(�

�

II. REVIEW OF LITERATURE

2.1. WEED FLORA IN DIFFERENT GARDENLAND CROPS

The floristic composition of weed flora in a particular locality is

determined by the complex interaction of edaphic, climatic and biotic factors of

which biotic factors like seed bank, their dispersal mechanisms, dormancy and

the associated crop along with cultivation practices play a major role. The

floristic composition of weeds in various localities have been brought out

varying nature and magnitude by different workers. List of references are

given below:

Crop Weeds References

Sunflower Cyperus rotundus,

Cyperus iria,

Eleusine indica (L),

A. viridis and

C. benghalensis

Singh et al. (1993)

C rotundus,

E. crusgalli,

D. aegyptium and

T. portulacastrum

Singh et al. (1994)

C rotundus ,

T. portulacastrum,

P. niruri and

E. colonum

Vedharethinam et al.

(2005)

Sesamum C. rotundus,

D. aegyptium,

P. repens,

A. viridis and

P. niruri

Kannan and Wahab

(1995)

C. rotundus,

D. sanguinalis,

Cornopus didymus,

Venkatakrishnan and

Gnanamurthy (1999)

�

)�

�

C. benghalensis and

C. indica

Groundnut C. rotundus and

D. aegyptium

Venkatakrishnan et al.

(1995)

A. viridis and

T. portulacastrum

Rafey and Prasad

(1995)

C. rotundus,

C. album,

C. arvensis and

P. hysterophorus

Wanjari et al. (2000)

C. rotundus ,

P. hysterophorus,

A. indica,

C. dactylon,

A. viridis and

C. oxycantha M. Bieb

Suryawanshi et al.

(2001)

Sugarcane C. rotundus,

C. dactylon,

E. crusgalli,

D. sanguinalis,

Panicum maximum Jaco,

C. album,

T. portulacastrum,

C. arvensis and

P. niruri.

Srivastava et al.

(2005)

T. portulacastrum,

A. viridis,

P. repens,

P. hysterophorus,

D. arvensis,

D. aegyptium and

F. australacium

Rana et al. (2005)

C. dactylon,

E. hirta,

D. aegyptium,

F. dichotoma L.,

D. sanguinalis L. Scop

E. indica (L.) Gaerth.

C. sativa L. and

X. struarium

Rohitashav Singh

et al. (2005)

*�

�

E. colonum,

Brachiaria ramose Staps

T. portulacastrum,

D. aegyptium,

E. indica and

C. benghalensis

Tomar et al. (2005)

C. rotundus,

C. dactylon,

D. aegyptium,

E. colonum,

P. repens,

A. indica,

C. benghalensis,

C. viscosa,

C. olitorius and

T. portulacastrum.

Issac Manuel and

Pannerselvam (2005)

C rotundus,

C. dactylon,

E. colonum,

C. viscose and

T. portulacastrum

Ramesh and Sundari

(2006)

Cotton E. colonum,

C. rotundus,

Fimbristylis miliaceae,

T. portulacastrum,

E. indica and

D. arvensis

Kathiresan and

Lakshmanan (1986);

Thirumurthy et al.

(1987)

D. aegyptium,

E. colonum,

E. barbata,

C. dactylon,

C. rotundus and

D. arvensis

Sivakumar and

Subbian (2002)

C rotundus,

T. portulacastrum,

C. trilocularis,

C. viscosa,

C. dactylon and

E. alba

Rajeshwari (2005)

�+�

�

2.2. WEED ASSOCIATED WITH MAIZE CROP

To evolve a satisfactory weed control programme and understanding of

the weeds associated with maize crop is very important. The weed flora differs

widely with environment and soil conditions. Wider adaptability under

different climatic, edaphic and biotic stress makes the weeds more vigorous.

This leads to the higher persistence of weeds in cultivated fields. The high

resistance nature of weeds could also be attributed to their ability to high seed

production, tuber production and seed viability. Several grasses, broadleaved

weeds and sedges have been reported in maize crop.

2.2.1. Weed flora in maize

The reports published on weed flora in maize by several workers are

furnished below:

Sl.

No. Weeds Location References

1. Trianthema portulacastrum,

Cyperus rotundus,

Amaranthus viridis,

Digitaria sanguinalis and

Bulbastylis barbata

Ludhiana, Punjab Harmohindar

Singh et al. (1994)

2. C. dactylon,

D. sanguinalis,

D. ciloris,

L. chinensis,

C. rotundus,

C. iria and

C. benghalensis

Orissa University of

Agriculture and

Technology, Orissa

Rout and

Satapathy (1996)

3. C. rotundus,

D. agypticum,

S. halepense,

H.P.K.V. Regional

Research Station,

Kullu

Thakur and

Sharma (1996)

���

�

E. indica,

C. arvensis and

C. benghalensis

4. P. repens,

D. aegyptium,

C. rotundus,

T. portulacastrum,

P. hysterophorus,

F. australica and

A. viridis

TNAU, Coimbatore Kandaswamy and

Chandrasekar

(1998)

5. C. rotundus,

T. portulacastrum,

C. viscosa,

C. dactylon,

D. aegyptium and

B. diffusa

Vallampadugai,

Tamil Nadu

Kumar (1998)

6. E. colonum,

C. rotundus,

C. benghalensis and

A. conyzoides

Almora,

Uttar Pradesh

Pandey et al.

(1999)

7. T. portulacastrum,

C. benghalensis,

D. arvensis,

C. viscosa,

E. aegyptium and

E. tenella

Ludhiana Sandhu et al.

(1999)

8. C. dactylon,

C. rotundus,

T. portulacastrum,

C. gyanandra and

P. niruri

Annamalai University,

Annamalainagar

Sureshkumar

(1999)

9. D. aegyptium,

E. indica,

C. rotundus,

C. benghalensis,

A. viridis and

Polygonum sp.

Mid hills and sub-

humid zones at

Himachal Pradesh

Sharma and

Nayital (1993)

10. C. rotundus,

C. dactylon,

T. portulacastrum,

E. alba and

P. niruri

Annamalai University,

Annamalainagar

Sureshkumar and

Sundari (1999)

���

�

11. E. colonum,

B. ramose,

D. sanguinalis,

E. indica,

S. glauco,

S. halepense,

Panicum spp.,

G. parviflora,

C. benghalensis,

P. hydropiper,

O. latizolia and

C. rotundus

Division at Crop

Production,

Bharathiya Krishi

Anusandhan,

Sangthan Almora

Uttaranchal

Pandey et al.

