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SUBMITTED TO:
Prof. (Dr.) THOMAS ABRAHAM
DEPARTMENT OF AGRONOMY
ALLAHABAD SCHOOL OF
AGRICULTURE
SUBMITTED BY:
GROUP NO # 13
What is WEED….????
“Plant whose virtues are yet to be
discovered”
“A plant out of place”
Weeds are unwanted or undesirable
plants that compete with crops for water,
soil nutrients, light and space (i.e. CO2)
and thus reduce crop yields. Weeds
account for 33% loss in agriculture
alone.(Jethro Tull, 1731)
Successful Management Requires
Multiple approaches
Continual effort
Knowledge of the biology of weeds
species
Reproduction, lifecycle,
establishment annual, perennial,
wandering perennial, broadleaf,
grass.
Weed : Top issues for Organic
Farmers
Principles Involved:
Eco Friendly :- i.e. it should cause no harm to
our environment.
Break the survival mechanism of the weed in
soil.
Easily acceptable by the progressive farmers.
Crop husbandry ( Crop Rotation, Mulching
etc.)
Multiple Prevention and
Elimination Strategies
(Practices):
Cultural
Biological
Physical
Mechanical
“Many hammers approach.”
Liebman and Gallandt, 1997
Cultural Strategies
Buy quality crop seed with low/no weed seeds
present.
Do not allow weeds to form seed.
Improve crop competitiveness
Improve soil tilth, aeration, and fertility to
optimize crop growth
Increase crop density through narrow
row spacing and increased seeding rate
Use transplants, rather than seed, when possible
Cultural Practices
Reduce weed numbers
Mulch (wood chips, mow and blow, paper,living, plastic, etc)
Use weed-suppressive cover cropsQuick germinating, high biomass
Field with high weed pressure may warrant full year ofcover cropping and fallow to reduce weeds
Crop rotationsaltering narrowly spaced crops with closely spacedcrops, shallow rooted/deep rooted crops, cold/warmseason crops
IntercropClover underseeded in sweetcorn.
Crop Rotations
• Weeds tend to infest crops with similar
life cycles.
• Change crop ecology: shallow/deep
roots, cold/warm season, row/drilled
crops, foliage density, and heavy/light
feeders.
Change cultural practices: cultivation,
mowing, fertilization, herbicide
application, and planting/harvest dates
Biological Control Practices
Insects: may consumelarge numbers of weedseeds or feeding injury toplant or vector virus
Phyllocoptes fructiphilus hasbeen shown to transmit roserosette disease on young fastgrowing roses
Selective grazingSheep: clean fields afterharvest
Weeder geese: useful againstgrass weeds and in perennialsystems
BiofumigationUse of Brassica species (canola, Indian mustard) as cover crop or in rotation
May be incorporated or left as residue
Brassicas produce glucosinolates, which may by converted to cyanate compounds during decomposition.
Sustainable Vegetable Production from Start-Up to Market, Grubinger, 1999
Allelopathy
Allelopathy is the direct or indirect chemical effect
of one plant on the germination, growth or
development of neighboring plants.
Species of both crops and weeds exhibit this
ability. Allelopathic crops include barley, rye,
annual ryegrass, buckwheat, oats, sorghum, sudan
sorghum hybrids, alfalfa, wheat, red clover, and
sunflower.
The alleopathic effect can be used to an advantage
when oats are sown with a new planting of alfalfa.
Physical and Mechanical
Practices
Mowing
Prevents seeding
Depletes storage reserves
Better control for broadleaves
Soil solarization
Effective control of winterannuals
Limited control of perennials
Cost prohibitive on largeacreages
Avoid tillage deeper than 3”after solarization
Hand weeding
Cultivation
( done with cultivators)
Flaming
Flaming
Intense heat sears the leaf,causing the cell sap toexpand and disrupt cellwalls
seedlings are mostsusceptible
Broadleaf weeds are moresusceptible than grasses
May be used in wet soilconditions Sustainable Vegetable Production from Start-Up to Market, Grubinger, 1999
Weed Management of RICE
( Major crop ) In Jharkhand.
