integrated weed management in rice in india -...

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Integrated Weed Management in Rice in India

Adusumilli. N. Rao

Consultant Scientist, IRRI/India

Formerly Agronomist (Weed Scientist), International Rice Research Institute (IRRI),

Philippines;

Plot: 1294A; Road: 63A; Jubilee Hills; Hyderabad – 500033; Andhra Pradesh;

email: [email protected]

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1. Introduction:

Rice is cultivated in India in a very wide range of ecosystems from irrigated to shallow

lowlands, mid-deep lowlands, deep water to uplands.Transplanting is the major method of rice

cultivation in India. However, transplanting is becoming increasingly difficult due to shortage and

high cost of labour, scarcity of water, and reduced profit. Thus, direct-seeding is gaining

popularity among farmers of India as in other Asian countries. Direct-seeding constitutes both

wet- and dry-seeding and it does away with the need for seedlings, nursery preparation, uprooting

of seedlings and transplanting. Upland rice, which is mostly dry-seeded, is found in parts of Assam,

Bihar, Chattisgard; Gujarat, Jharkhand, Kerala, Karnataka, Madhya Pradesh, Orissa, Uttar Pradesh

and West Bengal. The upland rice area is around 5.5 million hectares which accounts or 12.33% of

the total rice area of the country. Wet-seeded rice (WSR) is increasing in area in parts of Andhra

Pradesh, Punjab and Haryana. In the rice agro-ecosystems ideal environment conditions are

provided for optimal rice productivity are being exploited by the associated weeds.

Irrespective of the method of rice establishment , weeds are a major impediment to rice

production through their ability to compete for resources and their impact on product quality.

Weeds are responsible for heavy rice yield losses, to the extent of complete crop loss under

extreeme conditions. . Out of the losses due to various biotic stresses, weeds are known to

account for nearly one third. Weed competition would be less severe under transplanting than

those under direct-seeding (Singh et al., 2005; Savary et al., 2005; Rao and Nagamani, 2007; Rao et

al., 2007). Uncontrolled weeds reduced the grain yield by 75.8, 70.6 and 62.6% under dry-seeded

rice (DSR), WSR and transplanted rice (TPR), respectively (Singh et al., 2005). Experiments showed

that yields were comparable across all establishment methods of rice when competition from

weeds was removed. Thus, weed control is major prerequisit for improved rice productivity and

production using different methods of rice establishment.

The agricultural growth rate has slowed down (2008-2009 reported less than 2%) in India

(Government of India, 2010) and increased agricultural productivity is needed to meet the

increasing needs of the growing population. Proper weed management technologies if adapted

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can result in an additional rice production. Thus weed management would continue to play a key

role to meet the growing food demands of increasing population in India. As the weed problems

are multi-pronged, a holistic multi-disciplinary integrated approach would be imperative. In this

context, integrated weed management (IWM) may provide a more sustainable approach to rice

production.

The objective of this paper is to provide a summary on integrated weed management in

rice in India and suggest areas of future research on integrated weed management to combat

weed menace effectively, economically and ecologically.

2. Impact/losses due to weeds

Weeds were reported to reduce rice yields by 12 to 98%, depending on type method of

rice establishment (Table: 1). Rice yield losses due to uncontrolled weed growth and weed

competition were least (12%) in transplanted rice (Singh et al., 2011) and highest in aerobic direct-

seeded rice on a furrow-irrigated raised-bed systems (Singh et al., 2008) and in dry-seeded rice

sown without tillage (Singh et al., 2011).

Threshold levels for a few weed species were also worked out. For example: Cyperus iria at

density of 30 m–2

and Echinochloa crus-galli density of 20 m–2

, is considered the threshold level for

transplanted rice, as it causes the minimum loss of 6.57% and 8.74%, respectively, in grain yield,

above which control measures are to be undertaken (Singh and Angiras, 2003; 2008). Grass weed

seedlings of rice seedling nursery are unintentionally transplanted with rice seedlings (Rao and

Moody, 1987) and average rice yield reductions from transplanted E. glabrescens ranged from 6%

at the 5% infestation level to 73% at the 40% infestation level (Rao and Moody, 1992).

An on-farm study indicated that the yield loss from weeds in unweeded plots was highest

in the rice-wheat system. followed by rice-pea-rice, and was least in the sugarcane system (Singh

et al., 2005). Weeds not only cause huge reductions in rice yields but also increase cost of

cultivation, reduce input efficiency, interfere with agricultural operations, impair quality, act as

alternate hosts for several insect pests, diseases, they affect aesthetic look of the ecosystem as

well as native biodiversity, affect human and cattle health.

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3. Weed flora associated with different methods of rice establishment:

Weeds are dynamic and the composition and competition by weeds is dependent on soil,

climate, cropping and management factors. Rice fields can be colonised by terestrial, semiaquatic

or aquatic plants depending on the type of rice culture and season. The total number of weeds

species in a field largely depends on the associated environment and cropping systems. It s usually

lower (10-15) in highly productive and intensive systems with a low diversity o crops grown in

rotation, and higher (upto 50 or more) under highly diversiied crop rotations. In either of the case,

only few of the species account or most of the damage (Moody, 1990). The number of species

comprising the major portion of the weed flora in any field is usually less than 10 and rarely more

than 3 or 4 species are important.

