Open Journal of Soil Science, 2012, 2, 71-81
http://dx.doi.org/10.4236/ojss.2012.22011 Published Online June 2012 (http://www.SciRP.org/journal/ojss) 71
Tillage and Rice-Wheat Cropping Sequence Influences
on Some Soil Physical Properties and Wheat Yield under
Water Deficit Conditions
Sandeep Kumar1*, Pradeep K. Sharma2, Stephen H. Anderson3, Kapil Saroch4
1Carbon Management & Sequestration Center, School of Environment & Natural Resources, Ohio State University, Columbus, USA;
2Department of Soil Science, CSK HPKV, Palampur, India; 3Department of Soil, Environmental and Atmospheric Sciences, Univer-
sity of Missouri, Columbia, USA; 4Department of Agronomy, Forage and Grassland Management, CSK HPKV, Palampur, India.
Received February 2nd, 2012; revised March 10th, 2012; accepted March 18th, 2012
ABSTRACT
Adopting a better tillage system not only improves the soil hea lth and crop productivity but also improves the en viron-
ment. A field experiment was conducted to investigate the effects of tillage and irrigation management on wheat (Triti-
cum aestivum L.) production in a po st-rice (Oryza sativa L.) management system on silty clay loam soil (acidic Alfisol)
for 2003-2006. Four irrigation levels (RF: rainfed; I1: irrigation at crown root initiation (CRI); I2: irrigation at CRI +
flowering; I3: irrigation at CRI + tillering + flowering), and two tillage systems (ZT: zero tillage and CT: conv entional
tillage) were tested. Zero tillage compared to CT, resulted in higher bulk density (1.34 vs 1.23 Mg·m–3), lower total
porosity (48.7% vs 52.9%), higher penetration resistance (1.51 vs 1.37 MPa), lower saturated hydraulic conductivity
(1.60 vs 92.0 mm·h–1), lower infiltration rate (9.40 vs 36.6 mm·h–1) and higher volumetric available water capacity
(7.9% vs 7.5%) in the surf ace 0.15 m soil layer. Irrigation levels significantly affected crop water use, wheat yield, and
water use efficiency (WUE). Average total water use was 461, 491, 534 and 580 mm under RF, I1, I2 and I3 treatments,
respectively. Grain and straw yield of wheat were statistically the same under ZT and CT during 2003-2004; the values,
averaged over four irrigation levels were 2.10 and 2.38 Mg·ha–1 for grain, and 3.46 and 3.67 Mg·ha–1 for straw, respec-
tively. Grain yield declined by 22%, 11% and 8% of I3 (2.32 Mg·ha–1) with RF, I1 and I2 treatments, respectively, under
ZT; and by 13%, 8% and 5% of I3 (2.61 Mg·ha–1) with RF, I1 and I2 treatments under CT. Average values of WUE were
4.33 kg·ha–1·mm–1 and 2.35 m3·kg–1 grain for the ZT and CT treatments. Wheat yield increased with increased irriga-
tion levels for all the cropping seasons. Results from this study concluded that ZT system was better compared to the
CT system even with lower yields due to lower input costs for this treatment.
Keywords: Conventional Tillage; Soil Physical Properties; Infiltration; Water Retention ; Water Use Efficiency;
Zero Tillage
1. Introduction
Rice and wheat in sequence are cultivated in two contra-
sting soil environments. Rice requires soft, puddled and
water-saturated soil conditions, while wheat requires well
aggregated and well aerated soil with fine tilth. Puddling
(wet tillage) is the most common technique of land pre-
paration for rice in South Asian countries. Puddling cre-
ates soil conditions ideal for rice cultivation, but unsuit-
able for upland crops which follow rice [1,2]. After rice
harvest, puddled soils, upon drying shrink, b ecome com-
pact and hard, and develop surface cracks of varying
sizes and shapes. The draught power requirement for
tilling such soils is very high, sometimes beyond the
reach of local ploughs and small tractors. Nevertheless,
when tilled, these soils often br eak into larger clods, hav-
ing high breaking energy [3]. In spite of spending sig-
nificant time and energy, it is often difficult to obtain
seedbeds with the desired tilth for sowing wheat. Wheat
planted in seedbeds with coarse tilth, due mainly to poor
seed-soil contact, results in poor seedling emergence and
unsatisfactory crop stands. This lowers wheat producti-
vity.
Frequent stirring opens the soil, breaks soil clods and
aggregates, and enhances the oxidation of soil organic
matter [4,5]. The loose soils especially on sloping land-
scapes and in high rainfall areas, are excessively prone to
soil erosion. Thus, this system enhances land degradation
and results in a decline in soil quality.
To achieve satisfactory soil tilth , soils must be tilled at
optimum moisture content. The optimum water content
*Corresponding a uthor.

