differences occurred in the 0–30 cm soil
layer in the third experimental year (2021), with an average SWC decrease of 2.3% for NTNH compared to CTNH
and 10.2% for NTRH compared to NTNH. Simulated two-dimensional SWC distributions further confirmed theseexperimental results. There were lower CWF under NT and new film mulching. CWF at a depth of 30 cm was 8.5
mm lower for NTNH than for CTNH in 2021. There was a 4.2%, 30.1%, and 43.1% increase in CWF for NTRH
compared to NTNH due to higher soil evaporation evaluated from the soil water balance in 2019, 2020, and2021, respectively. The scenario simulation results showed that SWCs decreased linearly with an increase in DF
and that DF of 30% can be regarded as the maximum value for obtaining high WUE under NTR. The highest WUE
of 28.3 kg ha–1 mm–1 under NTR during two years was found when the local recommended irrigation depth was
reduced by 20% (to 252 mm). Therefore, this management can be recommended in arid regions to avoid plastic
pollution with higher WUE.

* Corresponding author at: College of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Huhhot 010018, China.
E-mail address: lixianyue80@126.com (X. Li).
https://doi.org/10.1016/j.still.2023.105849
Received 19 October 2022; Received in revised form 13 June 2023; Accepted 27 July 2023
0167-1987/© 2023 Elsevier B.V. All rights reserved.

Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 1. Potential evaporation (Ep) and transpiration (Tp), rainfall, and irrigation during the corn growing season in 2019, 2020, and 2021 (DAS–Days After Sowing).

1. Introduction

CT in the 0–100 cm soil layer. The SWC in topsoil also increased underplastic film mulching due to plastic film cutting off the vapor transport
path between the soil surface and the atmosphere (Chai et al., 2022). For
example, the SWC in the 0–40 cm soil layer increased by 15.9% underplastic film mulching compared with no mulching (Coelho et al., 2022).
The SWC is inevitably greatly influenced by NTR due to the dual
effects of NT and plastic film mulching (Ibrahim et al., 2020; Lamptey
et al., 2020). The SWC in topsoil decreases, and evaporation increases
with an increase in the disintegrated area of the residual plastic film
under NTR (Li et al., 2022; Zhang et al., 2022; Fang et al., 2022). For
example, when the film disintegrated during the growing period, thetopsoil SWC decreased by 10.0%, and soil evaporation increased by
33.8%, compared with plastic film mulching without disintegration(Chen et al., 2019). The SWC is also affected by the number of NTR years(Page et al., 2019), even though less so during the first two years. Whenthe number of NTR years was higher than six, the SWC in the 0–30 cm
soil layer decreased on average by 10.3% (Liebhard et al., 2022).
The number of suitable NTR years and optimal irrigation scheduling
can be determined using field experiments. However, this is timeconsuming and expensive due to the spatial variability of soils, crops,
meteorology, groundwater levels, irrigation, management, and thecomplexity of hydrological processes. The mathematical models (e.g.,
DSSAT, HYDRUS, RZWQM2, and DNDC) can make up for the shortage offield experiments and, as a result, have been widely used to simulate soil
water movement, solute transport, and crop growth under different ir­
rigations, fertigations, mulching types, tillages, among others (Maharjan
et al., 2018; Leng et al., 2021; Rana et al., 2022). Especially the HYDRUS
model has been widely used worldwide due to its flexibility in accom­
modating different types of boundary conditions (e.g., Yadav et al.,2020; Qi et al., 2018; Aggarwal et al., 2017; Ahmad et al., 2018).
It has been demonstrated that the HYDRUS-2D model can simulate
soil water dynamics under plastic film mulching, NT, CT, and othermanagement strategies with high accuracy (Parihar et al., 2019; Raiet al., 2019). For example, the scenario simulations showed that thecotton’s cumulative root water uptake under NT was 16.35% lower thanunder CT (Aggarwal et al., 2017). Saglam et al. (2017) simulated the soil
water dynamics for different types of film mulching and showed that the
SWC was higher in the 0–20 cm soil layer and soil evaporation was lower
under plastic film mulching than under mulching with a biodegradable
film.
The distribution and dynamics of soil water in the root zone under
NTR are still poorly understood. As the number of NTR years increases,
the soil water dynamic in the root zone becomes more complex due tochanges in soil hydraulic parameters and the upper boundary conditions
due to an increase in soil compaction and disintegrated area of the re­sidual plastic film. Therefore, it is necessary to study soil water dynamics
in the root zone under NTR to determine the suitable number of NTR
years and optimize the irrigation program.

Usually, the implementation of conventional tillage (CT), such asplow tillage, inevitably disturbs soil structure, lowers water and nutrient
availability levels, and sometimes even results in lower crop yield(Kumar et al., 2013; Wang et al., 2018; Wang et al., 2020). On the other
hand, no-tillage (NT) can compensate for the disadvantages of CT. It has
been considered an alternative management strategy to increase soil
quality, decrease farming costs, soil evaporation, and water leaching,and produce higher water use efficiency (WUE) and economic benefits(Valkama et al., 2020; Day et al., 2020; Zhai et al., 2021). As a result, NT
has been widely promoted in many countries, including Argentina,
Brazil, Australia, the United States, and China (e.g., Sokolowski et al.,2020; Llanillo et al., 2021; Souza et al., 2021; Kassam et al., 2019). In
2015/2016, the NT area was approximately 180 million ha worldwide,
corresponding to about 12.5% of the total agricultural areas (Kassam
et al., 2019).
Plastic film mulching is another excellent agricultural strategy withmany advantages, such as reducing soil evaporation (Thidar et al., 2020)
and increasing WUE and crop yield (Mo et al., 2020). Therefore, inte­
grating NT and plastic film mulching has been widely used in arid areas(Yin et al., 2017; Lamptey et al., 2020). However, long-term NT withplastic film mulching could cause a lot of adverse effects, including an
increase in soil compaction (Peixoto et al., 2019), enhancement of deep
percolation (Kaiser et al., 2014), and suppression of crop root growth(Esteban et al., 2019). Additionally, the accumulation of plastic film
residues in the root zone can also decrease WUE and crop yields(Badagliacca et al., 2020; Koskei et al., 2021).
A management strategy combining NT with residual plastic film
mulching from an earlier year (NTR), i.e., with plastic film mulching
applied in some prior season but not the current one, could tremen­
dously reduce the amount of applied plastic film. NTR has recently been
widely adopted voluntarily by some farmers to develop green agricul­
ture and enhance farming incomes in the Loess Plateau and Hexi Oasis
Region, China (Guo et al., 2021; Zhang et al., 2022). This management is
considered a potential and highly feasible strategy to reduce residual
plastic film and farming costs and increase soil health and economic
benefits (Kan et al., 2020; Valkama et al., 2020). However, the soil water
dynamic in the root zone is more complicated under NTR due to dy­
namic variations in the disintegrated area of the residual plastic film andsoil properties (e.g., physical and hydraulic) during NT years (Ajayi
et al., 2021).
The soil in the root zone is less disturbed under NT, resulting in lower
soil water infiltration and higher soil water retention capacity during NT
years (Burke et al., 2021). Soil water contents (SWCs) in the root zone
and WUE increased under NT (Lamptey et al., 2020; Mukherjee et al.,2022). For example, Fatumah et al. (2021) reported an increase of 9.9%
and 64.32% in soil water storage and WUE, respectively, compared with2

Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 2. Operational procedures for conventional tillage (CTNH) (first row), no-tillage (NTNH) with new plastic film mulching and high irrigation depths (second row),and no-tillage with residual plastic film mulching from an earlier year and high, medium, and low irrigation depths (NTRH, NTRM, and NTRL) (third row) in 2018,2019, 2020 and 2021 (different columns).

The main objectives of this study thus are: (i) to calibrate and vali­
date the HYDRUS-2D model to simulate soil water dynamics under CTN,
NT with a new plastic film mulching (NTN), and NTR with threedifferent irrigation depths, (ii) to compare the SWCs, two-dimensionalsoil water distributions, water fluxes, and soil water balances fordifferent tillage and mulching management, (iii) to optimize the irri­
gation program under NTR, and (iv) to determine the suitable number of
NTR years.

reference evapotranspiration of 1900 mm. The soil type is classified assilt loam soil (5% clay, 64% silt, and 31% sand) with an average bulk
density of 1.44 g cm− 3 and field capacity of 0.29 cm3 cm− 3 within the
top 100 cm soil layer. The groundwater table depth during the crop
growing seasons was between 128 and 238 cm in 2019–2021. Total
precipitation during the crop-growing seasons of 2019, 2020, and 2021
were 91.7, 151, and 97 mm, respectively (Fig. 1).
The experimental design was a completely random design
comprising three replicates of five treatments. The field with uniform
soil and similar agricultural practices was divided in 2018 into fifteenplots with an area of 140 m2 (20 × 7 m) for each plot (Fig. 2). The
surrounding boundary of each plot was insulated with a plastic cloth toprevent soil water from flowing between different plots. Corn seeds (Zeamays L, cv. Junkai 918) were planted, and all plots were mulched with a
new plastic film 0.01 mm thick and 80 cm wide (Linhe Tianyang Plastic
Products Inc., China). The row and plant spacings were 50 and 30 cm,
respectively, and the planting density was 66,670 plants ha− 1. Three

2. Materials and methods
2.1. Field experiment
The experimental station is located in the middle of the Hetao Irri­gation District, in the Yellow River basin of Northwest China (40º41’N,
107º18’E). The region has an arid continental monsoon climate with anaverage annual temperature of 6.8 ◦ C, precipitation of 138 mm, andFig. 3. Cropping pattern, modeling domain, and boundary conditions for conventional tillage (CTN), no-tillage (NTN) with new plastic film mulching, no-tillage(NTR) with residual plastic film mulching from an earlier year.
3

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Soil & Tillage Research 234 (2023) 105849

treatments were carried out from 2019 to 2021, including CTN (con­ventional tillage with a new plastic film), NTN (no-tillage with a newplastic film), and NTR (no-tillage with residual plastic film from anearlier year). Border irrigation with a locally recommended total irri­
gation depth of 315 mm (a high irrigation depth, CTNH, NTNH, andNTRH) was applied. Another two irrigation levels of 252 mm (80% of thelocal recommendation, a medium irrigation depth, NTRM) and 189 mm(60% of the local recommendation, a low irrigation depth, NTRL) wereapplied to plots with the NTR treatment. Irrigations of the same depths(one-third of the total irrigation depth) were applied in each treatment
at the corn jointing, tasseling, and filling stages in all three years.
In the CTN treatment, moldboard plowing (approximately 30 cm)
was carried out after harvesting and recycling of the residual plastic
film, followed by cultivator (approximately 12 cm) and harrowing(approximately 4 cm) before planting the following year. The soil of theplow layer was not disturbed in the NTN and NTR treatments, and corn
seed and fertilizer were placed in holes in the plastic film. Fine sand soil
was used to cover the disintegrated area of the plastic film in the NTR
treatment. Field management of each plot and each year was the sameand consistent with local conventional planting. Before sowing, urea
(56 kg N ha− 1), phospham (120 kg P ha− 1), and potassium (120 kg K
ha− 1) were applied as basal fertilizer. Also, Urea (N ≥ 46%) was applied
as topdressing in the field in the jointing and tasseling stages (112 kg N
ha− 1 in each stage).

and was measured by a digital camera (Canon, EOS 750D, Japan) every
20 days (Chen et al., 2020). The disintegrated fraction (DF) of the plastic
film was processed using the Image J software (National Institutes of
Health, USA) and the following equation:
DF =Ad
× 100%
Am(1)

where Am is the mulched area (cm2), and Ad is the disintegrated area(cm2).
2.3. Model description
2.3.1. Main equations
The HYDRUS-2D model is a finite element model that numericallysolves the Richards equation (Richards, 1931) for soil water flow invariably-saturated porous media. Root water uptake (RWU) is included
as a sink term that can be computed using the Feddes macroscopic model(Feddes et al., 1978). Details about the model are available in the
HYDRUS-2D technical manual (Šimůnek et al., 2011). The HYDRUS-2D
model (Šimůnek et al., 2016) was used in this study to simulate soil
water dynamics in a soil profile under border irrigation with different
tillage and plastic mulching treatments.
In the present study, the van Genuchten-Mualem model (Van Gen­uchten, 1980) without hysteresis was used to compute soil hydraulicproperties, which was required for the numerical simulation of SWCs
and water fluxes in the soil profile. The analytical functions of Van
Genuchten (1980) used to evaluate the soil hydraulic properties (i.e.,θ(h) and K(h)) are as follows:⎧θ s − θr⎪
⎨ θr +
n mh < 0(1 + (α|h|) )
θ=
(2)
⎪
⎩
θs h ≥ 0

