Sarhad J. Agric. Vol. 26, No. 4, 2010
475
IMPACT OF TILLAGE AND HERBICIDES ON WEED DENSITY
AND SOME PHYSIOLOGICAL TRAITS OF WHEAT
UNDER RICE-WHEAT CROPPING SYSTEM
KHALID USMAN*, SHAD KHAN KHALIL** and MUHAMMAD AZIM KHAN***
*
**
***
Department of Agronomy, Faculty of Agriculture, Gomal University, D.I.Khan, Pakistan
Department of Agronomy, Faculty of Crop Production Sciences, KP, Agricultural University, Peshawar, Pakistan
Department of Weed Science, KP, Agricultural University Peshawar, Pakistan
ABSTRACT
To evaluate the impact of various tillage systems in combination with herbicides on weed density and some
physiological traits under rice-wheat cropping system, an experiment using a winter wheat (Triticum aestivum L.)
cultivar “Nasir 2000” was conducted in arid region of Khyber Pakhtunkhwa, Pakistan during 2007–2009 growing
seasons. The experiment was laid out in randomized complete block design with split plot arrangements replicated
four times. The treatments comprised of 3 tillage treatments, including conventional tillage with deep ploughing
through disk plough (CT), reduced tillage with shallow ploughing through rotavator (RT), and zero tillage with
stubble direct drilling (ZT) as main plots while five weed control treatments viz. 2,4-D ester @ 1.25 L ha-1, Puma
super 75 EW @1.25 L ha-1, 2,4-D + Puma super @1.25 L ha-1 each, Affinity 50 WDG @ 2 kg ha-1 and weedy check
as subplots. Herbicides had significant effect on weed density, fresh and dry weed biomass (FWB & DWB), leaf area
tiller-1 (LAT-1), leaf area index (LAI), plant height, grains spike-1, and grain yield. Tillage x herbicides interaction
was significant for weed density and grain yield only. Maximum LAT-1 (141 cm2), LAI (3.4), plant height (88.2 cm),
grains spike-1 (72.4) and grain yield (6906.9 kg ha-1) were recorded with Affinity. Maximum weed density m-2 (75.5),
FWB (845.3 g m-2) and DWB (220.4 g m-2) were recorded in weedy check. Maximum grain yield (5583.8 kg ha-1)
was obtained from RT being statistically similar to grain yield (5575.1 kg ha-1) in ZT. The lower grain yield (5479.3
kg ha-1) in CT was due to maximum weed density m-2 (48.3), FWB (536.6 g m-2) and DWB (136.5 g m-2). Affinity was
the most effective herbicide against grasses as well as broad-leaved weeds in combination with either ZT or RT and
resulted in higher grain yield. ZT and RT in conjunction with affinity are recommended for significantly reducing
weeds population and enhancing wheat yield under rice-based cropping system.
Key words: Tillage, Herbicides, Weed density, Weed biomass, Wheat yield.
Citation:
Usman,. K, S. K. Khalil, and M. A. Khan. 2010. Impact of tillage and hervicides on weed density and
some physiological traits of wheat under rice-wheat cropping system. Sarhad J. Agric 26(4): 475-487
INTRODUCTION
Rice–wheat cropping system is one of the major cropping systems covering an area of 2.2 million ha in
Pakistan (Mann et al. 2004). The system is highly exhaustive in nature and is continuously practiced in the same belt
for several decades. Despite excessive use of chemical fertilizers, pesticides, high yielding cultivars, irrigation and
intensive tillage practices carried out through more sophisticated farm machinery, the yields of both the cereal crops
are still lower by 30-80 % than the potential yields of rice and wheat crops and remain stagnant or even declining for
the last several years (Ladha et al. 2000; Ladha et al. 2003; Khan, 2001). Wheat crop is more affected due to late
harvest of preceding fine rice. Traditional tillage practices consist of several tractor operations (8-16) including
mouldboard ploughing or disk ploughing, cultivator, rotavator, leveling and planking in order to ensure good seed
bed preparation for wheat sowing. This conventional method of wheat sowing in the paddy fields further delays
wheat sowing which results in low wheat yield. Wheat yield declines by 30-35 kg ha-1 day-1 if planting occurs after
mid-November (Gangwar et al. 2006). CT deteriorates soil and water quality due to excessive use of pesticides and
poor water management causing dropping of water table and increasing water logging and salinity (Qureshi et al.
2003). The potential yield of wheat can be limited by light interception, temperature, carbon partitioning, supply of
water, nutrients and weeds infestation. Several physiological traits have been proposed to increase the potential yield
of wheat under different growing conditions. These traits include an increased grains number, early anthesis, LAT -1,
LAI, plant height and an increased rate and duration of grain filling (Whan et al. 1991; Reynolds et al. 1996a;
Miralles and Richards, 1998).
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
476
Zero tillage (ZT) or reduced tillage (RT) technology for wheat establishment in the paddy fields meets the
needs of aforementioned problems. This technology reduces land preparation cost, saves fuel, equipment, labor, and
ensures good crop stand in addition to conservation of soil and water (Mann et al. 2002; Gupta et al. 2002).
However, this change of technology may affect weed density, weeds biology and insect pest infestation, which
needs to be explored. Weeds represent one of the most costly and limiting factors in crop production, posing
harvesting and storage problems (Rosskopf et al. 1999). Weeds pose serious threat to the companion crop through
its competition for nutrients, water, sunlight and space which cause considerable reduction in grain yield. Hence
effective weed management strategy should be implemented. The use of ZT for wheat planting is emerging as a new
tool in integrated weed management. In short it reduces weed population due to elimination of tillage (Mehla et al.
2000) and in conjunction with new herbicides provides effective weed control at lower rates (Ali and Tunio, 2002).
Looking to the scenario of unsustainable conventional tillage and its impacts on soil nutrients and
productivity decline, there is a need to modify current tillage practices while growing wheat after rice (Atreya et al.
2006). Zero tillage/reduced tillage must be perceived to provide a net economic benefit relative to conventional
tillage in terms of lower production costs and higher crop yields. Zero tillage and reduced tillage with suitable and
optimum use of herbicides have been suggested as the possible solution. However, a shift from an intensive tillage
system to zero tillage/reduced tillage system can cause major changes in soil micro climates due to different tillage
systems. No studies have been conducted in Pakistan to indicate whether use of herbicides should be adjusted to the
new tillage systems. The overall objective of this study was to know the impact of herbicides and tillage on weed
population and on some physiological traits of wheat which may contribute to wheat yield.
MATERIALS AND METHODS
Experimental Site
Field experiments were conducted at Research Farm, Faculty of Agriculture, Gomal University, Dera Ismail
Khan, Pakistan during the years 2007-08 and 2008-09. Dera Ismail Khan (31º 49΄ N, 70° 55΄ E) is the southern most
district of the Khyber Pakhtunkhwa Province, of Pakistan. Its elevation ranges from 121 to 210 m above sea level. The
average maximum temperatures in summer and winter are 45˚C and 8˚C, respectively. It is hot and dry in summer with
moderate spells of rain during the monsoon season; March, July, and August being the wettest months. Weather data were
collected from the meteorological station, D.I. Khan located near the experimental site. Total seasonal precipitation for the crop
growing season was 87.8 mm in 2007-08, and 131.6 mm in 2008-09. Monthly precipitation, maximum and minimum
temperatures for the two seasons are presented in Table I. Total rainfall in the second growing season was sufficiently
higher than the first growing season when average air temperature during first growing season was higher than the second
growing season.
