P.K Singh, Pr. Scientist (Agril. Extension) ICAR-Directorate of Weed Research, Jabalpur (M.P.)

Weed Management in Improving

Agricultural Production

TO PROVIDE SCIENTIFIC RESEARCH AND

TECHNOLOGY IN WEED MANAGEMENT FOR

MAXIMIZING THE ECONOMIC,

ENVIRONMENTAL AND SOCIAL BENEFITS FOR

THE PEOPLE OF INDIA

NET WORKING AND COLLABORATION

• There are 23 DWR centers all over India conducting research in

network mode with HQ at Jabalpur.

• In addition, 9 volunteer centres are involved in this network.

Weeds ?

Weed is a plant that is objectionable or interferes with the activities or welfare of man

Undesirable Plants or Unwanted plants

Aquatic ecosystems

Public amenity areas

Grasslands

Non-cropped areas

Forestry

Agriculture

• Affect fisheries/aquaculture • Interfere with navigation • Reduce aesthetic and recreational value of water • Result in excessive loss of water

• Affect the aesthetic look • Some cause allergy &

health problems • Invade open areas

• Reduce grazing area • Some are poisonous to

livestock • Affect milk quality • Alien weeds endanger

biodiversity

• Interfere with maintenance and inspection of installations • They mar the aesthetic look • They are a potential fire hazard

• Are a fire hazard • Affect productivity • Alien weeds

endanger biodiversity

• Interfere with management

• Reduce crop yields • Impair crop

quality • Act as alternate

hosts of disease, pest and nematodes

Our Concern

WEEDS

Weed Characteristics

Reproduce at a young age

Dual modes of reproduction

Very high seed production capacity

Seed dormancy

More than one generation per year

Special seed dispersal mechanisms

Capable of growing under adverse conditions

Posses extensive root system with large food reserves

Adaptations to repel grazing by animals

Have great competitive ability

Weeds resist control including resistance to herbicides

They exhibit allelopathy

SEED PRODUCTION POTENTIAL OF WEED

Sl no. Weed species Average no. of seeds

per plant

1 Amaranthus spp 1,96,000

2 Bidens pilosa 12,000

3 Brassica nigra 58,000

4 Chenopodium album 72,000

5 Commelina sp. 2,450

6 Cuscuta sp 16,000

7 Cynodon dactylon 170

8 Cyperus rotundus 40

9 C. esculentus 820

10 Eleusine indica 41,200

Why the weed problems increased in modern agriculture?

Globalization of agriculture

Large scale adoption of dwarf HYVs and hybrids

Increased use of irrigation & fertilizers

Altered agronomy of crops

Monocropping and multiple cropping

Reduced tillage

Projected Demand and Gap of Foodgrains in 2050

• The demand can be met only by vertical increase in the

production as horizontal increase i.e., bringing more area under

cropping has little possibility.

• The vertical increase can be achieved with better genotypes and

providing farmer-friendly technologies for input and pest

management.

• Proper weed management is of utmost importance as these

account for the maximum losses among various pests.

Then, What is the solution?

Source : ICAR, Vision 2050

Total losses caused by pests

Diseases 22%

Insects29%

Weeds37%

Others12%

Out of the losses due to various pests, weeds account for nearly one-third

Negative Impact of Weeds

Weeds reduce agricultural productivity

Crop % Yield

Reduction

Soybean 40 - 60

Groundnut 20 - 50

Rapeseed & mustard 15 - 30

Linseed 30 - 40

Sessame 50-55

Sun flower 30-35

Safflower 30-35

Castor 15-25

Niger 30-33

Rice DSR 50-90

Rice Transplanted 15-20

Wheat 25-40

Crops Nutrient removal (kg/ha)

