Directory UMM :Data Elmu:jurnal:S:Soil & Tillage Research:Vol57.Issue1-2.Sept2000:
Soil & Tillage Research 57 (2000) 43±52
Carry-over of residual soil moisture with mulching and
conservation tillage practices for sowing of rainfed
wheat (Triticum aestivum L.) in north-west India
Pradeep K. Sharma*, C.L. Acharya1
Department of Soil Science, Himachal Pradesh Agricultural University, Palampur-176 062 (HP), India
Received 6 September 1999; accepted 11 July 2000
Abstract
Lack of adequate seed-zone moisture is a major problem in the timely sowing of wheat (Triticum aestivum L.) after maize
(Zea mays L.) in rainfed areas of north-west India. Field experiments were conducted during 1993±1997 in an acid Al®sol
(typic Hapludalf) in north-west India to conserve rainwater in situ by using four combinations of mulch and tillage practices,
and using the conserved moisture for sowing of wheat at different dates. Fresh lantana (Lantana camara L.) biomass was used
as mulch during standing crop of maize before the recede of monsoon rains (LNT) or at maize harvest (LNTmh). Conservation
(CT, opening of furrow with hand plough for seeding plus mulch) and conventional tillage (CC, preparation of ®ne seed-bed
by digging soil to 12±15 cm depth) were the two tillage treatments. Treatment combinations during 1993 and 1994 were:
LNT CT, LNT CC, LNTmh CT and CC; during 1995 and 1996, LNTmh CT was replaced with CC LNT treatment.
Wheat was sown at three dates, viz. early (S1, mid-October), timely (S2, mid-November) and late (S3, mid-December). Annual
mean temperature of the area varies between 8.28C in January and 28.08C in June, and annual rainfall (1969±1997) between
1385 and 3259 mm. Mulching during standing crop of maize (LNT CT and LNT CC) was most effective in conserving
rainwater. Mulching at maize harvest (LNTmh CT) is either as good or inferior to mulching in the standing crop of maize,
depending on the rainfall events. The LNT CT and LNT CC, on an average, conserved more water than CC by 7.8 mm in
0±7.5 cm soil layer and by 15.1 mm in 0±45 cm soil layer at S1, 9.2 and 22.2 mm at S2, and 7.1 and 15.0 mm at S3 sowing
date, respectively. The corresponding values of moisture conserved with LNTmh CT over CC were 7.4 and 8.2 mm at S1, 3.6
and 20.1 mm at S2, and 3.9 and 5.8 mm at S3, respectively. The LNT CT and LNT CC always produced signi®cantly
higher wheat grain yield (0.58±2.96 Mg haÿ1) than CC (0.36±1.78 Mg haÿ1); except at S2 during the ®rst cropping cycle
where wheat yield was statistically the same with all the three treatments. The LNTmh CT and CC LNT, in general,
produced higher wheat yield than CC. The LNT CT produced signi®cantly higher wheat yield (1.93±2.84 Mg haÿ1 ) than
LNT CC (1.58±2.62 Mg haÿ1) during third cropping cycle onwards, while during the ®rst two years, the yield response
varied with tillage system and date of sowing. Mulching signi®cantly increased maize yield during third cropping cycle
onwards. After four cropping cycles, organic carbon content in 0±15 cm soil layer of mulched plots (LNT CT, LNT CC
and CC LNT) was signi®cantly higher (11.3±12.3 g kgÿ1) than control (CC) plots (9.0 g kgÿ1). # 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Organic carbon; Maize; Moisture conservation; Mulch; North-west India; Sowing date; Tillage; Wheat
*
Corresponding author. Tel.: 91-1894-30382/32397; fax: 91-1894-30511.
E-mail address: [email protected] (P.K. Sharma).
1
Address: Indian Institute of Soil Science, Nabi Bagh, Berasia Road, Bhopal-462 038 (MP), India.
0167-1987/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 0 0 ) 0 0 1 4 1 - 0
44
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
1. Introduction
Maize±wheat is an important annual cropping
sequence in rainfed areas of hills and foothills of
north-west India. Maize is sown by the end of May
to ®rst week of June and harvested by the end of
September. Monsoon rains usually recede by the
second week of September. The period between October and December most of the time is practically dry.
In the absence of rains after maize harvest, the major
problem in the timely establishment of spring wheat is
the lack of adequate moisture in the seed zone. Sometimes the sowing of wheat is delayed to as late as the
second week of January. Many times the farmers
practice dry seeding of wheat. The emergence and
crop establishment is then dictated by the late winter
rains, which are generally less than satisfactory. Late
emergence adversely affects tillering, and grain yield
is poor. Best wheat yields are obtained if the crop is
sown in November. Wheat is harvested in April±May.
The farmers in hills and foothills of north-west
India generally prefer to thrash and store grains and
stover of maize crop before starting the operations for
wheat cultivation, especially if the soil moisture is not
optimum for timely (November) sowing of wheat. In
the process, residual soil moisture further declines due
to evaporation. In some areas farmers go for repeated
shallow tillage with countryside plough to conserve
soil moisture by creating dust mulch (Sharma et al.,
1990). Nevertheless, most of the times the sowing of
wheat crop is delayed for want of adequate soil
moisture in the seed zone.
The possibility of increasing and stabilising wheat
yields in rainfed areas lies in the conservation of
residual soil moisture and its carry-over for early/
timely sowing of wheat. The role of mulches and
tillage practices in conserving soil moisture, with
the subsequent effect on crop yields, has long been
recognised (Gupta and Gupta, 1986; Grevers et al.,
1986; Sharma et al., 1990). Earlier studies have shown
that it is possible to conserve soil moisture by applying
mulch of waste organic residues, like dry leaves of sal
trees (Shorea robusta Gaertn. f.) or lantana (Lantana
camara L.) biomass, or eupatorium (Eupatorium
adenophorum Sprengel) biomass, during maize cropping season or at maize harvest (Sharma et al., 1990;
Acharya and Kapur, 1993; Acharya et al., 1998).
Mulching coupled with conservation tillage (opening
of a furrow with hand plough for seeding plus mulch)
has proved better than conventional tillage (two to
three ploughings with animal-drawn countryside
plough) in conserving moisture and producing wheat
yields (Sharma et al., 1990; Acharya et al., 1998).
In the present study, we used lantana biomass as the
mulch material. Lantana is an obnoxious weed, growing abundantly in waste lands and is fast encroaching
on cultivated areas. It is un®t for cattle feed but has a
potential as mulch material. It contains about 51%
carbon, 2.3% N, 0.22% P and 1.5% K on dry-mass
basis. Hence, its use as mulch in the long-run will also
improve chemical fertility of soil, in addition to
moderating hydro-thermal regime for wheat cultivation (Acharya et al., 1998).
The objective of the present investigation was to
study the period over which rainwater conserved in the
seed/root-zone during wet season with different combinations of mulch and tillage practices can be carriedover for timely/late sowing of wheat in rainfed areas.
For the in situ rainwater conservation, only those
treatments were considered which had given best
results in earlier studies. Reduced tillage plus mulch
(i.e., conservation tillage) had given better results than
reduced tillage without mulch (i.e., minimum tillage).
Hence, in this study we compared only the conservation tillage with conventional tillage for moisture
conservation.
2. Materials and methods
2.1. Experimental site
Field trials were conducted during 1993±1997 at the
farm of Himachal Pradesh Agricultural University,
Palampur (32860 N and 768320 E; 1300 m msl). The
climate of the area is wet temperate characterised by
severe winters and mild summers. Annual mean temperature varies between 8.28C in January and 28.08C
during the hottest month of June. The annual rainfall
varies between 1385 and 3259 mm, with an average of
2424 mm (based on rainfall data of 1969±1997). The
mean relative humidity in the region varies between
46% in May and 84% in July/August.