Soil Analysis
Before sowing of experiments soil samples were collected from the experimental site and analyzed for
physico-chemical characteristics. The soil of the experimental field Table II) was silty clay loam, calcareous,
alkaline in reaction (pH 7.8), low in organic matter (0.9 %), total N (0.1 %), AB-DTPA extractable P (7.8 mg P2O5
kg-1 soil) and high in available K (192 mg K2O kg-1 soil). Organic matter was determined through wet oxidation
based upon the Walkley and Black method (Nelson and Sommers, 1982). Total N in soil was determined by the
kjeldhal method as described in (Bremner and Mulvaney, 1982). Phosphorus was measured by spectrophotometer
and potash by flame photometer. The extractable P and K in soil sample were determined by the AB-DTPA
extractable method (Soltanpour, 1985).
Table-I Average air temperature and rainfall at Faculty of Agriculture, Gomal University, D. I. Khan, Pakistan during the
years 2007-08 and 2008-09 crop growing seasons
2007-2008
2008-2009
Temp. oC
Rainfall
Temp. oC
Rainfall
(mm)
(mm)
Month
Max
Min
Average
Max
Min
Average
October
34.2
17.1
25.7
0.0
33.9
20.0
27.0
0.0
November
26.5
13.1
19.8
1.1
28.9
10.9
19.9
0.0
December
21.4
6.8
14.1
1.4
23
6.7
14.9
17.3
January
18.3
4.1
11.2
5.2
21.4
6.0
13.7
7.6
February
22.1
6.8
14.5
24.2
23.7
9.2
16.5
25.0
March
31.4
15.4
23.4
1.8
28.0
13.4
20.7
36.6
April
33.1
18.9
26.0
37.2
33.2
18.4
25.8
21.1
May
39.1
24.2
31.7
16.9
37
23
30
24.0
Total rainfall
87.8
131.6
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Sarhad J. Agric. Vol. 26, No. 4, 2010
Table-II Physio-chemical characteristics of the soils used for the experiments
Characteristic
Unit
Sand
%
Silt
_
Clay
_
Textural class
_
pH (1:5)
_
Organic matter
_
Total N
_
Available P
mg kg-1
Available K
_
EC
d S m-1
CEC
m.e/100 g
CO3
m.e/L
HCO3mol/L
Cl_
Ca + Mg
_
Value
15
45
40
Silty clay loam
7.8
0.9
0.1
7.8
192
0.1
19.2
Nil
1.2
2.1
5.2
Experimental Procedure
To find out the effects of different herbicides and tillage systems on weeds and some physiological traits of
wheat in a rice-wheat growing system, an experiment was conducted for two consecutive years i.e. 2007-2009.
Three tillage practices viz. zero-tillage (ZT), reduced tillage (RT, with rotavator) and conventional tillage (CT, with
disk plough, cultivator, rotavator) and five herbicidal treatments (Table III) viz. 2,4-D, Puma super, 2,4-D + Puma
super, Affinity, and control (weedy check) were applied in randomized complete block design with split plots
arrangement and four replications. Tillage was allotted to main plots, while herbicides were assigned to sub-plots.
Seed of improved wheat variety Nasir-2000, recommended for irrigated areas in Khyber Pakhtunkhwa, was planted
on October 29, 2007 and November 3, 2008 after rice harvest. A uniform seed rate of 120 kg ha -1 was used for the
whole experiment. The size of each sub plot was 5 x 1.8 m2 having 6 rows 5 m long and 0.3 m apart. A standard
dose of 120:60 kg N: P2O5 ha-1 was used in the form of Urea and triple super phosphate (TSP). All the phosphorous
and half of the nitrogen were applied with sowing, while remaining half of the nitrogen was applied in two splits i.e.
at the first and second irrigation. The crops were harvested on May 16, 2008 and May 20, 2009 during 2 years of
experiments.
Table-III Detail of herbicidal treatments used in the experiment.
Trade Name
Common Name
2,4-D ester
2,4-Dichlorophenoxy acetic acid
Puma super 75 EW
fenoxaprop-p-ethyl
2,4-D ester + Puma super 75 EW
_
Affinity 50 WDG
carfentazone ethyl ester +
isoproturon
Weedy Check
_
Spectrum of activity
Broad leaf killer
Grass killer
Broad spectrum
Broad spectrum
Dose kg/L ha-1
1.25
1.25
1.25 +1.25
2.00
_
_
Data were recorded on weed density m-2 before herbicide’s spray, weeds density m-2 after herbicide’s spray, relative
weed density, fresh/dry weeds biomass (FWB/DWB g m-2), leaf area tiller -1 (LAT-1), LAI, plant height, and grains
spike-1. Weed density m-2 was recorded 30 days after sowing before herbicide’s spray. A square quadrate of 1m2 was
randomly put at three places in each treatment and average weed counts m -2 were recorded in each treatment. Thirty
days after herbicide’s spray, weed density m-2 was again recorded. Relative weed density m-2 was calculated by
dividing weed counts m-2 of each species by total weed density and multiplied by 100. For FWB, weeds were
harvested at above ground level at crop physiological maturity from 1 m2 area from each sub plot, bagged each
separately and weighed with an electronic balance. After taking FWB weeds samples were oven dried at 60 0C for
72 hours. The oven dried weeds were weighed for recording DWB (g m-2). Similarly, plant height was recorded by
measuring the height of ten randomly selected plants in each treatment in four central rows at physiological maturity
from ground surface up to the tip of spikes excluding awn and then their average was calculated. LAT-1 was
measured by collecting leaves from ten tillers in each sub-plot in four central rows at anthesis stage and their leaf
area was calculated by multiplying leaf length (excluding leaf sheath) x maximum width x 0.75 (factor) (Khalil et al.
2002) and leaf area of ten tillers was then averaged as LAT-1. LAI was calculated as per formula (leaf area/ground
area). Number of grains spike-1 data were recorded by counting the number of grains of ten randomly selected spikes
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
478
from each sub-plot in four central rows and then computing the mean as the number of grains spike-1. A random
sample of 500 grains was collected from the harvested material and weighed. Grain yield was recorded by grain
yield/area harvested and multiplying by 10,000 m2.
Statistical analysis
The data across two years of the experiment was statistically analyzed using analysis of variance technique
appropriate for split plot arrangement in randomized complete block design (Steel and Torrie, 1980) and the
significant means for main and interaction effects were compared using LSD test at 0.05 level of probability.
RESULTS AND DISCUSSION
Weather Data
The 2008-09 growing season was cooler and wet than 2007-08, the seasonal total precipitation was 87.8
mm in 2007-08 and 131.6 mm in 2008-09. The more favorable moisture and temperature conditions during the
2008-09 season resulted in higher yield than 2007-08. Timely rainfall was received in year 2008-09 in the month of
January and February (Table I), when canal water was closed for desilting of Chashma Right Bank Canal during
these two months, resulted in significant yield difference between 2007-08 and 2008-09.
Weed Density (m-2) before Spray
The weed species infesting the experiment were Phalaris minor, Rumex dentatus, Medicago denticulata,
Melilotus indica, Chenopodium album, Convolvulus arvensis, Malva parviflora, Avena fatua, and Cyperus rotundus.
The data recorded on weed density before application of herbicidal treatments revealed that maximum weed density
m-2 (113.6) was recorded in 2008-09 while minimum weed density m -2 (62.2) was recorded in 2007-08 (Table 4).