N P2O5 K2O

Soybean 26 - 65 3 - 11 43 - 102

Groundnut 15 - 39 5 - 9 21 - 24

Rapeseed & mustard 20 – 22 2 – 3 10 – 12

Linseed 30 - 32 2 -3 11 - 13

Rice (DSR) 20 - 37 5 - 14 17- 48

Wheat 20 - 90 2-13 28 - 54

Sugarcane 35 -162 22-44 135 - 242

Weeds deplete nutrients and soil moisture

Weeds increase cost of production and processing

Weeds reduce quality of farm produce

Argemone maxicana in mustard

Weedy rice in paddy field

Weeds as host of insect-pests and pathogen

Begomovirus infection in weeds which is ultimately transmitted to crop plants by white flies

Weeds harbour pests, diseases and nematodes

Vicia sativa provides shelter to Helicoverpa armigera

Ageratum and Lantana provide shelter to white fly

Solanum nigrum hosts Leuicinodes orbonalis

Chenopodium album host for aphids.

Portulaca oleracea is a host for Albugo candida causing white

rust in cruciferous crops.

Cynodon dactylon, Echinochloa crus-galli, Digitaria sp.

Cassia occidentalis serve as host for root lesion nematode

Pratylenchus sp.

Weeds endanger biodiversity

Severe Infestation of Mikania micrantha in plantations of Kerala, Orissa & NE

Mimosa rubicaulis has replaced the native grasses, the main food source of much-endangered single horned Rhinoceros, in the world famous Kaziranga National Park of Assam.

Weeds encroach public amenity areas, reduce land

value and restrict human activity

Weeds affect fodder supply to livestock by encroaching grasslands and pastures

Cows searching for fodder in weed infested grasslands

Parthenium hysterophorus

Ageratum sp.

Skin allergy caused by Parthenium hysterophorus

Weeds affect health of humans and livestock

Skin allergy developed on animals grazing Parthenium

at Mojo, Ethiopia

Critical period of crop-weed competition and losses

Crops Critical period Yield reduction (%)

Rice (direct seeded upland) 15-45 40-60

Rice (direct seeded puddled) 15-45 30-35

Rice (transplanted) 30-45 15-20

Cotton 15-60 40-50

Onion 30-70 40-50

Garlic 30-60 50-60

Cabbage 30-45 35-60

Cauliflower 25-30 50-70

Okra 15-30 40-50

Tomato 30-45 40-70

Chilli 30-45 60-70

Carrot 15-20 70-80

Brinjal 20-60 70-80

Potato 20-40 10-80

Vegetable peas 30-45 25-30

Critical period of crop-weed competition in pulses

Crops Critical period Yield reduction (%)

Pigeonpea 15-60 24-40

Greengram 15-30 30-50

Black gram 15-30 30-50

Chickpea 30-60 15-35

Lentil 30-60 20-30

Pea 30-45 20-30

Critical period of crop-weed competition in oilseeds crops

Crop

Critical period (days)

Reduction in yield (%)

Castor

30-60

30-35

Groundnut

40-60

40-50

Linseed

20-45

30-40

Mustard

15-40

15-30

Safflower

15-45

35-60

Sesame

15-45

15-40

Soybean

20-45

40-60

Sunflower

15-30

30-50

Methods of Weed Control

Utilization

Bio-technological

Biological

Chemical Mechanical

Cultural

Preventive

Different Approaches of Weed Management

Preventive methods

Use weed-free crop seed

Use well decomposed manure

Clean machinery/implements

Inspect nursery stock/transplants

Remove weeds near irrigation ditches, fence rows, rights-of-way etc.

Prevent reproduction of weeds

Use screens to filter irrigation water

Restrict livestock movement

Non-chemical Approaches

• Improved weeding tools will attain more significance resulting in labour saving (about 20-40 man days per hectare), better and timely weed control.

