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PRESENTED BY MARIA AYOUB
ROLL# 301
Assigned byDr.Muhammad Iqbal
Weed management in Rice Crop
What is a weed?
Any unwanted plant in the field is known as weed.
Any plant that compete with our main crop for space, sunlight, nutrient and water.
Principles of weed management
(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.
Seed banks must be managed at low densities to reduce the potential for a buildup of intractably high weed populations.
Weed Management in rice
I. Effect of weeds on riceII. Types of weeds found in riceIII. Critical period of crop weed competitionIV. Methods of weed control
I. Effect of weeds on rice
1. Reduce the yield and quality of rice by competing for nutrients, water and sunlight
Upland direct seeded rice : 35-45% reduction in
yield Direct seeded on puddle land : 20-25% reduction in
yield
Transplanted rice : 10-15% reduction in yield
2. Weeds intensify the pest and disease problem by serving as alternate host
3. Reduce the efficiency of harvesting
4. Reduce the land value
5. Problems of water contamination
Effect of weeds on shoot growth of rice
The number of tillers per plant was markedly reduced in rice varieties due to weed’s competition at all the three growth stages; 90, 120 and 150 days after sowing (DAS).
However, the effect was generally more pronounced at the later two growth stages as compared to the early one (90 DAS).
Effect of weeds on yield of rice
The results of various parameters of yield such as number of panicle, ear dry weight and grain yield reduced.
Effect of weeds on root growth of rice: Reduce the dry weight of root
II. Types of weeds
A. Low land rice
1. Annual grasses
Echinocloa crusgalliEnglish name:
Barnyard grass
Local name: Sawank
Family: Poacea
Echinocloa colonum L. English name: Wild rice Local name: chotta sawank Family: Poacea
2.Annual broad leaf weeds (dicotyledons)
Monochoria vaginalis Common name: Monochoria, oval-
leaf monochoria, pickerelweed
Family: Pontederiaceae
Marselia quadrifolia L.Common name: Four Leaf Clover,
Water Shamrock
Family: Marsileaceae
3.Annual sedges
Cyperus difformis L. English name: Sedge,
smallflower umberlla
Local name: motha
Family: Cyperaceae
Cyperus iria L. English name: Yellow sedge (Umbrella sedge) Local name: Dila
Family: Cyperaceae
Fimbristylis milacea L.
Common name: grasslike fimbry and globe fringerush
Family: Cyperaceae
4.Perennial grass
Panicum repense L.Common name: Torpedograss,
creeping panic
Family: Poaceae
Paspalum conjugatumCommon name: Buffalo grass,
carabao grass,
Family: Poaceae
5.Perennial sedges
Scirpus maritimus L.Common name: Bulrush, alkali
bulrush,
Family: Cyperaceae
B. Upland rice
1.Annual grasses (Graminae family)
Echinochloa colonum L.English name:
Wild rice Local name: chotta sawank
Family: Poacea
Digitaria sanguinalis L.
Common name:Hairy crabgrass
Family: Poacea
Dactyloctenium aegyptium L.
Common name: Egyptian crowfoot
Family: Poacea
2.Annual broad leaf weeds (dicotyledons)
Amaranthus spinosus L.
Common name: Spiny amaranth
Family: Amaranthaceae
Ageratum conyzoides L.
Common name: Goat weed
Family: Asteracae
Commelina benghalensis L.
Common name: Benghal dayflower
Family: Commelinaceae
Eclipta albaEnglish name: False daisyLocal name: Jal bhangra Family: Asteraceae
Portulaca oleracia L.
Common name: Green purslane
Family: Portulacacaeae
Trianthema portulacastrum L.
Common name: Desert horse purslane
Family: Aizoaceae
3.Annual sedges
Cyperus iria L. English name: Yellow sedge (Umbrella sedge) Local name: Dila
Family: Cyperaceae
4. Perennial grasses
Imperata cylindrica L.
Common name: Cogongrass
Family: Poaceae
Cynodon dactylon L.