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
72
range in puddled soils is generally narrow [1], and many
times difficult for farmers to observe. Further, puddled
soils may take from several weeks to months to dry and
reach a moisture content optimum for tillage. This in-
creases the lag time between rice harvest and wheat
planting. The delayed sowing of wheat is another cause
of low productivity in post-rice management. An esti-
mate suggests each day delay in planting after 15th of
November lowers wheat yield by about 0.04 Mg·ha–1
[6,7].
Conventional cultivation of wheat involves several
repetitions (3 to 7) of ploughing and planking with ani-
mal-drawn local p loughs and wood en planks. The idea of
repeated tillage is to create a seedbed with fine tilth and
create a dust mulch to conserve soil moistu re in the seed-
bed. In high rainfall areas (annual rainfall varying be-
tween 1500 - 2500 mm), these soils suffer from severe
soil erosion. Hence, a conservation tillage system is re-
quired which is less intensive, is better for the environ-
ment (reduces carbon emissions), and enhances soil
structural stability and helps to conserv e soil by reducing
erosion risks [8].
Field experiments with zero tillage in wheat at sev eral
locations in the Indo-Gangetic plains have shown encour-
aging results [9-11]. Farmers have found direct drilling
of wheat into post-rice systems without tillage feasible
and beneficial at several locations. Wheat yields with
zero tillage are either equal or even better than those ob-
tained with conventional tillage because of timely plant-
ing of wheat, efficient use of fertilizers and weed control.
In addition, zero tillage is fuel and energy efficient but
also reduces greenhouse gas emissions [12]. Zero tillage
systems conserve the land resource and are cost effective
and efficient. Moreover, this tillage system also avoids
challenges with clod formation.
Benefits of zero-till plan ting have been reported under
irrigated conditions. Whether similar benefits can be ob-
tained under deficit water conditions still remains a qu es-
tion. The issue is more relevant to hilly areas, as in the
Himachal Pradesh (HP) state of India, where wheat is
principally a rainfed crop. Irrigated areas under wheat in
HP, India are less than 18%. Deficit irrigation systems
also need to be evaluated relative to performance with
zero-till planting. The objectives of the current study
were to 1) compare soil physical properties under zero
and conventional tillage systems for a rice-wheat cropp-
ing system, and 2) compare wheat yields, and wheat wa-
ter use efficiency (WUE) for zero and conventional till-
age systems.
2. Materials and Methods
2.1. Experimental Site and Management
The experiment was conducted at the Experimental Farm
of the Department of Soil Science, CSK Himachal Pra-
desh Krishi Vishvavidyalaya, Palampur, Himachal Pra-
desh (HP). The experimental site was situated at 32˚6'N
latitude and 76˚3'E longitude at an elevation of about
1290 m above mean sea level. The area lies in th e Palam
Valley of Kangra district in the foothills of Dhauladhar
Range and represents the high rainfall, mid-elevation,
wet-temperate zone of Himachal Pradesh in the North-
west Himalayas.
The climate of the study area is wet temperate, char-
acterized by severe winters and mild summers. The ave-
rage annual rainfall of the study area in the last 10 years
was 2058 mm and pan evaporation was 1215 mm. The
annual maximum temperature is 22.4˚C and the mini-
mum temperature is 13.3˚C. Annual mean temperature
varies from 8.2˚C in January to around 28.0˚C during the
months of May-June. The soil temperature drops as low
as 2˚C during the winters and frost incidences are com-
mon.
The soils of the region are classified as Gray Brown
Podzols, as per the Genetic System of Classification. Ta-
xonomically, these soils fall under the order of Alfisols
[13]. These soils owe their origin to the fluvio-glacial
parent materials developed from rocks like slate, phyl-
lites, quartzites, schists and gneisses. The soils are acid ic
(pH 5.2 to 6.3). The experimental soils belonged to sub-
group Typic Hapludalfs.
2.2. Treatment Details
A field experiment was conducted in 2003-2006. Soil
physical properties were measured for 2003-2004 year,
and wheat yield and water use efficiency were also com-
pared for three cropping seasons from 2003 to 2006 for
different treatments. Two tillage systems (ZT: zero till-
age and CT: conventional tillage) and four irrigation le-
vels (RF: rainfed; I1: irrigation at CRI; I2: irrigation at
CRI + flowering; I3: irrigation at CRI + tillering + flow-
ering) were tested. The two tillage systems included 1)
zero tillage: wheat sown in lin es 0.20 m apart by opening
narrow slits with a hand plough in untilled plots (ZT),
and 2) conventional tillage: wheat was sown in lines 0.20
m apart with the help of a hand plough in well pu lverized
plots (CT). The four irrigation management systems in-
cluded 1) rainfed (RF), 2) irrigation at CRI (CRI), 3)
irrigation at CRI and flowering stage (CRI + F), and 4)
irrigation at CRI, active tillering and flowering stages
(CRI + T + F). It is noted that each irrigation of about 5
cm was applied as surface flooding per treatment. One
pre-sowing irrigation was applied to all plots.
The total number of treatment combinations was eight
with three replications for 24 total nu mber of plots (9 m2
areas). The treatment effect was investigated for wheat
crop (Surbhi, HPW-89) and the experimental design was