2.2. Measurements and methods
2.2.1. Meteorological data
An automatic meteorological station (Onset Computer Inc.; U30,
Hobo, USA) was located 500 m from the experiment field to record solar
radiation, air humidity, temperature, precipitation, air pressure, andwind speed. The Penman-Monteith equation (Allen et al., 1998) wasused to calculate reference crop evapotranspiration (ET0) during the2019, 2020, and 2021 seasons (Fig. 1). Potential crop evapotranspira­tion (ETp) was then calculated as ETp = Kc×ET0, where Kc is the crop
coefficient for corn. Kc values were adjusted according to local climaticconditions and crop growth (Allen et al., 1998) and were 0.7, 1.2, and0.35 during the early, middle, and late growth stages, respectively.

[() m ]2
1
K(h) = KS Sle 1 − 1 − S1/m
,m = 1− , n > 1
e
n
Se =

θ − θrθs − θr(3)(4)

where θs is the saturated volumetric water content (cm3 cm− 3), θr is theresidual volumetric water content (cm3 cm− 3), Ks is the saturated hy­
draulic conductivity (cm d− 1), α (cm− 1), n (− ), and m (− ) are empiricalparameters, Se is the effective saturation (− ), and l is the pore connec­
tivity parameter (− ).

2.2.2. Soil water content
SWCs in each plot were measured using two TDR probes (IMKO
GmbH Inc.; IPH, TRIME-PICO, Germany) installed in the middle of twocorn rows and the middle of the bare section (Fig. 3). Measurements
were taken about once a week in soil depths of 0–10, 10–20, 20–30,
30–50, and 50–100 cm. Furthermore, auger boring was used to obtainsoil samples to calibrate TDR readings every two weeks.

2.3.2. Root water uptake
Root water uptake is computed according to the Feddes macroscopic
model (Feddes et al., 1978):( )S(h) = α(h)β x, z Tp Lt(5)

2.2.3. Groundwater
The groundwater table was measured at a 1-hour interval using apressure transducer (Onset Computer Inc.; U20, Hobo, USA) installed in
an observation well (5 m depth, 5 cm internal diameter) in the experi­mental field. The data were manually verified, averaged, and recorded
at one-day intervals.

where S(h) is the root water uptake sink term (d− 1), Tp is the potential
transpiration rate (cm d− 1), Lt is the canopy width related to transpi­
ration (cm), β(x,z) is the normalized water uptake distribution function(cm− 2), and α(h) is the root water uptake stress response function(0 < α < 1). Inputs for the determination of β(x,z) were the maximum
rooting depth, the depth of the maximum root intensity, the maximum
rooting radius, and the radius of the maximum horizontal root intensity(all in cm). To determine the above root parameters, root samples werecollected at the third leaf (V3), sixth leaf (V6), tassel (VT), milk ripe
(R3), and physiological maturity (R6) stages. These samples werecollected using a root drill of 10 cm diameter at intervals of a 10 cm invertical direction until no roots were found. The root samples were firstwashed and then scanned (450 d.p.i. resolution) using a root systemscanner (Reagent Instruments Inc.; Perfection 4870 photo, Epson,
Japan). The root parameters were determined using the WinRHIZO
software.

2.2.4. Corn leaf area, height, and yield
Six plants in each plot were selected to measure the corn height andthe leaf area index (LAI) using a tape (with an accuracy of 0.1 cm) once
every 7–14 days. The leaf area index (LAI) was calculated using the FAO
method (Allen et al., 1998). Crop yield was determined by randomly
harvesting ten plants from each plot at the end of the crop growing
season. Water use efficiency (WUE, kg ha− 1 mm− 1) was defined as cornyield (Y, kg ha− 1) divided by total actual evapotranspiration (ET, mm)
during the growth stage.
2.2.5. The disintegrated fraction of the plastic film
The disintegrated area of the residual plastic film increased with time4

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Soil & Tillage Research 234 (2023) 105849

Table 1
Soil hydraulic parameters for the conventional tillage (CT) and no-tillage (NT) plots for the 0–30, 30–100, and 100–240 cm soil layers for the 2019, 2020, and 2021
seasons. BD is the soil bulk density (g cm− 3), θr is the residual soil water content (cm3 cm− 3), θs is the saturated soil water content (cm3 cm− 3), α (cm− 1) and n (–) are theshape parameters, and Ks is the saturated hydraulic conductivity (cm d− 1). Different letters in the same column indicate a significant difference (P < 0.05) among
treatments.

2019–2021

CT

2019

NT

2020

NT

2021

NT

Soil layers(cm)

BD(g cm− 3)θr(cm3 cm− 3)

θs(cm3 cm− 3)(cm− 1)

α

n
(–)

Ks
(cm d− 1)

0–30
30–100100–240
0–30
30–100100–240
0–30
30–100100–240
0–30
30–100100–240

1.45bcd
1.44 cd
1.42 cd
1.48bc1.44 cd
1.41d
1.52b
1.46bcd
1.42 cd
1.64a
1.46bcd
1.43 cd

0.040
0.037
0.039
0.039
0.037
0.039
0.038
0.036
0.039
0.037
0.036
0.039

0.373
0.360
0.368
0.357
0.360
0.369
0.348
0.358
0.361
0.341
0.356
0.366

0.01480.00810.00770.01560.00810.00760.01690.00830.00770.01780.00820.0078

1.48
1.17
1.19
1.45
1.17
1.18
1.40
1.18
1.18
1.38
1.17
1.17

54.8
52.4
38.3
50.8
52.4
40.1
47.6
51.8
38.6
45.0
52.3
38.7

2.3.3. Evaporation and transpiration
ETp needs to be divided in HYDRUS-2D into potential evaporation(Ep) and potential transpiration (Tp) using Beer’s law (Campbell andNorman, 1989), which can be done as follows:
ETP = TP + EP

(6)

)
(
TP = 1 − e− k⋅LAI ETP(7)