The experimental soil (USDA: Typic Hapludalf)
was silty clay loam in texture, and had 5.8 pH and
8.7 g kgÿ1 organic carbon (OC) in the 0±15 cm soil
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
45
layer at the start of the experiment. The soil was low in
available N and P, and medium in available K. The
surface soil retained, on mass basis, 303 g kgÿ1 moisture at 30 kPa suction and 181 g kgÿ1 moisture at
1500 kPa suction. The experimental soil prior to the
start of this experiment was being put to general
cultivation of maize and wheat in an annual sequence
under rainfed conditions.
during both the periods the climatic water balance is
negative. The wet season (mid-June±September)
receives about 74% of the total rainfall, which
amounts to about 1770 mm. It is much higher than
the evaporation during this period (323 mm). Hence,
there is ample scope of in situ moisture conservation
during wet season for use by the succeeding winter
crops in rainfed areas.
2.2. Climatic water balance
2.3. Treatments
Weekly rainfall and PAN-evaporation (PAN-E)
data, averaged over 29 years (1969±1997), are shown
in Fig. 1. According to these data, during the ®rst 12
weeks (up to third week of March) and 24 to 39 weeks
of the year (mid-June±September), rainfall exceeds
the evaporation, showing a positive water balance.
During 12th to 24th (last week of March±mid-June),
and 39th to 51st week of the year (September±third
week of December), evaporation exceeds the rainfall,
indicating a negative water balance. Thus, on an
average, for 28 weeks in a year the climatic water
balance is positive, and for 24 weeks the climatic
water balance is negative. The average annual rainfall
is 2424 mm, evaporation is 1290 mm, and the annual
water surplus is 1134 mm.
May±June is the period of sowing of wet season
crops (i.e., maize), while September±November is the
period for sowing of winter crops (i.e., wheat), and
A combination of 12 treatments, comprising mulch,
tillage and date of sowing of wheat, in maize±wheat
cropping sequence, were tested in 5 m3 m plots,
arranged in randomised complete block design, in
three replications. The treatment details are given in
Table 1.
Mulching in standing crop of maize utilized fresh
lantana biomass at 20 Mg haÿ1, having 55±60%
moisture content, during the last week of August
(before the recede of monsoon rains), when the soil
pro®le was almost saturated with rainwater. On drymass basis, the mulch material amounted to about 8±
9 Mg haÿ1. Maize (cv. Parvati) was cultivated as a
general crop with conventional tillage (by digging soil
manually to about 15 cm depth). It received 120 N±
26 P±33 K kg haÿ1 through urea, single superphosphate and muriate of potash, respectively. Wheat
(spring wheat) was sown with conventional and
Fig. 1. Average weekly rainfall and PAN evaporation at the experimental site (1969±1997).
46
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 1
Tillage treatments in maize±wheat cropping system and sowing dates of wheat
I. Maize
Date of sowing
Date of harvesting
1993
1994
1995
1996
May 29
September 28
May 28
September 28
June 16
September 27
June 15
October 3
II. Wheat
Mulch and tillage treatments
LNT CT
Lantana mulch (LNT) in standing crop of maize followed by sowing of wheat with conservation tillage (CT)a
LNT CC
Lantana mulch in standing crop of maize followed by sowing of wheat with conventional tillage (CC)b
LNTmh CTc
Lantana mulch at maize harvest followed by sowing of wheat with conservation tillage
CC
Sowing of wheat with conventional tillage
CC LNTc
Sowing of wheat with conventional tillage followed by LNT mulch
Date of sowing
S1: early sowing
(cv. VL 616)
S2: timely sowing
(cv. HS 240)
S3: late sowing
(cv. HPW 42)
1993±1994
1994±1995
1995±1996
1996±1997
October 8
October 8
October 6
October 9
November 11
November 12
November 15
November 11
December 23
December 22
December 23
December 17
a
Furrows were opened in mulched plots with a hand plough for sowing of wheat; the seeds were covered with soil manually and the
lantana mulch was retained.
b
Fine seed-bed was prepared by digging the top 12±15 cm soil layer manually; in mulched plots, mulch material was mixed with soil
during land preparation.
c
The treatment `LNTmh CT' was replaced with `CC LNT' after two cropping cycles, i.e., during 1995±1996.
conservation tillage. In conventional tillage, a ®ne
seed-bed was prepared by digging the top 12±15 cm
soil layer manually. In mulched plots, mulch material
was mixed with soil during land preparation. In conservation tillage, furrows were opened in mulched
plots with a hand plough for sowing of wheat; the
seeds were covered with soil manually and the lantana
mulch was retained. Wheat received 120 N±40 P±
25 K kg haÿ1 in all plots as urea, single superphosphate and muriate of potash, respectively. All of P and
K, and half of N were band placed at the time of
sowing, and remaining N was applied by broadcast
method in two equal splits, each at active tillering and
panicle initiation stage. Plots with conventional tillage
and without mulch (CC) were considered as control
and other treatments were compared with this treatment.
the data are presented in Table 2. Gravimetric moisture
content was determined in 0±7.5, 7.5±15, 15±30 and
30±45 cm soil layers at the time of sowing of wheat.
Organic carbon (OC) content of soil in the surface 15
cm layer was determined in all plots at the end of
fourth maize crop, using the rapid titration method of
Walkley and Black (Jackson, 1958). Bulk density was
also determined at the harvest of fourth maize crop and
30 days after sowing of wheat in 0±7.5, 7.5±15, 15±
22.5, 22.5±30 and 30±45 cm soil layers, using metal
cores of 7.5 cm length and 5.3 cm diameter. Equivalent water depth in 0±7.5 and 0±45 cm soil layers was
determined at the time of sowing of wheat. Soil
temperature at 5 cm depth was recorded at 7:00 h
on selected days during December and January (the
coldest months) using a soil thermometer. Grain yields
of maize and wheat were recorded at crop harvest.
2.4. Soil and crop measurements
2.5. Statistical analysis
Rainfall events during wheat cropping season were
recorded in a nearby meteorological observatory and
The data on organic carbon content, bulk density,
equivalent water depth in soil pro®le, and grain
47
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 2
Rainfall events during wheat cropping season at Himachal Pradesh Agricultural University, Palampur, in north-west India
Period
Rainfall (mm)
1993±1994
1994±1995
1995±1996
1996±1997
Maize harvest to S1
S1 to S2
S2 to S3
5.1
21.5
0
0
4.3
22.8
20.5
6.8
8.8
14.6
2.3
9.4
S1 to wheat harvesta
S2 to wheat harvestb
S3 to wheat harvestc
294.7
273.2
273.2
297.9
293.6
270.8
245.0
238.2
229.4
229.1
226.8
217.4
a
Early sowing of wheat.
Timely sowing of wheat.
c
Late sowing of wheat.
b
yield were analysed by analysis of variance in randomised complete block design. Soil temperature
with and without mulch was compared by using paired
t-test.
3. Results and discussion
3.1. Soil organic carbon
Soil incorporation of lantana (LNT CC) or its
application as surface mulch (LNT CT, LNTmh
CT=CC LNT) continuously for four years signi®cantly increased soil OC in the plough layer (0±15 cm
depth), but not in the subsoil (Table 3). Similar
observations were made in another experiment involving rice±wheat cropping sequence, where lantana
was applied to rice crop at the rates of 10±30 Mg haÿ1
per year (on fresh mass basis) for six years (Sharma
et al., 1995). Bhagat and Verma (1991) also reported
signi®cant build-up in soil OC in the plough layer with
rice straw applications for ®ve years in a soil under
rice±wheat cropping under the same environmental
conditions. These data show that the downward movement of OC from surface applied organic residues is
very slow. Increase in soil OC in the surface layer due
to four annual lantana applications at the rate of
20 Mg haÿ1 was around 25±35% over the control.
Tillage treatments did not affect soil OC signi®cantly, although OC values with conservation tillage
were numerically higher than with conventional tillage (Table 3). Tillage effects on soil OC may become
signi®cant when tillage is practised over a longer
period of time.
