reseach project ii
TRANSCRIPT
SOKOINE UNIVERSITY OF AGRICULTURE
FACULTY OF AGRICULTURE
DEPERTMENT OF CROP SCIENCE AND PRODUCTION
TITLE: GROWTH AND YIELD OF MAIZE (Zea mays) AS AFFECTED
BY WEED COMPETITION.
DEGREE PROGAM: BSc. AGRICULTURE GENERAL
STUDENT NAME: MAKENZA GODFREY. M
REG NO: AGC/D/10/T/0069
SUPERVISOR: Dr. A. B. KUDRA
A RESEARCH PROJECT REPORT IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE DEGREE OF BACHELOR OF SCIENCE IN
AGRICULTURE GENERAL OF SOKOINE UNIVERSITY OF SOKOINE OF
AGRICULTURE.
MOROGORO, TANZANIA.
JULY, 2013
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CHAPTER ONE
1.0. INTRODUCTION
1.1 . Background information
Maize (Zea mays L.) is an important food crop because it is consumed worldwide due to
its nutritive value (Anonymous, 2010). Maize is a grain crop belongs to the grass family
Poaceae (Paliwal, 2000) and is the only cultivated species of importance in the tribe
Mydeae (Salian, 2007). It is grown under diverse environmental conditions compared to
other important grain crops such as wheat and rice (Du Plessis, 2003; FSSA, 2007).
Wheat, rice and maize are the most important cereal crops in the world but maize is the
most popular due to its high yielding, easier of processing, readily digested and costs less
than other cereals (Jaliya et al., 2008). The crop is of significant economic importance
worldwide as human food, animal feed and as a source for a large number of industrial
products (Paliwal, 2000).
1.1.1: Origin and distribution of maize.
Maize is one of the oldest human-domesticated plants. It’s origin is believed to be 7000
years ago when it was grown in the form of a wild grass called teosinte in Central
Mexico. Maize was reported for the first time in West Africa in 1498, six years after
Columbus discovered the West Indies (Badu-Apreku et al., 2003). This process led to the
gradual transformation of teosinte to its present day form known as maize. It is grown in
all countries of Africa, from the coast through savanna regions to the semi-arid regions of
West-Africa, and from sea-level to the mid, and high-altitudes of East and Central Africa
become one of Africa's dominant food crop (Brink and Belay, 2006).
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1.1.2. Importance of maize
Maize (Zea mays L.), or corn, is the most important cereal crop in sub-Saharan Africa
and, with rice and wheat, becomes one of the three most important cereal crops in the
world. Maize is the most important grain crop in Tanzania and is produced throughout the
country under diverse environments. In industrialized countries, maize is largely used as
livestock feed and as a raw material for industrial products, while in developing
countries, it is mainly used for human consumption. Hamayun (2003) noted that maize
grain is a valuable source of protein (10.4%), fat (4.5%), starch (71.8%), fiber (3%),
vitamins and minerals like Ca, P, S and small amounts of Na.
Every part of the maize plant has economic value: the grain, leaves, stalk, tassel, and cob
can all be used to produce a large variety of food and non-food products (IITA, 2007).
The stalks are used for fuel, fodder and thatching and as compost. The cob leaves may be
made into cloth or mats, and be used for mattress filling (Brink and Belay, 2006).The
starch part used in other products such as adhesives, clothing, and pharmaceutical tablets
and in paper production. The oil from the embryo is used in cooking oils.
1.2. PROBLEM STATEMENT AND JUSTIFICATION
1.2.1: Problem statement
Maize production is constrained among other factors by poor crop management, notably
inadequate weed control especially during the first six weeks after sowing resulting in
maize yield losses ranging from 50% to 90% (Chikoye et al., 2005). Yield reduction in
maize results from high competition between the crop and weed for water, light and
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nutrients especially when the competing weeds are of the same family with maize.