EP = ETP − TP(8)bulk density (BD) using the Rosetta software package of HYDRUS-2D.
The soil is composed of 29.7% sand, 65.0% silt, and 5.3% clay at a
depth of 0–30 cm, 32.3% sand, 62.3% silt, and 5.4% clay at a depth of
30–100 cm, and 39.2% sand, 57.0% silt, and 3.8% clay at a depth of
100–240 cm. The longer the no-tillage (NT) treatment was applied, thehigher the BD in the 0–30 cm, e.g., BD in the NT treatment was higher by
1.7%, 5.2%, and 12.9% than that in the conventional tillage (CT)treatment in 2019, 2020, and 2021, respectively. Additionally, the soil
hydraulic parameters’ values were manually adjusted by comparing
simulated and observed values of SWCs (Table 1). θs, θr, Ks, and n in the
0–30 cm soil layer decreased with an increase in the number of NT years.
Also, the α value in the NT scenario was higher than in the CT scenario in
2019, 2020, and 2021.
SWCs observed during the corn growing season at different depths of
the CTN, NTN, and NTR plots were divided into calibration and vali­
dation sets. DAS 0–70 in 2019, DAS 0–72 in 2020, and DAS 0–70 in 2021
were used as calibration sets, and DAS 71–142 in 2019, DAS 73–144 in
2020, and DAS 71–142 in 2021 were used as the validation sets.

where k is the extinction coefficient of the corn (0.39), and LAI is the leaf
area index.
2.3.4. Transport domain, and initial and boundary conditions
A rectangular two-dimensional transport domain (60 cm wide and240 cm deep) was defined between the middle of two corn rows and the
middle of the bare area (Fig. 3). The depth of the modeling transportdomain was set to 240 cm since the groundwater table fluctuated within
the 128–238 cm range. The targeted finite element size of 5.00 cm wasused in the HYDRUS-2D model for spatial discretization and meshgeneration. The SWCs measured at the beginning of the experiment eachyear were used as initial conditions.
A time-variable pressure head boundary condition was used at thebottom boundary to represent the position of the groundwater table. Leftand right boundaries were assigned a no-flow boundary condition. The
atmospheric boundary condition was assigned to the top boundary,
40–60 cm away from the left side. The boundary condition for the top
0–40 cm boundary (i.e., the soil surface) depends on whether plastic
film mulching at the soil surface was disintegrated, reflecting two
different mulching scenarios. In the CTN and NTN scenarios, themulching soil surface (0–40 cm) was assigned the no-flow boundary
condition due to a very low disintegrated fraction (DF). In the NTR
scenario, the mulching soil surface (0–40 cm) was assigned a timevariable water flux boundary condition to represent the disintegrated
area of the residual plastic film (Fig. 3). Assuming rainfall did notevaporate, the surface flux (i.e., the difference between potential evap­oration and rainfall) is adjusted depending on the rate of disintegrationof the surface residual plastic film mulch as follows:
Ed = DF(EP − I) − R

2.3.6. Model performance criteria
The agreement between simulated and measured values was evalu­
ated using the mean relative error (MRE), the root mean square error(RMSE), and the coefficient of determination (R2) as follows:
MRE =

n
1∑
|Si − Mi |× 100%
Mi
n i=1

(10)

√̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅
n1∑(Si − Mi )2
n i=1

(11)

RMSE =n∑(Mi − M) (Si − S)
i=1√̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅
R2 = √̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅
nn∑∑(Mi − M)(Si − S)
i=1

(12)

i=1

where Si and Mi are simulated and measured values, respectively, S and
M are the mean values of simulated and measured values, respectively,
and n is the number of data. The MRE values range between 0% and100%, RMSE between 0 to + ∞, and R2 between 0 and 1. The MRE and
RMSE values close to 0, and R2 close to 1, indicate that the simulated
values are close to the measured values and the model performs well.
Conversely, it means the model performance is poor or insufficient.

(9)

where Ed is the surface flux (mm d− 1), Ep is potential evaporation (mmd− 1), and R is the rainfall rate (mm d− 1).
2.3.5. Soil hydraulic parameters
Soil hydraulic parameters (i.e., θs, θr, α, n, and Ks) were obtained
according to the percentage content of sand, silt, and clay and the soil
5

Q. Hu et al.

Table 2
Statistical performance of HYDRUS-2D for soil water contents (SWCs) in the 0–100 cm soil layers during 2019, 2020, and 2021 for the conventional tillage (CTNH) and no-tillage (NTNH) plots with new plastic film
mulching and high irrigation depths, and the no-tillage plots with residual plastic film mulching from an earlier year and high, medium, and low irrigation depths (NTRH, NTRM, and NTRL).
Depth (cm)

Error

CTNH

NTNH

NTRH

NTRM

NTRL

DAS 0–70 (2019)
Calibration

0–10
10–30
30–50

6

50–100

Validation

0–10
10–30
30–50
50–100MRE(%)
9.28
0.03
RMSE (cm3 cm− 3)2R
0.91
MRE(%)
5.69
3− 3
RMSE (cm cm )
0.02
R2
0.94
MRE(%)
2.41
RMSE (cm3 cm− 3)
0.01
0.94
R2
MRE (%)
1.30
3− 3
RMSE (cm cm )
0.01
R2
0.94
DAS 71–142 (2019)
MRE (%)
9.39
RMSE (cm3 cm− 3)
0.03
0.92
R2
MRE (%)
6.05
3− 3
RMSE (cm cm )
0.02
0.91
R2
MRE (%)
2.18
RMSE (cm3 cm− 3)
0.01
R2
0.92
MRE (%)
1.33
3− 3
RMSE (cm cm )
0.01
R2
0.92

CTNH

NTNH

NTRH

NTRM

NTRL

DAS 0–72 (2020)

9.35
0.03
0.91
5.77
0.02
0.92
2.34
0.01
0.94
2.07
0.01
0.93

9.39
0.04
0.89
6.58
0.04
0.87
2.52
0.02
0.90
1.35
0.01
0.93

9.65
0.02
0.88
7.01
0.03
0.88
2.35
0.01
0.91
1.43
0.01
0.90

10.01
0.02
0.84
5.78
0.04
0.87
2.43
0.01
0.90
1.39
0.01
0.91

9.49
0.03
0.87
7.23
0.02
0.91
2.44
0.01
0.93
1.49
0.01
0.94

10.06
0.04
0.85
7.38
0.02
0.86
2.57
0.01
0.90
1.55
0.01
0.93

9.52
0.04
0.82
7.01
0.03
0.81
2.81
0.02
0.86
2.07
0.01
0.90

10.21
0.04
0.83
6.69
0.03
0.83
2.98
0.02
0.84
1.88
0.01
0.89

9.31
9.22
0.02
0.04
0.90
0.88
6.15
5.34
0.03
0.03
0.93
0.89
2.42
3.23
0.01
0.01
0.94
0.95
1.56
2.70
0.01
0.01
0.94
0.94
DAS 73–144 (2020)
9.29
9.33
0.03
0.03
0.91
0.86
6.22
6.55
0.02
0.03
0.88
0.83
2.53
3.57
0.01
0.02
0.93
0.92
1.17
1.11
0.01
0.01
0.94
0.94