Table 3
Soil organic carbon (OC) and bulk density under different treatments (1996±1997)
Treatmentsb
LNT CT
LNT CC
CC LNT
CC
LSD (0.05)
a
OC (g kgÿ1)a
Bulk density (Mg mÿ3)
0±15 cm
(g kgÿ1)
15±30 cm
(g kgÿ1)
0±15 cm
(Mg haÿ1)
15±30 cm
(Mg haÿ1)
At maize harvest
At 30 DAS of wheat
0±7.5 cm
7.5±15 cm
0±7.5 cm
0±7.5 cm
12.3
12.0
11.3
9.0
1.1
8.1
7.9
8.0
7.8
NSc
24.2
23.4
22.0
18.4
2.2
16.9
16.6
16.7
16.4
NS
1.31
1.30
1.29
1.36
0.04
1.32
1.31
1.32
1.37
0.04
1.31
1.23
1.25
1.24
0.03
1.34
1.26
1.27
1.25
0.05
At maize harvest.
See Table 1 for description of tillage treatments.
c
Not signi®cant.
b
48
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Fig. 2. Relationship between organic carbon (OC) content and bulk density of soil.
3.2. Soil bulk density
At the time of maize harvest, bulk density in 0±7.5
and 7.5±15 cm soil layers of lantana-treated plots
(LNT CT, LNT CC and CC LNT) was signi®cantly lower than in control (CC) plots (Table 3). Bulk
density was negatively correlated with soil OC
(r ÿ0:701 , P 0:05) (Fig. 2), and lantana-treated
plots had signi®cantly higher soil OC. Signi®cant
negative correlation between bulk density and OC
has also been reported in earlier studies (Sharma
and Aggarwal, 1984; Sharma et al., 1995). Acharya
et al. (1998), in a similar study, reported increased
earthworm activity in lantana-treated plots, which can
also lower bulk density of soil. In this experiment,
however, we did not study the effect of lantana on
earthworm activity.
At 30 DAT, bulk density with conventional tillage
was signi®cantly lower compared to conservation
tillage, irrespective of lantana treatment. This
occurred because of the tillage operations performed
for preparing seedbed for wheat, which loosened the
soil and decreased bulk density. Tillage masked the
effect of soil OC on bulk density. Mulch and tillage
treatments, however, did not affect bulk density
below 15 cm soil depth. The average bulk density
in 15±45 cm soil layer varied between 1.39 and
1.43 Mg mÿ3 , indicating the presence of a relatively
compact subsoil layer.
3.3. Soil temperature
The minimum soil temperature at 5 cm depth,
recorded on selected days during December and
January, 1996±1997, was 0.5±28C higher under
lantana mulch than in control, and the differences
were statistically signi®cant (Table 4). Similar observations were made by Acharya et al. (1998). Under
conditions of suboptimal thermal regime, increase in
Table 4
Effect of lantana mulch on minimum temperature of soil at 5-cm
depth (1996±1997) t-value14df 2:257
Date
Soil temperature (8C) at 7 a.m.
No mulch
Mulch
December 4
December 11
December 18
December 27
January 3
January 10
January 21
January 28
6.5
5.5
4.0
4.5
3.0
3.5
4.5
5.5
8.5
7.0
4.5
6.0
4.5
5.0
5.5
7.0
Mean
4.6
6.0
49
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 5
Pro®le water content under different treatments at the time of sowing of wheat
Sowing
date
Mulch and tillage
treatmentsa
Equivalent water depth (mm)
Seed zoneb
Root zonec
1993±1994
1994±1995
1995±1996
1996±1997
1993±1994
1994±1995
1995±1996
1996±1997
S1
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
23.2
22.5
21.5
14.2
±
1.9
18.3
16.9
17.2
9.7
±
2.3
25.9
26.2
±
22.0
21.6
1.9
32.4
32.4
±
21.9
20.8
2.9
153.5
146.6
141.3
131.9
±
3.1
113.2
110.1
109.7
102.6
±
3.9
158.2
156.7
±
145.6
145.1
2.9
174.1
169.7
±
150.8
160.4
3.3
S2
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
22.1
21.6
18.6
17.6
±
2.3
16.8
16.5
10.3
4.1
±
2.8
19.2
18.5
±
9.8
8.7
3.0
21.6
18.7
±
9.3
10.3
2.7
137.3
136.6
137.7
132.4
±
3.9
137.0
136.0
133.0
98.0
±
3.8
134.4
133.1
±
105.2
104.8
2.7
138.3
124.8
±
113.0
112.3
3.1
S3
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
15.1
14.6
12.1
6.6
±
1.9
22.6
22.6
23.8
21.5
±
1.3
19.5
17.9
±
8.9
10.0
2.1
13.6
13.1
±
4.1
4.3
1.8
110.6
110.0
109.8
100.6
±
2.2
152.7
149.6
151.5
149.2
±
3.4
137.9
132.9
±
110.1
107.3
2.8
109.7
108.6
±
86.3
85.9
3.1
a
See Table 1 for description of tillage treatments.
Soil layer 0±7.5 cm.
c
Soil layer 0±45 cm.
b
soil temperature even by 0.5±28C signi®cantly affects
wheat growth and yield.
3.4. Moisture conservation
Seed zone (0±7.5 cm) as well as root-zone (0±45 cm)
moisture contents at the time of sowing of wheat crop
were signi®cantly higher in mulched than in unmulched
plots (Table 5). Mulching during standing crop of maize
was either superior or equal to mulching at maize
harvest, depending on rainfall pattern, in conserving
soil moisture. Tillage treatments (LNT CT and
LNT CC) did not differ signi®cantly in their effect
on seed-zone moisture content, but root-zone moisture
content was sometimes higher with conservation than
conventional tillage (Table 5). Soil moisture conserved
with mulching could be carried-over even for late
sowing of wheat in the third week of December. Mulch
applied after the sowing of wheat (CC LNT) probably affected wheat yield more through temperature
moderation rather than moisture conservation.
According to these data, mulching was more effective in conserving rainwater in situ when applied
during standing crop of maize before the recede of
monsoon rains. During this period, the soil pro®le is
almost saturated with water. In wet soils, the evaporation rate is weather controlled. Application of mulch at
this stage reduces evaporation ¯ux, and gives more
time for the water to redistribute within soil pro®le
(Hillel, 1980). If soil pro®le is wet at the time of maize
harvest due to late recede of monsoon rains, mulching
at maize harvest also will be equally effective in
moisture conservation. During fallow period (between
maize harvest and sowing of wheat), mulch helps in
the conservation of water received from intermittent
rain showers, if any, and maintains optimum moisture
in the seed zone.
3.5. Wheat yield
Changes in residual soil moisture storage caused by
different mulch and tillage treatments were signi®-
50
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 6
Effect of mulch and tillage treatments on grain yield (Mg haÿ1) of rainfed wheat sown at different dates
Sowing date
Treatmentsa
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
1993±1994
S1b
S2c
S3d
0.63
0.57
0.60
0.67
0.52
0.58
0.55
0.44
0.53
0.36
0.42
0.42
±
±
±
0.18
NS
0.17
1994±1995
S1b
S2c
S3d
1.92
1.83
2.87
1.71
2.14
2.96
1.31
1.77
2.86
1.10
1.09
1.75
±
±
±
0.20
0.18
0.16
1995±1996
S1b
S2c
S3d
1.96
2.31
1.93
1.64
2.08
1.58
±
±
±
0.78
0.91
0.86
1.47
1.35
1.29
0.22
0.17
0.20
1996±1997
S1b
S2c
S3d
2.69
2.80
2.84
2.60
2.62
2.62
±
±
±
1.29
1.16
1.78
1.40
1.48
1.96
0.17
0.17
0.19
a
See Table 1 for description of tillage treatments.
