Introduction of Weed and Rice Weed Identification

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Cereal System Initiative for South Asia Nepal
(CSISA-NP)
Program- Environment friendly and sustainable
weed management in rice production
Presentation Title- Rice weed identification
and characterization
Himalaya Subedi Research Associate CIMMYT
International CSISA-NP
Regional training center ADBL, Dhangadi,
Nepal Date - 25-26July, 2015
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Presentation outline

• Weed and its definition with example
• Weed crop competition
• Weed classification
• Identification and characterization of weeds
• Major weed of Rice

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Definition of weed

• A plant that is growing where it is not wanted
  Roberts et al. 1982
• A plant out of place Blatchley . 1912
• A plant that is growing where it is desired that
  something else growth Georgia, 1916
• Those plants with harmful or objectionable
  habits Muenscher , 1946

Thus, The weeds are those unwanted plant species
which is grown in unwanted place and time causing
competition for cultivated crop and economic loss.
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How many weed species are there?
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What makes a plant, a weed?

• Long seed life in the soil
• Quick emergence
• Rapid early growth
• No special environmental requirements for
  germination
• Ability to survive and prosper under disturbed
  conditions
• Source- Holm, 1978

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• Dubo or Hariali (Cynodon dactylon)
• Tori or Mustard (Brassica juncea)
• Jalkumbi or water hyacinth (Eichhornia crassipes)
• What happen if
• Cynodon dactylon grow in rangeland
• Eichhornia crassipes in aesthetic pond
• Brassica juncea in maize field

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Weed crop competition loss

• Loss

• Competition

• Yield loss due to weed depends on types of weed,
  density, crop stage for infestation etc.
• Yield 17-47 TPR, 14-93 DSR and 9-70 wheat
  (Ranjit and Bhattarai, 1988)
• Increase cultural operation cost
• No germination of crop due to allopathic effect

• Nutrient
• Light - Weed grow faster than crop causing
  shading (50reduce light intensity)
• Water - higher transpiration ratio (813 Dubo vs
  430 Junalo)
• CO2- C4 (mostly weed) can survive under higher
  level of CO2 and drought

Particular N P K Ca Mg
Maize 30 5.5 62.8 14 6
Weed 55 9.7 297.5 43 40
 Different 25 4.2 234.7 29 34
  higher in weed 83 76 374 207 567
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Weed classification
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Weed classification
Narrow leaf Broad leaf Sedges
Round/flattened steam Leaves in group of two Leaves are narrow Parallel leaf vein Prominent node Wide leaves Net like vein in leaves Leaves in cluster bunch with one or more leaflet Mostly dicot Solid angular stem Three leaf in group Semi-acquatic More problem in warmer climate
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What make difficult to identify weed

• Difficulty in identification
• Growing stage of weeds
• Soil types and environment
• Growing season

• Easy way of identification
• Season of Growing weed
• Morphological part (Leaf, stem, root, phyllotaxy
  etc)
• Reproductive stage with flower and fruit

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• Majors weeds on Rice

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Botanical NameCyprus

• Sedges types
• Perennial
• Propagated by seed, tuber, rhizome etc.
• Problem in both upland and lowland
• Nepali- dy, 5ltof

C.rotundus
C. difformis
C. iria
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• Fimbristylis miliaceae

• Annual weed
• Sedges leaf
• Commonly found in low land

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Scirpus maritimus

• Annual weed
• Sedges leaf
• Commonly found in low land
• Propagated by seed

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The Cyperaceae Family

• Cyperaceae or the Sedges include 17 different
  genera
• Those species most commonly viewed as troublesome
  weeds are found in the Cyperus genus.
• Of the 45 Cyperus species in the Southeast U.S.,
  29 are perennials
• 1 tuber then 10 tubers then 1000 tubers