Several studies were conducted in India on weed flora of rice under different methods of

rice establishment and major associated weeds were reported (Table: 2). Echinochloa colona and

E. crus-galli are the most serious weeds affecting rice in all methods of rice establishment. Other

weeds of major concern in rice include, Ammannia baccifera, Cyperus iria, Cyperus difformis,

Eclipta alba, Fimbristylis miliacea, Ischaemum rugosum, Leptochloa chinensis, Monochoria

vaginalis, Paspalum distichum and Spaenoclea zeylanica. E. colona requires less moisture than E.

crus-galli resulting in the predominance of E. colona in dry-seeded rice. Cyperus rotundus and

Cynodon dactylon are other major problems in upland conditions, particularly in poorly managed

fields. Significant variation occurrs in the dominance of the abundant weed species with crop

establishment and weed control methods (Singh et al., 2005). Weedy rice is emerging as a major

problem in direct-seeded rice (Rao et al., 2007).

4. Factors influencing weed competition and critical period:

Many factors inluence the presence and abundance of weed species or groups of weeds in

rice fields. Important factors include: rice seeding method, soil moisture, crop rotation, type and

amount of ferilisers applied, time of ferilisers application, rice cultivar, water management; crop

management and weed control methods used. These factors inluence the weed growth and

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subsequently the rice productivity and quality. These factors are managed to provide optimal rice

stand and create microenvironment favorable for optimal rice productivity.

The critical period for weed control is a period in the crop growth cycle during which weeds

must be controlled to prevent yield losses (Zimdahl, 1988, 2004). Studies on critical period of crop

weed competition conducted in India (Table: 3) revealed that first thirty to seventy days are

critical, depending of the type of rice cultivar and the method of rice establishment.

The loss in grain yield of direct-seeded rice caused by unchecked weed growth was greater

when N fertilizer was applied and when the conventional practice of ploughing the fields just

before sowing was followed (Sharma, 1997). In transplanted rice, C. iria competition for the first

30 days caused less than one fourth (12.9%) of the total losses in yield while competition for 40

days resulted in more than half (43.5%) of the total losses due to the weed (Dhammu and Sandhu,

2002). Maximum reduction in rice yield (35.2%) was observed by delaying C. iria removal from 30

to 40 DAT, indicating this period as the most critical period of C. iria competition in transplanted

rice. On the otherhand, Singh et al., (1991) recorded over 25% of the total loss in rice yield when

Ischaemum rugosum was allowed to compete for 40 days and opined that the most critical period

of competition was 40-70 DAT. Thus, knowledge of weeds associated with rice and weed

emergence patterns becomes essential for successful implementation of critical period o crop

weed competition concept.

5. Principles of weed management

The principles that underline ecologicaly and economically viable weed management

system in rice are: (a) adapting the weed management options that suits to the environment of

the region, including soil, water, climate and biota present at the site; (b) optimizing the use of

biological and chemical/physical resources for effective management of weeds in rice. An

important principle underlying long-term weed management is that weed seed banks maintain

emergent populations, and therefore, seed banks must be managed at low densities to reduce the

potential for a buildup of intractably high weed populations.

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Reviews on weed management practices or rice nursery and transplanted rice (Rajendran

and Lourduraj, 1998); dry-seeded rice (Rao and Nagamani, 2007) and wet-seeded rice (Rajkumara

et al., 2003) in India are available.There is no single weed control method for effectively and

economically managing weeds in rice to attain optimal rice productivity and production. Hence,

integrated weed management strategy using a combination of several weed control methods is

often envisaged. The principles of IWM are that it must be : (i) effective, (ii) economical; (iii) easy

to use; (iv) and environmentally safe.

6. Integrated weed management

Weed management must aim at reducing the weed population to a level at which weeds

occurrence has no effect on farmers economic and ecological interests. By using different

appropriate management practices against weeds, farmers have more options for controlling

weeds, thereby reducing the possibility of escapes and weed adaptation to any single weed

management tactic. IWM is a science-based decision-making process that coordinates the use of

environmental information, weed biology and ecology, and all available technologies to control

weeds by the most economical means, while posing the least possible risk to people and the

environment (Sanyal, 2008). The concept of IWM is not new. For example, the traditional practice

of puddling soil to kill existing weeds and aid water retention, transplanting rice seedlings into

standing water to achieve an optimum stand density, and maintaining standing water to suppress

weeds, followed by one or several periods of manual weeding, is a well established example of

integrated weed management (IWM) (Rao et al., 2007).

Effective IWM combines preventive, cultural, mechanical and biological weed control

methods in an effective, economical and ecological manner.

6. A. Non chemical IWM:

Limited number of research studies were reported on non-chemical methods of IWM. In

rice seedling nursery rabbing (pre-burning the nursery area) gave 100% weed control (Zagade et

al., 1992). In transplanted rice, the reduction in weed growth was observed with, (a) intensive

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puddling and shallow depth submergence (Reddy and Reddy, 1999), (b) higher dosage rate of

fertilizer i.e.180 kg N ha–1

and plant density of 41 plants m–2

(Brar and Walia, 2001).