Early sowing of wheat.
c
Timely sowing of wheat.
d
Late sowing of wheat.
b
cantly re¯ected in the grain yield of wheat (Table 6),
which was signi®cantly higher in mulched than in
unmulched control plots (CC). Mulching after the
sowing of wheat (CC LNT) also gave higher
yield than the control (CC). During the ®rst year of
experimentation (1993±1994), tillage treatments
(LNT CT and LNT CC) did not show signi®cant
difference in grain yield, but in the subsequent years in
six out of nine cases conservation tillage (LNT CT)
was superior to conventional tillage (LNT CC).
During 1993±1994, wheat crop was damaged by hail
storm at the time of its harvest, thus, producing a low
grain yield.
Wheat yields with mulching during standing crop of
maize (LNT CT and LNT CC) during different
years were 1.5±2.4 times higher, with mulching at
maize harvest (LNTmh CT) were 1.28±1.51 times
higher, and with mulching after the sowing of wheat
(CC LNT) were 1.14±1.61 times higher than that of
control (CC). On average, LNT CT was better than
LNT CC. LNT CT produced 1.6±2.4 times
higher wheat yield than CC, while LNT CC produced 1.5±2.1 times higher wheat yield than CC.
Crop yield under rainfed conditions depends largely
on the pro®le-stored available water at the time
of sowing and the seasonal rainfall (Sharma and
Kharwara, 1990). Application of mulch improved
the seed-zone and root-zone moisture status, and
raised the minimum soil temperature. Both the
changes bene®ted wheat yields. Acharya et al.
(1998) also reported that mulching under similar
environment improved wheat yields by suitably modifying moisture and temperature regimes of soil. In
addition to improving moisture and temperature
regimes, mulching with lantana biomass also added
plant nutrients to soil. They bene®t wheat crop.
The effect of moisture conservation through mulch
applied in the standing crop of maize (LNT CT and
LNT CC) on wheat yield sown at different dates
depended on the rainfall events. Early/timely sowing
of wheat was better than late sowing if rains occurred
after maize harvest, but failed between third week of
October and December, as during 1995±1996
(Table 2). During this season, early and timely sowing,
on an average, produced 1.0 and 1.3 times more
wheat yield than late sowing. During 1994±1995,
51
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
when rains failed between maize harvest and second
week of November, but occured after second week of
November (i.e., after the timely sowing of wheat), late
sowing produced 1.6 and 1.5 times more wheat yield
than early and timely sown wheat. During 1996±1997,
wheat yields were almost the same at all the three
sowing dates. But without moisture conservation, late
sown wheat produced higher grain yield than early and
timely sown wheat, except during 1993±1994 and
1995±1996 when timely sown wheat was as good
or superior to late sown wheat.
It is important to consider the yield potential and
sensitivity to hydrothermal regimes of wheat cultivars
recommended for different dates of sowing while
studying their response to moisture conservation treatments. The cultivars recommended for early (VL 616)
and timely (HS 240) sowing had higher yield potential
than the late sown cultivar (HPW 42). If early/timely
sown cultivars have optimum soil moisture until
December, they would yield better than late sown
cultivar. If, on the other hand, early/timely sown
cultivars experience moisture stress in the early
growth phase, they would produce lower yields than
late sown wheat. The yield differences between treatments of with (LNT CT and LNT CC) and without moisture conservation (CC) narrowed with the
delay in sowing date. The yield differences, on an
average (data for the year 1993±1994 not included
because the crop was damaged with hail storm), were
1.34, 1.22 and 1.02 Mg haÿ1 at S1, S2 and S3 sowing
dates, respectively (Table 6). It may suggest that the
late sown cultivar was less sensitive to hydrothermal
regime than the early and timely sown cultivars.Nevertheless, grain yields of wheat with moisture conservation (LNT CT and LNT CC) were always
higher than without moisture conservation (CC).
These data suggest that wheat yields under rainfed
conditions can be improved with conservation tillage
and mulching, but the conserved moisture should be
used for sowing of wheat as early as possible. Delayed
sowing may become risky if rains fail after maize
harvest and until December.
3.6. Maize yield
Application of mulch, irrespective of method of
application, also increased maize yield, grown in
sequence with wheat. The increase in maize yield
Table 7
Residual effect of different mulch and tillage treatments on maize
grain yield
Treatmentsa
Grain yield (Mg haÿ1)
1994
1995
1996
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
1.53
1.63
1.70
1.60
±
NS
3.64
3.69
3.33
2.87
±
0.40
4.12
4.45
±
2.75
3.53
0.48
a
See Table 1 for description of tillage treatments.
was recorded after two cropping cycles (Table 7).
Increase in maize yield could be attributed to the
improvement in soil physical and chemical properties
of soil due to lantana additions. Improvement in soil
physical properties due to soil incorporations of
organic residues is well documented in literature. In
®ne-textured soils, build-up in soil OC content with
additions of organic residues improves water transmission and drainage conditions of soil by increasing
soil aggregation and inter-aggregate pore spaces
(Sharma and De Datta, 1994). Maize is very sensitive
to excess water condition. Water stagnation in the
root-zone even for few hours can severely damage
maize crop (Sharma, 1992). Further, lantana biomass
at the rate of 8 Mg haÿ1 (on dry-mass basis) would add
about 184, 18 and 120 kg haÿ1 N, P and K, respectively, to soil every year. As the amount of chemical
fertilizers applied to each plot was the same and
independent of mulch application, the additional nutrients supplied through lantana biomass must have
contributed to the increase in maize yield in mulched
plots.
4. Conclusions
Establishment of wheat crop under rainfed environments is possible by conserving soil moisture with
the application of waste organic residues, like lantana,
during the standing crop of maize, preceding wheat
and before the recede of monsoon rains. The conserved soil moisture should be utilized for the early
sowing of wheat, although it can be carried-over for
the timely and late sowings, provided the soil moisture
is supplemented with rainfall events, may be of light
52
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
intensity, during the fallow period between maize
harvest and sowing of wheat. Conservation tillage
produced wheat yields higher or similar to those with
conventional tillage, and may have advantage over
conventional tillage in terms of time and energy
required in land preparation. Use of lantana biomass
as mulch material also improved maize yield. Lantana
is an obnoxious weed, has little alternate uses as
fodder and fuel, and is easily available locally. It
can be conveniently used as mulch material. Its
long-term use as mulch will not only improve soil
productivity under maize±wheat cropping in rainfed
environments by way of adding organic carbon and
other plant nutrients, but will also keep a check on its
spread to other cultivable areas. Other organic residues
growing on waste lands and having less alternate uses
may also be used as mulch.
References
Acharya, C.L., Kapur, O.C., 1993. In situ moisture conservation for
wheat (Triticum aestivum) through mulching previous standing
maize (Zea mays) crop with wild sage (Lantana camara). Ind.
J. Agric. Sci. 63, 461±466.
Acharya, C.L., Kapur, O.C., Dixit, S.P., 1998. Moisture conservation for rainfed wheat production with alternative mulches and
conservation tillage in hills of north-west India. Soil Till. Res.
46, 153±163.
Bhagat, R.M., Verma, T.S., 1991. Impact of rice straw management
on soil physical properties and wheat yield. Soil Sci. 152, 108±
115.
Grevers, M.C., Kirkland, J.A., De Jong, E., Rennie, D.A., 1986.
Soil water conservation under zero and conventional tillage
systems on the Canadian prairies. Soil Till. Res. 8, 265±276.
Gupta, J.P., Gupta, G.K., 1986. Effect of tillage and mulching on
soil environment and cowpea seedling growth under arid
conditions. Soil Till. Res. 7, 233±240.
Hillel, D., 1980. Applications of Soil Physics. Academic Press,
New York, p. 385.
