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