CTNH

NTNH

NTRH

NTRM

NTRL

10.22
0.03
0.90
5.44
0.03
0.91
2.76
0.01
0.93
1.24
0.01
0.94

10.77
0.03
0.84
6.39
0.02
0.88
2.35
0.01
0.89
1.10
0.01
0.90

11.12
0.02
0.81
7.00
0.02
0.86
2.81
0.01
0.90
1.23
0.01
0.91

12.34
0.03
0.91
6.19
0.03
0.90
2.14
0.01
0.93
1.09
0.01
0.95

12.11
0.03
0.80
6.23
0.02
0.81
2.58
0.01
0.84
1.51
0.01
0.92

12.29
0.04
0.74
7.08
0.02
0.77
2.59
0.02
0.82
1.70
0.01
0.89

DAS 0–70 (2021)
9.25
0.04
0.85
6.29
0.03
0.83
2.86
0.01
0.95
1.57
0.01
0.92

9.08
0.03
0.81
7.45
0.02
0.85
3.93
0.01
0.92
2.26
0.01
0.91

8.33
0.03
0.84
7.39
0.03
0.80
3.85
0.01
0.91
2.41
0.01
0.93

9.54
0.03
0.88
6.59
0.02
0.87
3.18
0.01
0.92
2.06
0.01
0.91

10.08
0.04
0.79
7.21
0.04
0.82
2.84
0.02
0.85
2.18
0.02
0.90

9.99
0.04
0.76
7.43
0.03
0.80
3.07
0.02
0.83
1.74
0.01
0.91

10.21
10.59
0.03
0.04
0.89
0.85
6.02
5.94
0.02
0.03
0.90
0.84
2.59
3.03
0.01
0.02
0.95
0.93
1.05
1.19
0.01
0.01
0.95
0.93
DAS 71–142 (2021)
11.57
11.72
0.03
0.04
0.93
0.88
5.96
6.09
0.03
0.03
0.93
0.89
1.78
1.95
0.01
0.01
0.94
0.94
1.01
1.04
0.01
0.01
0.95
0.92

Soil & Tillage Research 234 (2023) 105849

Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 4. Simulated (lines) and observed (dots) SWCs under the plastic film mulching in the 0–10 (top), 10–30 (middle), and 30–100 (bottom) cm soil layers in 2019(left), 2020 (middle), and 2021 (right) for conventional tillage (CTNH) and no-tillage (NTNH) plots with new plastic film mulching and high irrigation depths, and notillage plots with residual plastic film mulching from an earlier year and high, medium, and low irrigation depths (NTRH, NTRM, and NTRL). A plastic film’s dis­
integrated fraction (DF) for NTRH, NTRM, and NTRL.

3. Results

3.2. Differences of SWCs in soil profiles with different tillage, mulching,and irrigation depths

3.1. Model calibration and validation

In the plots with different tillage and mulching and the same irri­
gation depth, differences in SWCs mainly appeared in the upper soil
layer (0–30 cm) (Fig. 4). Only small differences were observed in the
30–100 cm layer. Overall, SWCs in the NTNH plots were lower than in
CTNH. On average, SWCs in the 0–30 cm layer of NTNH decreased by
0.2%, 2.0%, and 2.3% in 2019, 2020, and 2021, respectively. In addi­tion, SWCs of the 0–30 cm layer under NTRH were lower than thoseunder NTNH due to the plastic film’s high disintegrated fraction (DF),and a decrease in SWCs was in response to the rise in DF of the plastic
film.
During the early stage of crop growth (i.e., before the first irrigation),
the average SWC in the upper layer (0–30 cm) under NTRH decreased by
4.7%, 6.8%, and 10.2% in 2019, 2020, and 2021, respectively,
compared to NTNH. However, during the middle stage of crop growth (i.
e., between the first and third irrigations), although there was still
higher soil evaporation under NTRH than NTNH, the SWC in the upper
layer was higher due to higher infiltration from irrigation and precipi­
tation. For example, compared to NTNH, the SWC in the 0–10 cm soil
layer of NTRH increased by 5.4% and 0.6% in 2019 and 2020, respec­tively, and decreased by 5.1% in 2021. During the later stage of crop
growth (i.e., after the third irrigation), SWCs in the upper layer of NTRH
decreased by 7.7% compared with NTNH in 2021 due to high DF (Fig. 4),
while the SWC of NTRH only increased by 3.5% and 1.3% compared with
NTNH in 2019 and 2020, respectively.

The HYDRUS-2D model was calibrated and validated using themeasured SWCs from 2019, 2020, and 2021. Various statistical tests(MRE, RMSE, and R2) were calculated to investigate the model perfor­
mance (Table 2). The average R2 for the calibration and validation pe­
riods for conventional tillage (CTNH), no-tillage (NTNH) with newplastic film mulching and an irrigation depth of 315 mm, and no-tillage
with residual plastic film mulching from an earlier year and irrigation
depths of 315, 252, and 189 mm (NTRH, NTRM, NTRL) were 0.93, 0.91,
and 0.87, respectively, the average RMSEs were 0.02, 0.02, and0.02 cm3 cm− 3, respectively, and the average MREs were 4.9%, 5.1%,
and 5.4%, respectively. The model accuracy for NTRH and NTNH waslower than for CTNH; e.g., the MRE for NTNH and NTRH increased on
average by 5.4% and 6.6%, respectively, compared with CTNH. SWCs in
the topsoil layer (0–10 cm) strongly fluctuated, reflecting individual
irrigation and precipitation events, and the accuracy decreased in thissoil layer compared to the subsoil layers. Generally, there was good
agreement between simulated and measured SWCs for CTNH, NTNH, andNTR (i.e., NTRH, NTRM, NTRL) during both calibration and validation
periods. It can be concluded that the HYDRUS-2D model can well cap­
ture the SWC dynamics in the root zone for different scenarios of tillage,
plastic film mulching, and irrigation depths and could meet the re­quirements of soil water simulations.

7Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 5. Cumulative water fluxes (CWFs, upward fluxes are positive) at the 30 (top) and 100 (bottom) cm soil depths in the conventional tillage (CTNH) and no-tillage(NTNH) plots with new plastic film mulching and high irrigation depths, and the no-tillage plots with residual plastic film mulching from an earlier year and high,medium, and low irrigation depths (NTRH, NTRM, and NTRL) in 2019 (left), 2020 (middle), and 2021 (right). Also shown (the right axis) are rainfalls in 2019, 2020,
and 2021.

With a decrease in the irrigation depth, SWCs of the 0–30 cm soil
layer decreased, as expected, during the entire corn growth period(Fig. 4). The higher the DF, the more obvious the SWC decrease. For
example, compared with NTRH in 2019, 2020, and 2021, the SWC under
NTRM decreased by 7.2%, 7.8%, and 13.1%, respectively; and under
NTRL, it decreased by 15.5%, 18.4% and 33.2%, respectively. In addi­tion, the SWC of NTRL in the 30–100 cm soil layer also decreased,
mainly in 2021. The DF of the residual plastic film was as high as 57.2%.
As a result, the SWC of NTRL decreased, as expected, by 8.2% comparedwith that of NTRH in 2021.

to 57.2% during 2019–2021 (Fig. 4).
3.4. Effects of different tillage, mulching, and irrigation depths on twodimensional SWC distributions
Two-dimensional SWC distributions in the 0–100 cm soil layer under
CTNH, NTNH, NTRH, NTRM, and NTRL were compared on DAS 83, 91,
and 99 (i.e., before irrigation), and 85, 93, and 101 (i.e., one day after
irrigation) in 2019, 2020, and 2021, respectively (Fig. 6). Differences in
SWC distributions for different tillage and mulching patterns mainly
appeared in the top 0–30 cm soil layer. NT reduced the infiltration rate
due to an increase in the soil bulk density, and this considerable effect
was found in the third year of NT (2021). SWCs under the bare section(zone II) of NTNH in the upper soil layer were 4.5% lower than under
CTNH one day after irrigation in 2021 (DAS 101). This resulted in lower
SWCs (9.9% lower) under the film mulching section (zone I) of NTNH
than under CTNH. In addition, SWCs in zone I of NTRH decreased by
2.9%, 1.7%, and 6.7%, while the average DF value increased by 13%,28%, and 47% in 2019, 2020, and 2021, respectively, compared withthose of NTNH, because of higher soil evaporation caused by plastic film
disintegration. However, SWCs in zone I under NTRH were 6.2%, 2.7%,
and 1.5% higher than under NTNH, respectively, since irrigation water
infiltrated directly into the soil through the disintegration zone of theplastic film. Moreover, there were similar SWC distributions for different
irrigation depths under NTR. The maximum difference in SWCs occurred
before irrigation (Fig. 6). In 2019, 2020, and 2021, SWCs in zone I under
NTRM decreased by 8.3%, 8.7%, and 9.9%, and under NTRL decreased
by 17.3%, 18.9%, and 22.2%, respectively, compared with NTRH. A
positive linear correlation (y = 0.0002x + 0.2504, R2 = 0.99) can befound between SWCs in the 0 − 100 cm soil layer and the irrigation
depth.

3.3. Differences in cumulative water fluxes in soil profiles with different
tillage, mulching, and irrigation depths
The cumulative water fluxes (CWFs) are reduced under NT due tohigher soil compaction compared to those under CT (Fig. 5). The longer(more years) the NT management is applied, the lower the CWFs (Fig. 5).
For example, CWFs at depths of 30 cm (CWF30) and 100 cm (CWF100)
were 8.5 and 20.2 mm lower, respectively, under NTNH than under
CTNH in 2021. In general, larger disintegration areas under NTRH
compared to NTNH resulted in an increase in evaporation due to adecrease in the mulched area and higher upward water flow (i.e.,
capillary rise). Therefore, CWF under NTRH was higher than under
NTNH (Fig. 5). For example, CWF30 under NTRH increased by 4.2%,
30.1%, and 43.1% compared with those under NTNH in 2019, 2020, and2021, respectively; and CWF100 increased by 1.3%, 6.6%, and 45.6%,
respectively.
Overall, irrigation and rainfall did not meet corn water requirementsin the experiment. As a result, CWFs under NTR were upward during thecrop-growing season. Also, CWFs under NTRM and NTRL were higher
than under NTRH due to a lower irrigation depth (Fig. 5). For instance,
CWF30 under NTRM were 16.1%, 17.2%, and 19.7% higher than under
NTRH during 2019, 2020, and 2021, respectively; increasing by 33.9%,
40.1%, and 43.9% under NTRL. Differences in CWFs increased with time
between NTRM, NTRL, and NTRH due to an increase in the disintegrated
area under NTR. For example, differences in CWF30 between NTRL and
NTRH increased from 4.6 mm to 8.0 mm, with DF increasing from 8.1%

3.5. Effects of different tillage, mulching, and irrigation depths on soil
water balance components
Generally, there were no obvious differences in soil water balancecomponents between NTNH and CTNH (Table 3). However, considerable
8Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 6. Two-dimension SWC distributions before irrigation and one day after irrigation for the conventional tillage (CTNH) and no-tillage (NTNH) plots with newplastic film mulching and high irrigation depths, and the no-tillage plots with residual plastic film mulching from an earlier year and high, medium, and low
irrigation depths (NTRH, NTRM, and NTRL) in the 0–100 cm soil layer during 2019, 2020, and 2021. DF is the disintegrated fraction of a plastic film in %. Zones I andII refer to plastic film mulching and bare sections, respectively.
9Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Table 3
Soil water balance components in 0–100 cm for the conventional tillage (CTNH) and no-tillage (NTNH) plots with new plastic film mulching and high irrigation depths,
and the no-tillage plots with residual plastic film mulching from an earlier year and high, medium, and low irrigation depths (NTRH, NTRM, and NTRL) in 2019, 2020,
and 2021. ΔW is the change in soil water storage between the end and beginning of the season (mm), Drainage is the cumulative bottom water flux (at a depth of∑
100 cm; positive out of the region) (mm), ET is total evapotranspiration during the growth stage, w is the total water balance error (mm). Corn yield is the average− 1− 1
value of corn yield from three replicates (kg ha ), and WUE is water use efficiency (kg ha mm− 1).