Common name: Ber-muda grass or
Dub grass
Family: poacea
5. Perennial sedges
Cyperus rotandus L. English name:
Purple nut sedge Local name: motha Family: Cyperaceae
III. Crop-weed competition - Depends on
1. Type of rice cultureUp land- severe competitionLow land- Less competitionDeep water- Less competition
2. Method of crop establishment
Transplanting- Less to moderateDirect seeding- Severe competition
3. Variety
Tall - Less competitionSemi dwarf- More competitionLow tillering- More weed competitionHigh tillering- Less competition
4. Cultural practices
Land preparationPuddled - Less competitionun puddled- More competition
Critical period of crop weed competition:
The period from sowing up to which the crop has to be maintained in a weed free environment for remunerative crop production.
30-40 DAT
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.
How long we should keep the rice field free of weeds?
Transplanted rice: 30-45 days after transplanting
Direct seeded rice: 15-45 days after seeding
IV. Methods of weed control
I. Preventive methodsThey check weed introduction and spread of
weed seeds.Easy and economicalPreventive measures include use of weed free
seeds; weed free seed bed, clean tools and machinery, clean irrigation canals.
II. Complementary practices
1. Land preparation: Puddling before transplanting incorporates
weeds and gives rice seedlings a head start over weeds.
Pre-planting control
The pre-planting method consisted of land preparation in dry soils, followed by fast irrigation, puddling, draining the field for the emergence of new weed flushes, application of glyphosate, flooding again and rice seeding over a slight water layer.
Land preparation began with puddling, draining the field, glyphosate application, flooding and seeding as above. The control of weed flushes in some areas was conducted mechanically after drainage.
2. Using weed free crop seed and seedlings
3. Planting methods:Straight-row planting: Easy to weed by hand
or by mechanical toolRandom planting : Difficult to weed and to
pass mechanical tool Transplanting: Weed competition is lessDirect seeding: Weed competition is severe
4. Variety:Tall growing traditional varieties: Compete
more with weedsModern semi dwarf varieties : weed
problem is more 5. Plant spacing and densityCloser spacing: Minimize weed competitionHigher density: Minimize weed competition
6. Fertilizer application: Apply fertilizer after weeding 7. Water managementContinues submergence: Minimize weed
growthAlternate wetting and drying: More weed
growth
8.Sowing IMI rice 9. Crop rotationThe two year rotation consists of one year
of rice followed by one year of no-tilled green fallow.
The four year rotation is rice, beans, wheat and corn.
Biological control
Weed Species Natural Enemies
Cyperus rotundusAthesapenta cyperi (Rhizome and stem boring weevil), Bactra minima (Tertric stem borer), Bactra venesoma.
Salvinia molesta(Water fern)
Grasshoppers (Paulinia acuminata)
Hydrilla, Chara(Water fern)
White amur, Tilapia (Fishes).
Direct methods of weed control
A. Transplanted rice
1. Hand weeding:Pulling by hand or using tools like hoe, spade
or sickleTake up one or two hand weeding between
20-42 days after transplanting Advantages: Most common, easy and effective. Can be
taken up even where random planting is done Disadvantage: Costly, Laborious
2. Mechanical weeding
Rotary weeder: Pushed by hand or powered between straight rows
Advantages:Saves labour Disadvantage:Require row transplanting or seeding
3. Chemical weeding
Herbicides: Chemicals that is capable of killing some plants (weeds) without significantly affecting the other plants (crops).
Advantages of herbicide
1. Pre emergent herbicides provide early season weed control. This is beneficial as weed competition is more severe during early stages than later stages.
2. Herbicides can be applied to weed control in crop rows where cultivation is not possible.
3. Very effective than other methods. 4. Systemic herbicides can control many
perennial weed and brush species which cannot be efficiently controlled by other methods.
5. They reduce the need for pre planting tillage
Herbicides Trade Name
Dose(kg/ha)
Time of application
(Days after transplanting)
a.i Commercial product
Pre-emergent
2,4-D Ethyl ester Weedex 5%G 0.75 15 5-7
ButachlorMachete 50EC
1.25 2.5 5-7
Butachlor Machete 5%G 1.5 30 5-7
Thiobencarb Saturn 4 5
Pretilachlor Eraze-x50 EC 0.5 1.00 5-7
Oxadiazon 25 EC
Ronstar 0.5-1.0 3-5
OxadiargylOxadiargyl
80%WP0.1 0.125 3-5
AnilofosAnilogaurd
30EC0.45 1.50 5-7
Quinclorac50%WP Facet 0.186 0.375 3-5
Bensulfuron methyl 60%DF Londax 0.1 0.166 5
Pendimethalin Stomp 30EC 0.9-1.0 3.0-3.5 3-5
Pyrazosulfuron ethyl 0.02-0.03 3
Post emergent
2,4-D Sodium salt 80%EC
Fernoxone 2.0 2.5 21-28
Propanil 35 EC
Stam 2.5 7.5 1-2 leaf stage
Triazolopyramidine sulfonamide 0.015-0.025 15
Integrated weed Management (IWM): Creative application of agronomic,
mechanical biological and chemical methods usually referred to as integrated weed management.