Worldwide maize production is hampered up to 40 percent by competition from weeds
which are the most important pest group of this crop (Oerke and Dehne, 2004). Weeds
interfere with harvesting and increase the cost involved in crop production. Overall,
weeds have the highest loss potential (37%) which is higher than pathogens (16%) and
viruses 2% (Oerke, 2005).
1.2.2: Problem justification
The farmer should be aware about proper weed management as a major key to increase
and sustain maize crop production. Early weeding in maize crop may produce maximum
yield if soil parameters and climate are favourable. The recommended time for weeding
in maize should be known by the farmers in order to improve their production (Malik et
al. 2006). Farmer will benefit from research after knowing the time for weeding in maize
crop so as to reduce maize-weed competition, early weeding before critical period for
weed control (CPWC) is important. CPWC is the period in the crop growth cycle during
which weeds must be controlled to prevent unacceptable yield losses. CPWC it is
possible to make decisions on the need for and timing of weed control, and to control
weeds only when efficient weed control is required. The CPWC could be used also to
enhance the efficiency of other methods of weed management, including cultivation
(Abbaspour and Moghaddam, 2004).
If the farmers could not be able to control weed at critical period for weed control they
will suffer serious loss in productivity. Vissoh (2004) identified poor timing of weed
control as one of the main constraints that face farmers in crop production. Losses of
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maize yield due to weed competition reach 66-90 % (Dalley et al., 2006 and Abouziena
et al., 2007).
1.3. OBJECTIVES
1.3.1: Overall objective
The overall objective of study is to demonstrate the effect of weeds on maize growth rate
and yield.
1.3.2: Specific objectives
1. To determine the effect of emergency pattern of weed species on maize growth
rate and yield.
2. To determine the duration of weed competition and the time of weeding in maize
crop.
3. To evaluate the loss that encountered by weeds on maize crops.
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CHAPTER TWO
1.0. LITERATURE REVIEW
2.1. Botanical descriptions of maize crop
Maize is a tall, monecious annual grass with overlapping sheaths and a broad
conspicuously distichous blade, it belongs to the tribe Maydeae of the grass family
Graminae (Hitchcock and Chase, 1971). Crop has adventitious fine root system. Leaves,
consists of a sheath, ligules, and a blade, it arranged spirally on the stem, and alternately
in two opposite rows. Inflorescence, the male and female flowers are borne on the same
plant (Dhillon and Prasanna, 2001).
2.2. Ecological Requirements of maize
Maize can grow on a wide range of ecological zones and soils, especially in well drained
aerated soil loam or silty loams or alluvial soils with the pH of 5.5 to 7. Maize crop
cannot tolerate water logging. It can grow to ecological zones with altitude ranging from
0 to 3000 m above the sea level, at very low or high altitudes result in poor yield, maize
crop require an optimum temperature of 30°C and rainfall ranging from 600 to 900 mm
for well maize growth (MOA, 2008). Availability of soil moisture at the time of tasselling
is essential for the production of high yields (Tweneboah, 2000).
2.3. Weeds
Weeds are undesirable plants, which infest different crops and inflict negative effect on
their yield. Generally weed-crop competition is complicated as weeds compete with the
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crop plants by occupying a space, which would otherwise be available to the crop plant.
Anything that reduces this space reduces the plant growth (Wright et al., 2001). Water
requirement for the growth of weeds is primarily of interest from the stand-point of
competition with the crop plant for the available moisture (Gibson, 2000).
2.4. Effects of weed on maize growth and yield.
Each area for maize growing is characterized by the presence of certain weed species, the
specific weed encroachment being influenced by climatic condition, soil conditions, and
technologies used for maize crop production. Each area needs specific weed control
strategies (Berca, 2004). Weeds course stunted growth of maize crop, poor development
due to crop weed competition for water, light and nutrients (Silva et al., 2004) and weeds
are also often poisonous.