Few weed species are
Echinochola crus-galli
Echinochloa colona
Eclipta alba
Monochoria vaginalis
Cynodon dactylon
Cyperus iria
Cyperus difformis
Cyperus rotundus
If these weeds are not
controlled from very
beginning the
reduction in rice
yield may be as high
as 12-98%.
Critical Period :
30 t0 70 DAS
Control:
Cultural control :
Keeping a layer of water (7 cm -15cm) on rice is said to
suppress germination of weeds completely.
Biological control :
Very little is known about natural enemies of this
sedge; the fungi, Corticum sasaki , and the
nematode Meloidogyne graminicola, may be considered
for biological control.
Mechanical Control:
Hand picking is the most commonly used process
practiced for weed management in Jharkhand.
Weed Management of POTATO(
Major crop ) In Meghalaya.
Most common weed associated are:
Witchgrass-Panicum capillare
Dense hairs cover the leaf blades on both
sides and the sheath
Leaves are rolled in the bud and lack
auricles
Leaves have a white mid-vein
Its is a nuisance in lawns and gardens
It has a fibrous root system
Mature plants are 1 to 2’ tall
A.K.A. ‘ticklegrass’
Control:
Prevention:Learn to identify plants; start
monitoring early in the season.
Cultural Weed Control:
Plant competitive grass or other cover
crops. Witchgrass does not compete well with
perennial grasses.
Mechanical Weed Control
Cultivation or mowing before seed develops will
control this plant. Witchgrass can also be hand
pulled.
Biological Control :
No known biological control in our area.
Weed Management of SUGARCANE
( Major crop ) In Uttar Pradesh.
Most common
weeds associated
are:
Sorghum halepense
Cyperus rotundus
Eleusine indica
Saccharum
spontaneum
Digera arvensis
Eclipta alba
Cynodon dactylon
Pyllanthus niruri
If these weeds are not
controlled from very
beginning the
reduction in
sugarcane yield may
be as high as 10-70%.
Critical period for
weed competition
is 4 months after
sowing.
Control:
Cultural Weed Control:
Selection of cultivars that have quick canopy closure.
Seed cane from clean fields.
Trash mulch at 45 DAP @ 7-10 t/ha,10 cm thick is
effective against many weeds.
Mechanical Weed Control
Plant cane-scratchers are used over the top of the
cane and tines are removed as the can gets larger.
Ratoon cane-disk cultivators are used for weed
control in row middles.
Biological Control : Not practiced in Uttar Pradesh.
Weed Management of PINEAPPLE
( Major crop ) In Nagaland
Matricaria matricarioides ( Pineapple weed ):the most common associated weed.
Plant stems grow erect up to 1’ tall
Heads are cone-shaped and a yellowish green colour
with each head surrounded by overlapping bracts with
no ray petals
Crushed heads give off an odour likened to pineapple.
An annual plant reproducing by seeds
It is a nuisance in lawns and gardens and is also found
in croplands and along roadsides.
Control:
Prevention – Learn to identify plants; start monitoring
early in the season
Biological – No known biological control in our area
Cultural –
One hand weeding in May/June.
For the treatment involving mulching, non-decomposed
coffee husk was uniformly applied at a rate of 20 tons ha-
1 as per the schedule & mulched treatments significantly
out- yielded treatments without mulch and the clean
weeding with 100% weed control efficiency.
Conclusion
Using multiple approaches (“many
hammers”) to manage weeds will yield
greater impact than relying on a few
practices.
Develop a weed management strategy
that is designed for the needs of your
farm.
Although weeds can serve as host plants
for pests, they can also serve as hosts to
beneficial organisms
Conclusion
Today, however, with the increase in organic
farming and the decrease in the use of
herbicides, breeding for weed suppression
has become a higher priority.
Instead of eradicating weeds, farmers
especially organic farmers-- are learning to
manage weeds.