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

1

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).

2

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

3

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

4

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.

5

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

6

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).

7

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).

8

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.

10

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)

14

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).

15

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.

16

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.

17

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).

18

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.

19

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.

20

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