2.5. Duration of weed competition and time of weeding
At early stage of a maize plant growth is very sensitive to weed competition. If maize
growth is checked by weeds in its early stages of growth it never recovers fully. However
weeds are controlled subsequently. Weed infestation should be minimized for the first 10
weeks to maximize final yield (Baghestani et al., 2007). Beyond this period, well planted,
and healthy growing maize would chock weeds sufficiently. The integrated effect
between plant density and weed control management had positive effect on maize grain
yield (Acciares and Zuluaga, 2006; Abouziena et al., 2007; Waheed Ullah et al., 2008).
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2.6. Losses that encountered by weeds on maize crop
Weeds are considered as a major problem in maize fields. They cause serious reduction
in productivity. The reduction in maize yield due to weed competition reached 66-90 %
(Dalley et al., 2006 and Abouziena et al., 2007). Some weeds become alternative hosts of
pests and diseases. They reduce profits by lowering the quality, quantity, yields and value
of maize. Inefficient weed control is one of the main causes of low maize yields. Some
weeds are parasitic and poisonous to maize; a thick growth of weeds in maize makes
harvesting difficult (Baghestani et al., 2007; Kir and Dogan, 2009); Pannacci and
Covarelli, 2009).
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CHAPTER THREE
2.0. METHODOLGY
3.1: Location
The experiment was conducted under the field condition at Crop Museum in the
Department of Crops Science at Sokoine University of Agriculture (SUA) which found at
about 4 km from town centre. SUA-Crop Museums located at latitude of 5º 40ʼS and
longitude 37º 39ʼE and altitude of 525 m above the sea level. The average annual rainfall
is about 1200 mm and the temperature range of this area is about 27-32o C, where the
climate of this area is suggested to be tropical climate.
Table 3.1: Climatic data during growing season February- June 2013.
Months Temperature
(˚C)
Relative
humidity (%)
Rainfall
(mm)
Radiation
(MJ/M2)
Sunshine
(hours)
Min Max
Februar
y
21.8 33.3 46.6 2.7 22.8 8.8
March 22.1 32.1 58.7 3.2 17.8 6.2
April 21.4 30.0 64.9 4.5 15.6 5.6
May 19.6 29.6 56.4 0.8 15.9 7.1
June 16.2 29.2 44.7 0.03 18.3 7.8
* Agro-meteorological agency weather data from SUA station, February –June 2013.
3.2: Pre planting information and land preparation
The site has no history of noxious weeds like Striga spp, the soil colour is brown reddish
clay loamy. The land was prepared by hand hoe.
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3.3: Experimental materials
Maize seeds (Variety Situka-1) certified, hand hoes, note book, pen, ruler, tape measure,
rope, dry oven, weighs balance and calculator.
3.4: Experimental design and treatment applications
The experimental design employed was Randomized Complete Block Design (RCBD)
with three repetitions. The planting space was 75 cm × 30 cm. Number of rows was four
(4) per plot and the number of plants per row was five (5). Total number of plants per plot
was 20 plants. Plot size was 3 m ×1.5 m = 4.5 m2 and experimental area was191.25 m2.
The treatments was
1. Continuously weeded from emergence up to maturity.
2. Continuously unweeded from emergence up to maturity.
3. Unweeded for first 3weeks after emergence then weeded up to maturity.
4. Unweeded for first 6 weeks after emergence then weeded up to maturity.
5. Weeded for first 3weeks after emergence then unweeded up to maturity.
6. Weeded for first 6 weeks after emergence then unweeded up to maturity.
3.5. Data collection and analysis
3.5.1: Parameters collected
Some of the parameters were collected 3, 6 and 9 weeks after sowing and other
parameters were collected at maturity stage and harvesting.
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Collected parameters were;
1. Leaf area indexes
Leaf area was measured by selecting 5 plants from each plot thereafter the
average leaf area of each leaf was determined. The leaf area index was calculated
by using formula given
LAI= Leaf area per plant (cm2)
Ground area per plant (cm2)
The leaf area and the leaf area index had a significant role in the competitive
activity of certain maize genotypes against weeds. (SIMIC, 2003; SIMIC et al.,
2003).