Integrated weed Management (IWM) in transplanted rice:
1.Puddling , Pre.em application of Butachlor 50EC @2.5kg/ha 5-7 days after transplanting + one hand weeding 30-40 days after transplanting
or2. Puddling, Pre.em application of Butachlor 50EC
@2.5kg/ha 5-7 days after transplanting + post emergent application of 2, 4-D EE @1.0 kg/ha at two to three leaf stage of weeds.
or3. Puddling, Pre.em application of Oxadiargyl @0.075
kg/ha 5-7 days after transplanting + continuous submergence of water.
B. Wet seeded rice on puddled land
1. Hand weeding:Pulling by hand or using tools like hoe, spade
or sickle.Take up one or two hand weeding between
20-42 days after sowing.
2. ChemicalHerbicide Trade Name Dose(kg/ha) Time of application
(Days after sowing )
a.i commercial
Pre-emergent
Anilofos Anilogaurd
30EC
0.45 1.5 7
Pyrazo-sulfuron ethyl 0.025 10
Pretilachlor + safener Eraze-x 0.75 1.5 7
Halosulfuron methyl 0.015 3
Bensulfuron methyl Londax 60%DF 0.1 0.166 5
Integrated weed Management (IWM) in wet seeded rice:
1. Pre.em application of Anilofos @ 0.4 kg/ha + 2 hand weedings at 30 and 60 DAS
1. Pre.em application of Pretilachlor @ 0.5 kg/ha + 2 hand weedings at 30 and 60 DAS
C. Upland dry seeded rice
1. Hand weeding:Pulling by hand or using tools like hoe, spade
or sickle.Take up one or two hand weeding between
20-42 days after sowing. 2. Mechanical weeding: Repeated inter cultivation by passing hoe or
small blade harrow 2-3 times between 20-45 days after sowing.
Herbicide Trade Name Dose (kg/ha) Time of application (DAS)
a.i commercial
Pre-plant
Molinate Ordram 2-3 Before sowing
Trifluralin Treflan 1.0-1.5 Before sowing
Pre-emergent
Alachlor Lassso 50EC 0.5-1.0 1-2 3-5
Butachlor 1.25 2.5 5
Thiobencarb 1.5 3.0 5-7
Anilofos 0.4 1.5 5-7
Oxadiargyl
Topstar 0.1 0.125 3-5
Bensulfuron methyl Londax 60%DF 0.1 0.166 5
Pendimethalin Stomp 30EC 1.0 3.0 5
Post emergent
Propanil 35 EC
Stam 2.5 7.5 4 weeks after sowing
Ethoxy sulfuron 0.018 21
Triclopyr 0.5
Integrated weed Management (IWM) in dry sown rice
1. Pre.em application of Butachlor 1.5+ 2,4-D 0.5kg/ha 5-7 days after sowing + one hand weeding 30 DAS.
2. Pre.em application of Thiobencarb 1.5+ 2,4-D 0.5kg/ha 5-7 days after sowing + one hand weeding 30 DAS.
3.Pre.em application of Anilofos 0.4+ 2,4-D 0.5kg/ha 5-7 days after sowing + one hand weeding 30 DAS.
D. Deep water rice
1. Hand weeding:Pulling by hand or using tools like hoe, spade
or sickle.Take up one or two hand weeding between
20-42 days after sowing. 2. Mechanical weeding: Repeated inter cultivation by passing hoe or
small blade harrow 2 times between 20-42 days after sowing.
3. ChemicalHerbicide Trade Name Dose(kg/ha) Time of application (DAS)
a.i commercial
Post-emergent
2,4-D 0.75 4-6 weeks after establishment
MCPA 0.75
Thanks