In rainfed upland rice, better land preparation (2 ploughings at 15 d before sowing and 2 at

sowing), timely sowing (in the last week of June), the application of fertilizer and an additional

hand weeding markedly decreases the infestation of all categories of weeds, compared to the

traditional farmers' practice, (Singh and Ghosh, 1992). In rice-rice cropping system, the least weed

growth was recorded with: (a) ploughing the land twice, during off-season followed by twice hand

weeding in the crop, (b) raising green manure of Sesbania aculeata (c) incorporation of pressmud

at 10 t ha–1

+Azolla inoculation at 1 t ha–1

(Gnanavel and Kathiresan, 2002). In rice/wheat cropping

system, inclusion of greengram in summer or summer cowpea for fodder or Sesbania for green

manuring, resulted in lowest grasses and sedges (Singh et al., 2008).

6. B. IWM with herbicides as a component:

In rice seedling nurseies, use of effective herbicides such as pretilachlor plus safener (Rao

and Moody, 1988; Balasubramanian, and Veerabadran, 1998); cyhaloop bytyl (Jayadeva et al.,

2002; Sharma et al, 2004a), propanil and quinclorac+bensulfuron (Rao and Moody, 1988) either

alone or in combination with hand weeding results in healthy rice seedlings for transplanting.

Several herbicides were found effective in managing weeds in different methods of rice

establishment (Table: 4, 5, 6). However, only about 17% area out of 42 mha under rice is treated

with herbicides, almost entirely in transplanted rice. Herbicides form only 12% of the pesticides

used on crops in India (Saksena, 2003; Bhat and Chopra, 2006). The rice herbicides such as

butachlor and anilofos have recorded huge increase in use upto 1650 and 500 MT, respectively. As

direct-seeded rice area is increasing in India, there exists a very good scope for their use in future.

Research on IWM was carried out to use herbicide as a component of weed management rather

than using herbicides alone.

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6. B. A. Crop rotations, cropping systems and herbicides:

Crop rotation is an important component of IWM. The choice and sequencing of crops

affects long-term weed population dynamics, and consequently weed management. In traditional

farming, rotations comprised of crops with different life cycles were a key component of weed

management. Different planting and harvest dates among these crops provide more opportunities

for farmers to prevent either plant establishment or seed production by weeds.

In rice/wheat cropping system, sequences involving summer cowpea for fodder or

Sesbania for green manuring, resulted in significantly lowest population of grasses and sedges

(Singh et al., 2008). However, the different cropping sequences failed to affect broadleaf weeds.

Rice-lentil+mustard (3: 1)-cowpea, rice-maize + pea (1: 1) - cowpea and rice –potato - greengram

gave high yield (Singh et al., 2008).

Effective weed control in terms of reduced weed density and dry weight was achieved by

pretilachlor with safener at 400 g ha–1

combined with sesbania (Daincha) intercropping and azolla

dual cropping in wet-seeded rice (Subramanian and Martin, 2006). The conoweeder incorporation

of daincha and azolla resulted in higher weed control during early stages.

In greengram intercropped with rice, pre-emergence application of pendimethalin 1.0 kg

ha–1

with hand weeding at 25 DAS significantly reduced the weed biomass and increased the yield

of both the crops (ICAR, 2007). In upland direct-seeded rice, an integrated strategy of growing

cowpea or dhaincha as an intercrop and pre-emergence application of pendimethalin (1.0 kg ha–1

)

followed by a manual weeding at 20 DAS has been found appropriate for reducing weed

competition (ICAR, 2007).

In rice-wheat system, sequential application of butachlor (rice) and isoproturon (wheat)

and butachlor fb hand weeding have been found effective against Echinochloa sp. and Fimbristylis

sp. in rice. Continuous use of butachlor in rice and isoproturon in wheat has reduced the problem

of Echinochloa colona in rice (ICAR, 2007). The effectiveness of crop rotation in weed suppression

may be enhanced by crop sequences that create varying patterns of resource competition,

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allelopathy, soil disturbance, and mechanical damage to certain weed species. Many aspects of

crop rotation and intercropping and their effects on weeds are yet to be explored.

6. B. B. Tillage and herbicides as components of IWM:

Tillage prior to crop establishment serves mainly to prepare a weed free seed bed. It

eliminates established and emerged prior to crop seeding and also moves weed seeds near the

soil surface vertically, resulting in weed seed burial. It is suggested that an integrated weed

management strategy involving summer ploughing, thiobencarb application and inter-crop

cultivation is essential for effective weed control in direct-sown, flood-prone, lowland rice, in

order to ensure higher N-use efficiency and crop productivity (Sharma, 1997).

In dry-seeded rice stale seedbed preparation was found better than traditional seedbed

preparation (Sharma et al., 2004). In transplanted rice: (a) frequent cultivations were better than

growing green manure or keeping field undisturbed after wheat harvest, (b) application of

pyrazosulfuron 0.015 kg ha–1

or two HW controlled L. chinensis and produced higher rice grain

yield rice (Aulakh and Mehra, 2006).

6. B. C. Integration of crop competitiveness with herbicides:

Farmers normally prefer high yielding varieties. Using high yielding crop variety

competitive against weeds in combination with other methods of weed control is one of the most

economical approach to attain optimal crop yield. Upland rice cultivars Vandana, Kalinga-III and

RR-151-3 have shown better weed competitive ability and higher yield potential under sub-

optimal weed management condition (ICAR, 2007). Rice cultivar ‘Gautam’ (high yielder) and

cultivar ‘Prabhat’ (better weed minimizer) + butachlor at 1.5 kg PE +2,4-D at 0.5 kg ha–1

POE

recorded highest rice yield with minimum weed dry weight (Singh et al., 2004).