2. Plant height
Plant height was measured by selecting 10 plants at random so as to reduce bias
between plant and within plot. Then the height of each plant was measured from
the ground surface to the top with the help of tape measure, thereafter the average
height of 10 plants from each plot was calculated.
3. Crop growth rate (CGR)
Crop growth rate was calculated as proposed by Beadle (1987) in gm day-1
CGR= W2-W1
T2-T1
Where W1 and W2 are the total dry weight harvested at time T1 and T2
respectively.
4. Dry (biomass) weight
Since plants have a high composition of water when still in the field, therefore 2
plants was selected at random from each plot and removed from the soil and
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washed off any loosed soil particles, finally the plants was dried in an oven set to
low heat 70° C for 72 hours thereafter the average dry weight from each plot was
calculated.
5. 100 seed weight
Three samples each of 100 seeds was selected randomly from the seed lot of each
plot, and were weighed by using weigh balance.
6. Weight per cob.
Five cobs ware selected at random from each plot and the weight of each cob was
measured and the average weight of five cobs was calculated from each plot to
give weight per cob.
7. Number of days to 50% tasselling
Ten randomly plant was selected from each plot then was tagged and the date was
noted when half number of plant shows tasselling.
8. Weeds population density.
A quadrate measure 1 m × 1 m was placed at each plot and the number of weed
species was counted.
3.5.2: Data analysis
Data was subjected to Analysis of Variance (ANOVA) by using GENSTAT statistical
program with ANOVA table. The mean separation test was performed using Duncan
multiple range test (DMRT), where the data was tested at 5% level of significant.
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CHAPTER FOUR
1.0. RESULTS
1.1. Effect of weed on plant height: There was no significant different at (P≤0.05) on
maize plant height between weeded and unweeded treated plot at 3 and 6 weeks after
sowing. However means for plant height ranged for 54.93-61.37 cm after three weeks and
86.33-102.83 cm after 6 weeks (Table 4.1).
1.2. Effect of weeds on leaf area index: Weeded and unweeded plots had no significant
different (P ≤ 0.05) on leaf area index at first 3 weeks after sowing and it was ranged
between 0.5-0.7. However weeded, weeded plot for 3 and 6 weeks after sowing had
significantly higher leaf area index than unweeded and unweeded plot for 6 weeks at 6
weeks after sowing in growing season (Table 4.1).
1.3. Weed population: Emergency pattern of weed species had highly significantly
different (P≤0.05) between weeded and unweeded plot (Table 4.1).
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Table 4.1: Weed population and effect of weeds on maize height and leaf area indexes at
SUA Crop Museum in 2013 cropping season.
Treatments Plant height (cm) Leaf area index Weed pop/M2
3 wk a.s 6 wk.a.s 3 wk.a.s 6 wk.a.s 3 wk a.s 6 wk.a.s
Weeded 54.93a 94.27a 0.5900a 1.593c 0.0a 0.0a
Unweeded 61.37a 102.07a 0.6267a 1.230a 1336.0c 2489.3b
Unweeded 3 wk.a.s 57.80a 102.83a 0.5767a 1.280ab 741.7b 0.0a
Unweeded 6 wk.a.s 55.90a 86.33a 0.6033a 1.243ab 1177.7bc 2151.7b
Weeded 3 wk a.s 55.50a 91.87a 0.6833a 1.600c 0.0a 336.0a
Weeded 6 wk.a.s 56.10a 91.17a 0.6900a 1.320b 0.0a 0.0a
LSD (P≤0.05) NS NS NS 0.07439 529.4 551.9
CV (%) 7.0 12.7 19.4 3.0 53.6 36.6
S.e.d 3.248 9.86 0.0996 0.03339 237.6 247.7
*wk.a.s = weeks after sowing* *LSD = Least significant differences of means (5% level)* *S.e.d = Standard errors of differences of means* * coefficients of variation * *NS = No significant.