(2001)

12. E. crusgalli,

E. colonum,

P. niruri,

C. benghalensis,

D. arvensis,

C. rotundus,

A. conyzoides and

E. alba

Rajasthan College of

Agriculture, Udaipur

Shekhawat et al.

(2001)

13. T. portulacastrum,

C. rotundus and

C. dactylon

Annamalai University,

Annamalainagar

Sureshkumar

Reddy and Sundari

(2002)

14. C. rotundus,

E. colonum,

C. arvensis and

A. retroflexus

Ramin Agricultural

Research and

Education Center of

Shahid Chamran

University

Ghodratolla Fathi

(2005)

15. E. colonum,

T. portulacastrum,

C. dactylon,

C. viscosa,

C. rotundus,

A. indica and

P. niruri

Annamalai University,

Annamalainagar

Meyyappan and

Kathiresan (2005)

16. E. crusgalli,

E. colonum,

C. benghalensis,

T. portulacastrum and

P. niruri

Instructional Farm of

Rajastan College of

Agriculture, Udaipur

Chalka and

Nepalia (2006)

�$�

�

2.3. COMPETITION FOR LIGHT, MOISTURE AND NUTRIENTS

A heavily shaded plants suffers from reduced photosynthesis leading to

poor growth, a smaller root system and ultimately reduced capacity for water

and nutrient uptake (Donald, 1963).

Among plant communities, each plant is in a state of continuous

competition with its neighbouring plants for varied growth elements both above

and under the ground. Our concern here is with such a competition between

weeds and crops, which is a short span of time or overall growth period, weeds

compete more with the crop plants and remove very high amount of moisture,

nutrients, light and space. The environment varies in physical characteristics to

which plant respond, plants compete for some of these factors, water, nutrients

and light, but not for other factor such as planting and time of emergence

(Sagar, 1968).

Weeds deplete more soil moisture at the top 15 cm soil layer and the

weedy plots become drier than weed free plots (Schwezel and Thomas, 1971).

Weeds usually absorb nutrients faster and it relatively higher amounts than

crops driving greater benefit (Alkamper, 1976). According to Brunside (1978),

adequate weed control during the entire crop rotation is very important, since

allowing a heavy stand of weeds to produce seeds affect the subsequent crop

production potential.

�%�

�

Coble et al. (1981) described the water stress or moisture availability

also may influence the duration of critical weed free period for crop. Jain et al.

(1981) observed that weeds removed 5-6 times N, 5-12 times P and 2-5 times

K under gardenland conditions. At low weed densities, high N rates can

markedly increased crop yield and minimized weed competition (Moody, 1981).

According to Patterson (1982), both purple and yellow nutsedges (Cyperus

rotundus and Cyperus esculentus) shading 60 and 30 per cent of full sunlight,

respectively reduced dry matter production, leaf area production, rhizome and

tuber formation.

Plant height and vertical leaf distribution define effective components of

the competitive struggle for light (Graf and Hill, 1992). According to Patterson

and Nalewaja (1992), increased uptake of minerals by weeds often resulted in a

competitive advantage over cover crop species. Stressful levels of environmental

factors such as nutrient availability, water, light and temperature influenced

crop weed interaction and also interfered with weed control and weed

management strategies.

Purple nutsedge (Cyperus rotundus L.) is one of the most noxious

perennial weeds of the world, which causes 30-80 per cent reduction in crop

yield. The nomenculture Cyperus rotundus originated from the Latin word

‘rotundus’ meaning circular or round. The growth habit and mode of

propagation of the weed pose tremendous problems on its control. So,

�&�

�

knowledge of the weed biology is essential for evolving an economically viable

and environmentally acceptable weed management strategy. Traditional methods

of hand weeding and cultivation are not effective for the control of this weed

due to the underground production of the propagating units. This particular

nature of the weeds makes it difficult to control by adopting a single control

measure. So, different approaches comprising of both chemical and cultural

methods can be effective in controlling this noxious weed.

2.4. BIOLOGY OF PURPLE NUTSEDGE (Cyperus rotundus L.)

Purple nutsedge Cyperus rotundus has been cited as one of the world’s

worst weeds in major crops (Holm, 1969). It propagates mainly by tubers, that

possess several buds with potential for prolific sprouting. The longevity of

tubers, the ability of tubers to sprout several times and the lack of herbicides

that can kill dormant tubers have made the control of purple nutsedge difficult.

The probable origin of nutsedge assumed by Bech (1964) is Eurasia, but it is

very commonly found on the tropical and subtropical areas of Asia, Africa,

South and North America.

2.4.1. Flowering

Flowering of Cyperus rotundus can occur within 21 day after emergence

under field conditions (Okafor, 1973). In the tropics, flowering occurs almost

round the year (Mercado, 1979). Jha and Sen (1981) have recorded two seasons

of its flowering i.e., during September-October and January-April in India.

�'�

�

As per the reports, the Wills (1987) in purple nutsedge the rachis

supports a terminal inflorescence which is simple or slightly compound, loose

umbel. Each inflorescence is subtended by two or more involucral leaves or

leaf like bracts that are as long or longer than the flower bearing rays. The rays

are formed from three to nine slender, spreading, three sided peduncles of

unequal length. Near the ends are clusters of narrow spikelets, 0.8 to 2.5 cm

long and 2 mm wide, 10 to 40 flowers, acute and compressed with a red,

reddish brown or purplish brown colour.

2.4.2. Tuber sprouting

Andrews (1960) reported that at least 30 per cent of field moisture

capacity was needed for adequate germination. However, with the moisture

content below 16 per cent, the tuber generally died within five weeks.

Dormant tubers sprouted at 20°C and a temperature of 36.11°C was ideal for

subsequent growth. Jangaard et al. (1971) reported that tuber sprouting is

regulated some way by the growing plant as well as by the photoperiod,

temperature and moisture. Upon the death of foliage, inhibition of tuber

sprouting is relieved and one or more tubers on the rhizome chain may sprout.