Mechanical Weed Control

Mechanical weed control

Cultural methods of weed control

Soil Solarization

Tillage

• Timely inter-cultivation may not be practical

• The operation needs to be repeated

• Does not control weeds in crop rows/ intra-row

• May damage crop roots

Mechanical Method-Limitations

Cultural Methods

Crop rotation

Stale seed bed

Optimum plant population

Selection of crop cultivars

Optimum planting date

Optimum planting geometry

Selective stimulation of crop

Use of ‘live mulches’ or smother crops

Intercropping

Stale seed bed technique

Intercropping

Identify suitable cover crops, intercrops and green manure crops

Intercropping suppresses weeds better than sole

cropping and thus provides an opportunity to utilize

crops themselves as tools of weed management

Intercropping of cowpea in maize

Profitable Intercropping Systems

Castor + groundnut (1:3/5) Castor + mungbean (1:2)

Castor + clusterbean (1:2) Castor + pigeonpea (1:1)

• Reduced cost of cultivation,

• Better management of problem weeds like Phalaris

minor in rice-wheat system.

Resource conservation technologies (RCTs)

RCTs like Zero tillage, bed planting etc., will lead to:

Planting of Wheat on FIRBS Sowing of wheat under Zero tillage

• Minimizing soil disturbance – no tillage and minimum

traffic for agricultural operations

• Maximizing soil cover – leave and manage crop

residues on soil surface

• Stimulating biological activity through suitable crop

rotations including use of cover crops, green

manures

Conservation agriculture – 3 pillars

• Conservation agriculture (CA) is a holistic approach

towards increased productivity and improved soil health.

It does have several advantages over conventional tillage

(CT) based agriculture in terms of soil health parameters.

• CA is a machine-, herbicide– and management-driven

agriculture for its successful adoption.

• Integrated weed management involving chemical and

non-chemical methods (residue, cover crops, varieties

etc.) is essential for success of CA systems in the long-

run.

Beneficial effects of crop residue retention on soil

surface

• Reduction in soil erosion due to wind and water

• Soil moisture conservation due to reduction of

evaporation

• Temperature moderation in soil and crop

canopy

• Reduction in weed emergence

• Addition of soil organic matter and nutrients

• Better soil infiltration, porosity and biological

health

• Build-up of organic carbon and arrest decline in factor

productivity

• Saving top fertilized soil from erosion

• Enhance nutrient-use efficiency by creating favourable

environment for microflora and fauna

• Reduce water requirement of crops by checking

evaporation

• Check non-point pollution of nearby water bodies

• Help in sequestering GHG in the soil

• Improve biological activity and diversity

Overall – reduce costs, efficient input use, stable yields,

better use of natural resources

Benefits of Conservation Agriculture

Two sides of no-till conservation agriculture

• Reduces soil erosion

• Conserves water

• Improves soil health

• Reduces fuel and labour costs

• Reduces sediment and fertilizer pollution of lakes and streams

• Sequesters carbon

• Mindset: Transition from conventional farming to no-till farming is difficult

• Necessary equipment is costly

• Heavier reliance on herbicides

• Requires greater precision – levelled field, proper soil moisture, sowing depth, fertilizer placement, weed management

• May initially require more N fertilizer

• Prevalence of weeds, disease and other pests may shift in unexpected ways

Benefits Bottlenecks

34

• Happy seeder / double disc drill for zero-till wheat sowing under residue conditions

• It helps in managing weeds through retention of crop residues as mulch , besides providing efficient seeding and fertlizer placement.

Conservation agriculture and weed management

Zero-till wheat sowing after rice harvest using

Happy Seeder

Zero-till sown winter season crops after rice harvest

Conventional tillage Zero-tillage

Zero-till sown rabi crops of maize, mustard and chickpea

On-farm research trials on zero-till wheat

On-farm demonstrations in ZT greengram

• It is possible to achieve the same or even higher

yield with zero-tillage as with conventional tillage.

• Retention of crop residues on soil surface is

essential for success of zero-tillage in the long-run.

• Zero-tillage along with residue has beneficial effects

on soil moisture, temperature moderation and weed

control.