Conventional tillage (CT) had the maximum weed density m-2 of 79.5 and 152.0 in 2007-08 and 2008-09,
respectively, while zero tillage (ZT) had the minimum weed density m-2 of 35.0 and 77.6 in 2007-08 and 2008-09,
respectively. However, reduced tillage (RT) showed intermediate density by recording 72 and 111.2 weeds m-2 in
2007-08 and 2008-09, respectively. Mean values for tillage revealed that tillage treatments significantly affected
weed density m-2. Maximum weed density m-2 (115.7) was recorded in CT, while minimum weed density m-2 (56.3)
was recorded in ZT. The data recorded on relative weed density showed that Phalaris minor had the maximum
infestation of 36.8 and 45.4 % during the years 2007-08 and 2008-09, respectively. Rumex dentatus was the next
obnoxious weed infesting the crop 25.8 and 32.4 % during the years 2007-08 and 2008-09, respectively (Table V).
Infestation % age for Medicago denticulata, Melilotus indica, and Chenopodium album was 21.8, 9.4 and 4.3 %, in
2007-08 while 13.2, 3.9, and 2.8 % in 2008-09, respectively. The rest of the weeds were of little importance having
negligible weed infestation. Mean values for tillage revealed that P. minor had minimum infestation (37.6 %) under
ZT. The probable reason for lower P. minor population in ZT compared to RT or CT might be the soil strength and
hard compact surface in the former in addition to the allelopathic effects of rice residues and broad leaved weeds on
P. minor as reported by Om et al.. (2003). However, R. dentatus was significantly higher (33.7 %) under ZT
compared to RT (24.3 %) and CT (29.4 %). Mohler (1993) communicated analogous results who reported that weed
seedling emergence was greater for some weeds with ZT compared to CT. This might have happened in case of R.
dentatus where seed is covered with perianth and might protect it from environmental variation on the surface and
causing higher infestation under ZT (Chhokar et al.., 2007). However, if seed formation is prevented then weed
infestation in ZT will be lower than CT. There is rapid loss of viability in addition to predation on the soil surface in
ZT compared to CT where seeds are buried in the soil and prevented from environmental hazards.
Table-IV Weed density (m-2) before herbicide spray in wheat as affected by year and tillage
Tillage
2007-08
2008-09
Means
Zero Tillage
35.0
77.6
56.3 B
Reduced Tillage
72.0
111.2
91.6 AB
Conventional Tillage
79.5
152.0
115.7 A
Means
62.2 B
113.6 A
LSD value for tillage at P < 0.05 (Averaged over years) = 37.2
Means followed by same letter (s) or no letter in each category are not significantly different (P≤ 0.05) using LSD test (This
definition will apply to all other data tables).
ZT = Zero tillage, CT = Conventional tillage, DT =Deep tillage, RD Reduced tillage,
FWB = Fresh weed biomass, DWB =Dry weed biomass, LAT-1 = Leaf area per tiller
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Sarhad J. Agric. Vol. 26, No. 4, 2010
Table-V Relative weed density (%) before spray in wheat as affected by year and tillage
Weed species
Tillage
2007-08
2008-09
P. minor
Zero tillage
33.4
41.8
Reduced tillage
43.2
44.2
Conventional tillage
33.8
50.2
Mean
36.8
45.4
CV % = 23.7
R. dentatus
Zero tillage
24.8 b
42.5 a
Reduced tillage
23.6 b
24.9 b
Conventional tillage
29.0 b
29.8 b
Mean
25.8
32.4
CV % = 22.9
LSD value for tillage at P < 0.05 (Averaged over years) = 7.3
LSD value for years x tillage at P < 0.05 = 10.3
M. denticulata
Zero tillage
24.8
9.8
Reduced tillage
18.0
19.1
Conventional tillage
22.4
10.8
Mean
21.8
13.2
CV % = 36.9
M. indica
Zero tillage
9.8
2.9
Reduced tillage
10.7
4.1
Conventional tillage
7.9
4.8
Mean
9.4 a
3.9 b
CV % = 53.8
C. album
Zero tillage
5.5
2.3
Reduced tillage
2.5
2.5
Conventional tillage
4.7
3.8
Mean
4.3
2.8
CV % = 69.4
Mean
37.6
43.7
42.0
33.7 a
24.3 b
29.4 ab
17.3
18.5
16.6
6.4
7.4
6.3
3.9
2.5
4.2
Weed Density (m-2) after Spray
Weed density m-2 was significantly affected by years, tillage, herbicides and tillage x herbicides interaction
(Table VII). More weed density m-2 (40.7) was recorded in 2008-09 as compared to lower weed density m -2 (28.3)
recorded in 2007-08 (data table not shown). The probable reason for higher weeds density m-2 in 2008-09 could be
higher rain fall and multiplication / dissemination of previous year left over weeds seeds. All herbicidal treatments
significantly affected weed density m-2. Maximum weeds density m-2 (75.5) was recorded in weedy check followed
by 51.8 in 2,4-D, and 34.8 in Puma super. The lowest weed density m -2 (3.2) was recorded in Affinity which was
statistically comparable to 2,4-D + Puma super (7.2). Years x herbicides interaction also showed significant effect
on weed density m-2 and maximum weed density m-2 (95.0) was recorded in weedy check in 2008-09 while
minimum weed density m-2 (2.6 and 3.7) were recorded in Affinity treated plots in 2008-09 and 2007-08,
respectively. These findings are in agreement with the work of Khalil et al. (1999) and Kotru et al. (1999) who
managed weeds significantly in wheat crop with different herbicides. The lowest weeds counts m -2 in Affinity could
be attributed to its highest phytotoxic effect against diverse flora of weeds. Analogous results were reported by Khan
et al. (2004) who reported that Affinity proved to be the best for controlling weeds compared to other herbicidal
treatments when applied as post emergence. They reported that herbicidal treatments significantly reduced weed
density as herbicides are time saving and economical in comparison to hand weeding or cultural methods.
Mean values for tillage revealed that highest weed density m-2 (48.3) was recorded in CT (Table 7) while
lowest weed density m-2 (22.0) was recorded in ZT which was statistically on par with RT (33.2). The higher weed
density m-2 in CT may be attributed to its favorable environment for diverse flora of weeds particularly for P. minor
which was dominant in CT. The hard compact surface in ZT might have created adverse environment for both
grassy and broad leaf weeds and hence lowest weed density was recorded therein. These results are in line with the
findings of Mann et al. (2004) and Mehla et al. (2000). They reported that the mean grain yield in ZT was higher
than CT timely sown wheat. They further reported that 52 % lesser weeds were found in the ZT fields than the crop
established with CT. Population of P. minor was reduced to nearly one-fourth in ZT plots compared to CT. They
ascribed the increase in productivity primarily to enhanced fertilizer- and water-use efficiency and to a significant
reduction in weed population. If ZT is practiced with rice residue retention then weed infestation will be lesser. This
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
480
is because crop residues alter environmental conditions related to weed seed germination, physically impede
seedling growth, or inhibit germination and growth by allelopathy (Crutchfield et al. 1986).
Tillage x herbicides interaction had also significant effect on weed density m-2. Maximum weed
density m-2 (112.7) was recorded in CT x weedy check, where no herbicide was applied. Lowest weed density
m -2 (1.9) was recorded in CT x Affinity closely followed by 2.9 in ZT x Affinity (data not shown in table). The
results presented are consistent with the findings of Acciaresi et al. (2003). They reported that tillage in combination
with herbicide was effective way of controlling weeds in wheat. The results mentioned in Table VII clearly indicate
superiority of ZT / RT over CT and that of Affinity over other herbicidal treatments regarding weed control
strategies. Similar results were reported by Chhokar et al. (2007). They reported that ZT in combination with
herbicides drastically reduced P. minor population and economically more preferable over traditional tillage
practices.