2019

2020

2021

CTNH
NTNH
NTRH
NTRM
NTRL
CTNH
NTNH
NTRH
NTRM
NTRL
CTNH
NTNH
NTRH
NTRM
NTRL

Irrigation

RainfallDrainage(capillary rise)

ΔW

E

RWU

∑

w

Corn yield

WUE

mm

mm

mm

mm

mm

mm

mm

kg ha–1

kg ha− 1 mm− 1

315
315
315
252
189
315
315
315
252
189
315
315
315
252
189

91.7
91.7
91.7
91.7
91.7
151.0
151.0
151.0
151.0
151.0
97.0
97.0
97.0
97.0
97.0

−
−
−
−
−
−
−
−
−
−
−
−
−
−
−

21.8
21.5
21.4
14.5
10.2
40.8
41.3
40.7
37.1
29.7
32.4
32.0
33.5
23.3
19.9

76.4
75.5
82.3
71.1
61.2
82.2
79.5
90.0
81.3
76.1
75.5
71.5
134.5
129.6
117.1

391.2
387.2
381.5
340.8
298.2
419.8
406.8
400.9
359.8
316.8
402.8
387.0
358.3
321.3
287.4

-1.8
0.4
-3.8
2.1
-1.9
-0.5
1.5
1.0
-1.4
-0.5
-1.2
0.2
-1.6
1.8
-2.6

12,087.6a
12,005.4a
11,679.8a
10,861.6b8078.2c
13,875.1a
13,471.2a
13,402.7a
12,498.8b
9374.2c12,514.1a
11,518.2b
10,123.3c
8684.5d6062.9e

25.8
25.9
25.2
26.4
22.5
27.6
27.7
27.3
28.3
23.9
26.2
25.1
20.5
19.3
15.0

82.8
77.5
78.5
82.7
88.9
76.8
61.6
65.6
75.2
82.6
98.7
78.5
114.3
125.3
138.4

differences occurred between NTRH and NTNH, primarily in soil evap­oration (E). Soil evaporation under NTRH increased by 9.0%, 13.2%, and88.1% compared with NTNH in 2019, 2020, and 2021, respectively.
Differences in E resulted in differences in CWF at the bottom of the rootzone (i.e., capillary rise) under NTRH and NTNH, with 1.3%, 6.6%, and45.6% increases for NTRH compared with NTNH in 2019, 2020 and
2021, respectively (Fig. 5). On the other hand, root water uptake (RWU)
under NTRH was considerably restrained due to lower SWCs caused byhigher E from the topsoil. RWU under NTRH was 1.5%, 1.4%, and 7.4%
lower than under NTNH in 2019, 2020, and 2021, respectively.
Furthermore, the yield and water use efficiency (WUE) under NTRH
decreased by 19.1% and 21.5% compared with NTNH in 2021, respec­tively, while no obvious differences appeared in 2019 and 2020. E andRWU decreased during three seasons with a decrease in the irrigation
depth (Table 3), with an average E decrease of 8.1% and 17.1% for
NTRM and NTRL, respectively, compared with NTRH, and an average
RWU decrease of 10.4% and 20.9%, respectively. The highest WUE wasfound under NTRM in 2020, with an increase of 3.8% and 18.8%
compared with NTRH and NTRL, respectively. The corn yield increased
when the irrigation depth was enhanced in a suitable range, e.g., cornyield increased by 33.3% and 7.2% when the irrigation depth wasincreased from 189 to 252 mm and 252–315 mm, respectively. There­
fore, NTR (after two years) combined with an irrigation depth of
252 mm was an excellent alternative to CTNH in arid regions to avoid
plastic pollution and maintain higher corn production in the region.

conductivity (Ks) were lower under NT than under CT, likely due tolower soil macroporosity (Rai et al., 2019). However, the residual soil
water content (θr) under NT was very close to that under CT in the firsttwo years, as θr depends mainly on soil texture (Mari et al., 2011).
Water infiltrates more easily into the soil that is broken up andturned by tilling compared to the soil under NT (Parihar et al., 2019),
helping to increase soil water content (SWC) in the root zone (Sasal
et al., 2017; Dai et al., 2021). However, SWCs are not significantly
affected by short-term NT because early low soil compaction results inhigher microporosity and increased effective soil water available to thecrop (Mondal et al., 2020; Mondal and Chakraborty, 2022). In this study,
there were no obvious differences in SWCs between CT (CTNH) and NT(NTNH) with new plastic film mulching under an irrigation depth of
315 mm during three years of NT (Fig. 4). In addition, crop root water
uptake (RWU) under NT was reduced due to lower SWCs and higher soil
compaction. The groundwater contribution to crop water consumption
also decreased in shallow groundwater regions (Humphreys et al., 2010;
Parihar et al., 2019). For example, cotton RWU and groundwater
contribution to RWU was 8.92% and 12.74% lower under NT than underCT, respectively (Aggarwal et al., 2017). In this study, corn RWU andgroundwater contribution to RWU were reduced by 3.9% and 20.5%,
respectively, under NTNH compared to CTNH in the third year of NT.
4.2. The effects of the disintegrated fraction of the residual plastic film on
SWCs and crop water consumption

4. Discussion

Film mulching may reduce the water-vapor exchange between theatmosphere and the soil surface, reduce soil surface radiation, decreasesoil evaporation, and increase SWCs (Monday et al., 2015; Ospanbayev
et al., 2017; He et al., 2018). However, soil evaporation and soil water
losses were enhanced when the plastic film disintegrated (Chen et al.,2020). For example, in this study, SWCs in the topsoil and RWU under
NT with residual plastic film mulching from an earlier year (NTRH) wereconsiderably lower than those under NTNH. The longer NT was practiced(in years), the larger the plastic film’s disintegrated fraction (DF) and thelower the topsoil SWCs. Similarly, the large DF of the biodegradable film
(54.4%) caused the soil water deficit in the top 0–20 cm soil layer (Chenet al., 2019). However, there were higher groundwater contributions tocrop RWU in shallow groundwater regions with a higher DF of theplastic film (Forkutsa et al., 2009; Liu et al., 2016; Chen et al., 2019). In
this study, the capillary rise in the NTRH scenario with a DF of 57.2%
increased by 45.6% compared with NTNH under the same irrigation