Ray (1975) opined that first tuber in a chain inhibited the sprouting of

the lower tubers. Also, in a single tuber, the apical sprouts first and suppresses

the lateral buds from sprouting. Al-Ali et al. (1978) reported that all pH levels

between 2.2 to 9.0 allowed high sprouting percentage but the sprouted tubers

�(�

�

did not survive at pH below 3 and survival beyond pH 7 was very poor.

Pandey (1984) observed that tuber did not sprout in humid tropical climate

during December when minimum and maximum temperature varied between

8.7° to 23.4°C. Sprouting started towards third week of January with rise in

temperature and plants continued to grow vigorously till October end.

Critical moisture level of the perennating organ, the tubers is 43 per cent

of soil moisture required is about 2.4 per cent, for its survival (Jha and Sen,

1985). Purple nutsedge produces viable seed (nutlets) from mid to late-summer

which germinate in the following spring. Within a few weeks of seedling

emergence, tubers begin to form and continue to produce additional tubers in

chain along the rhizome until frost (Steller and Sweet, 1987).

Sprouting characteristics of purple nutsedge was studied and found that

sprouting and initial growth of tubers were increased with a 35/25°C day/night

temperature. Also tubers that were cut latitudinally had similar growth of intact

tubers (Kim et al., 1994). Once bud break occurs, little shoot elongation

occurred at constant temperatures, but shoot elongation was greatly stimulated

by diurnally altering temperature (Nishimoto et al., 1995).

Miles et al. (1996) conducted experiments to determine the response of

purple nutsedge tuber sprouting to diurnally altering temperature. Tuber

sprouting was more rapid and complete with alternating temperature than with

constant temperatures. Increasing temperature fluctuation from 0 to 6°C for

�)�

�

12 hours daily increased total number sprouting linearly. Both the bud break

and shoot elongation processes were regulated by temperature; most purple

nutsedge tubers produce bud break at constant temperature, and only a short

(30 min) high temperature pulse caused bud break in the tubers that were left

over (Sun and Nishimoto, 1999).

Sprouting percentage is higher and shoot emergence is faster from

tubers located closer to the soil surface. Sprouting can occur at different times

during the growing season (Bhowmik, 1997). Sprouting and growth of

nutsedge, tubers were faster at 40°C than at room temperature and multiple

sprouts arose from some tubers so that there was more than one shoot per tuber

(Chase et al., 1999). Tubers of Cyperus rotundus can sprout within 7-10 days

and produce new basal bulbs and shoots within 3-4 weeks (Terry, 2001). The

perennial species of Cyperus rotundus has aggressive presentation through

tubers is shown with a biomass of 151.6 g from 10 tubers and with a higher

tuber germinability of 81 per cent (Prabukumar et al., 2005).

2.5. CRITICAL PERIOD OF CROP WEED COMPETITION

The crop may be affected severely if it is not kept weed free during the

critical stages of weed competition. It is well established that the first 30 days

after sowing is critical period of weed competition in maize (Krishnamurthy

et al., 1981). Crop weed competition in sorghum was during the initial 15 to

30 DAS (Kanagasabai, 1983). Maize needs a weed free period of 30 to

�*�

�

60 DAS for higher yields (Kantaprasad and Mani, 1985). Noyital et al. (1989)

stated that critical stage of crop weed competition was the first 2 to 5 weeks after

sowing in maize. For obtaining satisfactory yield levels in maize a weed free

condition was needed for the first 20 days only (Channabasappa and Nanjappa,

1990). Varshney (1991) indicated that 20-40 DAS was the most critical period

for weed removal in maize. Zimdahl (1993) concluded that in maize weeding

must be done in most cases between 3 and 6 weeks after seeding.

Maize is sensitive to weed competition and losses due to weeds may range

from 33 to 72 per cent (Thakur and Sharma, 1996). Ferrero et al. (1996) reported

that the critical period of weed interference in maize was between 7 and 10 leaves

stage of the crop. Anil Dixit and Goutham (1996) found that weeds pose serious

threat to maize between 20 and 60 DAS. The critical period of weed competition

is from 15 to 45 DAS (Sureshkumar, 1999). Maize being a wide row spaced crop

allows the weeds to grow well after the first irrigation, faces competition with all

types of weeds throughout the crop season and also emergence of maize and

weeds start simultaneously and first 20 to 30 days are most critical for crop weed

competition (Porwal, 2000). Kamble et al. (2005) reported that the critical stage

of crop weed competition in maize crop is 30 to 45 DAS.

2.6. EFFECT OF WEED COMPETITION ON YIELD PARAMETERS AND

YIELD LOSSES

The weeds which lowered the availability of nutrients in early stages of

crop growth affected the growth components, which was reflected on yield

�+�

�

components and a consequently on reduction of maize yield. Krishnamurthy

et al. (1981), Kantaprasad and Mani (1985) reported that weed might reduced

maize yield by 30-100 per cent. Channabasappa and Nanjappa (1990) reported

that weeds are detrimental to crops and their competition affects crop yield

negatively and losses to the tune of 30 to 74 per cent. Ramachandra Prasad

et al. (1990) stated that a yield reduction of 23 to 84 per cent in maize due to

weeds of 27 families. Vafabaksh and Rasheed (1996) stated that weeds caused

reduction in hundred seed weight, number of grains cob-1

and weight. The

difference in floristic composition and intensity of infestation of weeds were

attributed to cause wide range of yield reduction from 40 to 60 per cent in

maize (Mishra, 1997).

Similarly, variation in the floristic composition of weeds were shown to

influence the intensity of damage as reflected by yield reduction varying from

30 to 50 per cent of maize (Sandhu et al., 1999). Weeds emerging in and

between crop rows reduced the corn yield differently (Donald, 2006).

2.7. WEED MANAGEMENT METHODS

2.7.1. Effect of mechanical methods of weed control

It is oldest method of controlling weeds. It is still practical and efficient

method of eliminating weeds in cropped and non-cropped lands. It is very

effective against weeds.

���

�

Field trials conducted in Hamirpur district of Himachal Pradesh showed

that manual weeding twice increased the maize grain yields by 0.36 t ha-1

(Bhopal Singh et al., 1991). Sandhu and Bhatia (1991) reported that hand

weeding twice in maize field gave yield to that of application of atrazine upto 5

weeks. Adoptation of hand weeding at 20 and 40 days after sowing resulted

minimum weed infestation in rainfed maize (Saha and Srivastava, 1992).