1.4. Effect of weed on crop dry matter (grams): There was no significant (P≤0.05)
among weeded and unweeded plot for the first 3 weeks after sowing. At six weeks after
sowing weeded plot for 3 and 6 weeks and unweeded for 3 weeks had significantly
higher dry matter at (P≤0.05) than unweeded plot for 6 weeks (Table 4.2).
1.5. Effect of weed on crop growth rate (grams/day): There was significant different
(P≤0.05) in growth rate in maize plants between weeded and unweeded plot (Table 4.2)
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1.6. Days to 50% tasselling: There was no a significant different (P ≤ 0.05) on the days
to 50% tasselling formation on maize between weeded and unweeded treated plot (Table
4.2).
Table 4.2: Effect of weeds on maize dry matter (biomass) growth rate and Days to 50%
tasselling at SUA Crop Museum in 2013 cropping season
Treatments Crop dry matter (g) Crop growth rate
(grams/day)
Days to 50%
tasselling3 wk.a.s 6 wk.a.s
Weeded 27.37a 67.38b 1.903bc 58.00a
Unweeded 27.17a 59.33ab 1.450ab 58.67a
Unweeded 3 wk.a.s 21.80a 63.60b 1.993c 59.00a
Unweeded 6 wk.a.s 25.15a 54.47a 1.397a 58.00a
Weeded 3 wk a.s 24.98a 65.32b 1.920bc 58.00a
Weeded 6 wk.a.s 29.23a 66.90b 1.793abc 57.67a
LSD(P≤0.05) NS 7.482 0.4440 NS
CV (%) 14.6 6.5 14.0 1.9
S.e.d 3.088 3.358 0.1993 0.915
*wk.a.s = weeks after sowing* *LSD = Least significant differences of means (5% level)* *S.e.d = Standard errors of differences of means* * coefficients of variation * *NS = No significant.
1.7. Effect of weed on 100- Seed grains weight: Data concerned with effect of weeds on
100-grains weight is expressed and none of the weeded and unweeded treated plot
exhibited significant effect on 100-seed grains weight at (P ≤ 0.05). However means for
100 seed weight ranged from 31.67-38.80 (Table 4.3).
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1.8. Effect of weed on weight per cob: There was significant different in weight per cob
between unweeded and unweeded plot for 6 weeks with other treated plots at (P≤0.05)
(Table 4.3).
1.9. Effect of weeds on grain yield tons/ha: Data pertaining to the grain yield in (Table
4.3) indicate that it was affected significantly at (P≤0.05) between weeded plot,
unweeded plot for 3 weeks, weeded plot for first 3 and 6 weeks after sowing and
unweeded treated plot, unweeded plot for 6 weeks after sowing.
Table 4.3: Effect of weeds on maize weight per cob, 100 seed weight and yield/ha at
SUA Crop Museum in 2013 cropping season
Treatments Weight/cob (g) 100 seed weight (g) Yield tons/ha
Weeded 259.8c 38.03a 3.307b
Unweeded 165.3ab 33.73a 2.577a
Unweeded 3 wk.a.s 219.6bc 34.00a 3.357b
Unweeded 6 wk.a.s 145.6a 31.67a 2.547a
Weeded 3 wk a.s 278.1c 37.87a 3.373b
Weeded 6 wk.a.s 233.9bc 38.80a 3.780b
LSD (P≤0.05) 66.64 NS 0.5619
CV (%) 16.9 14.9 9.8
S.e.d 29.91 4.35 0.2522
*wk.a.s = weeks after sowing* *LSD = Least significant differences of means (5% level)* *S.e.d = Standard errors of differences of means* * coefficients of variation * *NS = No significant.
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1.2: DISCUSION
Leaf area index (LAI), from the result at 3 weeks after sowing for both treatments does
not affected by weeds. LAI in un weeded was affected at 6 weeks after sowing, this could
be probably due to underground competition (water and nutrients) that was existing
between weeds species and maize, which resulted to poor development of maize plant
hence poor leaf expansion. Utilization of all environmental resources by crop plants in
weed free treatments could be the reason of high LAI of maize for this treatment.