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
73
a randomized complete block. Land preparation was
done with the help of a power tiller (Model CT-85, V.S.T.
Tillers Tractors Ltd., Bangalore, India). Different field
operations and irrigation scheduling during the experi-
ment are summarized in Tables 1 and 2.
ples (0 - 0.15 and 0.15 - 0.30 m) was done using the pi-
pette method [14]. Particle density of the soil was deter-
mined by the pycnometer method [15]. The soil textural
class was silty clay loam and the particle density of the
soil was 2.60 and 2.61 Mg·cm–3, respectively for 0 - 0.15
and 0.15 - 0.30 m soil depths. The soil bulk density (b

)
was determined before land preparation and 30-d ays after
sowing of wheat by the core sampler method [16], using
metallic cores having 0.138 m length and 0.103 m inter-
nal diameter. Undisturbed soil cores were collected from
the 0 - 0.60 m depth at 0.15 m depth intervals in all plots.
Four soil cores were removed at each depth and the moist
mass was recorded. Gravimetric moisture content was
determined in a sub-sample of each soil core and was
used to determine the dry mass of soil in each core.
Each plot received a uniform application of 120 N
kg·ha–1, 60 kg·ha–1 P2O5 and 40 kg·ha–1 K2O as urea, sin-
gle super phosphate and muriate of potash during the
growing season. For the rainfed treatment (no irrigation
applications), all fertilizers were band-placed at the time
of sowing in November. For the irrigation treatment at
crown root initiation (CRI; I1), 50% of the N and all of
the P and K were band-placed at the time of sowing with
50% of N broadcast applied at CRI stage during No-
vember and December. For the irrigation treatments at
CRI + flowering (I2) and irrigation at CRI + active tiller-
ing + flowering (I3), 50% of the N and all of the P and K
were band-placed at sowing with 25% of N broadcast
applied, each at CRI and flowering stage.
The total porosity (ƒ) of the 0 - 0.15 m soil layer was
determined at 30-days after seeding from data on particle
density and b

, using the following relationship:


1 100
bs
f   (1)
2.3. Soil Physical Properties where, ƒ is the total porosity (%), b

the bulk density
(Mg·m–3) and

s the particle density (Mg·m–3).
Particle size analysis of surface and sub-surface soil sam-
Table 1. Summary of field operations performed during the study for the 2003-2004 cropping season. The same operations
were performed for the 2004-2005 and 2005-2006 cropping years within a couple days of the dates for the 2003-2004 season.
Date Field operation Remarks
Nov. 6 Pre-plant irrigation Flood-irrigation method.
Nov. 9 Land preparation in conventionally-tilled plotsLand prepared using a power tiller.
Nov. 11 Planting of wheat Wheat sown in rows at 0.20 m spacing using hand p lough
at 100 kg·ha–1 seed rate.
Dec. 27 Hand weeding and hoeing Weeding in all plots. Hoeing only in conventionally-tilled plots.
Jan. 28 Hand weeding and hoeing Weeding in all the plots. Hoeing only in conventionally-tilled plots.
May 6 Crop harvesting Wheat harvested in 5.76 m2 area in centre of each p l ot.
Table 2. Irrigation timing and amount of water applied to the zero tillage (ZT) and conventional tillage (CT) treatments for
the irrigation regime treatments for the 2003-2004 cropping year. The same amounts were applied within a couple of days of
the dates for the 2003-2004 cropping years for the 2004-2005 and 2005-2006 cropping years.
Amount of Irrigation Water Applied (mm)
Irrigation Application Dates
Irrigation Regime
Treatment Tillage Treatment Nov. 6 Dec. 12 Jan. 11 March 3 Total water applied
ZT 50 - - - 50
RF CT 50 - - - 50
ZT 50 50 - - 100
I1 CT 50 50 - - 100
ZT 50 50 - 50 150
I2 CT 50 50 - 50 150
ZT 50 50 50 50 200
I3 CT 50 50 50 50 200
RF = Rainf ed; I1 = Irrigation at crown root initiation (CRI); I2 = Irrigation at CRI and flowering stage; I3 = Irrigation at CRI and active tillering and flowering
stage.