Hand weeding at 20 and 40 DAS of rainfed maize gave the highest weed

control efficiency (Thakur, 1994). According to Eleftherohorinos et al. (1995),

maize yield in hand weeding treatment was significantly greater than that of

integrated weed control and similar to that of herbicide treatment. The hand

weeding significantly reduced the density and dry matter of weeds in maize

compared to chemical treatment because the chemicals were able to control

weed growth upto 30 days after which their efficacy decreased (Intodia et al.,

1996). Krishnamurthy and Krishnamurthy (1996) reported that manual

weeding was the most common method of weed control under rainfed situation.

Kandasamy and Chandrasekar (1998) showed that the traditional non-chemical

method of weed control (two hand weedings) effectively minimized weed

yield. Sharma et al. (2000) reported that hoeing at 15 days and earthing up at

30 days of growth resulted in weed free condition.

Sinha et al. (2003) showed that weed control efficiency was maximum

under hand weeding. Kolage et al. (2004) opined that lower weed intensity was

���

�

observed with two two hand weedings at 20 and 40 DAS. The pooled data of 3

years revealed that hand weedings at 20 and 40 DAS recorded substantially

higher grain yield and fodder yields over the rest of treatment (Kamble et al.,

2005).

Tripathi et al. (2005) reported that manual weeding twice at 15 and 30

DAS registered 22.2 and 17.6 per cent reduction of C. rotundus and D. arvensis

population and also heavy decline in weed dry weight WCE (87.7 WCE%).

Hand weeding twice at 3 and 6 weeks after sowing showed significant effect in

reducing weeds and also increased the yield when compared with weedy check

(Nagalakshmi et al., 2006).

2.7.2. Effect of chemical methods of weed control

Scarcity of labour during peak times of agricultural operations, different

herbicides based weed control technologies have been developed and test

verified. Selective control of weeds in crop rows, early season of weed control,

control of perennial weeds are some of the key advantage of chemical methods.

Mechanical weeding alone could not eradicate weeds in groundnut. Hence,

herbicide application followed by mechanical tillage was essential (Amir and

Lifshitz, 1976). Vairavan and Sankaran (1996) opined that hand weeding was

time consuming and uneconomical, whereas chemical weeding is easier, time

saving and economical as compared to hand weeding alone.

�$�

�

2.7.2.1. Alachlor

Application of alachlor @ 1.0 kg ha-1

in maize intercropped with

blackgram or soyabean was more persistent, control the weeds and resulted in

lower weed biomass at harvest compared to nitrofen (Yaduraju et al., 1986). In

maize + soybean intercropping system, application of alachlor @ 2.5 kg ha-1

effectively controlled the weeds (Baskar Tripathi and Singh, 1987).

Singh and Kaushik (1989) reported higher mean maize grain yield in

weed free condition (weeds were removed manually) and alachlor application

@ 4 l ha-1

in maize + soybean intercropping system. Singh (1991) reported that

application of alachlor @ 2 kg ha-1

in maize + soybean intercropping system

increased the maize grain yield and nitrogen uptake by reducing the weed

population.

Maize grain yield of 46.5 g plant-1

was reported in maize + soyabean

intercropping system due to pre-emergence application of alachlor @ 2 kg ha-1

compared with 17.3 g plant-1

from unweeded plots (Kumar and Singh, 1992).

Application of alachlor @ 1.25 kg ha-1

reduced the total weed population and

increased the maize yield (Madhu and Nanjappa, 1994).

Application of alachlor @ 1.5 kg ha-1

significantly reduced the density

and dry weight of weeds upto 60 DAS compared with weedy control in maize

(Prasad and Rafey, 1996).

�%�

�

Application of alachlor @ 1.5 kg ha-1

in maize + French bean intercropping

system resulted in highest maize equivalent yield (Sinha et al., 2001).

Application of alachlor @ 2.0 kg ha-1

in maize was most effective in

controlling weeds in maize and increased the stover yield by 26.65 per cent

(Pandey and Ved Prakash, 2002).

Application of alachlor @ 1.0 kg ha-1

in maize + cowpea intercropping

system increased the total green fodder yield by 42.9 per cent over unweeded

control (Laxmi Parveen and Bhanumurthy, 2005).

2.7.2.2. Fluchloralin

Application of fluchloralin 0.67 kg ha-1

in maize intercropping with

blackgram or greengram or soybean resulted in significant reduction in weed

population and biomass production compared to linuron and nitrofen (Yaduraju

et al., 1986). Application of fluchloralin @ 1.5 kg ha-1

in maize + soybean or

maize + groundnut intercropping system increased yield components of maize

(Prusty et al., 1987).

Application of fluchloralin @ 1.5 kg ha-1

in maize based intercropping

system significantly increased grain and stover yield over unweeded condition

(Prusty, 1988). In Fluchloralin application @ 0.67 kg ha-1

in maize + soybean

intercropping system resulted in 2.8 per cent increase in cob number over

control (Singh and Kaushik, 1989).

�&�

�

Application of fluchloralin @ 1.0 kg ha-1

in maize + intercropping

system, significantly reduced the density and dry weight of weeds compared

with weedy control at 30 and 60 DAS (Prasad and Rafey, 1996). Pre-emergence

application of fluchloralin in maize intercropping system, hindered the

germination of weeds, killed by the seedlings and effectively reduced the weed

dry matter accumulation (Saikia and Jitendra Pandey, 2001).

When blackgram was intercropped in maize application of fluchloralin

was found to be the most economical weed control treatment. Further in this

system, significantly higher nitrogen uptake was noticed in herbicidal and

manually weeded treatments compared to weedy check (Deshveer and Amar

Singh, 2002).

2.7.2.3. Imazethapyr

Sandhya Rani et al. (2011) reported that application of sulfosulfuron +

imazethapyr 15 + 25 g ha-1

effectively control the weeds in sweet corn.

Kalhapure et al. (2013) reported that application of imazethapyr 0.150 kg ha-1

as post emergence + one hand weeding at 40 DAS found to be most

economically feasible weed management practices for groundnut.

2.7.2.4. 2,4-D Na salt

Bogdan et al. (2004) reported that pre-emergence application of

pendimethalin and post emergence application of 2,4-D Na salt provided the

best control of weeds.