Jackson, M.L., 1958. Soil Chemical Analysis. Prentice-Hall,
Englewood Cliffs, NJ.
Sharma, P.K., 1992. Relative susceptibility of maize and soybean
to ¯ooding at seeding and seedling stage. Seed Res. 20, 99±
103.
Sharma, P.K., Aggarwal, G.C., 1984. Soil structure under different
land uses. Catena 11, 197±200.
Sharma, P.K., De Datta, S.K., 1994. Rainwater utilization
ef®ciency in rainfed lowland rice. Adv. Agron. 52, 85±120.
Sharma, P.K., Kharwara, P.C., 1990. Soil-stored available water
and seasonal rainfall as an index of success or failure of rainfed
crops. Ind. J. Agric. Sci. 60, 165±168.
Sharma, P.K., Kharwara, P.C., Tewatia, R.K., 1990. Residual soil
moisture and wheat yield in relation to mulching and tillage
during preceding rainfed crop. Soil Till. Res. 15, 279±284.
Sharma, P.K., Verma, T.S., Bhagat, R.M., 1995. Soil structural
improvements with the addition of Lantana camara biomass in
rice±wheat cropping. Soil Use Mgmt. 11, 199±203.
Carry-over of residual soil moisture with mulching and
conservation tillage practices for sowing of rainfed
wheat (Triticum aestivum L.) in north-west India
Pradeep K. Sharma*, C.L. Acharya1
Department of Soil Science, Himachal Pradesh Agricultural University, Palampur-176 062 (HP), India
Received 6 September 1999; accepted 11 July 2000
Abstract
Lack of adequate seed-zone moisture is a major problem in the timely sowing of wheat (Triticum aestivum L.) after maize
(Zea mays L.) in rainfed areas of north-west India. Field experiments were conducted during 1993±1997 in an acid Al®sol
(typic Hapludalf) in north-west India to conserve rainwater in situ by using four combinations of mulch and tillage practices,
and using the conserved moisture for sowing of wheat at different dates. Fresh lantana (Lantana camara L.) biomass was used
as mulch during standing crop of maize before the recede of monsoon rains (LNT) or at maize harvest (LNTmh). Conservation
(CT, opening of furrow with hand plough for seeding plus mulch) and conventional tillage (CC, preparation of ®ne seed-bed
by digging soil to 12±15 cm depth) were the two tillage treatments. Treatment combinations during 1993 and 1994 were:
LNT CT, LNT CC, LNTmh CT and CC; during 1995 and 1996, LNTmh CT was replaced with CC LNT treatment.
Wheat was sown at three dates, viz. early (S1, mid-October), timely (S2, mid-November) and late (S3, mid-December). Annual
mean temperature of the area varies between 8.28C in January and 28.08C in June, and annual rainfall (1969±1997) between
1385 and 3259 mm. Mulching during standing crop of maize (LNT CT and LNT CC) was most effective in conserving
rainwater. Mulching at maize harvest (LNTmh CT) is either as good or inferior to mulching in the standing crop of maize,
depending on the rainfall events. The LNT CT and LNT CC, on an average, conserved more water than CC by 7.8 mm in
0±7.5 cm soil layer and by 15.1 mm in 0±45 cm soil layer at S1, 9.2 and 22.2 mm at S2, and 7.1 and 15.0 mm at S3 sowing
date, respectively. The corresponding values of moisture conserved with LNTmh CT over CC were 7.4 and 8.2 mm at S1, 3.6
and 20.1 mm at S2, and 3.9 and 5.8 mm at S3, respectively. The LNT CT and LNT CC always produced signi®cantly
higher wheat grain yield (0.58±2.96 Mg haÿ1) than CC (0.36±1.78 Mg haÿ1); except at S2 during the ®rst cropping cycle
where wheat yield was statistically the same with all the three treatments. The LNTmh CT and CC LNT, in general,
produced higher wheat yield than CC. The LNT CT produced signi®cantly higher wheat yield (1.93±2.84 Mg haÿ1 ) than
LNT CC (1.58±2.62 Mg haÿ1) during third cropping cycle onwards, while during the ®rst two years, the yield response
varied with tillage system and date of sowing. Mulching signi®cantly increased maize yield during third cropping cycle
onwards. After four cropping cycles, organic carbon content in 0±15 cm soil layer of mulched plots (LNT CT, LNT CC
and CC LNT) was signi®cantly higher (11.3±12.3 g kgÿ1) than control (CC) plots (9.0 g kgÿ1). # 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Organic carbon; Maize; Moisture conservation; Mulch; North-west India; Sowing date; Tillage; Wheat
*
Corresponding author. Tel.: 91-1894-30382/32397; fax: 91-1894-30511.
E-mail address: [email protected] (P.K. Sharma).
1
Address: Indian Institute of Soil Science, Nabi Bagh, Berasia Road, Bhopal-462 038 (MP), India.
0167-1987/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 0 0 ) 0 0 1 4 1 - 0
44
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
1. Introduction
Maize±wheat is an important annual cropping
sequence in rainfed areas of hills and foothills of
north-west India. Maize is sown by the end of May
to ®rst week of June and harvested by the end of
September. Monsoon rains usually recede by the
second week of September. The period between October and December most of the time is practically dry.
In the absence of rains after maize harvest, the major
problem in the timely establishment of spring wheat is
the lack of adequate moisture in the seed zone. Sometimes the sowing of wheat is delayed to as late as the
second week of January. Many times the farmers
practice dry seeding of wheat. The emergence and
crop establishment is then dictated by the late winter
rains, which are generally less than satisfactory. Late
emergence adversely affects tillering, and grain yield
is poor. Best wheat yields are obtained if the crop is
sown in November. Wheat is harvested in April±May.
The farmers in hills and foothills of north-west
India generally prefer to thrash and store grains and
stover of maize crop before starting the operations for
wheat cultivation, especially if the soil moisture is not
optimum for timely (November) sowing of wheat. In
the process, residual soil moisture further declines due
to evaporation. In some areas farmers go for repeated
shallow tillage with countryside plough to conserve
soil moisture by creating dust mulch (Sharma et al.,
1990). Nevertheless, most of the times the sowing of
wheat crop is delayed for want of adequate soil
moisture in the seed zone.
The possibility of increasing and stabilising wheat
yields in rainfed areas lies in the conservation of
residual soil moisture and its carry-over for early/
timely sowing of wheat. The role of mulches and
tillage practices in conserving soil moisture, with
the subsequent effect on crop yields, has long been
recognised (Gupta and Gupta, 1986; Grevers et al.,
1986; Sharma et al., 1990). Earlier studies have shown
that it is possible to conserve soil moisture by applying
mulch of waste organic residues, like dry leaves of sal
trees (Shorea robusta Gaertn. f.) or lantana (Lantana
camara L.) biomass, or eupatorium (Eupatorium
adenophorum Sprengel) biomass, during maize cropping season or at maize harvest (Sharma et al., 1990;
Acharya and Kapur, 1993; Acharya et al., 1998).
Mulching coupled with conservation tillage (opening
of a furrow with hand plough for seeding plus mulch)
has proved better than conventional tillage (two to
three ploughings with animal-drawn countryside
plough) in conserving moisture and producing wheat
yields (Sharma et al., 1990; Acharya et al., 1998).
In the present study, we used lantana biomass as the
mulch material. Lantana is an obnoxious weed, growing abundantly in waste lands and is fast encroaching
on cultivated areas. It is un®t for cattle feed but has a
potential as mulch material. It contains about 51%
carbon, 2.3% N, 0.22% P and 1.5% K on dry-mass
basis. Hence, its use as mulch in the long-run will also
improve chemical fertility of soil, in addition to
moderating hydro-thermal regime for wheat cultivation (Acharya et al., 1998).
The objective of the present investigation was to
study the period over which rainwater conserved in the
seed/root-zone during wet season with different combinations of mulch and tillage practices can be carriedover for timely/late sowing of wheat in rainfed areas.