4.1. The effects of tillage on soil properties and water balance components
The no-tillage (NT) system has been shown to have many advantages
compared to the conventional tillage (CT) system, such as reduced soil
structure destruction by less use of machinery (Gao et al., 2021; Val­kama et al., 2020). However, since the soil is not disturbed for many
years under long-term NT, the soil bulk density (BD) would increase intime due to the gravitational action of the soil itself (Schmidt et al.,2018; Li et al., 2020). In this study, the BD in the third year under NT
was also significantly higher than under CT. Reichert et al. (2016)
pointed out that the longer NT is practiced, the higher BD and the lower
soil porosity, which also strongly affects soil hydraulic properties (Ajayi
et al., 2021; Blanco-Canqui and Ruis, 2018). In this study, both thesaturated soil water content (θs) and the saturated hydraulic10

Q. Hu et al.

Soil & Tillage Research 234 (2023) 105849

Fig. 7. Simulated soil water contents (SWC, a) in the 0–30 cm soil layers, root water uptake (RWU, b), soil evaporation (E, b), and evapotranspiration (ET, b) for
different disintegrated fractions (DF) of the plastic film (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%) for no-tillage with residual plastic film
mulching from an earlier year and a medium irrigation depth (NTRM) in 2020.

depth. However, there was lower WUE due to higher evaporation and ahigher DF.
Irrigation program is the main factor affecting the effective water
utilization of crops in arid environments (Guo et al., 2019). Irrigation
depth optimization can increase soil water use and reduce evaporation
losses (Feng et al., 2017). The present study found that evaporation
under NTR decreased with decreasing irrigation depth, but WUE did notincrease linearly. A decline in WUE can also occur with excessive irri­
gation. It may be caused by relatively larger evapotranspiration (ET)than a corresponding increase in yield (Zwart and Bastiaanssen, 2004).
A reduction in WUE due to severe deficit irrigation may be related toyield decline with water stress (Oweis et al., 2011). In addition, thedegree of plastic film disintegration under NTR also affected crop water
utilization in this study, with the highest WUE (28.3 kg ha− 1 mm− 1,
Table 3) occurring when the DF was below 35.2% (2020), and the irri­
gation depth was 80% of the locally recommended irrigation depth. It
can be seen that when the DF of the plastic film was larger than 35.2%,
WUE decreased with a decrease in the irrigation depth.
As discussed above, the no-tillage practice with a residual plastic film
and an irrigation depth of 252 mm (NTRM) had the highest WUE in thesecond year of NT (2020). To explore the effects of different DFs on soil
water dynamic, HYDRUS-2D simulations for the entire crop growing
season in 2020 were carried out for ten NTRM scenarios with different
DFs of the plastic film from 0% to 100% (on the last day of the crop
growing season, DAS 144) (Fig. 7). The simulation results showed that
SWCs
decreased
linearlywithanincreaseinDF(y = − 0.0012x + 0.2490, Fig. 7a). An average 3.0% (7.2%) increase in
SWCs was achieved for a 10% increase in DF when DF was lower(higher) than 30%. This is in line with earlier results that SWCs decrease
with an increase in DF (Saglam et al., 2017; Fang et al., 2022). Chenet al. (2019) reported that when the DF of the biodegradable film
increased from 38.1% to 100%, RWU decreased by 4.9%, and soil
evaporation increased by 48.3%. A negative linear relationship between
RWU and DF was found in this study (y = − 1.892x + 411.42, Fig. 7b).
On the other hand, soil evaporation increased linearly with DF(y = − 1.815x + 46.28, Fig.7b). When DF was lower than 30%, RWU
increased on average by 3.7% when DF increased by 10% and soil
evaporation decreased on average by 2.9%. On the other hand, adecrease of 6.4% for RWU and an increase of 16.9% for soil evaporation
occurred when DF was higher than 30%. Therefore, a DF of 30% can be
regarded as the maximum value for obtaining high WUE under NTRM.

experimental data from 2019 to 2021. In general, there was good
agreement between the results of numerical simulations and measure­ments. The SWCs and components of the soil water balance for the NTNH
management strategy were similar to CTNH. NTRH and NTNH functioned
similarly in the first two years (2019 and 2020). Obvious differences
occurred only in the third year of NT (2021) when the plastic film
disintegration rate was equal to or higher than 35.2%. In addition, dif­ferences in SWCs were only found in the top 0–30 cm soil layer. Cu­
mulative water fluxes at depths of 30 and 100 cm increased with adecrease in the mulching area from NTNH to NTRH. Two-dimensionalsoil water content distributions showed that the SWCs in the topsoil
layer of NTRH were lower than in NTNH before irrigation and decreased
considerably in 2021. Moreover, the NTR management integrated with areduced irrigation depth can further increase the water utilization of
corn; the highest WUE was found for NTRM in 2020. Therefore, the NTR
management strategy coupled with low irrigation (252 mm) represents
a promising strategy to reduce plastic pollution and irrigation costs inarid regions.
This study provides a reference point for future irrigation manage­
ment decisions in conservation agriculture in arid regions. However,
only three irrigation depths of 315, 252, and 189 mm under borderirrigation were considered in this study. Further research should eval­uate the suitability of various water-saving irrigation technologies forconservation agriculture in arid regions and consider a wider range of
irrigation depths to formulate an optimal irrigation strategy for saving
water and maintaining satisfactory crop production.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Data Availability
Data will be made available on request.
Acknowledgments
This research was jointly supported by the Inner Mongolia Scienceand Technology Program (2022YFHH0039), the Fundamental ResearchFunds for the Inner Mongolia Universities-Science Foundation forDistinguished Young Scholars of Inner Mongolia Agricultural University(BR220302), the National Key Research and Development Program ofChina (2021YFC3201202), and the National Natural Science Founda­tion of China (52079064 and 51969024).

5. Conclusions
The HYDRUS-2D model was used in this study to simulate the effectsof tillage, film mulching, and irrigation on SWCs, water fluxes, andcomponents of soil water balance. The model was first calibrated using
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Soil & Tillage Research 234 (2023) 105849

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