Fresh Weed Biomass (g m-2)
FWB was significantly affected by years, tillage, and herbicides (Table VII). Maximum FWB (681.7 g m -2)
was recorded in 2008-09 while minimum FWB (66.0 g m-2) was recorded in 2007-08 (year-wise data not shown).
The possible reason for higher FWB in 2008-09 could be due to frequent and higher rainfall and multiplication /
dissemination of the previous year left over weeds seeds. All herbicidal treatments significantly affected FWB.
Maximum FWB (845.3 g m-2) was recorded in weedy check (infested with both broad leaf and grassy weeds)
followed by 589.7 g m-2 in Puma super, where broad leaf weeds were dominant. The lowest FWB (30.4 g m -2) was
recorded in Affinity which was statistically comparable to 2,4-D + Puma super (124.7 g m-2). The difference in
FWB may be due to the different phytotoxic effects of different herbicides. Similar results were reported by Khan et
al.. (2003). They reported that herbicides application decreased FWB compared to weedy check. These findings are
also in conformity with that of Shahid (1994), who reported that herbicides significantly reduced FWB.
Tillage significantly affected FWB and the highest FWB (536.6 g m-2) was recorded in CT, while lowest
FWB (272.4 g m-2) was recorded in ZT being statistically at par with RT (312.4 g m-2). The higher FWB in CT may
be attributed to higher weed density and its favourable growth environment for diverse flora of weeds particularly
for P. minor which was dominant in CT. ZT had lowest weed density, unfavourable growth environment for weeds
and hence lowest FWB was recorded. These findings are in agreements with the work of Mehla et al. (2000), who
managed weeds significantly in wheat crop with different herbicides in combination with ZT. However, Mas and
Verdú (2003) reported that tillage system had no significant effect on total weed biomass. Year x herbicides also
showed significant effect on FWB and maximum FWB (1505.1 g m-2) was recorded in weedy check in 2008-09,
while minimum FWB (3.9 g m-2) was recorded in Affinity in 2007-08. It is evident from the results (Table VII) that
ZT / RT and Affinity actively suppressed the weeds growth resulting in lowest FWB compared to CT and other
herbicidal treatments. Dominant weeds of wheat in rice wheat cropping system were P. minor and R. dentatus.
These two species offered tough competition to wheat crop in CT method due to soft and well prepared land in
which weeds developed vigorous roots system in the early vegetative growth stage and drew moisture and nutrients
more vigorously than crop leading to crop stunted growth. In ZT both these noxious weeds were suppressed in the
very early stage due to hard compact surface and soil strength. Weeds could hardly survive under ZT when sprayed
with Affinity, which had more phytotoxic effects on weeds compared to other herbicides. Similar results were
reported by Dadari and Mani (2005), who reported reduced weight of weeds with herbicides.
Dry Weed Biomass (g m-2)
Statistical analysis of the data revealed that dry weed biomass (DWB) was significantly affected by years,
tillage, herbicides, years x tillage and years x herbicides (Table VI & VII). Higher DWB (180.3 g m -2) was recorded
in 2008-09 as compared to lower DWB (11.7 g m-2) recorded in 2007-08 (data not shown). The possible reason for
higher DWB in 2008-09 could be higher weed infestation due to rainfall and multiplication / dissemination of the
previous year left over weeds seeds. All herbicidal treatments significantly affected DWB. Maximum DWB (220.4 g
m-2) was recorded in weedy check (infested with both broad leaf and grassy weeds) followed by 108.9 g m -2 in Puma
super and 104.2 g m-2 in 2,4-D, both being statistically non significant. The lowest DWB (9.5 g m-2) was recorded in
Affinity which was statistically comparable to 2, 4-D + Puma super (37.1g m -2). Years x herbicides interaction also
occurred for DWB. Maximum DWB (412.6 g m-2) was recorded in weedy check in 2008-09, while minimum DWB
(0.9 and 1.6 g m-2) was recorded in 2,4-D + Puma super and in Affinity treated plots in 2007-08. The difference in
the DWB in different treatments may be due to variable efficiencies of different herbicides against weed species.
Sarhad J. Agric. Vol. 26, No. 4, 2010
481
Similar results were reported by Khan et al. (2003); Om et al. (2004) and Shahid (1994). They reported that
herbicides decreased DWB compared to weedy check.
Mean values for tillage showed that highest DWB (136.5 g m-2) was recorded in CT while lowest DWB
(73.8 g m-2) was recorded in ZT being statistically on par with RT (77.7 g m-2). The higher DWB in CT may be
attributed to its suitable growth environment having enough moisture and well prepared land to a sufficient depth for
sustaining vast flora of weeds particularly P. minor and R. dentatus which were dominant in CT. The adverse
physical environment in ZT might have negative impact on weeds population and growth which ultimately resulted
in lowest DWB as reported by Mehla et al. (2000).
Years x tillage interaction significantly affected DWB. Maximum DWB (257.2 g m-2) was recorded in CT
in 2008-09, while minimum DWB (7.3 g m-2) was recorded in ZT in 2007-08. The results (Table VII) illustrate that
ZT and RT proved better than CT in suppressing weeds growth. Similarly among herbicidal treatments, Affinity and
2,4-D + Puma super both treatments with broad spectrum activities were most effective against broad leaf as well as
grassy weeds. However, none of the herbicides showed any response against Cyperus rotundus being carried over
from rice, though its population was limited in wheat. The prevailing weeds of wheat in rice-wheat cropping system
were P. minor, R. dentatus, Medicago denticulta, Melilotus indica and Chenopodium album. They provided tough
competition to wheat crop in CT method due to soft and deeply ploughed well prepared land, while in ZT these
weeds were suppressed in the very early growth stage due to hard compact surface and soil strength. Weeds could
hardly emerge from hard compact surface of ZT while the emerged weeds remained under stress due to poor root
growth and were effectively controlled by spraying with broad spectrum herbicides such as Affinity or 2,4-D +
Puma super which had more phytotoxic effects on weeds compared to other herbicides. However, it was also
observed during the course of study that although Affinity was far better in controlling weeds than either of the
herbicidal treatments under study including 2,4-D + Puma super, but higher dose than the manufacturer
recommended one might result in phytotoxic effect on crop, and Affinity might lose its selectivity in herbicidal
action. The higher dose of 2,4-D + Puma super also showed phytotoxic effects against wheat crop, however this
treatment even at recommended dose was less economical compared to Affinity. These findings are in agreement
with Baghestani et al. (2007); Lemerle et al. (1986); Hassan et al. (2005) and Soltani et al. (2006). They reported
that increasing dose of carfentrazone-ethyl, the herbicide ability to damage weeds increased but this was at the
expense of higher wheat injury. The post application of 2,4-D ester and Puma super plus 2,4-D ester tank mix results
in unacceptable injury in winter wheat.
Leaf Area Tiller-1 (LAT-1)
Statistical analysis of the data revealed that herbicides and years significantly affected LAT -1 (Table VIII).
More LAT-1 (131.7 cm2) was recorded in 2007-08, while lower LAT-1 (116.2 cm2) was recorded in 2008-09.
Average of the two years revealed that LAT-1 increased with the application of herbicides in comparison to weedy
check. Minimum LAT-1 (108.8 cm2) was recorded in weedy check and maximum LAT-1 (141.0 cm2) was recorded
in Affinity followed by combination of 2.4-D and Puma super (130.246 cm 2). Individual application of 2,4-D and
Puma super have also increased LAT-1 but there was no significant difference between them. Combination of grassy
and broad leaf herbicides was superior to their separate application for weed control in wheat as reported by Cheema
and Akhtar (2005). They reported that herbicide application to wheat during early stages of development have
greatly decreased weed population over weedy check which ultimately increased LAT-1 by reducing competition
among weeds and crop plants for light, nutrients, and moisture etc. Tillage showed no increase in LAT -1, however,
favorable response of LAT-1 was recorded and maximum LAT-1 (125.6 cm2) was recorded in RT plots while
minimum LAT-1 (121.0 cm2) was recoded in ZT (Table 8). Su-Juan et al. (2008) also reported analogous results.