Enhanced dry-seeded rice competitiveness against weeds was observed with 100 kg ha–1

seed rate + oxyfluorfen 0.25 kg ha–1

(3 DAS) + halod (Angiras and Sharma, 1998). The increase in

transplanted rice density from 22 to 44 hills m–2

+ application of pyrazosulfuron 0.015 kg ha–1

was

found to be significantly better in controlling L. chinensis (Aulakh and Mehra, 2006).

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6. B. D. Integration of herbicides with mulching:

Covering or mulching the soil surface can reduce weed problems by preventing weed seed

germination or by suppressing the growth of emerging seedlings. Mulches can be made from a

number of materials: a living plant ground cover, loose particles of organic or inorganic matter

spread over soil, and sheets of artificial or natural materials laid on the soil surface. Pre-

emergence application of pendimethalin at 1.0 kg ha–1

+ farm wastes as mulch (7.5 t ha–1

) + one

hand weeding at 45 days after sowing (DAS) of direct-seeded rice resulted in effective weed

control and higher crop yield (Singh et al., 2001).

6. B. E. Integration of zero tillage with herbicides:

The use of zero tillage would also reduce the costs of seeding. In rice-wheat system, under

zero tillage, the time taken between rice harvest and wheat sowing is considerably shortened and

early sowing of wheat after rice results in increased wheat yield (Vincent and Quirke, 2002).

Herbicide (pendimethalin at 1.0 kg ha–1

) as pre-emergence supplemented with two hand weedings

were needed to reduce weed growth in zero till dry-seeded rice (Singh et al., 2005a). In rained

lowland rice, Zero tillage and conventional tillage were similar in weed control efficacy when

supplemented with butachlor or hand weeding (Moorthy et al., 2002). In irrigated dry-seeded rice:

(a) zero tillage significantly reduced the total population and dry matter of weeds compared with

conventional tillage, but the difference in yield was not significant, (b) Integration of

pendimethalin 1.0 kg ha–1

or pretilachlor 0.75 kg ha–1

with 1 hand-weeding at 30 DAS or sequential

application of pre-emergence herbicides followed by post-emergence application of 2, 4-D (0.5 kg

ha–1

) and fenoxaprop (0.07 kg ha–1

), being on a par with each other, proved quite effective against

weeds (Mishra and Singh, 2008).

If weed seed production was minimized during the growing season, weed seedling

emergence in no-till would decline more across years compared with tilled systems as the surface

weed seed pool in no-till is depleted more rapidly by emergence and mortality. Burial of weed

seeds in soil by tillage favours persistence across time, thus leading to more weed seedlings in

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later years. Farmers can get additional benefits from this pattern of weed seedling emergence in

no-till systems when combined with crop diversity in their rotations.

6. B. F. Integration of hand weeding with herbicides:

Hand weeding is being practiced by farmers in India since they initiated agriculture. It is

effective on annual weeds. Hand weeding is ineffective against perennial weeds due to their

regenerative capability. Raising cost of labor and their non availability lead to the search for

alternative methods such as herbicide use either alone or in combination with hand weeding

(Singh et al., 2001; Rao and Nagamani, 2007; Rao et al., 2007). Several research publications have

proved that integration of herbicides with hand weeding is the most effective and economical

method of weed management (Table: 7).

7. Herbicide resistance and genetically modified rice

Continuous use of some herbicides has led to development of resistant weeds and has

exacerbated weed problems. For example, in rice–wheat cropping system of Punjab and Haryana,

Phalaris minor has developed resistance against isoproturon (Malik and Singh, 1995; Yaduraju and

Ahuja, 1995; Walia, and Brar. 2006). However, among weeds of rice, such resistance against

herbicides was not reported, yet, in India.

Incrasing concern o enviroment, toxicity to animals and persistence of residues in soil and

water lead to efforts to confer crops resistence against broadspectrum herbicides by applying

modern biotechnological techniques. The major direct benefits of introducing Herbicide-resistant

rice (HR-rice) are to: (1) improve control of weeds specifically associated with rice, such as weedy

Oryza species; (2) substitute currently used herbicides with new ones that are more efficient and

that have better environmental profiles; (3) provide new tools for managing weeds that have

already developed resistance to current herbicides and (4) facilitate adoption of resource

conservation technologies by improving weed management options. These benefits must be

weighed against risks beore the adoption o HR-rice in India. Malik et al. (2003) have suggested

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that herbicideresistant rice (HR-rice) would dramatically overcome weed problems in direct-

seeded zero till rice and reduce the need to puddle soils and keep them continuously submerged.

Three major HR systems currently commercialized are based on resistance to amino acid

biosysnthesis inhibiting herbicides viz. imidazolinone (IMI), glyphosate and glufosinate and in rice,

all three HR systems are being developed (Rao et al., 2007). Glufosinate-resistant and glyphosate-

resistant rice cultivars convey resistance to glufosinate and glyphosate, respectively, both of which

are broad-spectrum, nonselective, post-emergence herbicides with no soil or residual activity.

Both glufosinate and glyphosate-resistant rice are transgenic in nature. In contrast to IMI-rice,

development of glufosinate-resistant crops was accomplished through metabolic detoxification of

the herbicide. Information is limited on the developmentn of glyphosate-resistant rice. In India,

HR-rice is yet to be commercialised.