For the in situ rainwater conservation, only those
treatments were considered which had given best
results in earlier studies. Reduced tillage plus mulch
(i.e., conservation tillage) had given better results than
reduced tillage without mulch (i.e., minimum tillage).
Hence, in this study we compared only the conservation tillage with conventional tillage for moisture
conservation.
2. Materials and methods
2.1. Experimental site
Field trials were conducted during 1993±1997 at the
farm of Himachal Pradesh Agricultural University,
Palampur (32860 N and 768320 E; 1300 m msl). The
climate of the area is wet temperate characterised by
severe winters and mild summers. Annual mean temperature varies between 8.28C in January and 28.08C
during the hottest month of June. The annual rainfall
varies between 1385 and 3259 mm, with an average of
2424 mm (based on rainfall data of 1969±1997). The
mean relative humidity in the region varies between
46% in May and 84% in July/August.
The experimental soil (USDA: Typic Hapludalf)
was silty clay loam in texture, and had 5.8 pH and
8.7 g kgÿ1 organic carbon (OC) in the 0±15 cm soil
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
45
layer at the start of the experiment. The soil was low in
available N and P, and medium in available K. The
surface soil retained, on mass basis, 303 g kgÿ1 moisture at 30 kPa suction and 181 g kgÿ1 moisture at
1500 kPa suction. The experimental soil prior to the
start of this experiment was being put to general
cultivation of maize and wheat in an annual sequence
under rainfed conditions.
during both the periods the climatic water balance is
negative. The wet season (mid-June±September)
receives about 74% of the total rainfall, which
amounts to about 1770 mm. It is much higher than
the evaporation during this period (323 mm). Hence,
there is ample scope of in situ moisture conservation
during wet season for use by the succeeding winter
crops in rainfed areas.
2.2. Climatic water balance
2.3. Treatments
Weekly rainfall and PAN-evaporation (PAN-E)
data, averaged over 29 years (1969±1997), are shown
in Fig. 1. According to these data, during the ®rst 12
weeks (up to third week of March) and 24 to 39 weeks
of the year (mid-June±September), rainfall exceeds
the evaporation, showing a positive water balance.
During 12th to 24th (last week of March±mid-June),
and 39th to 51st week of the year (September±third
week of December), evaporation exceeds the rainfall,
indicating a negative water balance. Thus, on an
average, for 28 weeks in a year the climatic water
balance is positive, and for 24 weeks the climatic
water balance is negative. The average annual rainfall
is 2424 mm, evaporation is 1290 mm, and the annual
water surplus is 1134 mm.
May±June is the period of sowing of wet season
crops (i.e., maize), while September±November is the
period for sowing of winter crops (i.e., wheat), and
A combination of 12 treatments, comprising mulch,
tillage and date of sowing of wheat, in maize±wheat
cropping sequence, were tested in 5 m3 m plots,
arranged in randomised complete block design, in
three replications. The treatment details are given in
Table 1.
Mulching in standing crop of maize utilized fresh
lantana biomass at 20 Mg haÿ1, having 55±60%
moisture content, during the last week of August
(before the recede of monsoon rains), when the soil
pro®le was almost saturated with rainwater. On drymass basis, the mulch material amounted to about 8±
9 Mg haÿ1. Maize (cv. Parvati) was cultivated as a
general crop with conventional tillage (by digging soil
manually to about 15 cm depth). It received 120 N±
26 P±33 K kg haÿ1 through urea, single superphosphate and muriate of potash, respectively. Wheat
(spring wheat) was sown with conventional and
Fig. 1. Average weekly rainfall and PAN evaporation at the experimental site (1969±1997).
46
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 1
Tillage treatments in maize±wheat cropping system and sowing dates of wheat
I. Maize
Date of sowing
Date of harvesting
1993
1994
1995
1996
May 29
September 28
May 28
September 28
June 16
September 27
June 15
October 3
II. Wheat
Mulch and tillage treatments
LNT CT
Lantana mulch (LNT) in standing crop of maize followed by sowing of wheat with conservation tillage (CT)a
LNT CC
Lantana mulch in standing crop of maize followed by sowing of wheat with conventional tillage (CC)b
LNTmh CTc
Lantana mulch at maize harvest followed by sowing of wheat with conservation tillage
CC
Sowing of wheat with conventional tillage
CC LNTc
Sowing of wheat with conventional tillage followed by LNT mulch
Date of sowing
S1: early sowing
(cv. VL 616)
S2: timely sowing
(cv. HS 240)
S3: late sowing
(cv. HPW 42)
1993±1994
1994±1995
1995±1996
1996±1997
October 8
October 8
October 6
October 9
November 11
November 12
November 15
November 11
December 23
December 22
December 23
December 17
a
Furrows were opened in mulched plots with a hand plough for sowing of wheat; the seeds were covered with soil manually and the
lantana mulch was retained.
b
Fine seed-bed was prepared by digging the top 12±15 cm soil layer manually; in mulched plots, mulch material was mixed with soil
during land preparation.
c
The treatment `LNTmh CT' was replaced with `CC LNT' after two cropping cycles, i.e., during 1995±1996.
conservation tillage. In conventional tillage, a ®ne
seed-bed was prepared by digging the top 12±15 cm
soil layer manually. In mulched plots, mulch material
was mixed with soil during land preparation. In conservation tillage, furrows were opened in mulched
plots with a hand plough for sowing of wheat; the
seeds were covered with soil manually and the lantana
mulch was retained. Wheat received 120 N±40 P±
25 K kg haÿ1 in all plots as urea, single superphosphate and muriate of potash, respectively. All of P and
K, and half of N were band placed at the time of
sowing, and remaining N was applied by broadcast
method in two equal splits, each at active tillering and
panicle initiation stage. Plots with conventional tillage
and without mulch (CC) were considered as control
and other treatments were compared with this treatment.
the data are presented in Table 2. Gravimetric moisture
content was determined in 0±7.5, 7.5±15, 15±30 and
30±45 cm soil layers at the time of sowing of wheat.
Organic carbon (OC) content of soil in the surface 15
cm layer was determined in all plots at the end of
fourth maize crop, using the rapid titration method of
Walkley and Black (Jackson, 1958). Bulk density was
also determined at the harvest of fourth maize crop and
30 days after sowing of wheat in 0±7.5, 7.5±15, 15±
22.5, 22.5±30 and 30±45 cm soil layers, using metal
cores of 7.5 cm length and 5.3 cm diameter. Equivalent water depth in 0±7.5 and 0±45 cm soil layers was
determined at the time of sowing of wheat. Soil
temperature at 5 cm depth was recorded at 7:00 h
on selected days during December and January (the
coldest months) using a soil thermometer. Grain yields
of maize and wheat were recorded at crop harvest.
2.4. Soil and crop measurements
2.5. Statistical analysis
Rainfall events during wheat cropping season were
recorded in a nearby meteorological observatory and
The data on organic carbon content, bulk density,
equivalent water depth in soil pro®le, and grain
47
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 2
Rainfall events during wheat cropping season at Himachal Pradesh Agricultural University, Palampur, in north-west India
Period
Rainfall (mm)
1993±1994
1994±1995
1995±1996
1996±1997
Maize harvest to S1
S1 to S2
S2 to S3
5.1
21.5
0
0
4.3
22.8
20.5
6.8
8.8
14.6
2.3
9.4
S1 to wheat harvesta
S2 to wheat harvestb
S3 to wheat harvestc
294.7
273.2
273.2
297.9
293.6
270.8
245.0
238.2
229.4
229.1
226.8
217.4
a
Early sowing of wheat.
Timely sowing of wheat.
c
Late sowing of wheat.
b
yield were analysed by analysis of variance in randomised complete block design. Soil temperature
with and without mulch was compared by using paired
t-test.