• Zero-till systems cause shift in weed flora, and may

result in emergence of perennial weeds.

• Restricting tillage also reduces weed control options

and increases reliance on herbicides.

• Altering tillage practices change weed seed depth in

the soil, which play a role in weed species shifts and

affect the efficacy of control practices .

Conclusions

Crop rotation

Differentiation of crops grown over time on the same

field is a well-known primary means of preventive

weed control.

Different crops obviously bring about different

cultural practices, which act as a factor in disrupting

the growing cycle of weeds and, as such, preventing

selection of the flora towards increased abundance

of problem species.

Mulching

Several types of mulches e.g. plastic films, dry straw and

crop residues are used

Besides weed control they moderate soil temperature and

retain soil moisture

Mulches smother weed growth by preventing light from

falling on the photosynthetic parts of the weeds, which

eventually inhibits their growth.

Soil-Solarization Method of heating the

surface by using plastic sheets placed on moist soil to trap the soil radiation

Soil surface temperature is raised by 8-100C as compared to non solarized soils

A duration of 4-6 weeks is sufficient

Winter weeds are generally more susceptible

Soil solarisation kills several soil borne fungi, bacteria

and nematodes and alters physical and chemical

properties of the soil.

Non-solarized soybean

Solarized soybean

Solarized sesamum Non-solarized sesamum

Limitations

Cost of treatments Disposal of plastic film is the greatest problem. Removal and reuse of the film is not feasible in large-scale

operations that utilize machines to lay plastic films. Lack of persistence of nematode control and poor control of

some weeds In some climates cloudiness and rainfall during the hottest part

of the year can limit effectiveness. Difficult to retain the films intact during period of heavy winds.

Chemical Approaches of Weed Management

HERBICIDES - Benefits Save labour

Permit early planting

Control difficult weeds (perennial/parasitic)

Efficient and economical control of weeds

Reduce number of tillage operations

Mechanical damage to crop is prevented

Offers gender equality

Enthuse youth to take up farming

Herbicides Dose

(g ai/ha)

Time of

application

Remarks

Chlorimuron+met

sulfuron (Almix)

4 15-20

DAS/DAT

Controls annual broad-leaved weeds

and sedges

2,-4 DEE 500-750 20-25

DAS/DAT

Controls annual broad-leaved weeds

and sedges

Pendimethalin 1000-1250 0-3 DAS Controls annual grasses and some

broad-leaved weeds. Ensure sufficient

moisture at the time of application.

Pretilachlor +

safener

750 3-7

DAS/DAT

Controls annual grasses and some

broad-leaved weeds

Pyrazosulfuron 25 15-20

DAS/DAT

Controls broad-leaved weeds and

sedges

Fenoxaprop-p-

ethyl

65-70 25-30

DAS/DAT

Controls annual grasses especially

Echinochloa spp.

Bispyribac-sodium 25 20-25 DAS Controls annual grasses and broad-

leaved weeds

Bensulfuron +

Pretilachlor

(Londex Power)

660 0-3 DAT Controls annual grasses and broad-

leaved weeds and sedges

Promising herbicides for weed control in rice

Herbicides Dose

(g ai/ha)

Time of

application

Remarks

2,4-D 500-750 25-30 DAS Broadleaved weeds

Sulfosulfuron 25 25-30 DAS Both broad-leaved weeds

and grasses

Clodinofop-propagyl 60 25-30 DAS Grasses

Metsulfuron 04 25-30 DAS Broadleaved weeds

Mesosulfuron+Iodo

sulfuron (Atlantis)

12+2.4 30-35 DAS Both broad-leaved weeds

and grasses

Clodinafop+

metsulfuron (Vesta)

60+4 25-30 DAS Both broad-leaved weeds

and grasses

Sulfosulfuron +

metsulfuron (Total)

32 25-30 DAS Both broad-leaved weeds

and grasses

Promising herbicides for weed control in wheat

Herbicides Dose

(g ai/ha)