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
74
Undisturbed soil cores were collected from the 3 rep-
licates in metal cores of 0.11 m length and 0.081 m dia-
meter in the 0 - 0.15 m soil depth in both zero-till and
conventionally-tilled plots at crop harvest. The saturated
hydraulic conductivity (Ksat) was determined by the con-
stant head method [17].
2.4. Soil Water Content
Soil water content was determined gravimetrically in the
0 to 0.60 m profile at 0.15 m depth intervals at sowing,
one-day before and after each irrigation and at crop har-
vest. The mass wetness was converted into volume wet-
ness for each soil layer using the b

of each respective
soil layer.
2.5. Soil Penetration Resistance
Soil penetrometer resistance (SPR) refers to the resis-
tance offered by the soil to a metal pro be (representing a
plant root) pushed into soil. The SPR at field moisture
content was determined in the 0 - 0.03 and 0.10 - 0.13 m
soil depths at tillering stag e. A Proctor penetrometer hav-
ing a 0.18 m long prob e with a flat tip of 6 mm diameter
was used for SPR determination. About seven observa-
tions were made per plot at each depth for computing the
average SPR. After recording the SPR value, soil sam-
ples from the layer of the same depth thickness were col-
lected with the help of a tube auger for determining gra-
vimetric moisture content.
2.6. Soil Water Retention
Undisturbed soil core samples, 0.03 m long and 0.054 m
diameter were collected from each replication in the
middle of the 0 - 0.075 m soil layer with metal cores at
the flowering stage of wheat. Moisture content at –33,
and –1500 kPa matric potential was determined with a
pressure plate apparatus (Soil Moisture Equipment Co.,
Santa Barbara, California, USA). Soil samples were satu-
rated for 24 hours on the porous plate and then equili-
brated to the applied pressures.
Plant-available water capacity (PAWC) was deter-
mined for each treatment at flowering stage of wheat as
follows: PAWC = FC – PWP (2)
where FC is the moisture retained at –33 kPa matric po-
tential, and PWP (permanent wilting point) is the mois-
ture retained at –1500 kPa matric potential.
2.7. Infiltration Measurements
The infiltration behavior of the soil under zero and con-
ventional tillage treatments was studied at the time of
wheat harvest using double ring infiltrometers. The infil-
trometers were pushed into the ground to a depth of 0.15
m. Care was taken to avoid formation of cracks at the
soil surface while the infiltrometers were driven into the
soil. Water was filled almost to the same level in the in-
ner and outer rings with 0.25 and 0.30 m of inner and
outer diameter, respectively. The volume of water which
infiltrated into the soil as a function of time was meas-
ured. The depth of water infiltrated was computed by
dividing the volume by the cross-sectional area of the
inner infiltrometer. Regular determinations were made at
periodical intervals until a steady water flux was reached.
The water intake rate (i) and the cumulative intake (I)
were plotted on a simple scale as a function of time. The
Gree-Ampt model (1911) was used to fit the infiltration
data.
The Green-Ampt [18] infiltration equation was modi-
fied by Philip [19] for time (t) vs. cumulative infiltration
(I), as follows:
2
2
2
2
ln 1
2
s
ss
IK
S
IS
tKK










 (3)
where t (T) is time (h), I (L) is the cumulative infiltration
(mm), S (L·T–0.5) is the sorptivity (mm·h–0.5), and Ks
(L·T–1) is the saturated hydraulic conductivity (mm·h–1).
For estimating the S and Ks parameters, the method pro-
posed by Clothier et al. [20] was used.
The method to estimate field saturated hydraulic con-
ductivity (Kfs) suggested by Reynolds et al. [17] was
used for estimating this parameter. It assumes one-di-
mensional water flow in the infiltration ring, and uses th e
following equation:

*
12 12
11
s
fs
q
K
H
CdCaCdC a



















(4)
where Kfs is the field-saturated hydraulic conductivity
(mm·h–1), qs is the quasi-steady infiltration rate
(mm·hr–1), a is the radiu s of the infiltration ring (mm), H
is the hydraulic h ead of ponded water in the ring ( mm), d
is the depth of ring insertion into the soil (mm), C1 and
C2 are dimensionless quasi-empirical constants (C1 =
0.993 and C2 = 0.578 for this infiltrometer), and α* is the
soil macroscopic capillary length, assumed to be equal to
0.0036 mm–1 for the conventional tillage, and 0.012
mm–1 for the zero tillage treatment [17].
2.8. Wheat Yield and Water Use Efficiency
The wheat crop was harvested from ground level from
the net plot area of 5.76 m2, centered in the plot, with the
help of sickles, and was left in the respective plots for