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Patch Expansion 6 months of growth from a
single tuber
Purple Nutsedge Cyperus rotundus
Yellow Nutsedge Cyperus iria
Patch Area 7.85 m2 518 Purple Nutsedge
Shoots Max. Density 280 shoots/m2
Patch Area 0.18 m2 177 Yellow Nutsedge
Shoots Max. Density 7000 shoots/m2
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Preliminary Conclusions

• Purple nutsedge (Cyperus rotundus) produced
• Similar number of shoots at 3 months
• 2-fold more shoots than did yellow nutsedge
  (Cyperus iria) at 6 months
• Purple nutsedge (Cyperus rotundus) expanded to a
  patch size 31-fold greater than yellow nutsedge
  (Cyperus iria)
• Yellow Nutsedge (Cyperus iria) does not
  distribute itself far from the mother tuber

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Botanical NameUnknown

• Broadleaf

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Commelina diffusa

• Annual Weed
• Broadleaf
• Common in DSR
• Nepali- sGo

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Echinochloa colona

• Annual weed
• Narrow leaf
• Commonly found in maize and rice
• Very fast grow than rice and seed without awn
• Nepali- aGf

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Echinochloa crusgalli

• Annual and narrow leaf weed
• Maize and rice field
• Seed with awn
• Major rice problematic weed
• Nepali- fdf

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Alternanthera sessilis

• Broad leafs
• Perennial Weed
• Problem in low land
• Nepali-

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Unidentify

• Found in low land at DSR

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Marsilea minute

• Broad leaf
• Rainy season
• Vegetative propagated

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Eclipta prostata

• Annual weed
• Broad leaf
• Commonly found in lowland
• Nepali - eunf

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Sagittaria guayanensis

• Annual weed
• Broad leaf
• Commonly found in lowland

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Cyanotis axillaris

• Annual weed
• Broad leaf
• Commonly found in lowland

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Ludwigia hyssopifolia

• Annual Weed
• Broadleaf

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Ageratum conyzoides

• Annual weed
• Broadleaf
• Commonly found in upland
• Nepali - uGw

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Monochoria vaginalis

• Perennial weed
• Narrow leaf
• Commonly found in low land

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Caesulia axillaris

• Biennial weed
• Broadleaf
• Commonly found in low land
• Nepali- 7flof

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Unidentify

• Annual weed
• Broadleaf
• Commonly found in upland

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Paspalum disticum

• Perennial weed
• Narrow leaf
• Commonly found in low land
• Vegetative ( rhizome) propagated

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Panicum dichotomiflorum

• Annual weed
• Narrow leaf
• Commonly found in upland
• Nepali- aGf

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P-1
P-2
P-3
P-4
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SUMMARY - 1 (source- V. Sridevi et al, 2013)

• The dominant weed under puddled condition of
  sandy clay loam soil during rainy season.
• Grass weed species were Echinochloa
  crusgalli and Echinochloa colona,
• Sedges were Cyperus iria, C. rotundus and
  Fimbristylis miliacea
• Broad-leaved weed species were Ammania
  baccifera, Marsilia quadrifolia and Potamogeton
  distinctus
• The broad leaved constituted 34.1 per cent,
  grasses 42.2 per cent and sedges 23.6 percent of
  the total weed population under weedy conditions
  (Singh et al., 2007a).
• The wet seeded rice
• Infested with composite weed flora comprising of
  51.5 grasses, 30.9 sedges and 17.5
  broad-leaved weeds (Ravisankar et al., 2008).

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SUMMARY - 1 (source- V. Sridevi et al, 2013)

• Dominant weed species in transplanted rice
  Ramachandra (2010)
• Grasses weed- Echinochloa crus-galli and E.
  colona
• Sedges- Cyperus difformis, Cyperus iria and
  Cyperus rotundus
• broad leaved weeds - Eclipta alba and Ammania
  baccifera.
• Dominant weed species direct seeded rice Reddy
  (2010)
• Grasses- Echinochloa crus-galli
• Sedges- Cyperus difformis and Fimbristylis
  miliacea
• Eclipta alba and Ammania baccifera under the
  broad leaved weeds.

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