�'�

�

Ramesh and Nadanassabapathy (2005) reported that one hand weeding

followed by post emergence application of 2,4-D @ 0.5 kg ha-1

kept the weed

density and dry weight below economic threshold level. Upadhyay et al. (2005)

reported that pre-emergence application of isoprofuron 0.5 kg ha-1

followed by

2,4-D as post-emergence 0.5 kg ha-1

showed the highest weed control efficiency

and grain yield of wheat.

2.7.2.5. Glyphosate

Glyphosate was used to control purple nutsedge (Suwannemek and

Parker, 1975). Effective herbicides such as glyphosate provided control of

emergence of purple nutsedge (Doll and Piedrahita, 1977; Zandstra and

Nishimoto, 1977; Chase and Appleby, 1979).

Mehta (1991) observed that glyphosate application at 0.45 per cent

significantly reduced the number plot-1

of tubers, dry weight of shoot, roots and

rhizomes of nutsedge as compared to control. While Tewari and Singh (1991)

stated that deep ploughing during summer followed by 1.2 kg ha-1

of glyphosate

application was effective on nutsedge.

Madhavi et al. (1992) reported that application of glyphosate with 2 per

cent ammounium sulphate effectively controlled nutsedge. Significant reduction in

nutsedge biomass was achieved through spraying of 10 per cent glyphosate with

0.5 per cent 2,4-D salt or one per cent ammonium sulphate (Manickam and

Gnanamoorthy, 1992). Split application of glyphosate twice @ 1 kg ha-1

of

commercial product was effective for nutsedge control (Sandhu and Bhatia, 1992).

�(�

�

Glyphosate @ 2 kg ha-1

was an effective in reducing Cyperus rotundus

shoot numbers (Hawton et al., 1992). Glyphosate at 1.64-2.46 kg ha-1

resulted

in 100% mortality of Cyperus rotundus tubers (Liu and Twu, 1993).

Satisfactory control of nutgrass with glyphosate was reported by Ahiya and

Yaduraju (1995) under non-crop soil situation in India. Glyphosate was very

quickly absorbed by Cyperus rotundus that too even under dry spells and as

quickly as 1 h after spraying was sufficient for adequate weed control

(Melntyre and Baske, 1995).

Based on their study conducted at Raichur, Desai et al. (1996) reported

that higher drying per cent was recorded with glyphosate @ 4 kg a.i. ha-1

.

Efficacy of glyphosate in reducing tuber viability of Cyperus rotundus by

cutting of treated shoots and trucking their regeneration were effective with the

addition of adjuvants like urea, 2,4-D and (NH4)SO4 (Inderdev et al., 1996).

The response of purple nutsedge population to glyphosate application was

studied by Zaenudin et al. (1996) and they observed that post emergence

application of 0.73 kg glyphosate ha-1

at 4-8 weeks after weed emergence

resulted in good control of the weed.

A range of herbicide for controlling nutgrass was evaluated and found

that multiple application of glyphosate reduced tuber density by upto 96 per cent

over two seasons. This was improved with successive application of glyphosate

(Charles, 1997). Double application of glyphosate resulted in 90.8 per cent

�)�

�

reduction in number of plants and 76.3 per cent reduction in number of tubers

(Freita et al., 1997). The effectiveness of different herbicides was studied for

nutsedge control and the lowest tuber dry weight and tuber numbers was recorded

with glyphosate @ 2.0 and 2.5 kg ha-1

(Muniyappa et al., 1998). Glyphosate @

1.5 kg a.i. ha-1

was sufficient for complete kill of nutsedge in experimental area

and there was no re-growth upto 6 weeks after spraying (Ameena, 1999).

Glyphosate @ 2.24 kg a.i. ha-1

in 17 days old and at 4.48 kg in 10 week

old plants controlled purple nutsedge by 96 per cent (Barivan et al., 1999).

Glyphosate @ 1.8 kg a.i. ha-1

reduced 95 per cent of tuber population of

Cyperus rotundus (Darkwa et al., 1999).

Glyphosate required a rainfree period of atleast 24 h to show its

potential activity on the control, tuber production and sprouting capacity of

purple nutsedge (Kogan, 2000). The efficiency were studied and it was

observed that glyphosate @ 2.45 kg ha-1

controlled Cyperus rotundus effectively

and economically compared to other treatments with no residual toxicity

(Sukhadia et al., 2000). The maximum reproduction and regeneration potential

was obtained with glyphosate applied in three splits (Bhatia et al., 2001).

Tuber population of Cyperus rotundus could be reduced by 95 per cent after

glyphosate @ 18 kg a.i. ha-1

was applied at the beginning of the season

(Darkwa et al., 2001). Glyphosate is one of the herbicide that killed the

foliage, rhizomes and tubers of C. rotundus (Terry, 2001).

�*�

�

Wangchengyuh (2001) reported that effect of glyphosate on aromatic

amino acids metabolism in purple nutsedge (Cyperus rotundus) sprouted tubers

and shoots and reported that glyphosate caused inhibition of bud elongation.

Increased total free amino acids concentration and casual rapid accumulation of

shikimic acid in sprouted tubers.

Oster et al. (2002) compared the efficacy of glyphosate and other

herbicide against Cyperus rotundus tuber viability and reported that glyphosate

was most effective among the herbicide with 37 per cent tuber mortality after

eight months and 38 per cent after 30 months. Yellow nutsedge was controlled

by glyphosate @ 840 g a.i. ha-1

(40 to 70 per cent control) (Nelson and Renner,

2002). Glyphosate reduced yellow nutsedge tuber density by 51 per cent tuber

fresh weight by 59 per cent and tuber sprouting by 17 per cent at 42 weeks after

treatment in the field (Kelly et al., 2002). Use of glyphosate in the preceding

off-season continued to serve as the promising control option for Cyperus

rotundus (Kathiresan and Bhowmik, 2006).

2.8. OFF-SEASON LAND MANAGEMENT PRACTICES

2.8.1. Summer ploughing

The interaction of nutgrass could be effectively managed through

exposing the propagating parts to the sun during summer by repeated deep

ploughing. These tubers and rhizomes brought to the surface and were

desiccated by solar heat resulting in moisture depletion below critical limit and

subsequent mortality.