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions 75
sun-drying for 2 - 3 days. When most of the straw in a
handful bundle broke up on folding, total produce was
weighed and recorded as biological yield. The produce
was then threshed with thresher and grains were sepa-
rated out. The grains thus collected were weighed and the
yield was recorded as Mg·ha–1.
The water use efficiency (WUE) was computed as: 1)
WUE (kg·grains·ha–1·mm–1) = Grain yield (kg·ha–1)/Total
water use (mm), and 2) WUE (m3·kg–1) = Total water use
(m3)/Wheat grains (kg).
2.9. Statistical Analysis
The statistical design for the study was a factorial ex-
periment with two levels of tillage and four levels of ir-
rigation arranged in a randomized complete block design
with three replicates. Some parameters were only evalu-
ated for tillage plots; these were sampled from the rain-
fed (RF) irrigation treatment. Statistical differences were
declared significant at the α = 0.05 level. The statistical
analysis was conducted with SAS sof tw are [21].
3. Results and Discussion
3.1. Soil Penetration Resistance
Soil penetration resistance (SPR) values, determined im-
mediately before the application of irrigation at the tille-
ring stage of wheat in the 0.10 - 0.13 m soil layer, are
shown in Table 3. The SPR was significantly affected by
tillage, but the effect of irrigation treatments for the CT
tillage system on SPR was non-significant. SPR values
varied between 1.40 and 1.61 MPa with a mean value of
1.51 MPa under ZT, and between 1.31 and 1.35 MPa
with a mean value of 1.34 MPa under CT. The SPR was
significantly higher under ZT than CT for all irrigation
levels. The gravimetric soil moisture content was 17.6%
- 20.0% under ZT, and 19.1% - 21.8% under CT (Table
3).
Soil penetration resistance (SPR) values averaged over
four irrigation levels, determined at 0 - 0.03 m and 0.10 -
0.13 m soil depths at crop harvest are shown in Table 4 .
The SPR at field moisture content (9.3% - 12.2%) was
higher in the ZT system than the CT system with a mag-
nitude of about 4 times in the 0 - 0.03 m layer, and about
2.5 times in 0.10 - 0.13 m layer. Higher SPR in the ZT
plots were found due to the higher soil b

value (1.34
Mg·m–3) in ZT plots compared to CT plots (1.23 Mg·m–3;
Table 5).
3.2. Soil Bulk Density, Saturated Hydraulic
Conductivity and Porosity
The b

was about 8.9% higher in ZT compared to CT
plots (Table 5). The soil Ksat (0 - 0.15 m depth), deter-
mined at wheat harvest, was 57 times higher under CT
than ZT (Tab le 5). Infiltration rate and Ksat are both func-
tions of pore size distribution. Both of these processes
increase with an increase in soil macroporosity. Conven-
tional tillage caused loosening of the surface soil layer
thereby increasing the macroporosity and hence increas-
ing the infiltration rate and Ksat.
Singh et al. [22] also observed an increase in Ksat in a
post-rice soil after tillag e. Higher values of infiltration as
well as Ksat under CT than ZT were also reported by
Barzegar [23]. The situation, however, may be different
under continuous zero till systems than in rice-wheat
system. A soil, continuously under zero till manag ement,
especially when crop residues are left on the soil surface,
may show higher infiltration rates and Ksat values due to
root channels formed in soil and enhanced earthworm
Table 3. Soil penetration resistance (SPR), and soil water content in the subsurface soil layer (0.10 - 0.13 m) at tillering stage
of wheat under different tillage and irrigation treatments measured during the 2003-2004 cropping season.
Tillage Treatment Irrigation Regime Treatment Gravimetric soil water content (g/g %)SPR (MPa)
RF 17.9de 1.61a
I1 17.6e 1.55b
I2 20.0bc 1.44c
ZT
I3 19.5c 1.40d
RF 19.8bc 1.35e
I1 21.8a 1.31f
I2 19.1dc 1.33ef
CT
I3 21.0ab 1.35e
Analysis of variance P > F
Treatment <0.01 <0.01
ZT = Zero tillage; CT = Conventional tillage; RF = Rainfed; I1 = Irrigation at CRI s tag e; I2 = Irrigation at CRI and flowering stage; I3 = Irrigation at CRI, tiller-
ing and flowering stage; Note: The SPR values have been averaged over different irrigation treatments because of small differences in soil moisture content.

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
76
Table 4. Soil penetration resistance (SPR) and soil water content for two soil depths at crop harvest in the zero tillage (ZT)
and conventionally-tilled (CT) treatments measured at crop harvest during the 2003-2004 cropping season.
Tillage 0 - 0.03 m soil depth 0.10 - 0.13 m soil depth
Water content SPR Water content SPR
ZT (g/g %)
12.2a† (MPa)
5.16a (g/g %) 9.3a (MPa) 8.36a
CT 11.7b 1.28b 11.4b 3.39b
Treatment <0.01 <0.01 <0.01 <0.01
†Means with different letters are significantly different at the 0.05 probability level.
Table 5. Saturated hydraulic conductivity (Ksat), bulk density, and total porosity of the surface soil layer (0 - 0.15 m) under
zero tillage (ZT) and conventional tillage (CT) treatments at 30 days after seeding of wheat for the 2003-2004 cropping sea-
son.
Tillage Ksat (mm·h–1) Bulk density ( Mg·m–3) Total porosity (%)
ZT 1.62a† 1.34a 49.3a
CT 92.0b 1.23b 53.7b
Analysis of variance P > F
Treatment <0.01 <0.01 <0.01
†Means with different letters are significantly different at the 0.05 probability level.
activity as was observed by Barnes and Ellis [24]. Seve-
ral other workers reported higher infiltration rate under
ZT system due to the formation of continuous soil bio-
pores [25-27]. Loch and Coughlan [28] reported higher
deep drainage under ZT than CT due to the presence of
continuous macropor es under ZT.
3.3. Soil Water Retention
Water retention of the surface 0.075 m soil layer on a
mass basis at –33 kPa and –1500 kPa soil water pressure
was always higher in CT than in ZT plots. The differ-
ences, however, narrowed with the decrease in water
potential. Water con tent on a volume basis was higher in
the ZT system than the CT system at –33 and –1500 kPa
pressure due to differences in b