3. Results and discussion
3.1. Soil organic carbon
Soil incorporation of lantana (LNT CC) or its
application as surface mulch (LNT CT, LNTmh
CT=CC LNT) continuously for four years signi®cantly increased soil OC in the plough layer (0±15 cm
depth), but not in the subsoil (Table 3). Similar
observations were made in another experiment involving rice±wheat cropping sequence, where lantana
was applied to rice crop at the rates of 10±30 Mg haÿ1
per year (on fresh mass basis) for six years (Sharma
et al., 1995). Bhagat and Verma (1991) also reported
signi®cant build-up in soil OC in the plough layer with
rice straw applications for ®ve years in a soil under
rice±wheat cropping under the same environmental
conditions. These data show that the downward movement of OC from surface applied organic residues is
very slow. Increase in soil OC in the surface layer due
to four annual lantana applications at the rate of
20 Mg haÿ1 was around 25±35% over the control.
Tillage treatments did not affect soil OC signi®cantly, although OC values with conservation tillage
were numerically higher than with conventional tillage (Table 3). Tillage effects on soil OC may become
signi®cant when tillage is practised over a longer
period of time.
Table 3
Soil organic carbon (OC) and bulk density under different treatments (1996±1997)
Treatmentsb
LNT CT
LNT CC
CC LNT
CC
LSD (0.05)
a
OC (g kgÿ1)a
Bulk density (Mg mÿ3)
0±15 cm
(g kgÿ1)
15±30 cm
(g kgÿ1)
0±15 cm
(Mg haÿ1)
15±30 cm
(Mg haÿ1)
At maize harvest
At 30 DAS of wheat
0±7.5 cm
7.5±15 cm
0±7.5 cm
0±7.5 cm
12.3
12.0
11.3
9.0
1.1
8.1
7.9
8.0
7.8
NSc
24.2
23.4
22.0
18.4
2.2
16.9
16.6
16.7
16.4
NS
1.31
1.30
1.29
1.36
0.04
1.32
1.31
1.32
1.37
0.04
1.31
1.23
1.25
1.24
0.03
1.34
1.26
1.27
1.25
0.05
At maize harvest.
See Table 1 for description of tillage treatments.
c
Not signi®cant.
b
48
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Fig. 2. Relationship between organic carbon (OC) content and bulk density of soil.
3.2. Soil bulk density
At the time of maize harvest, bulk density in 0±7.5
and 7.5±15 cm soil layers of lantana-treated plots
(LNT CT, LNT CC and CC LNT) was signi®cantly lower than in control (CC) plots (Table 3). Bulk
density was negatively correlated with soil OC
(r ÿ0:701 , P 0:05) (Fig. 2), and lantana-treated
plots had signi®cantly higher soil OC. Signi®cant
negative correlation between bulk density and OC
has also been reported in earlier studies (Sharma
and Aggarwal, 1984; Sharma et al., 1995). Acharya
et al. (1998), in a similar study, reported increased
earthworm activity in lantana-treated plots, which can
also lower bulk density of soil. In this experiment,
however, we did not study the effect of lantana on
earthworm activity.
At 30 DAT, bulk density with conventional tillage
was signi®cantly lower compared to conservation
tillage, irrespective of lantana treatment. This
occurred because of the tillage operations performed
for preparing seedbed for wheat, which loosened the
soil and decreased bulk density. Tillage masked the
effect of soil OC on bulk density. Mulch and tillage
treatments, however, did not affect bulk density
below 15 cm soil depth. The average bulk density
in 15±45 cm soil layer varied between 1.39 and
1.43 Mg mÿ3 , indicating the presence of a relatively
compact subsoil layer.
3.3. Soil temperature
The minimum soil temperature at 5 cm depth,
recorded on selected days during December and
January, 1996±1997, was 0.5±28C higher under
lantana mulch than in control, and the differences
were statistically signi®cant (Table 4). Similar observations were made by Acharya et al. (1998). Under
conditions of suboptimal thermal regime, increase in
Table 4
Effect of lantana mulch on minimum temperature of soil at 5-cm
depth (1996±1997) t-value14df 2:257
Date
Soil temperature (8C) at 7 a.m.
No mulch
Mulch
December 4
December 11
December 18
December 27
January 3
January 10
January 21
January 28
6.5
5.5
4.0
4.5
3.0
3.5
4.5
5.5
8.5
7.0
4.5
6.0
4.5
5.0
5.5
7.0
Mean
4.6
6.0
49
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 5
Pro®le water content under different treatments at the time of sowing of wheat
Sowing
date
Mulch and tillage
treatmentsa
Equivalent water depth (mm)
Seed zoneb
Root zonec
1993±1994
1994±1995
1995±1996
1996±1997
1993±1994
1994±1995
1995±1996
1996±1997
S1
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
23.2
22.5
21.5
14.2
±
1.9
18.3
16.9
17.2
9.7
±
2.3
25.9
26.2
±
22.0
21.6
1.9
32.4
32.4
±
21.9
20.8
2.9
153.5
146.6
141.3
131.9
±
3.1
113.2
110.1
109.7
102.6
±
3.9
158.2
156.7
±
145.6
145.1
2.9
174.1
169.7
±
150.8
160.4
3.3
S2
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
22.1
21.6
18.6
17.6
±
2.3
16.8
16.5
10.3
4.1
±
2.8
19.2
18.5
±
9.8
8.7
3.0
21.6
18.7
±
9.3
10.3
2.7
137.3
136.6
137.7
132.4
±
3.9
137.0
136.0
133.0
98.0
±
3.8
134.4
133.1
±
105.2
104.8
2.7
138.3
124.8
±
113.0
112.3
3.1
S3
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
15.1
14.6
12.1
6.6
±
1.9
22.6
22.6
23.8
21.5
±
1.3
19.5
17.9
±
8.9
10.0
2.1
13.6
13.1
±
4.1
4.3
1.8
110.6
110.0
109.8
100.6
±
2.2
152.7
149.6
151.5
149.2
±
3.4
137.9
132.9
±
110.1
107.3
2.8
109.7
108.6
±
86.3
85.9
3.1
a
See Table 1 for description of tillage treatments.
Soil layer 0±7.5 cm.
c
Soil layer 0±45 cm.
b
soil temperature even by 0.5±28C signi®cantly affects
wheat growth and yield.
3.4. Moisture conservation
Seed zone (0±7.5 cm) as well as root-zone (0±45 cm)
moisture contents at the time of sowing of wheat crop
were signi®cantly higher in mulched than in unmulched
plots (Table 5). Mulching during standing crop of maize
was either superior or equal to mulching at maize
harvest, depending on rainfall pattern, in conserving
soil moisture. Tillage treatments (LNT CT and
LNT CC) did not differ signi®cantly in their effect
on seed-zone moisture content, but root-zone moisture
content was sometimes higher with conservation than
conventional tillage (Table 5). Soil moisture conserved
with mulching could be carried-over even for late
sowing of wheat in the third week of December. Mulch
applied after the sowing of wheat (CC LNT) probably affected wheat yield more through temperature
moderation rather than moisture conservation.
According to these data, mulching was more effective in conserving rainwater in situ when applied
during standing crop of maize before the recede of
monsoon rains. During this period, the soil pro®le is
almost saturated with water. In wet soils, the evaporation rate is weather controlled. Application of mulch at
this stage reduces evaporation ¯ux, and gives more
time for the water to redistribute within soil pro®le
(Hillel, 1980). If soil pro®le is wet at the time of maize
harvest due to late recede of monsoon rains, mulching
at maize harvest also will be equally effective in
moisture conservation. During fallow period (between
maize harvest and sowing of wheat), mulch helps in
the conservation of water received from intermittent
rain showers, if any, and maintains optimum moisture
in the seed zone.