$+�

�

Hauser (1962) reported that the irrespective of soil texture most of the

tubers were found in 10-15 cm depth followed by 6-10 cm depth of soil.

Exposure of underground tubers of the weed to the soil surface by deep

ploughing twice in April and May gave the best control of Cyperus rotundus

(65.39, 69.00 and 70.08 per cent, respectively and reduction in aerial shoots,

tubers and rhizomes respectively).

Diop and Moody (1984) reported that the problematic perennial weed

was substantially reduced when the field received one ploughing in the

off-season.

Tillage operation associated with conventional –tillage crop production

are an effective method for controlling of perennial weeds (Triplett, 1985).

Eswarappa and Ananthanarayanan (1988) reported that deep tillage enhance the

water utilization by the crop and also it creates the deeper layer of the soil by

loosening them, thereby accelerating the biological activities of flora and fauna

which decide the benefit to plant growth.

Exposing the underground tubers of Cyperus rotundus to sun through

deep ploughing in summer was observed to be the best method of controlling

the weed (Tewari and Singh, 1991). Off-season ploughing particularly in

summer exposed the weeds, dried them in the sun and their population and

dry weight were decreased (Sharma and Das, 1993). Browning et al. (1994)

reported that the favourable effect of summer ploughing and FYM

incorporation on growth and yield of rainfed pearl millet.

$��

�

Summer ploughing decreased the total buried weed seed population by

3-4 times compared to no ploughing (Sahoo et al., 1995). Deep mould board

ploughing (40 cm deep) and exposure of the soil to high temperature during the

summer significantly reduced nutsedge infestation (Aly et al., 1998).

Summer ploughing + FYM + herbicide + insecticide recorded the

maximum values of yield attributing characters (Jat and Gautham, 2000). The

mechanical combination of ploughing, repeated twice during the dry season of

the year integrated with two application of glyphosate during the rainy season

offered 99.4 per cent Cyperus rotundus shoot reduction (Durigen, 2000).

Pankaj Chopra and Angiras (2005) observed that zero tillage caused significant

increase in dry matter of weeds over conventional tillage. Increasing the

ploughing + harrowing frequency through land preparation, substantially

reduced the weed count and weed dry weight (Nanjappa et al., 2005).

Alternate wetting and drying is necessary for the control of world worst

weed Cyperus rotundus (Marambe, 2006). According to Safaur Rahman and

Mukherjee (2008) effective reduction of weed density and weed dry weight

was noticed in tilled practice than no-tillage practice.

2.8.2. Soil solarization

2.8.2.1. Effect of soil solarization on soil temperature

In soil solarization, major factor causing soil disinfestations is its effect

on increasing the soil temperature to lethal levels. Typical maximum soil

$��

�

temperature in solarized plots were 8 to 12°C higher than that in the

corresponding non-mulched plots (Katan, 1980). Solarization with transparent

polythene film increased the temperature of the top soil layer and decreased the

dissipation of soil heat (Chen et al., 1983).

At IARI New Delhi, there was significant increase in soil temperature in

0 to 15 cm depth of soil due to mulching with transparent polythene film

(Choudhary and Chopra, 1983). Though solarization is reported to be very

effective only in summer, solarizing the soil during autumn with lower air

temperature and less intense solar radiation was observed to result in a

significant but much smaller increase in soil temperature at Jerusalem, Israel

(Rubin and Benjamin, 1983). At Louisiana, USA, solarization on a bright

sunny day was observed to raise the temperature at 1 cm depth, from 27°C at

6.30 a.m. to 36°C at 3.30 p.m. But on a cloudy day, the highest temperature

attained was only 35 to 40°C (Standifer et al., 1984). The extent of increase in

temperature varied with the situations. Soil temperature at 5 cm depth was

increased by 44°C due to solarization for 30 days with transparent polythene

(Braun et al., 1987). Temperature in solarized plots reached upto 51°C (Cartia,

1987). The extent of increase in temperature at 5 cm soil depth was 18°C in

Taiwan (Tu et al., 1987). Extremely high temperature of 6°C achieved at 10

cm depth by solarization with transparent polythene films at Valencia in Spain

(Del Busto et al., 1989). At CAZRI, Jodhpur, India, solarization in the month

$$�

�

of June with transparent polyethylene increased the soil temperature at 5 cm

depth by 9 to 12°C (Lodha and Vaidya, 1990). Increase in soil temperature by

6 to 13°C due to solarization was noticed at Cohima, Mexico (Stapleton, 1991).

In Delhi, soil temperature at 5 cm in mulched plots were 51.7°C, 54.4°C and

36.5°C respectively in trails conducted in March-May, May-June and January-

March (Khandar and Bhowmik, 1990). At Jodhpur, Rajastan maximum soil

temperature was 55°C in mulched plots (Lodha et al., 1991). Temperature

increase of 9.9°C due to 0.05 mm thickness of transparent polythene sheets

(Harti, 1991).

In studies of Dharwad, the maximum soil temperature was increased by

10-14°C, 5-10°C and 2-5°C respectively due to thin transparent polythene

(0.025-0.05 mm), thick transparent polythene (0.05-0.10 mm) and black

polythene (Emani, 1991; Habeeburrahaman, 1992). Habeeburrahaman and

Hosmani (1996) revealed that TPE recorded the highest soil temperature in

comparison with control (Vijayabhaskar, 1996; Mudalagiriyappa et al., 1999).

Kirankumar (1999) reported that soil solarization with TPE increased

the soil temperature to an extent of 57°C. Soil solarization with TPE recorded

the highest soil temperature of 54.2°C compared to the control which attained

temperature of 44°C (Lalitha et al., 1999). In soil solarization treatment, the top

15 cm layer of the soil temperature due to solarization was also the highest in the

top 5 cm layer in second year (Sundari, 1999). Nanjappa et al. (2001) confirmed

$%�

�

that soil solarization with TPE recorded the highest soil temperature at 54.3°C

compared to control. At 5 cm soil depth, the temperature in solarized plot

reached upto 50.1°C (Sureshkumar, 2005; Kalaisudarson, 2007; Nambi, 2010).