Decrease in LAI with increase in competition duration seems to be the result of decreased
supply of moisture and nutrients.
Plant height, the results clearly show that plant height at 3 and 6 weeks after sowing does
not affected by the weeds. This might be due to late weeds emergency pattern due to
climatic condition during growing season that enable early crop canopy closure so weed
plants could not get sufficient amount of solar radiation for their survival and ultimately
resulted in less effect of weed plants to compete light with maize per unit area. The
results of this study are in good agreement with those of reported by Irshad (2000).
Crop growth rate (CGR), higher CGR in weeded plot may be attributed to availability of
more environmental resources than in unweeded plot, which enabled crop to accumulate
more dry weight per unit area and hence faster CGR. However, decrease in CGR in
unweeded plot with increase in weed competition duration could be due to increased
competition of weeds with maize for different growth factors. (Zanin et al., 1988)
reported that competition of weeds with maize crop reduced maize growth rate
considerably than weed free conditions.
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High weight per cob in weeded plot indicate that weed free were more appropriate for
maize crop most probably due to more resources available and their best utilization.
Decrease in cob weight in unweeded with an increase in weed competition duration could
be due to competition of weeds with maize for different environmental factors such as
water, nutrients and gases for a longer time (Nawab et al., 1999).
The critical period for weed control
The critical period for weed control (CPWC) is a period in the crop growth cycle during
which weeds must be controlled to prevent yield losses (Nieto et al., 1968). Implicit in
the above definition is the period of time the crop can exist with weeds (the weedy
period) just after emergence without yield loss (Hall et al., 1992). The second component
of CPWC is the period of time the crop has to be kept weed-free to avert yield loss (Hall
et al., 1992). The CPWC, therefore, determines when weeding must begin and the
number of times the crop must be weeded to avert yield loss. Results of experiments of
this study show that late weeds emergency patterns affect CPWC and, therefore,
potentially increase the number of times the maize crop needs to be weeded to attain
maximum yields (figure 1).
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week 3 a.e week 6 a.e week 9 a.e0
102030405060708090
Critical Period for Weed Competition
WeededUnweeded
Rel
ativ
e yi
eld
(gra
ms)
*a.e- after emergency
Figure 1: Critical Period for Weed Competition.
Yield is a function of interaction among various yield-contributing factors, which are
affected differentially by the growing conditions such as deficiency of water during any
growth stage of the crop can reduce grain yield. Water stress during vegetative
development reduces expansion of leaves, stems and roots and ultimately affects the
development of reproductive organs and potential grain yield. However yield/ha was
increasing with decreasing the time of maize weed competition for resources. Yield/ha
from unweeded was lower compared with weeded plot this could be due to competition
for nutrients and water from the soil that contribute to maize growth, since water,
nutrients are important for development of plant into high yield. The result show that
unweeded plot produce poor yield this is probably due to deficiency of water and nutrient
to crops in which most of it was taken up by weeds.
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1.3. Conclusion
Competition is the negative interaction between weeds and crops where make
simultaneous demands that exceed limited resources and while both suffer but weeds
suffer less. The degree of interference between maize and weeds is determined by
limiting resources like water, nutrients, and light. Maize size and final yield is therefore
the result of its ability to capture available resources throughout the growing season. So
crop weed competition indicates competition between crop and weed in natural
ecosystem in response to resources struggle for their existence and superiority. However
in order to reduce the competition between weeds and crops, the weeds should be
removed from the field before the Critical Period for Weed Competition is attained.
1.4. Recommendations
The protection of maize crops against weeds must have in view a few factors, which are
typical to the area, such as high weed seed stock from soil, diverse rainfall regimes (very
wet periods, followed by very dry ones), favouring weed encroachment of maize crops,
gradual emergence of dominant weed species and their biological characteristics. The
experiment should be repeated in further studies to find out the most appropriate time for
weeds and crops interactions that could be used to achieve best weed control strategy in
maize during the critical period in which will help the farmers in optimizing the timing of
weed control as well as in developing an integrated weed control strategy.
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