Transcript Harmful Effects of weeds - agronomy society of pakistan

Harmful Effects of weeds
 What is weed ?
 Competition for mineral nutrients
 Competition for water
 Competition for solar energy
 Competition for space
 Reduce the crop quality and quantity
 Impair the quality of the animal produce
 Harm animal health
CONTINUE………
 Harbor insect pest and diseases
 Damage human health
 Competition for solar energy
 Contaminate water bodies
 Quicker wear and tear to farm implements
 Reduce the value of land
 Less efficient use of land
 Increase in cost of cultivation
 Disturbance in public places
What is weed?
 Any plant which is out of its proper place is called
weeds
 Types of weeds
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Annual weeds
Biennials
Perrineals
 e.g wheat weeds, rice weeds, sugarcane weed
Weeds in wheat
 Dumbi sitti
 P. Minor
Competition for mineral nutrients
 Being hardy and vigorous in growth habit; they soon
outgrow the crops and consume large amount of water and
nutrients.
 In general, weeds removed N and K from soil in much
greater quantity than P.
Competition for water
 Weeds consume large amount of water as compared to
other crop plants
 For producing equal amount of dry matter, the weeds, in
general transpire more water than most crop plants e.g.
wild mustard transpires about four times more water than
a crop of oat.
Competition for Solar Energy
 About 99% of dry matter in plants is made up of organic
matter that is dependent on solar energy.
 When plants are mutually shaded, their production
potential is greatly reduced even though water and other
nutrients are available to them in abundance.
 Emerging plants are shaded by quick growing weeds
Competition for space
 Weeds compete for space both in the rhizo sphere and
atmosphere. In the presence of weeds, crop plants also
have limited space to develop their shoots, which amounts
to reduced photosynthesis in them.
 More seed production of weeds
 Growth habits of weeds
reduce the crop quality
 Weeds may reduce the quality of the crop produce in
many ways.
 Weed seed like wild mustard, sweet clover, a Mexican
poppy and bulblets of wild garlic and wild onion when
threshed and ground with winter grains can results in
serious consequences besides imparting objectionable
odour to the flour.
impair the quality of the animal
produce
 Many weeds in pastures and forage crops impart
undesirable flavors to milk and meat of animals.
 For e.g. Pivali tilwan (Cleome viscosa) imparts
undesirable flavour to milk.
 Gokharu or Landaga (Xanthium strumarium) get attached
to the body of sheep and seriously impair the quality of
wool.
Harm animal health
 Several weeds of grasslands and forage crops contain high
alkaloids, tannis, oxalates, gulcosides, and other
substances that prove poisonous to animals when ingested.
 For e.g. Silky lupine ( Lupinus sericeus) is responsible for
crooked calf disease.
 Some weeds are noxious and produce poisonous chemical
which are injurious to animal health
Harbor insect pests or diseases
 Weeds either give shelter to various insect pests and
diseases or serve as alternate host. For e.g. Weed around
paddy bunds harbour the gallfly.
 Weeds act as a host
 Cause of many diseases
Damage human health
 Health, comfort and work efficiency of man are also
affected by weeds directly or indirectly.
 For e.g. people in U.P. are plagued year after year with
hay fever and asthma aggravated by pollens of rag weeds.
 Lantana flower leaves are dangerous for humans.
Contaminate water bodies
 Aquatic weeds change the
flavor appearance and taste of
drinking
water.
Aquatic
weeds are a menace to
fisheries too. Aquatic weeds
on decomposition
gives
offensive odors and pollute
atmosphere.
Himalayan balsam
 Himalayan balsam grows
fast and can reach two to
three metres in height. It
rapidly spreads on the
banks of slow-moving
watercourses and becomes
dominant, stopping other
plants growing.
Quicker wear and tear to farm
implements
 Being hardy and deep-rooted, the tillage implements get
worn early.
Reduce the value of the land
 Agricultural
lands
heavily infested with
perennial weeds like
Kans
(Saccharum
spontaneum)
always
fetch less price.
 Giant hogweed
Less efficient use of land
 In case of perennial weeds, the carrying capacity of the
grazing lands is reduced and cause depreciation of land
value.
Increase in cost of cultivation
 In fields of crops infested with weeds, the tillage
operations require high cost.
Disturbance in Public places
 It is desirable that public places be kept clean of weeds.
 Presence of weeds around our living and working places
makes the surroundings dull.
 Any Question