(Table 6). The plant
available water capacity (PAWC) on a volume basis was
lower for the CT (7.5%) than ZT (7.9%) treatment (Ta-
ble 6).
Soil water retention (0 - 0.75 m soil layer) at –33 and
–1500 kPa water pressures varied with tillage system.
These differences could be explained with differences in
pore size distribution since the water retention of soils
depends primarily on 1) the number and size distribution
of soil pores and 2) the specific surface area of soils.
Pore size distribution affects water retention mainly at
higher water potentials, such as those at saturation and
field capacity, where the water retention is a function of
soil structure. At lower water potentials, close to the per-
manent wilting point, the water retention is a function of
soil texture, and also depends on the specific surface area
of soil particles [29]. Tillage modified the soil structure
thereby affecting water retentio n at –33 kPa water poten-
tial; however, tillage did not affect soil texture, hence
differences in water retention between CT and ZT nar-
rowed at –1500 kPa water potential.
The water retention on a volume basis at –33 and
–1500 kPa pressure was higher under ZT than CT (Table
6). This occurred in part because of the higher b

under
ZT than CT. Although differences in PAWC between ZT
and CT were not very large, the soil water retention un-
der ZT was slightly better than under CT.
3.4. Infiltration Rate
The steady-state infiltration rate in conventionally-tilled
plots (32.6 mm·h–1) was more than 4 times higher than
that of zero tilled plots (7.2 mm·h–1). The cumulative
infiltration was also higher in CT (665 mm) than in ZT
plots (278 mm). The steady-state infiltration in both
cases was achieved in about an 11-hour period (Figure
1).
The Green-Ampt (GA) model was fitted to measured
infiltration data. The GA model appeared to fit the mea-
sured infiltration data (Figure 1). The Ks parameter was
significantly different, whereas, the S parameter was not
significantly different between the tillag e systems (Table
7). The Ks parameter was 47 times higher for the conven-
tional tillage compared to zero tillage treatment (Table
7).
The Kfs and qs parameters were significantly different
between the CT and ZT systems (Table 8). The Kfs was
about 5.4 times higher for CT compared to ZT (Table 8 );
whereas the qs was about 4.5 times higher for this system

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions 77
Table 6. Effect of tillage treatment on soil water retention at
selected water potentials (0 - 0.075 m soil layer) for the
2003-2004 cropping season.
Water potential (kPa) Volume wetness, (m3/m3 %)
ZT CT
–33 36.5a 33.5b
–1500 28.6a 26.0b
PAWC 7.9 7.5
†Means with differen t letters are sign ificantly differ ent at the 0.05 prob abil-
ity level. The comparisons were made between ZT and CT at respective
pressures; Note: average bulk density values of soil cores were 1.34 and
1.23 Mg·m–3 in ZT and CT plots, respectively; ZT = Zero tillage; CT =
Conventional tillage; PAWC: plant available water capacity.
Table 7. Means of saturated hydraulic conductivity (Ks) and
sorptivity (S) fitted parameters estimated with the Green-
Ampt model for the zero and conventional tillage treatments
under a rice-wheat cropping system along with analysis of
variance for the 2003-2004 cropping season.
Ks S
Tillage Mean (mm·h–1) Mean (mm·h–0.5)
ZT 0.63a† 62.55a
CT 29.88b 61.28a
Analysis of variance P > F
Treatment <0.01 0.95
†Means with differen t letters are sign ificantly differ ent at the 0.05 prob abil-
ity level.
Table 8. Means of quasi-steady state infiltration rate (qs)
and field-saturated hydraulic conductivity (Kfs) for the zero
and conventional tillage systems along with analysis of va-
riance for the 2003-2004 cropping season.
qs K
fs
Tillage Mean (mm·h–1) Mean (mm·h–1)
ZT 7.19a† 4.49a
CT 32.59b 24.1b
Analysis of variance P > F
Treatment <0.01 <0.01
†Means with differen t letters are sign ificantly differ ent at the 0.05 prob abil-
ity level.
compared with the ZT treatment.
3.5. Crop Yield
The wheat yield was observed for three cropping seasons
during 2003-2004, 2004-2005 and 2005-2006. The yield
was not consistent for all the three cropping seasons.
Grain yield was affected significantly by irrigation levels
but not by tillage treatments during 2003 -2004 and 200 5-
2006 (Table 9).
During 2003-20 04 , g rain yield d ecr eased progr essive ly
0
100
200
300
400
500
600
700
0510 15
Infiltration (mm)
Ti me (h r)
GA Predicted
Measured Data
(a)
0
50
100
150
200
250
300
350
0510 15
Infiltration (mm)
Ti me ( hr )
GA Predicted
Measured Data
(b)
Figure 1. The Green-Ampt (GA) model fitted to measured
ponded infiltration data for typical replicates under (a) con-
ventional and (b) zero tillage for a rice-wheat cropping sys-
tem.
with the reduction in irrigation levels under both ZT and
CT systems, but yield differences were significant be-
tween RF and I2 in ZT, and RF and I3 in CT; I 1, I2 and I3
were statistically at par for grain yield und er both ZT and
CT. Grain yields with RF, I1 and I2 were about 80%, 89%
and 92% of I3 under ZT, and about 77%, 92% and 95%
of I3 under CT, respectively (Table 9). Thus grain yield
declined by about 8%, 11% and 20% under ZT, and 5%,
8% and 23% under CT, respectively, with reduction in
irrigation levels from I3 to I2, I1 and RF. According to
these data, ZT was relatively more sensitive to moisture
stress than CT for RF and I1 levels. At each irrigation
level, CT numerically produced more grain than ZT. Av-
eraged over four irrigation levels, grain yield with CT
was about 13 % higher th an ZT. The gr ain yield show ed a
significant linear relationship with total water use with r2
ranging from 0.36 to 0.69 for CT and ZT, respectively
(Figure 2).
Tillage system had a significant effect on wheat yield;
however, results were different between the 2003-2004
and 2004-2005 seasons. During 2004-2005, average yield
across four irrigation levels was higher with ZT (2.56
Mg·ha–1) by about 22 percent relative to CT (2.10
Mg·ha–1). This difference was attributed to good precipi-
tation distribution during the 2004-2005 cropping year;