2.8.2.2. Effect of soil solarization on soil temperature as varying soil depths

It is proven fact that with increase in soil depth the maximal soil

temperature attained through solarization decrease. The highest soil temperature

attained was 45° to 53°C at 5 cm depth while the same was only 40 to 42°C at 20

cm depth at Israel (Grinstein et al., 1979). At Torino, Italy, solarization increased

soil temperature from 38.9 to 48.0°C at 6 cm depth and from 28.5°C 35.6°C at

24 cm depth (Garibaldi and Tamietti, 1980). However, the increase in soil

temperature was observed to the similar with an increase upto 56°C at both the

surface and depth 5 cm depth of soil at Israel (Jacobson et al., 1980).

The soil temperature at 5 cm depth was observed to increased from 44 to

57°C and the same was observed to from 36° to 45°C at 10°C depth, at Naples,

Italy (Aloi and Noviello, 1982). At Texas, USA, the soil temperatures were

raised to 58, 53, 46, 88 and 36°C at 2, 5, 10, 20 and 30 cm soil depths,

respectively (Hartz et al., 1985). Dwivedi and Dubey (1987) reported that

temperature attained at 10 and 30 cm were 54°C and 44°C, respectively, at

Varanasi, India. Szteynberg et al. (1987) reported that in solarised apple

orchards in Israel soil temperature at 10, 30 and 50 cm depth were raised from

35°C to 46°C, 33 to 35°C and 31°C to 37°C respectively.

$&�

�

The mean maximum temperature in the vertisols of ICRISAT, India

reached 53.9, 46.6 and 38.3°C at 5, 10 and 15 cm depth at against 43.7, 37.6

and 32.4°C in non-solarized plots (Chauhan et al., 1988). At Hawaii, the rise in

soil temperature at 5, 15 and 30 cm was from 35 to 44°C, 30 to 35°C and 29 to

33°C respectively (Ragone and Wilson, 1988).

The time required from the attainment to the highest temperature in upper

10 cm layer was within four to five days and it took five to six days to attain the

highest to lower depths of 20 to 45 cm (Kaewruang et al., 1989). Solarization

treatment with clear polyethylene recorded 53°C temperature at 5 cm soil depth

(Meti and Hosmani, 1994; Hebeeburrahaman and Hosmani, 1996). At Beirut,

solarization plots recorded temperature of 53°C, 48°C and 43°C at 5 cm, 15 cm

and 25 cm depths respectively (Sobh and Abou-Jawadah, 1997). Lower soil

depths registered minimum temperature than upper 5-10 cm soil layer

(Mudalagriyappa, 1998).

Kirankumar (1999) reported that increase in temperature (12°C) was at

higher rate at 5 cm depth than at 10 cm (11.6°C) depth over control. Lalitha

et al. (1999) observed that soil solarization with TPE in temperature at 50°C to

54.2°C and 46.0°C to 52.0°C at 10 cm soil depth at 15 days after polyethylene

spreading. Nanjappa et al. (2001) confirmed that solarization with TPE resulted

in higher soil temperature of 54.33°C at 5 cm soil depth and there was 13°C

rise in temperature compared to control.

$'�

�

2.8.2.3. Effect of soil solarization on weed control

Soil solarization as a cultural practice has been offering several

advantages like disinfestations of soil pathogens, nematodes, increased enzyme

activity leading to mineralization at nutrients etc., of which weed control is the

most important one, thermal inactivation and weakening of propagules had

been the primary mode of action of solarization in weed control. The weed

control effect of solarization has been reported to varying magnitudes, in

several crops at several locations by different authors.

The reduction in weed population in solarized plots over non-solarized

plots was evident after 13 months of mulching (Grinstein et al., 1979). Many

annual and perennial weeds were effectively controlled by soil solarization

(Katan, 1980). Soil solarization was reported to offer satisfactory weed control

over a period of one month at Spain (Del Busto et al., 1984). Polythene

mulching for 32 days decreased the emergence of the dominance weed Cyperus

rotundus by 90 per cent (Kumar et al., 1993).

Biradar (1996) reported that solarization has significantly reduced the

weed count and weed dry weight in groundnut and thinner sheet were superior

over thicker ones. Chase et al. (1998) stated that solarization period of 8 to 10

weeks be more effective for the control of purple nutsedge and other perennial

weeds. The 0.05 mm TPE mulched plots recorded lower weed count and weed

dry weight than the 0.10 mm TPE in groundnut (Mudalagiriyappa et al., 1999).

$(�

�

Kirankumar (1999) observed that TPE 0.05 mm followed by TPE 0.10 mm

during March and April months recorded significantly lower weed count and

weed dry weight. Lower weed count and weed dry weight were obtained with

0.05 mm TPE followed by 0.10 mm TPE during April and May months

compared to control (Lalitha et al., 1999).

Soil solarization with transparent polyethylene sheet reduced weed

count and weed dry weitght (Biradar et al., 2001). Weeds like Cyperus

rotundus, Amaranthus retroflexus, Protulaca oleraceae and Digitaria

sanguinalis were reduced to the half due to solarization. Lower weed count

and weed dry weight at harvest in sunflower were obtained with soil

solarization (Thimmegowda et al., 2007).

2.8.2.4. Effect of duration of solarization on weed control

Soil solarization is most effective when it is done during the warmest

part of summer and the polyethylene sheets should be kept in place for the

desirable period as long as practical. Though annual weeds can be controlled

by short periods, long periods are necessary for perennials. Partial control of

perennial weeds such as C.rotundus, S. halapens and C.dactylon. But the

control was significantly improved by larger period of solarization over ten

weeks. The soil solarization treatment was most effective when practiced

during the warmest summer months (Stapleton and Devay, 1986). Solarization

for six weeks controlled several weeds in Egypt (Fahim et al., 1987). A sharp

$)�

�

reduction in soil seed bank and the highest depth of propagules of Cyperus

rotundus and Bidens pilosa were observed due to solarization for seven weeks

(Herrera and Ramirez, 1996).

2.8.2.5. Effect of duration of solarization on soil temperature

Four weeks of soil solarization with transparent polyethylene sheets

increased the temperature of the soil (Horowitz et al., 1973; Choudhary and

Chopra, 1983). Rubin and Benjamin (1983) reported that four to six weeks of

solarization effectively controlled most of the weeds atleast five months after

plastic removal. Soil temperature at 5 cm depth was increased to 44°C by

solarization for 30 days with transparent polyethylene (Braun et al., 1987).

