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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