Unit 1
Introduction to weeds
Weed is a plant that grows occasionally in a particular place where it is not desired for a specific span of time
weeds are usually evolved when some disturbances occur in a stable natural environment through the action of human activities.
Characteristics of weeds
1. smaller in sizeable aggregate as well as may cooperate into reserver material of the seeds
2. weed seeds also possess dormancy
3. produces large quantities of seeds as compared to arable crops
4. seed germinate earlier and grow faster
5. most the weed species have often possessed a C4 photosynthetic type process, benefit at the time of moisture stress condition
6. extensive root system
Harmful effects of weeds on the ecosystem
The weeds can reduce the productivity of crops its of physical and chemical interaction
the weeds can reduce the quality of crops through direct contamination
the weeds can cause a decrease in the quality of grass/pasture land. It decreases the carrying capacity of pastures/grazing lands by physical presence and weediness.
some weeds are poisonous to the grazing animals.
The weeds may cause deterioration in the quality of animal-derived products
some weeds often cause serious harm to grazing animals.
weeds can enhance the actual cultivation cost
weeds present in the field may also obstruct the water flow in the irrigation canals, channels and other water systems
reduce water holding capacity
weeds can interfere with various field operations (harvesting) in crop area
weeds impose limitations on the farm size of the farmer
weeds can also serve as the source of fire hazards
Beneficial Effects of Weeds on Ecosystem
1. The weeds can be a source for alternative host as well as act as nectar that fulfills the purpose of shelter for useful insect"s activities.
2. Weeds can reduce alarming problem of soil erosion
3. help in landscape beautification
4. can be used as medicine
5. help in recycling of essential nutrients through decomposition and decay of several vegetative plant parts
6. may serve as food material / vegetable
7. feeding material for livestock
8. alternative source of pesticide
9. can serve as trap crops for control of parasitic weeds
8. weeds can be used as suitable habitat for wild life flora and plant species
9 serve as trap crops for control of parasitic weeds
10. c - recycling
12 source of gentic material for desirable characters