8. Future Research:

The research carried out on IWM in rice in India was mostly herbicide based. However,

majority of the farmers have not been benefited by herbicides in India. Herbicides must be made

economically and ecologically affordable to farmers by innovatively integrating with other

components of IWM. There is significant scope of growth in herbicides, as a component of IWM,

specifically as exports and domestic consumption of food grows. Need to step up coordinated

extension efforts to educate farmers on judicious use of herbicides in India, in integration with

other weed management methods.

Although herbicide-based systems have benefitted the agricultural community in many

ways, the heavy reliance on herbicides creates an environment favorable for weed resistance to

herbicides, weed population shifts, and off-site movement of herbicides. The current challenge for

producers is to manage herbicides and other inputs in a manner that prevents adapted species

from reaching troublesome proportions. Other major areas of future IWM research include:

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(a) On-farmassessment of losses caused by weeds: The yield losses caused by weeds in different

rice and rice based cropping systems in the farmers’ fields at different agro-ecological regions

need to be assessed.

(b) Understanding ecology of weeds associated with rice: Knowledge of intererence thresholds,

biology and growth habits of weeds of rice is essential to shift the crop weed balance in favor of

crop rather than weeds. For farmers to completely benefit from integrated weed management

technologies, mechanistic research must be conducted in weed ecology, genetics, and physiology

to increase basic understanding of the processes that regulate weed–crop interactions, weed

population dynamics, adaptation, and persistence under various management practices. IWM

should have a primary focus on practices that affect propagule production, survival, and the

propagule–seedling transition within the agro-ecosystem.

(c) Interdisciplinary effort: is needed to environmentally and economically viable components of

IWM practices in rice cropping systems. To tackle the complex weed problems, research must

involve, systems analysis, weed population and community analysis, weed traits eco-physiology,

molecular biology and genetics, assessment of pre- and post-control shifts in weed community,

herbicide resistance, issues related to transgenic plants, environmental issues, and potential

benefits of weeds.

(d) On-farm assessment of available IWM options: The IWM options identified by researchers

must be tested in the farmers’ fields to assess their effectiveness and economic viability. Despite

decades of research and extension efforts in popularizing the integrated weed management

(IWM) practices, its importance and effectiveness are not completely understood and hence less

adopted by the farmers. Closer linkage between research and extension is needed in evolving

IWM strategies and popularising effective and economical options to farming community.

(e) Exploiting the potentiality of biocontrol : Trichoderma viride and Gliocladium virens have been

found to control Phalaris minor in wheat and Echinochloa spp. in rice under laboratory conditions

without any adverse affect on the crop (ICAR, 2007). Role of biocontrol in IWM needs to be

exploited.

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(f) Developing knowledge based decision making tools: developing a larger database of weed

ecology and biology characteristics; developing, improving and refining integrated weed

management system simulation models; and determining the utility of these models as a

integrated weed management tool for growers and extension staff, as well as for predicting

further areas where research is required.

The challenge for weed scientists is to develop innovative, effective, economical, and

environmentally safe IWM systems that can be integrated into current and future cropping

systems to bring a more diverse and integrated approach to weed management in rice.

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9. References:

Anbhazhagan, R. and Kathiresan, R. M. 2008. Weed management in integrated rice+fish+poultry

farming system. Green Farming. 2, 50-52.

Angiras, N.N. and V. Sharma. 1998. Integrated weed management studies in direct seeded upland

rice (Oryza sativa). Indian J. Weed Sci. 30, 32-35.

Arokiaraj, A. Chandrasekaran, B. Chinnaswami. and K. N. Sankaran, S. 1989. Effect of critical

period of crop weed competition in transplanted rice. Oryza. 26, 201-203.

Arya, M.P.S., Singha, R...V. and Singh, G. 1991. Crop Weed Competition Studies in Rainfed Rice

With Special Reference to Oxalis latifolia. Indian J. Weed Sci. 23, 40-45.

Aulakh, C.S. and S. P. Mehra. 2006. Integrated management of red sprangletop [Leptochloa

chinensis (L.) Nees] in transplanted rice. Indian J. Weed Sci. 38, 225-229.

Balasubramanian, R. and Veerabadran, V. 1998. Herbicidal weed management in lowland rice

(Oryza sativa) nursery. Indian J. Agronomy. 43, 437-440.

Bhat, R. and V. L. Chopra. 2006. Choice of technology for herbicide-resistant transgenic crops in

India: Examination of issues. Current Sci. 91, 435-438.

Brar,L. S.,Kolar, J. S. and L.S. Brar. 1995. Critical period of competition between Caesulia axillaris

Roxb. and transplanted rice. Indian J. Weed Sci. 27, 154-157.

Chitale, S., Pandey, N. and Urkurkar, J. S. 2007. Effect of planting method, tillage and weed

management on productivity and physico-chemical properties of rice (Oryza sativa)-wheat

(Triticum aestivum) cropping system. Indian J. Agronomy. 52, 283-288.

Dhammu, H. S. and Sandhu, K. S. 2002. Critical period of Cyperus iria L. competition in

transplanted rice. Proc. 13th Australian Weeds Conference: weeds "threats now and

forever?", Sheraton Perth Hotel, Perth, Western Australia, 8-13 September 2002: Pp. 79-

82.