3.5. Wheat yield
Changes in residual soil moisture storage caused by
different mulch and tillage treatments were signi®-
50
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
Table 6
Effect of mulch and tillage treatments on grain yield (Mg haÿ1) of rainfed wheat sown at different dates
Sowing date
Treatmentsa
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
1993±1994
S1b
S2c
S3d
0.63
0.57
0.60
0.67
0.52
0.58
0.55
0.44
0.53
0.36
0.42
0.42
±
±
±
0.18
NS
0.17
1994±1995
S1b
S2c
S3d
1.92
1.83
2.87
1.71
2.14
2.96
1.31
1.77
2.86
1.10
1.09
1.75
±
±
±
0.20
0.18
0.16
1995±1996
S1b
S2c
S3d
1.96
2.31
1.93
1.64
2.08
1.58
±
±
±
0.78
0.91
0.86
1.47
1.35
1.29
0.22
0.17
0.20
1996±1997
S1b
S2c
S3d
2.69
2.80
2.84
2.60
2.62
2.62
±
±
±
1.29
1.16
1.78
1.40
1.48
1.96
0.17
0.17
0.19
a
See Table 1 for description of tillage treatments.
Early sowing of wheat.
c
Timely sowing of wheat.
d
Late sowing of wheat.
b
cantly re¯ected in the grain yield of wheat (Table 6),
which was signi®cantly higher in mulched than in
unmulched control plots (CC). Mulching after the
sowing of wheat (CC LNT) also gave higher
yield than the control (CC). During the ®rst year of
experimentation (1993±1994), tillage treatments
(LNT CT and LNT CC) did not show signi®cant
difference in grain yield, but in the subsequent years in
six out of nine cases conservation tillage (LNT CT)
was superior to conventional tillage (LNT CC).
During 1993±1994, wheat crop was damaged by hail
storm at the time of its harvest, thus, producing a low
grain yield.
Wheat yields with mulching during standing crop of
maize (LNT CT and LNT CC) during different
years were 1.5±2.4 times higher, with mulching at
maize harvest (LNTmh CT) were 1.28±1.51 times
higher, and with mulching after the sowing of wheat
(CC LNT) were 1.14±1.61 times higher than that of
control (CC). On average, LNT CT was better than
LNT CC. LNT CT produced 1.6±2.4 times
higher wheat yield than CC, while LNT CC produced 1.5±2.1 times higher wheat yield than CC.
Crop yield under rainfed conditions depends largely
on the pro®le-stored available water at the time
of sowing and the seasonal rainfall (Sharma and
Kharwara, 1990). Application of mulch improved
the seed-zone and root-zone moisture status, and
raised the minimum soil temperature. Both the
changes bene®ted wheat yields. Acharya et al.
(1998) also reported that mulching under similar
environment improved wheat yields by suitably modifying moisture and temperature regimes of soil. In
addition to improving moisture and temperature
regimes, mulching with lantana biomass also added
plant nutrients to soil. They bene®t wheat crop.
The effect of moisture conservation through mulch
applied in the standing crop of maize (LNT CT and
LNT CC) on wheat yield sown at different dates
depended on the rainfall events. Early/timely sowing
of wheat was better than late sowing if rains occurred
after maize harvest, but failed between third week of
October and December, as during 1995±1996
(Table 2). During this season, early and timely sowing,
on an average, produced 1.0 and 1.3 times more
wheat yield than late sowing. During 1994±1995,
51
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
when rains failed between maize harvest and second
week of November, but occured after second week of
November (i.e., after the timely sowing of wheat), late
sowing produced 1.6 and 1.5 times more wheat yield
than early and timely sown wheat. During 1996±1997,
wheat yields were almost the same at all the three
sowing dates. But without moisture conservation, late
sown wheat produced higher grain yield than early and
timely sown wheat, except during 1993±1994 and
1995±1996 when timely sown wheat was as good
or superior to late sown wheat.
It is important to consider the yield potential and
sensitivity to hydrothermal regimes of wheat cultivars
recommended for different dates of sowing while
studying their response to moisture conservation treatments. The cultivars recommended for early (VL 616)
and timely (HS 240) sowing had higher yield potential
than the late sown cultivar (HPW 42). If early/timely
sown cultivars have optimum soil moisture until
December, they would yield better than late sown
cultivar. If, on the other hand, early/timely sown
cultivars experience moisture stress in the early
growth phase, they would produce lower yields than
late sown wheat. The yield differences between treatments of with (LNT CT and LNT CC) and without moisture conservation (CC) narrowed with the
delay in sowing date. The yield differences, on an
average (data for the year 1993±1994 not included
because the crop was damaged with hail storm), were
1.34, 1.22 and 1.02 Mg haÿ1 at S1, S2 and S3 sowing
dates, respectively (Table 6). It may suggest that the
late sown cultivar was less sensitive to hydrothermal
regime than the early and timely sown cultivars.Nevertheless, grain yields of wheat with moisture conservation (LNT CT and LNT CC) were always
higher than without moisture conservation (CC).
These data suggest that wheat yields under rainfed
conditions can be improved with conservation tillage
and mulching, but the conserved moisture should be
used for sowing of wheat as early as possible. Delayed
sowing may become risky if rains fail after maize
harvest and until December.
3.6. Maize yield
Application of mulch, irrespective of method of
application, also increased maize yield, grown in
sequence with wheat. The increase in maize yield
Table 7
Residual effect of different mulch and tillage treatments on maize
grain yield
Treatmentsa
Grain yield (Mg haÿ1)
1994
1995
1996
LNT CT
LNT CC
LNTmh CT
CC
CC LNT
LSD (0.05)
1.53
1.63
1.70
1.60
±
NS
3.64
3.69
3.33
2.87
±
0.40
4.12
4.45
±
2.75
3.53
0.48
a
See Table 1 for description of tillage treatments.
was recorded after two cropping cycles (Table 7).
Increase in maize yield could be attributed to the
improvement in soil physical and chemical properties
of soil due to lantana additions. Improvement in soil
physical properties due to soil incorporations of
organic residues is well documented in literature. In
®ne-textured soils, build-up in soil OC content with
additions of organic residues improves water transmission and drainage conditions of soil by increasing
soil aggregation and inter-aggregate pore spaces
(Sharma and De Datta, 1994). Maize is very sensitive
to excess water condition. Water stagnation in the
root-zone even for few hours can severely damage
maize crop (Sharma, 1992). Further, lantana biomass
at the rate of 8 Mg haÿ1 (on dry-mass basis) would add
about 184, 18 and 120 kg haÿ1 N, P and K, respectively, to soil every year. As the amount of chemical
fertilizers applied to each plot was the same and
independent of mulch application, the additional nutrients supplied through lantana biomass must have
contributed to the increase in maize yield in mulched
plots.
4. Conclusions
Establishment of wheat crop under rainfed environments is possible by conserving soil moisture with
the application of waste organic residues, like lantana,
during the standing crop of maize, preceding wheat
and before the recede of monsoon rains. The conserved soil moisture should be utilized for the early
sowing of wheat, although it can be carried-over for
the timely and late sowings, provided the soil moisture
is supplemented with rainfall events, may be of light
52
P.K. Sharma, C.L. Acharya / Soil & Tillage Research 57 (2000) 43±52
intensity, during the fallow period between maize
harvest and sowing of wheat. Conservation tillage
produced wheat yields higher or similar to those with
conventional tillage, and may have advantage over
conventional tillage in terms of time and energy
required in land preparation. Use of lantana biomass
as mulch material also improved maize yield. Lantana
is an obnoxious weed, has little alternate uses as
fodder and fuel, and is easily available locally. It
can be conveniently used as mulch material. Its
long-term use as mulch will not only improve soil
productivity under maize±wheat cropping in rainfed
environments by way of adding organic carbon and
other plant nutrients, but will also keep a check on its
spread to other cultivable areas. Other organic residues
growing on waste lands and having less alternate uses
may also be used as mulch.
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