They reported lowest leaf area in ZT compared to other tillage treatments.
Leaf Area Index (LAI)
Statistical analysis of the data revealed that herbicides and years significantly affected LAI (Table VIII).
More LAI (3.0) was recorded in 2007-08, while lower LAI (2.5) was recorded in 2008-09. Average of the two years
revealed that LAI increased with the application of herbicides compared to weedy check. Minimum LAI (2.1) was
recorded in weedy check and maximum LAI (3.4) was recorded in plots treated with Affinity. Combination of 2,4-D
and Puma super gave next higher LAI (3.042), while individual application of 2,4-D and Puma super have also
increased LAI compared to weedy check but there was no significant difference between them. Increase in LAI with
application of herbicides was also reported by Cheema and Akhtar (2005). They reported that herbicide application
to wheat crop at 3-4 leaf stage have increased LAI by diverting competition among weeds and crop plants in favor
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
482
of crop plants. Tillage showed no increase in LAI, however, favorable response of LAI was recorded and maximum
LAI (2.8) was recorded in reduced tillage while minimum LAI (2.7) was recoded in ZT. CT gave more LAI than ZT
(2.8). Gangwar et al. (2004) and Su-Juan et al. (2008) also reported higher LAI in CT than ZT. They attributed
lower LAI in ZT to lower plant population. The positive response of LAI to RT may be due to better utilization of
inputs and increased inputs use efficiency in case of RT technology. The results are corroborated by the work of
Hobbs et al. (2001). They reported that ZT / RT improve water use efficiency, soil physical structure over time,
reduce the need for applying herbicides, conserve natural resources and reduce soil compaction, all these lead to
optimum growth of leaf area.
Plant Height (cm)
Plant height of wheat as recorded in the two growing seasons is given in (Table VIII). Statistical analysis of
the data revealed that different herbicidal treatments have significant effect on plant height, while years, tillage and
herbicides x tillage have no significant effect on plant height (Table VIII). Averaged across herbicides and tillage,
maximum plant height (86.6 cm) was recorded in 2007-08, while lower plant height (85.7 cm) was recorded in
2008-09. Among herbicidal treatments, maximum plant height (88.2 cm) was recorded in Affinity, while minimum
plant height was recorded in weedy check (83.7 cm). The rest of the three herbicidal treatments i.e. 2,4-D, Puma
super and 2, 4-D + Puma super gave about similar plant height ranging from 85.7 cm to 87.2 cm. However, plant
height in 2, 4-D + Puma super treated plots was not statistically different from that of Affinity. These results are in
agreement with the findings of Soltani et al. (2006). They reported that plant height was affected by post emergence
herbicides; however, in their study plant height was reduced by herbicides due to herbicides injury to crop. Arif et
al. (2004) reported significant effect of herbicides on plant height and maximum plant height was observed with
mixture of Buctril M 40 EC and Puma super 75 EW. When averaged across years and herbicides, almost similar
plant heights were recorded in ZT, RT and CT. The similarity in plant height among the tillage treatments and their
interaction with herbicides show that plant height is strictly governed by genetic control and environment has a
meager effect on it. The non significant effects of various tillage treatments on plant height may be due to the
reduced growth of weeds from hard compact surface of ZT plots, moisture conservation due to surface residues of
the previous rice crops and efficient utilization of fertilizer due to band placement and thus ZT/RT had equal
performance in comparison to CT with regard to plant height.
Grains Spike-1
Grains spike-1 of wheat as affected by tillage and herbicides in the two growing seasons is given in Table
VIII. Grains spike-1 were significantly affected by years, herbicides, years x herbicides, years x tillage. Higher
number of grains spike-1 (64.6) were recorded in 2008-09 while lower grains spike-1 (58.8) were recorded in 200708. Grains spike-1 were significantly increased with all herbicidal treatments with the highest grains spike (72.4) in
Affinity treated plots. Minimum grains spike-1 (53.3) were recorded in weedy check while grains spike-1 of 2,4-D
(60.0 ) and Puma super (58.5) were statistically on par with one another. Years x herbicides interaction had also
significant effect on grains spike-1. Maximum grains spike-1 were recorded in Affinity in 2008-09, while minimum
grains spike-1 (52.3, 54.4) were recorded in weedy check (2007-08 and 2008-09, respectively). 2,4-D alone
superceded Puma super in both years. Cheema et al. (2006), Cheema and Akhtar (2005), Khan et al. (2004) and Arif
et al. (2004) reported analogous results.
Years x tillage interaction significantly affected grains spike-1. Maximum grains spike-1 (67.6) were
recorded in RT in 2008-09 followed closely by 65.0 in ZT (2008-09) while minimum grains spike-1 (56.9), (58.3),
(61.3), and (61.2) were recorded in RT (2007-08), ZT (2007-08), CT (2007-08) and CT (2008-09), respectively.
Interactions of tillage and herbicides combined over years as well as in individual years were statistically non
significant (Table VIII). The increased number of grains spike-1 is attributed to the effective weed control by
herbicidal treatments and conservation and efficient use of inputs in ZT/RT and consequently efficient utilization of
available resources by wheat crop. Findings of Khan et al. (2004) also support our inferences. They reported that
weed density decreased in herbicides treated plots which enhanced grains spike-1 in wheat.
Grain Yield (kg ha-1)
Statistical analysis of the data revealed that grain yield was significantly affected by years, tillage,
herbicides, tillage x herbicides and years x tillage x herbicides interactions (Table VI-VIII). Maximum grain yield
(5600.8 kg ha-1) was recorded in 2008-09 while minimum grain yield (5491.4 kg ha-1) was recorded in 2007-08. The
lower yield in 2007-08 may be due to unfavorable solar radiation, precipitation and an increase in minimum
temperature resulting in declining yield of wheat. Similar results were reported by Pathak et al. (2003). They
483
Sarhad J. Agric. Vol. 26, No. 4, 2010
analyzed weather data and reported negative trends in solar radiation and an increase in minimum temperature
resulting in declining trends of potential simulated yield of rice and wheat. Grain yield increased with herbicidal
treatments and maximum grain yield (6906.9 kg ha-1) was recorded in plots treated with Affinity followed by 6348.2
and 5548.6 kg ha-1 in 2, 4-D + Puma super and 2,4-D alone. Weedy check and treatment with Puma super showed
the lowest grain yield of 3765.9 and 5160.8 kg ha-1, respectively. Herbicides with broad spectrum activity showed
better performance than their alone application. The years x herbicides had also significant effect on grain yield of
wheat. Maximum grain yield (6995.6 kg ha-1) was recorded in plots treated with Affinity in 2008-09 while minimum
grain yield (3689.8 kg ha-1) was recorded in weedy check in 2008-09. Similar results were reported by Cheema and
Akhtar (2005); Arif et al. (2004); Zand et al. (2007); Baghestani et al. (2008); and Chhokar et al. (2008). They
reported that herbicides significantly increased grain yield in wheat corresponding to their weed control spectrum.
Tillage significantly increased grain yield and maximum grain yield (5583.8 kg ha-1) was recorded in RT,
however, it was statistically similar with ZT (5575.1 kg ha-1). Minimum grain yield was recorded in CT (5479.3 kg ha-1).