Time of

application

Remarks

2,4-D 500-750 30 DAS Broadleaved weeds

Atrazine 750-100 0-3 DAS Both broad-leaved weeds and

grasses

Pendimethalin 500-750 0-3 DAS Grasses

Tembotrione

(Laudis 42 SC)

120 15-20 DAS Mostly grasses and some

broadleaved-weeds

Topramezone

(Tynzer mix)

25

20-30 DAS Mostly grasses and some

broadleaved-weeds

Promising herbicides for weed control in Maize

Crops Herbicides Dose (g ha-1) Time of application

Pigeonpea,

Mungbean, Urdbean and

Cowpea

Pendimethalin 750-1000 PE

Metribuzin 250-500 PE

Oxyfluorfen 150-250 PE

Imazethapyr 75-100 PO

Pea , chickpea

and lentil Oxyfluorfen 150-250 PE

Pendimethalin 750-1000 PE

Metribuzin

(Not in chickpea

and lentil)

250-500 PE

French bean Oxyfluorfen 0.20 PE

Pendimethalin 1.0 PE

Promising herbicides for weed control in Pulses

Promising herbicides for weed control in oilseed crops

Crops Herbicide Dose (Kg/ha) Time of

application

Weeds controlled

Soybean Chlorimuron ethyl 0.008-0.012 Post-em Broad leaved weeds

Imazethapyr 0.075-0.10 Post-em Broad leaved weeds and

annual grasses

Quizalofop ethyl 0.06-0.07 Post-em Grassy weeds and some

BLWs

Fenoxaprop +

Chlorimuron

0.08+.008 Post-em Broadleaved and Grassy

Imazethapyr +

Imazamox

0.07 Post-em Broadleaved and Grassy

Groundnut Oxadiazon 0.5-0.75 Pre-em Broadleaved, Grassy &

Sedges

Pendimethalin 0.75-1.0 Pre-em Broadleaved and Grassy

Quizalofop 0.06-0.07 Post-em Grasses

Rapeseed-

Mustard

Fluchloralin 1.0 PPI Broadleaved and Grassy

Isoproturon 1.0 Pre-em Grasses and broadleaved

Oxadizon 0.75 Pre-em BLW, Grassy & Sedges

Pendimethalin 1.0 Pre-em Broadleaved and Grassy

Sunflower Fluchloralin/

Trifluralin

1.0 PPI Broadleaved and Grassy

Oxadiazon 0.50-0.75 Pre-em BLW, Grassy & Sedges

Pendimethalin 0.75-1.0 Pre-em Broadleaved and Grassy

• Weeds in non-cropped areas can be managed through exotic insect-pests as successfully proved in the management of Parthenium by the Mexican beetle (Zygrogramma bicolorata), water hyacinth by Neochetina spp. and Salvinia by Cyrtobagous salviniae.

Biological control of weeds

Biological control of weeds is the deliberate use of natural enemies, primarily insects or fungi, to suppress growth or reduce the population of weed species.

Successful control of Parthenium in and around Jabalpur

A site before the release of beetle

Same site after the release of beetle

Biocontrol of water hyacinth with Neochetina spp

Key elements of transformation

Conventional agriculture Conservation agriculture

Cultivating land, using science and technology to dominate nature

Least interference with natural processes

Excessive mechanical tillage and soil erosion

No till / drastically reduced tillage (Biological tillage)

Residue burning or incorporation Surface retention of residues

Use of ex-situ FYM/composts Use of in-situ organics/ composts

Green manuring (incorporated) Brown manuring (surface drying)

Residue burning in situ is widespread in north-western India

Conventional agriculture Conservation agriculture

Free-wheeling of farm machinery

Controlled traffic

Crop-based management Cropping system-based management

Single or sole crops Intercropping / relay cropping

Uneven field levels Precision laser land leveling

Interventionist paradigm Agro-ecological paradigm

Key elements of transformation