Weeds are the plant that grows where
it is unwanted or grow and spread fast and takes the place of native plants.
Effects of weeds: They are able to grow fast and
spread in native areas. They compete successfully for light, space, water and
nutrients with native plant species. They are more vulnerable to pest and
diseases attack. Thereby they take place gradually of the native plants and reduce
biodiversity. Alternation of plant community directly affects their pollinators
and seed dispersal agents. Weeds cause the loss of the nesting places of native
birds. So animal diversity is also gradually become reduced as they moves into
new area or die. Weeds increase the cost of agriculture because once weeds have
established, it is very difficult to eliminate it. Some weed may cause allopathic effect. They
produce toxic chemicals that interfere with metabolic pathways or suppress the
growth native plants seedling within their vicinity of roots. Ex: Chromalaena
odorata. Some are cause allergic reactions in humans. Alternanthera
philoxeroides( Alligator
weed)is misused by people due to the same appearance with Alternanthera sessils but toxic to human.
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Although
the weeds are often disadvantageous, they are useful in many ways.
Erosion protection: Weeds grow as a thick layer in the
agricultural lands so it prevents wind contact with top soil particles. Thereby
it reduces the erosion by wind. The weed have strong either fibrous or tap root
system that hold the soil particles together. The secrete glues that bond soil
particles together intro large aggregates. Thereby the weeds reduce the erosion
by rain.
Add nutrients and organic matter: Weed can be buried as a green
manure crop with main crop so that its decompositions of its plant materials
release nutrient and organic matter into the soil. Chromalaena odorata as a
green manure crop, it adds large amount of nitrogen as its leaves are rich in
nitrogen. If Crotalaria retusa is grown as a green manure crop, it adds
directly nitrogen to the soil because it belongs to legume.
Leafy vegetable: Amaranthus spinosus is perennial weed. It is often found in
agricultural lands. It contains protein, minerals, and vitamins in large
quantity so it is able to heal some health problems. Its higher fiber content
is good for the health of digestive tract. It is rich in potassium which helps
to lower the blood pressure. High concentration of vitamin A lower or stop the
cataracts in eyes and keep the vision healthy. It contains amino acids which
are not produced by human body and they increases calcium uptake. Thereby they
bind tightly hair to the head so prevent the hair losses.
Feedstock for livestock: Panicum maximum is a perennial shrub. It possesses a
erect system. It is eaten by all
classes of grazing livestock. Its young leaves are more palatable compare to
the mature ones. In Vietnam, its leaves are used for fish feeding. Commelina
diffusa is another weed which grows in wet areas. It is comprised with
creeping stem. It grows as annual in temperate countries while it grows as
perennial in tropical countries. In addition to feed, it gives water in large
quantities. Thereby it reduces the water requirement for livestock.
Medicinal value: Cyperus rotundus is also known as nut grass. It grows as perennial. It has an
underground stem. It is used as an
ingredient in traditional ayurvedic medicine.it helps to treat digestive
problems, menstrual disorders and nausea. Scoparia dulcis is another medicinal
herb in traditional
ayurvedic medicine. It grows as perennial. Its whole plant is boiled and drink
for diabetes. In addition diabetes, it is used for treat eye disorders, ear
disorders, menstrual irregularities and parasitic infections.
Economic important: weed has potential for been using
as a feedstock for biofuel production. Growing energy crops increases the
demand for land and nutrient available for world food production. It has to be
pump money on growing them. But use of weed as a feedstock, it does not affect
the agriculture. Cost of the biofuel production is lowered. Thereby customers
can apply biofuel for their vehicles at reasonable price. It gives additional
income for farmer. It is one of best
solutions for weed management other than environmental degrading methods. Panicum
maximum is grown in Central America for bio alcohol production. Whole
plant body of weed can be used as feedstock in anaerobic digester for methane
production. Leaves of Panicum maximum is used for
thatching. Its culms are used for basket manufacturing.
Ornamental and hedge plant: Lantana camera is
perennial flowering plant.it is native to the tropical areas of America and
Africa. But it now has included in 100 of world worst invasive plants. It
possesses erect or subscandent stem. It grows individually in clumps or as
dense thicket. It attracts and provides nectar for many species of butterflies
and moths. But its spread into land which are used as pasture for livestock
because it produces toxic substances that are able to kill livestock which is
result in economic loss. Lantana
camera as a hedge plant, it helps to keep away livestock from gardens.
Raw material: Exactions from young twigs of Eclipta
prostrata are used as a raw material for hair oil productions.it has
ability promote the hair growth.
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