The lower yield under CT may be due to higher weed density, leaching of N fertilizer and immobilization due to crop
residues incorporation (Mandal et al. 2004). The higher yield in ZT and RT is ascribed to reduced weed growth; enhanced
fertilizer- and water use efficiency and to a significant reduction in weed population; particularly population density of P.
minor. These results are in line with the findings of Mehla et al. (2000); Radford et al. (1995); Nayyar and Randawa,
(1998); McMaster et al. (2002); Guy and Cox (2002); Mari et al. (2003); Ozpinar and Cay (2005); Ozpinar (2006);
Hemmat and Eskandari (2006); Lafond et al. (2006); Su et al. (2007); Wang et al. (2007); DeVita et al. (2007) and
Erenstein et al. (2008). They reported higher productivity for ZT over CT due to early sowing, reduced population of P.
minor and enhanced water and fertilizer use efficiency and improved fertility level of the soil in the organic matter
compared to CT. Years x tillage also showed significant effect on grain yield of wheat. Maximum grain yield (5845.6 and
5646.5 kg ha-1) was recorded in RT and ZT, respectively in 2008-09 while minimum grain yield (5310.1 kg ha -1) was
recorded in CT in 2008-09 (data not shown).
Mean values for tillage x herbicides interaction revealed that maximum grain yield (6994.9 kg ha-1) was
obtained from the interaction of Affinity x CT followed by Affinity x ZT (6928.5 kg ha-1) while minimum grain yield
(3580.5 kg ha-1) was obtained from the interaction of CT x weedy check, where no herbicide was applied. The data further
revealed that grain yield of weedy check x RT was higher than ZT x weedy check and CT x weedy check in both years.
One of the reasons may be higher density of Medicago denticulata and Melilotus indica in RT plots which are leguminous
in nature having complementary effects on wheat crop and detrimental effects on other weeds. Banik et al. (2007) reported
that association of M. denticulata with winter wheat controlled weeds, improved soil fertility, saved weeding costs, and
increased yield. The observed increase in grain yield of wheat with the use of ZT and herbicides is in agreement with the
findings of Chhokar et al. (2007). They reported that combination of ZT and herbicides have significantly increased wheat
yield in different environments of the world by reducing weeds infestation and resulting in higher grain yield compared to
CT. However, the magnitude of increase varied is rather site specific and dependent on the type of tillage and herbicides
used. The years x tillage x herbicides interaction was significant. Maximum grain yield was recorded in ZT treated with
Affinity in 2008-09. However, it was statically similar with RT x Affinity (6995.0 kg ha -1), CT x Affinity (6995.3 kg ha-1)
in 2008-09 and with CT x Affinity (6994.5 kg ha -1) in 2007-08. Minimum grain yield (3497.0 and 3527.0 kg ha-1) was
recorded in weedy check x ZT and weedy check x CT in 2008-09.
Table-VI
Source
Probability of the significance of main effects and their interaction for grain yield, weeds and physiological related
parameters
DF
Years (Y)
1
Rep (y*)
6
Tillage
2
Y X Tillage
2
Error 1
12
Herbicides
4
Y X Herbicides
4
Tillage X Herbicides
8
Y X Tillage X Herbicides
8
Error 2
72
Total
119
NS
= Non- Significant
FWB = Fresh weed biomass
DWB = Dry weed biomass
Weed
density
*
FWB
DWB
LAI
**
Leaf area
tiller-1
**
**
**
NS
*
NS
*
*
**
*
**
NS
**
**
NS
NS
**
**
NS
NS
**
Plant
height
NS
Grains
spike-1
**
Grain
yield
**
NS
NS
NS
NS
NS
NS
NS
**
**
**
**
NS
NS
NS
**
NS
NS
NS
**
NS
NS
NS
**
**
NS
NS
**
**
**
**
** = Significant at 1 % level of probability
* = Significant at 5 % level of probability
Rep (y*) = represent replication over year
LAI = Leaf area index
DF = Degrees of Freedom
484
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
Table-VII Main effect of tillage and herbicides on weeds density (m-2) after spray, fresh weed biomass and dry weed biomass
(averaged over years)
Fresh weed biomass (g m-2)
Dry weed biomass (g m-2)
Tillage
Weed density (m-2)
Zero tillage
22.0 b
272.4 b
73.8 b
Reduced tillage
33.2 ab
312.4 b
77.7 b
Conventional tillage
48.3 a
536.6 a
136.5 a
Herbicides
2,4-D
51.8 b
279.1 c
104.2 b
Puma super
34.8 c
589.7 b
108.9 b
2,4-D + Puma super
7.2 d
124.7 cd
37.1c
Affinity
3.2 d
30.4 d
9.5 c
Weedy check
75.5 a
845.3 a
220.4 a
Tillage X Herbicides
**
NS
NS
* = Significant at P ≤ 0.05, ** = Significant at P ≤ 0.01, NS= Non Significant
Table-VIII Effect of tillage and herbicides on grain yield and some physiological traits of wheat under rice-wheat growing
system (averaged over years)
Leaf area tiller-1
Tillage
Zero tillage
Reduced tillage
Conventional tillage
Herbicides
2,4-D
Puma super
2,4-D + Puma super
Affinity
Weedy check
Tillage X Herbicides
* = Significant at P ≤ 0.05
** = Significant at P ≤ 0.01
NS = Non Significant
Grains spike-1
Grain yield (kg ha-1)
LAI
Plant height (cm)
121.0
125.6
125.4
2.7
2.8
2.8
85.2
86.4
86.8
61.7
62.2
61.3
5575.1 a
5583.8 a
5479.3 b
121.1 c
118.8 c
130.2 b
141.0 a
108.8 d
NS
2.7 c
2.6 c
3.0 b
3.4 a
2.1 d
NS
85.7 b
85.9 b
87.2 ab
88.2 a
83.7 c
NS
60.0 c
58.5 c
64.3 b
72.4 a
53.3 d
NS
5548.6 c
5160.8 d
6348.2 b
6906.9 a
3765.9 e
**
CONCLUSION AND RECOMMENDATIONS
i.
ii.
iii.
The following conclusions are drawn from the experiments:
The herbicides controlled weeds to a varying level and significantly affected all parameters such as weed
density m-2, fresh and dry weed biomass, leaf area tiller -1, plant height, grains spike-1 and grain yield.
Among the herbicidal treatments, Affinity was the most effective broad-spectrum herbicide which
controlled both grassy and broad-leaved weeds and gave the highest grain yield.
Tillage significantly affected weed density, fresh and dry weed biomass and grain yield while physiological
parameters such as leaf area tiller -1, leaf area index, plant height and grains spike-1 had no significant
response to tillage treatments. Zero tillage and reduced tillage had minimum weed density m -2, minimum
fresh and dry weed biomass and maximum grain yield while conventional tillage had maximum weed
density m-2, maximum fresh and dry weed biomass, and minimum grain yield.
Long term impact of zero tillage or reduced tillage on weeds and soil properties should be explored and the
economics should be studied to justify the benefits of tillage and herbicide application. This will lead us to
the conservation of natural resources and non-chemical weed control that are sustainable, environment
friendly and acceptable to the farming community in developing countries.
Acknowledgements
This study is a part of PhD dissertation research and the authors thank Gomal University, D.I.Khan, Khyber
Pakhtunkhwa, Pakistan, which partially supported these experiments.
REFERENCES
Acciaresi, H.A., H.V. Balbi, M.L. Bravo and H.O. Chidichimo. 2003. Response of weed populations to tillage, reduced herbicide
and fertilizer rates in wheat (Triticum aestivum) production. Plant. Daninha Vicosa 21(1): 49-55.