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
78
y = 0.0043x - 0.1033
r²= 0.69
0.00
0.50
1.00
1.50
2.00
2.50
3.00
400 450 500 550 60
0
-
1
)
Profile Water Use (mm)
Grain Yield (Mg·ga
–1
)
(a)
y = 0.0045x + 0.0023
r²
= 0.36
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
400 450 500 550 60
0
-
1
)
Profile Water Use
(
mm
)
Grain Y ield (Mg·g a
–1
)
(b)
Figure 2. Relationship between wheat yield and total water
use for zero tillage (a) and conventional tillage (b) for the
2003-2004 cropping season.
no irrigation (except, pre-sown irrigation) was needed
during the entire cropping season. During the 2005-2006
cropping year, wheat grain yield increased significantly
over the RF treatment by 18, 46 and 52 per cent with the
I1, I2 and I3 irrigation treatments, respectively (Figure 3).
According to these data (2005-2006), wheat yield under
both tillage systems (zero and conventional) responded
similarly to deficit irrigation.
Higher SPR in ZT plots probably resulted in higher
root resistance and less root growth and less wheat yield
during the 2003-2004 cropping year. In contrast, the
lower b

, higher Ksat and infiltration rate in CT plots
probably resulted in less runoff and better plant growth
and wheat yield compared to ZT plots.
Yield data for tillage treatments showed that in 2003-
2004, CT performed better; for 2004-2005, ZT produced
higher yield; and for 2005-2006, no differences occurred
in the wheat yield between tillage treatments. Compared
to irrigation management, grain yield increased with in-
creased number of irrigations; except for 2004-2005
since during this year rainfall distribution was enough to
meet the irrigation requirement for the wheat crop. Re-
sults from this study conclude that irrespective of irriga-
tion levels; there were not large differences in yield be-
tween the ZT and CT systems; however, ZT was more
economical compared to CT system because of low input
cost. When compared to rainfed treatments, ZT per-
formed better compared to CT, hence farmers can make
more profit by relying on the ZT treatment rather than on
the CT system.
3.6. Water Use Efficiency
Tillage treatments as well as irrigation levels showed a
significant effect on water use efficiency (WUE) during
the 2003-2004 cropp ing year (Table 9). Numerically, th e
highest WUE of 4.93 kg·ha–1·mm–1 was found under CT
with I1 treatment and the lowest of 3.99 kg·ha–1·mm–1
under ZT with I3. Conversely, the amount of water used
(m3) to produce 1 kg of wheat gr ain varied be tween 2.03
m3·kg–1 in I1 (CT) and 2.51 m3·kg–1 in I3 (ZT) treatments.
Similar to grain yield data, the WUE for 2003-2004 and
2004-2005 cropping seasons were different. During
2004-2005, the highest WUE (3.47 kg·ha–1·mm–1) was
obtained with the I1 and ZT treatment, and the lowest
(2.48 kg·ha–1·mm–1) with the RF and CT treatment (Ta-
ble 10). During 2005-2006, WUE was statistically the
same with zero and convention al tillage (data not shown ).
The WUE increased progressively with the level of irri-
gation from rainfed through the three irrigation treat-
ments (Figure 3).
Averaged over two tillage and four irrigation levels,
WUE values were 4.33 kg·grain·ha–1·mm–1 and 2.32
m3·kg–1 grain. The interaction of tillage × irrigation was
also significant (P < 0.01) for WUE for the 2003-2004
cropping season (Table 9). It was concluded that more
water was needed for less grain production with ZT
compared to CT plots.
4. Conclusions
The irrigation treatments did not affect soil physical pro-
perties but tillage systems did affect these properties. The
b