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Gnanavel, I. and Kathiresan, R. M. 2002. Sustainable weed management in rice-rice cropping

system. Indian J. Weed Sci 34, 192-196.

Gogoi, A.K., Rajkhowa, D.J. and R. Kandali. 2001. Integrated weed control in rainy season rice

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Gopal Naidu, N. and Bhan, V.M.. 1980. Effect of Different Groups of Weeds and Periods of Weed

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Pp. 109-129.

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Table: 1. Estimated yield losses caused by weeds in different methods of rice establishment in

India.

Method of rice

establishment

Weeds % reduction in yield due to weeds Reference

TPR Season long

competition

12 to 69.5% Rammohan et

al., 1999*;

Kathirvelan, and

Vaiyapuri,

2003*; Singh et

al., 2011*

Wet-seeded rice Season long

competition

85 Singh et al.,

2011*

Upland direct-

seeded rice

Season long

competition

93.6% Ladu, and Singh,

2006*

Dry-seeded rice-

zero tillage

Season long

competition

98 Singh et al.,

2011*

Dry-seeded rice pre-, post-flooding

periods

and complete crop

growth period

17.4 to 25.8; 10.03 to 48.3 and

34.4 to 72.6%

Moorthy and

Saha, 2001*

Upland rice Uncontrolled weeds 97.2% Singh et al.,

1988*

Rice-wheat In farmers fields 13.1 to 22.4 Singh et al.,

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cropping system 2005b*

Table: 2. Most reported weeds in different methods of rice establishment in India*.

Weed Name TPR WSR DSR

Echinochloa colona 1 2 1

Echinochloa crusgalli 2 3 6

Cyperus iria 3 1 3

Cyperus difformis 4 4 9

Fimbristylis miliacea 5 8 11

Eclipta alba 6 5 7

Cyperus rotundus 7 8 2

Ammannia baccifera 8 7 +

Ludwigia parviflora 9 6 +

Monochoria vaginalis 10 12 +

Cynodon dactylon 11 15 5

Commelina benghalensis 11 11 4

Marselia quadrifolia 12 10 +

Spaenoclea zeylanica 13 18 -

Paspalum distichum 14 20 +

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Panicum repens 15 16 +

Caesulia axillaris 15 + +

Leptochloa chinensis 16 17 -

Ischaemum rugosum 17 + 13

Digitaria sanguinalis 18 + 8

Phyllanthus niruri 19 + 6

Leersia hexandra 20 + -

Caesulia axillaris + 12 +

Fimbristylis dichotama + 19 -

Eluesine indica + + 10

Trianthema portulacastrum + + 12

Oriza sativa + + 20

Ageratum conyzoides + + 9

Cleome viscosa + + 13

Digera arvens + + 14

Dactyloctenium aegyptium + + 15

Celosia argentia + + 16

Aeschynomene indica + + 17

Setaria glauca + + 18

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Panicum dichotomiolia + + 19

Euphorbia heterophylla + + 20

TPR = Transplanted rice., WSR = Wet-seeded rice., DSR = Dry-seeded rice

1 = Most reported weed; 20= Less reported; + reported

* = Based on a survey of several published research papers in various journals

Table: 3. Critical period of crop weed competition (CPCWC) for rice under different methods of

rice establishment in India.

Method o rice establishment CPCWC* Reference

Transplanted rice (TPR) first 20 to 45 DAT Arokiaraj et al., 1989*;

Mukherjee et al., 2008*

TPR (between Caesulia axillaris

and TPR)

The initial period of 40–70 DAT Brar et al., 1995*

TPR between 4-6 weeks after

transplanting

Shetty and Gill, 1974*

TPR - Wrinkle Grass

(Ischaenllim rugosum Salisb.)

Between 50 and 70 DAT Singh et al., 1991*

Wet-seeded rice (WSR) 15 to 60 DAS Mukherjee et al., 2008*

Upland rice-direct-seeded rice first 30 DAS Tewari and Singh, 1991*; Ladu

and Singh, 2006*

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Upland bunded rice weed-free situation of 60 days

in monsoon and 70 days in

summer was found essential.

Mohamed Ali and Sankaran,

1984*

Drilled rice upto 45 days after sowing Gopal Naidu and Bhan, 1980*

Dry-seeded rice and Oxalis

latifolia

Upto 90 DAS Arya et al., 1991

* DAS = Days after seeding; DAT = Days after transplanting.

Table: 4. Herbicides reported to be effective in transplanted rice in India*

Herbicide Rate (kg ha–1

) Time of Application - Days

After Transplanting (DAT)

Acetachlor 0.10 to 0.150 3 DAT

Acetachlor+bensulfuron-methyl 0.250 5 DAT

Anilofos 0.4 3 -4 DAT

Anilofos fb HW 0.4 fb 1 HW 7 DAT

Anilfos+chlorimuron 0.300+0.008 3 DAT

Anilofos + [Chlorimuron ethyl +

metsulfuron mthyl ] (ready mix)

0.280 3 DAT

Anilofos+2,4-D 0.3 to 0.4 fb 0.5 Pre fb Post

Anilofos+2,4-DEE 0.875 5 DAT

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Anilofos+ethoxysulfuron 0.312 to 0.4 +0.012 to

0.015

10 DAT

Anilofos+ethoxysulfuron (ready

mix)