Ali, Q.M. and S. Tunio. 2002. Effect of various planting patterns on weed population and yield of wheat. Asian J. Plant Sci. 1
(93): 216–217.
Sarhad J. Agric. Vol. 26, No. 4, 2010
485
Arif, M., I.U. Awan and H.U. Khan. 2004. Weed management strategies in wheat (Triticum aestivum L). Pak. J. Weed Sci. Res.
10(1-2): 11-16.
Atreya, K., S. Sharma, R.M. Bajracharya and N.P. Rajbhandari. 2006. Applications of reduced tillage in hills of central Nepal.
Soil Till. Res. 88: 16–29.
Baghestani, M.A., E. Zand, S. Soufizadeh, M. Beheshtian, A. Haghighi, A. Barjasteh, D.G. Birgani and R. Deihimfard. 2008.
Study on the efficacy of weed control in wheat (Triticum aestivum L.) with tank mixtures of grass herbicides with
broadleaved herbicides. Crop Prot. 27: 104–111.
Baghestani, M.A., E. Zand, S. Soufizadeh, N.Bagherani and R. Deihimfard. 2007. Weed control and wheat (Triticum aestivum
L.) yield under application of 2,4-D plus carfentrazone-ethyl and florasulam plus flumetsulam: Evaluation of the
efficacy. Crop Prot. 26: 1759–1764.
Banik, P., P. Pramanik, R.R. Sarkar, S. Bhattacharya and J. Chattopadhayay. 2007. A mathematical model on the effect of M.
denticulata weed on different winter crops. Biol. Syst. 90: 818–829.
Bremner, J.M. and C.S. Mulvaney. 1982. Nitrogen – total. In: Page, A.L., Miller, R.H., Keeney, D.R. (Eds.). Methods of Soil
Analysis. Part II. Chemical and microbiological properties, second ed. Amer. Soc. Agron, Madison, WI, USA. pp. 595682.
Cheema, M. S. and M. Akhtar. 2005. Efficacy of different post emergence herbicides and their application methods in controlling
weeds in wheat. Pak. J. Weed Sci. Res. 11(1-2): 23-30.
Cheema, M.S., M. Akhtar and M.S. Iqbal. 2006. Performance of different herbicides in wheat under irrigated conditions of
Southern, Punjab. Pak. J. Weed Sci. Res. 12 (1-2): 53-59.
Chhokar, R.S., R.K. Sharma, G.R. Jat, A.K. Pundir and M.K. Gathala. 2007. Effect of tillage and herbicides on weeds and
productivity of wheat under rice–wheat growing system. Crop Prot. 26: 1689–1696.
Chhokar, R.S., S. Singh and R.K. Sharma. 2008. Herbicides for control of isoproturon-resistant littleseed canarygrass (Phalaris
minor) in wheat. Crop Prot. 27:719–726.
Crutchfield, D.A., G.A. Wicks and O.C. Burnside 1986. Effect of winter wheat (Triticum aestivum) straw mulch level on weed
control. Weed Sci. 34: 110–114.
Dadari, S.A. and H. Mani. 2005. The effect of post-emergence weed control on irrigated wheat (Triticum aestivum L.) in the
Sudan savannah of Nigeria. Crop Prot. 24: 842–847.
De Vita, P., E. Di Paolo, G. Fecondo, N. Di Fonzo and M. Pisante. 2007. No-tillage and conventional tillage effects on durum
wheat yield, grain quality and soil moisture content in southern Italy. Soil Till. Res. 92: 69–78.
Erenstein, O., U. Farooq, R.K. Malik and M. Sharif. 2008. On-farm impacts of zero tillage wheat in South Asia’s rice–wheat
systems. Field Crops Res.105: 240–252.
Gangwar, K.S., K.K. Singh, S.K. Sharma and O.K. Tomar. 2006. Alternative tillage and crop residue management in wheat after
rice in sandy loam soils of Indo-Gangetic plains. Soil Till. Res. 88: 242-252.
Gangwar, K.S., K.K. Singh and S.K. Sharma. 2004. Effect of tillage on growth, yield and nutrient uptake in wheat after rice in
the Indo-Gangetic Plains of India. J. Agric. Sci. 142: 453-459.
Gupta, R.K., P.R. Hobbs, J.K. Ladha and S.V.R.K. Prabhakar. 2002. Resource conservation technologies. In: transforming the
rice–wheat system of the Indo-Gangetic Plains, Asia-Pacific Association of Agricultural Research Institutions, FAO
Regional Office for Asia and Pacific, Bangkok. 42 p.
Guy, S.O. and D.B. Cox. 2002. Reduced tillage increases residue ground cover in subsequent dry pea and winter wheat crop in
the Palouse region of Idaho. Soil Till. Res. 66: 69-77.
Hassan, G., H. Khan, I. Khan and M.G. Rabbani. 2005. Quantification of tolerance of different wild oats (Avena fatua L.)
biotypes to clodinafop proparrgyl and fenoxaprop-p-ethyl. Pak. J. Weed Sci. Res. 11(3-4): 61- 65.
Hemmat, A. and I. Eskandari. 2006. Dryland winter wheat response to conservation tillage in a continuous cropping system in
northwestern Iran. Soil Till. Res. 86: 99–109.
Hobbs, P. R., R. Gupta, R. K. Malik and S.S. Dhillon. 2001. Conservation agriculture for the rice–wheat systems of the IndoGangetic plains of South Asia: a case study from India. In: Proc 1st World congress on Conservation Agric. Madrid, 1-5
Oct. 2001.
Khalil, S.K., A.Z. Khan, P. Shah, A.R. Baloch and M.F. Malik. 1999. Herbicides and row spacings effect on leaf characteristics
and grains spike-1 of wheat. Sarhad J. Agric. 16(1): 13-17.
Khalid Usman et al. Impact of tillage and herbicides on weed density and some physiological…
486
Khalil, S.K., K. Zeb and A.Z. Khan. 2002. Changes in leaf area, assimilate accumulation and partitioning of wheat varieties planted on
different dates. Pak. J. Soil Sci. 21: 15-19.
Khan, I., G. Hassan, M.I. Khan and E.A. Khan. 2004. Efficacy of some new herbicidal molecules on grassy and broadleaf weeds
in wheat-II. Pak. J. Weed Sci. Res. 10(1-2): 33-38.
Khan, M.H., G. Hassan, N. Khan and M.A. Khan. 2003. Efficacy of different herbicides for controlling broadleaf weeds in
wheat. Asian J. Plant Sci. 2(3): 254-256.
Khan, S.R.A., 2001. Crop management in Pakistan: Focus on soil and water. Agric. Depatt. Govt. of Punjab, Lahore, Pakistan.
Kotru, R., B.S. Azad, H. Singh. 1999. Chemical control of weeds in wheat (Triticum aestivum L). Envir. Ecol. 17 (3): 646-649.
Ladha, J.K., D. Dawe, H. Pathak, A.T. Padre, R.L. Yadav, B.J. Singh, Yadvinder Singh, Y. Singh, P. Singh, A.L. Kundu, R.
Sakal, N. Ram, A.P. Regmi, S.K. Gami, A.L. Bhandari, R. Amin, C.R. Yadav, E.M. Battarai, S. Das, H.P. Aggarwal,
R.K. Gupta and P.R. Hobbs. 2003. How extensive are yield declines in long term rice-wheat experiments in Asia? Field
Crops Res. 81:159-180.