Mudalagiriyappa et al. (1999) reported that soil temperature exceeding 40°C

and 45°C was 100 per cent for the treatment with 0.05 mm for 45 days when

compared to 30 and 15 day solarization. Soil solarization with TPE of 0.05 mm

thickness for 40 days during summer resulted in increase the soil temperature

(Sureshkumar, 2005).

2.8.2.6. Efficiency of transparent polyethylene sheets on weed control

Mulching with thin transparent polyethylene (0.03 to 0.05 mm)

increased the upper layer soil temperature by 10 to 12°C (Chen and Katan,

1980). Soil solarization with thin transparent polyethylene of 50 mm thickness

on fine soil leads to an increase in soil temperature by 7°C at Israel, Giza and

Egypt (Osman and Sahab, 1983). Rubin and Benjamin (1983) reported that

$*�

�

mulching on wet soils with thin transparent polyethylene (0.04 to 0.05 mm)

increased the soil temperature by 10 to 18°C.

Melero et al. (1989) reported that efficiency of 0.05 mm TPE in

increasing the soil temperature was more than 0.10 mm TPE. The similar

results were also reported by Lodha (1989), Harti (1991) and Biradar (1996).

In studies at Dharwad, the maximum soil temperature was increased by 10 to

14°C and 5-10°C respectively due to thin TPE (0.025-0.05 cm) and thick TPE

(0.05-0.10 cm) (Mudalagiriyappa et al., 1999). The same was also confirmed

by Lalitha et al. (1999) and Nanjappa et al. (2001).

2.8.2.7. Effect of solarization on growth and yield

Solarization is reported to decrease the infestation of weeds and

pathogens resulting in 52 per cent increase in yield of groundnut (Grinstein

et al., 1979). Katan (1980) reported that solarization decrease the incidence of

Rhizoctonic and Fusarium and thereby improved the plant stand, plant growth

and yield of onion by 109 to 125 per cent.

Katan et al. (1983) observed that increase in yield of cotton from 2.46 to

4.17 t ha-1

due to reduction in weeds and Fusarium on account of solarization.

Chauhan et al. (1988) reported that soil solarization with polythene film

increased dry matter accumulation of sorghum from 1.4 to 3.5 t ha-1

. In cowpea,

thin plastic mulching for one month and thick plastic mulching for two months

recorded the highest leaf area index (Emani, 1991). Habeeburrahman (1992)

%+�

�

stated that higher leaf area, leaf area index in nodule number and total dry

matter production in groundnut under clean polyethylene mulching than non-

solarized plots at Dharwad.

Solarization for 30 days increased the plant height, leaf area and dry

weight of soybean (Kumar et al., 1993). Gruenzweigh et al. (1993) observed

the increased growth response in solarized plots of cucumber, sorghum,

tobacco and tomato crops. Lalitha et al. (1999) reported that growth and growth

components of groundnut such as plant height, number of branches, number of

leaves, leaf area index and dry matter accumulation were significantly higher in

solarized plots than control.

Mudalagiriyappa et al. (1999) reported that higher yield and yield

components of groundnut in solarized plots. Kirankumar (1999) suggested that

solarization, with 0.05 mm TPE for 30 days during April registered

significantly higher yield of 21.6 t ha-1

in tomato, while, the non-solarized plots

yielded 9.56 to 12.36 t ha-1

in tomato. Groundnut yield was increased from

11.98 to 18.97 q ha-1

in solarized plots compared to control 7.61 q ha-1

. TPE

0.05 mm gave 18.97 q followed by 0.1 mm TPE mulching in groundnut

(Lalitha et al., 2000). Similar results were confirmed by Nanjappa et al. (2001)

and Sureshkumar (2005).

%��

�

2.8.3. Mulching

Mulching is a protective covering material maintained on soil surface

and kills the weed by cutting the light availability to them. Mulching provide a

stronger mechanical barrier of all kinds of germinating weeds (Gupta, 1988).

2.8.3.1. Effect of mulching on weeds

Kaliappa (1980) reported that application of sugarcane trash @ 10 t ha-1

reduced weed dry matter production in sorghum. Mulching with sugarcane

trash was reported to reduce the weed population (Gavin and Brain, 1982).

Sharma et al. (1984) suggested that application of mulches suppressed

the weed growth and increased the yield of garlic. It was reported that

application of trash mulch was more effective in reducing the number of weeds

and weed dry matter production (Mann and Chakor, 1989). Mulching not only

controlled the weed infestation but also reduced run-off and soil loss,

minimized evaporation, increased soil moisture status, controlled temperature

fluctuations, improved physical and chemical properties and recorded

50-60 per cent yield increase (Dilipkumar et al., 1990). Sugarcane trash at 5 cm

thickness was effective in controlling weeds in sugarcane (Raja, 1994).

Elumalai (1997) reported that application of sugarcane trash mulching at 10 cm

thickness was observed to reduce the weed biomass in maize. Mulching with

either subabul logging or bagasse straw @ 6 t ha-1

recorded significantly lower

weed population and weed dry matter accumulation than the unmulched control

%��

�

(Solaiappan and Chellaiah, 1998). Black polythene sheet mulching followed

by fluctuation 1.5 kg ha-1

+ sugarcane trash mulching was observed to be

efficient weed management programme in brinjal cv. Annamalai (Shah, 2000).

2.8.4. Intercropping

According to Tarhalkar and Rao (1975), intercropping system involves

growing together more species with the assumption that two species could

exploit the environment better than one, besides providing insurance against

the unpredictable weather, when two crops grown together, it is imperative that

the peak periods of the two species do not coincide (Rajat De and Singh, 1979).

The main objectives of intercropping is to obtain higher total economic returns,

eventhough there will be a marginal sacrifice in the yield of base crop. Further,

the selected intercrop should not be competitive with the main crop for soil

moisture, nutrients and sunlight (Sankaran and Balasubramanian, 1982).

The crop selected for intercropping will normally be of different species,

differing in their duration, canopy structure, rooting behaviour, requirement for

water, nutrient and solar radiation (Rao, 1986). Gurbachan Singh (2005)

reported that intercropping reduced the weed emergence, improvement in crop,

competitive ability and improved the soil fertility status. Javanmard et al.

(2009) reported that intercropping is popular because of its advantages over

sole cropping which include security of returns and higher profitability due to

higher combined returns per unit area of land.