and SPR values of CT plots were 8.2% and 13%, re-
spectively, lower compared to ZT plots which increased
the porosity (8.9%), Ksat (57 times) and the steady infil-
tration rate (4.5 times) under CT plots.
The rice crop management, rice crop was grown pre-
vious to the wheat crop, created adverse soil conditions
which partially caused the lower values of infiltra- tion
rate and Ksat in wheat plots which followed rice. When
comparing tillage systems, the soil was loosened with a
plough for CT which decreased the b

, increased soil
porosity and also increased Ksat as well as the steady in-
filtration rate compared to zero -tilled wh eat at the time of
crop harvest. The improved soil properties under CT
systems improved the wheat yield; however the yield dif-
ferences were not significant between tillage treatments
during the 2003-2004 cropping year. The results were

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
79
0.00
0.50
1.00
1.50
2.00
2.50
3.00
2003 - 2004
2004 - 2005
2005 - 2006
Grain Y ield (Mg·ha
–1
)
(a)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
RF I1 I2 I3
Irri
g
ation Levels
2003 - 2004
2004 - 2005
2005 - 2006
Water Use Efficiency (kg·ha
–1
·mm
–1
)
(b)
Figure 3. Wheat yield (a) and water use efficiency (b) for RF (rainfed), I1 (irrigation at CRI), I2 (irrigation at CRI and flow-
ering), and I3 (irrigation at tillering, CRI and flowering stages) irrigation levels during the 2003-2004, 2004-2005 and 2005-
2006 cropping seasons.
Table 9. Effect of different irrigation regime treatments on total water use, grain yield, and water use efficiency (WUE) for
wheat under zero tillage (ZT) and conventional tillage (CT) treatments for the 2003-2004 cropping season.
Irrigation regime Treatment Tillage Treatment Total water use (mm) Grain yield (Mg·ha–1) WUE (kg·grain·ha–1·mm–1)
ZT 458.9d 1.85c 4.03f
RF CT 463.2d 2.02bc 4.36d
ZT 491.9c 2.07bc 4.21e
I1 CT 489.1c 2.41ab 4.93a
ZT 534.8b 2.14ab 4.00gf
I2 CT 533.5b 2.47abc 4.62b
ZT 581.1a 2.32ab 3.99g
I3 CT 578.7a 2.61a 4.51c
Analysis of variance P > F
Tillage 0.95 0.06 <0.01
Irrigation <0.01 0.01 <0.01
Tillage × Irrigation 0.69 0.81 <0.01
RF = Rainf ed; I1 = Irrigation at CRI stage; I2 = Irrigation at CRI and flowering stage; I3 = Irrigation at CRI, tillering and flowering stage; WUE = Water use
efficiency.

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and
Wheat Yield under Water Deficit Conditions
80
Table 10. Effect of different irrigation regime treatments on total water use, grain yield, and water use efficiency (WUE) for
wheat under zero tillage (ZT) and conventional tillage (CT) treatments during the 2004-2005 cropping season.
Irrigation regime Treatment Tillage Treatment Total water use* (mm) Grain yield (Mg·ha–1) WUE (kg·grain·ha–1·mm–1)
ZT 820 2.48b 3.02e
RF CT 820 2.03f 2.48c
ZT 820 2.85a 3.47d
I1 CT 820 2.22d 2.71a
ZT 820 2.41c 2.93f
I2 CT 820 2.08e 2.54b
ZT 820 2.48b 3.02e
I3 CT 820 2.06ef 2.51c
Analysis of variance P > F
Tillage - <0.01 <0.01
Irrigation - <0.01 <0.01
Tillage × Irrigation - <0.01 <0.01
*No irrigation other than pre-sown was given to wheat crop dur ing 2004-2005 season as enough rai nfall received during this season.
different for the 2004-2005 and 2005-2006 cropping
seasons. Irrespective of the tillage system, however,
grain yield and WUE increased with increased level of
irrigation (except for the 2004-2005 cropping season
which received frequent rains) and values were higher
with the three irrigation treatments for the cropping sea-
sons which had deficit rain. Although grain yield was
inconsistent between the tillage systems over years, eco-
nomic costs were lower for the ZT tillage system which
implies it may be the best system for occasional increases
in yield and consistently lower input costs. Furthermore,
this ZT system conserves soil moisture and reduces soil
erosion as residues are left on the plots.
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