Ladha, J.K., K.S. Fisher, M. Hossain, P.R. Hobbs and B. Hardy (Eds.). 2000. Improving the productivity and sustainability of
rice-wheat systems of the Indo-Gangetic Plains: A synthesis of NARS-IRRI partnership research. IRRI Discussion
paper series No. 40. IRRI, Los Banos, Philippines.
Lafond, G.P., W.E. May, F.C. Stevenson and D.A. Derksen. 2006. Effects of tillage systems and rotations on crop production for
a thin black chernozem in the Canadian Prairies. Soil Till. Res. 89: 232–245.
Lemerle, D., R.B. Hinkley, C.R. Kidd and A.R. Leys, 1986. Symptoms of injury caused by herbicides in wheat and barley.
Advisory Bull. Deptt. Agric., New South Wales. 4: 1-14.
Mandal, K.G., A.K. Misra, K.M. Hati, K.K. Bandyopadhyay, P.K. Ghosh and M. Mohanty. 2004. Rice residue-management
options and effects on soil properties and crop productivity. Food Agric. Envir. 2 (1): 224-231.
Mann, R.A., M. Ashraf and M.A. Gill. 2002. Sustainable wheat production system through conservation tillage technology. In
Proc. Int. Conf. on Environmentally Sustainable Agric. for Dry Areas, Shijiazhuang, China.
Mann, R.A., M. Ashraf and G. Hassan. 2004. Wheat establishment with zero tillage for integrated weed management. Pak. J.
Weed Sci. Res. 10(1-2): 17-24.
Mas, M.T. and A.M.C. Verdú. 2003. Tillage system effects on weed communities in a 4-year crop rotation under Mediterranean
dry land conditions. Soil Till. Res.74:15–24.
McMaster, G.S., D.B. Palic and G.H. Dunn. 2002. Soil management alters seedling emergence and subsequent autumn growth
and yield in dry land winter wheat-fallow systems in the Central Great Plains on a clay loam soil. Soil Till. Res.
65:193-206.
Mehla, R.S., J.K. Verma, R.K. Gupta and P.R. Hobbs. 2000. Stagnation in the productivity of wheat in the Indo-Gangetic plains:
zero-till-seed-cum-fertilizer drill as an integrated solution: Rice-wheat consortium paper series 8. New Delhi, India:
Rice-wheat consortium for the Indo-Gangetic Plains. 12 p.
Miralles, D.J. and R.A Richards. 1998. Sensitivity to photoperiod during the reproductive phase changes grain number in wheat
and barley. Combined conference Abstracts. 42nd Annual ASBMB-38th Annual ASPP and 20th Annual NZSPP Conf.
Adelaide, Australia.
Mohler, C.L., 1993. A model of the effects of tillage on emergence of weed seedlings. Ecol. Appl. 3: 53–73.
Nayyar, M., M. Muhammad and N. Randhawa. 1998. Research Report. Ayub Agric. Res. Instt., Faisalabad.
Nelson, D.W. and L.E. Sommers. 1982. Total carbon, organic carbon, and organic matter. In: Page, A.L., Miller, R.H., Keeney,
D.R. (Eds.), methods of soil analysis, part 2. Agron. No. 9, Madison, Wisconsin, USA. 539-579.
Om, H., S. Kumar and S.D. Dhiman. 2004. Biology and management of Phalaris minor in rice–wheat system. Crop Prot. 23:
1157–1168.
Om, H., S.D. Dhiman, H. Kumar and S. Kumar. 2003. Biology and management of Phalaris minor in wheat under a rice-wheat
system. Weed Res. 43: 59–67.
Ozpinar, S. 2006a. Effects of tillage on productivity of a winter wheat-vetch rotation under dry land Mediterranean conditions.
Soil Till. Res. 89: 258–265.
Ozpinar, S. 2006b. Effects of tillage systems on weed population and economics for winter wheat production under the
Mediterranean dry land conditions. Soil Till. Res. 87: 1–8.
Sarhad J. Agric. Vol. 26, No. 4, 2010
487
Ozpinar, S. and A. Cay. 2005. Effects of minimum and conventional tillage systems on soil properties and yield of winter wheat
(Triticum aestivum L.) in clay-loam in the Anakkale region. Turk. J. Agric. 29: 9-18.
Pathak, H., J.K. Ladha, P.K. Aggarwal, S. Peng, S. Das, Y. Singh, B. Singh, S.K. Kamra, B. Mishra, A.S.R.A.S. Sastri, H.P.
Aggarwal, D.K. Das and R.K. Gupta. 2003. Trends of climatic potential and on-farms yields of rice and wheat in the
Indo-Gangetic Plains. Field Crops Res. 80: 223-234.
Qureshi, A.S., T. Shah and M. Akhtar. 2003. The ground water economy of Pakistan. IWMI working paper 64. Pakistan country
series No. 19. Inter. Water Mgt. instt. Lahore, Pakistan.
Radford, B.J., A.J. Key, L.N. Robertson and G.A. Thomas. 1995. Conservation tillage increases soil water storage, soil animal
populations, grain yield and response to fertilizer in the semiarid subtropics. Aust. J. Exp. Agric. 35: 223-232.
Reynolds, M.P., S. Rajaram and A McNab.1996a. Increasing yield potential in wheat: Breaking the barriers. Ciudad Obrego´n,
Sonora, Mexico.
Rosskopf, E.N., R. Charudattan and J.B. Kadir. 1999. Handbook of Biological Control. Pp. 891-918.
Shahid, I. 1994. Screen of different herbicides for controlling weeds in wheat crop. M.Sc. (H) Thesis, Faculty of Agric. Gomal
Univ. D.I.Khan, Pakistan.
Soltani, N., C. Shropshire and P.H. Sikkema. 2006. Responses of winter wheat (Triticum aestivum L.) to autumn applied postemergence herbicides. Crop Prot. 25:346–349.
Soltanpour, P.N., 1985. Use of ammonium bicarbonate-DTPA soil test to evaluate elemental availability and toxicity. Comm.
Soil Sci. Plant Anal. 16: 322-38.
Steel, R.G.D. and J.H. Torrie. 1980. Principles and procedures of statistics. McGraw Hill Book Co. Inc., New York.
Su, Z., J. Zhang, W. Wu, D. Cai, J. Lv, G. Jiang, J. Huang, J. Gao, R. Hartmann and D. Gabriels. 2007. Effects of conservation
tillage practices on winter wheat water-use efficiency and crop yield on the Loess Plateau, China. Agric. Water Mgt.
87: 307–314.
Su-Juan, L., C. Ji-Kang, C. Fu, L. Lin and Z. Hai-Lin. 2008. Characteristics of growth and development of winter wheat under
zero tillage in North China Plain. Acta Agron Sin. 34(2): 290–296.
Wang, X.B., D.X. Cai, W.B. Hoogmoed, O. Oenema and U.D. Perdok. 2007. Developments in conservation tillage in rainfed
regions of North China. Soil Till. Res. 93: 239–250.
Whan, B.R., W.K. Anderson, R.F Gilmour, K.L. Regan and N.C. Turner. 1991. A role for physiology in breeding for improved
wheat yield under drought stress. In: Acevedo, E., Conesa, A.P., Monneveux, P., Srivastava, J.P. (Eds.), Physiologybreeding of winter cereals for stressed Mediterranean environments. Montpellier, France, pp. 179–194.
Zand, E., M. A. Baghestani, S. Soufizadeh, R. P. Azar, M. Veysi, N. Bagherani, A. Barjasteh, M. M. Khayami and N.
Nezamabadi. 2007. Broadleaved weed control in winter wheat (Triticum aestivum L.) with post-emergence herbicides
in Iran. Crop Prot. 26: 746–752.
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