0.390 to 0.780 8 DAT

Anilofos+triclopyr 0.375+0.521 3 to 9 DAT

bentazon 1.5 10 DAT

Bentazone +2,4-D EE 1+0.5 6 DAT

Bensulfuron-methyl 50 and 60 g/ha 3 DAT

Bensulfuron-methyl 0.05 23 DAT

Bensulfuron-methyl+butachlor 0.050+0.938 5 DAT

Butachlor 1.5 to 2 3 to 5 DAT

Butachlor + [Chlorimuron ethyl +

metsulfuron mthyl]

1.0 to 1.25 +0.004 2 to 5 fb 20 to 25 DAT

Butachlor fb 2,4-D 0.5 to 1.5 fb 0.4 to 0.5 4 fb 25 DAT

Butachlor+ ethoxysulfuron 1.5+0.015 3 DAT

Butachlor fb propanil 1 to 1.5 fb 1 to 2 4 to 7 fb 21 to 30 DAT

Butachlor fb 1 HW 1.25 to 1.50 fb 1 HW 3 DAT fb 25 to 40 DAT

Cinmethalin 0.075 7 DAT

Cinosulfurom 0.010 10 DAT

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2,4-D 0.6 20-25 DAT

Clomazone+2,4-D EE 0.175+0.270 in Kharif

0.2+0.180 in Boro

3 DAT

[Chlorimuron ethyl +

metsulfuron mthyl ] +2,4-D EE

0.015+0.5 8 DAT

Clomazone+2,4D-EE (ready mix) 1 to 1.5 pproduct 3 DAT

Cyhalofop-butyl 0.18 7-8 DAT

Dicamba+2,4-D EE 0.5+0.8 21 DAT

Dinitramin 2 1 DBT

Fenoxaprop-p-ethyl 0.056 10 to 20 DAT

Fenoxaprop-

ethyl+ethoxysulfuron

0.060+0.015 15 DAT

Fentazamide 0.103-0.120 3-5DAT

Flufenacet 0.120 7 or 10 DAT

Fluroxypyr 0.4 10 DAT

Glyphosate (Zero tillage) fb

butachlor

1.25 fb 1.25 Before transplanting fb 7

DAT

Metsulfuron-methyl 0.010 20-25 DAT

Molinate granules 2 1 DBT

Naproanilide 1.5 10 DAT

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Oxadiargyl 0.07 to 0.1 3 to 5 DAT

Oxadiargyl + 1 HW 0.075+ 1 HW 4 DAT+40 DAT

Oxadiazon 0.75 to 1 2 to 4 DAT

Oxyfluorfen fb *Halod 0.25 fb One 3 DAT fb 20 DAT

Pendimethalin 1 to 1.5 3 to 4 DAT

Penoxsulam 0.0225 8 to 12 DAT

Piperofos 0.75 3 DAT

Piperophos/dimethametryn 1 6 DAT

Pyrazosulfuron-ethyl 0.020 3 DAT

Pretilachlor 0.4 to 1 3 DAT

Pretilachlor fb triasulfuron 0.009+0.045 3-5 DAT fb 12-15 DAT

Pretilachlor+2,4-D 0.3+0.3 3 DAT

Propanil 2 21 DAT

Pyrazosulfuron ethyl 0.015 to 0.25 3 to 10 DAT

Pyrazosulfuron methyl +

butachlor

0.025 + 0.939 3 DAT

Quinclorac 0.187 to 0.375 3 DAT

Thiobencarb 1.5 to 2.5 6 DAT

Thiobencarb +2,4-D 1 to 1.5 +0.5 5 to 6 DAT

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Triazolopyramidine sulfonamide 0.015 to 0.025 15 DAT

Tridiphane 0.48 10 DAT

Trisulfuron+pretilachlor 0.009+0.5 6 DAT

fb = followed by; * Summarised based on several published papers.

Table: 5. Herbicides reported to be effective in wet-seeded rice in India*


) Time of Application (DAS)

Anilofos 0.3 to 0.4 8 DAS

Anilofos 0.3 to 0.4 6 Days Before Seeding

Anilofos + ethoxysulfuron 0.312+0.012 Preemergence

Anilofos+2,4-D 0.30 + 0.40 10 DAS

Anilofos+ethoxysulfuron 0.312+0.012 10 DAS

Anilophos + 2,4-D EE fb 1 HW 0.30 + 0.40 fb 1 HW 6 DAS fb 25 DAS

Butachlor 1.0 to 1.5 6-8 DAS

Butachlor + pretilachlor 1.0 + 0.5 4-6 DAS

Butachlor + safener 1.0 to 1.5 1 to 5 DAS

Butachlor fb almix 1 fb 0.004 8 DAS fb 25 DAS

Butachlor+2,4-D 1.5+0.5 7 DAS

Butachlor+propanil 1.120+1.120 10-12 DAS

Butanil 1 8 DAS

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Chlorimuron+metsulfuron 4 g 15 to 20 DAS

Cyhalofop butyl 0.080 to 0.090 10 to 15 or 25 DAS

Cyhalofop-butyl fb butachlor+2,4-

DEE

0.075 fb 1.0+1.0

20 DAS fb 30 DAS

Cyhalofop-butyl fb2,4-DEE 0.090 fb. 1.0 20 DAS fb 30 DAS

Ethoxysulfuron 0.015 to 0.03 15 to 18 DAS

Fenoxaprop-ethyl +

ethoxysulfuron

0.060 + 0.015

15 DAS

Fenoxaprop-p- ethyl 0.015 20-35 DAS

glyphosate+pretilachlor+safener+2

HW

0.5 fb 0.4 fb 2 HW 20 DBS fb 3 DAS fb 25 and 45

DAS

Oxadiargyl 0.10 4 DAS

Oxyfluorfen 0.125 to 0.15 7 DAS

Pendimethalin 1 to 1.25 6 to 7 DAS

Pretilachlor 0.4 to 0.80 4 to 8 DAS

Pretilachlor + safener 0.4 3 to 8 DAS

Pyrazosulfuron 0.015 20-25 DAS

Thiobancarb 1.0 to 1.5 6 to 7 DAS

fb = Followed by; DAS = Days after seeding; * Summarised based on several published papers.

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Table: 6. Herbicides reported to be effective in dry-seeded rice in India*


)

Time of Application -

Days after seeding

(DAS)

Anilofos 0.4 7 DAS

Anilofos + 2,4-D 0.4+0.6 7 fb 25DAS

Anilophos fb Cyhalofop butyl 0.4 fb 0.09 3 DAS fb 35 DAS

Butachlor + safener 1.5 4 DAS

Butachlor fb 2,4-D 1.25 fb 0.5 PRE fb POST

Cyhalofop butyl 0.120 15 DAS

Dithiopyr 0.180 3 DAS

Fenoxaprop-p- ethyl 0.07 POE

Fluchloralin 1.5 PRE

Oxadiazon 0.5 PRE

Oxadiazon fb oxadiazon 0.4 b 0.4 PRE fb 45 DAS

Oxyflourfen 0.25 3 DAS

Pendimethalin 1.5 3 DAS

Pendimethalin fb 2,4-D 1 fb 0.6 PRE fb POST

Pretilachlor 1 2 DAS

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Pretilachlor+ safener 0.3 4 DAS

Pyrazosulfuron 0.015 to 0.030 6 DAS

Pyrazosulfuron ethyl + molinate 15 to 30 + 1.5 6 DAS b 15 DAS

Quinclorac 0.375 PRE

Thiobencarb fb 2,4-D 1 fb 0.5 PRE fb 20 DAS

Thiobencarb fb Cyhalofop butyl 1 fb 0.09 4 fb 35 DAS

PRE=Pre emergence application; POST = Post emergence; * Summarised based on several

published papers.

Table: 7. Most economical IWM methods for managing weeds in rice grown under

different methods of rice establishment in India.

Method of

rice

establishmen

t

IWM*

Reference

TPR (i) Application of butachlor 1.0 kg ha–1

,

anilofos 0.4 kg ha–1

along with closer planting

(ii) anilophos 0.6 kg ha–1

7 DAT + HW - 27 DAT

(i) Gogoi et al.,

2001

(ii) Singh and

Kumar, 1999

TPR rice+fish+poultry farming system+ oxyfluorfen at 0.25 Anbhazhagan

and Kathiresan,

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kg ha–1

2008

DSR butachlor @ 1.25 kg ha–1

as pre-plant surface

application+brown manuring+2,4-D @ 0.50 kg ha–1

at

40 DAS.

Maity and

Mukherjee, 2009

WSR the PSA of glyphosate at 1.6 kg ha–1

, PEA of butachlor

at 1.25 kg ha–1

fb one or 2 HW (at 35 and 55 DAS )

Sathyamoorthy

et al., 2004

WSR pre-sowing weed control (by conjunctive use of burn

down herbicide paraquat at 0.12 kg or tank mix of

glyphosate and 2,4-D Na salt at 0.20 kg + 0.20 kg a.i.

ha–1

, followed by subsequent weed submergence to

40 cm depth for 10 days) + sowing on clean seedbed

with preemergence herbicide (pretilachlor + safener

at 0.4 kg ha–1

) + post-emergence 2,4-D Na salt at 0.80

kg a.i. ha–1

Latif and

Wahab, 2007

DSR Mulching (pine needles (5 t ha–1

) or farm wastes (7.5 t

ha–1

)) + PE of pendimethalin at 1.0 kg ha–1

supplemented with one hand weeding at 45 days

after sowing or post-emergence application of 2,4-D

at 0.6 kg ha–1

Singh et al., 2001

DSR Stale seedbed preparation+pendimethalin+one

handweeding

Sharma et al.,

2004

DSR Stale seedbed preparation+criss-cross sowing

(CCS)+one handweeding

Sharma et al.,

2004

Rice - dry-Butachlor at 1.0 kg ha–1

f.b. one hand Singh and Singh,

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seeded rice weeding at 30 DAS by local tool 'Kutla' 2001

TPR/Wheat

cropping

system

Transplanting of rice after Sesbania aculeata (green

manure, GM) incorporation followed by conventional

tillage + Post-emergence application of sulfosulfuron

at 25 g ha–1

in wheat

Chitale et al.,

2007

* DAS = Days after seeding; DAT = Days after transplanting; DAP= Days after planting; HW=Hand

weeding; f.b. = followed by; PE = Pre emergence. DSR = Dry-seeded rice; TPR=Transplanted rice;

WSR= Wet-seeded rice.

integrated weed management in rice in india -...

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