Subject :Agricultural science
CLASSIFICATION OF WEEDS
Basic 7 / JSS 1
Instructional Materials :
- pictures of weeds
- samples of weeds
- Scheme of Work
- Online Information
- 9 Year Basic Education Curriculum
Previous Knowledge :
The pupils have previous knowledge of
USES OF WEEDS; METHODS OF WEED CONTROL
Behavioural Objectives : At the end of the lesson, the pupils should be able to
- list classes of weeds
- mention at least four classes of weeds
- mention the effects of weed control on plants
- write out the effects of weed control on vegetation
EFFECTS OF WEED CONTROL METHODS ON VEGETATION AND SOIL
- Effects of Chemical Control of Weeds on Vegetation and Soil
- Effects of Bush Burning on Vegetation and Soil
- Effects of Mechanical/Physical Control of Weeds on Vegetation and Soil
- Effects of Biological Control of Weeds on Vegetation and Soil
- Adverse Effects of Weeds/Problems Posed by Weeds in Agriculture/Economic Importance of Weeds
Effects of Chemical Control of Weeds on Vegetation and Soil
The following are the effects of chemical control of weeds on vegetation and soil:
- Herbicides can be poisonous to human beings.
- Beneficial organisms may be destroyed.
- Herbicides can pollute soil and ground water.
- Herbicides can contaminate livestock pasture thereby killing the animals that feed on them.
- Some herbicides, when used, can kill both good and unwanted plants and animals.
Effects of Bush Burning on Vegetation and Soil
The following are the effects of bush burning on vegetation and soil:
- Burning can kill beneficial soil organisms.
- Burning also exposes the soil to erosion.
- Fire destroy organic matter in the soil.
Effects of Mechanical/Physical Control of Weeds on Vegetation and Soil
The following are the effects of mechanical/physical control of weeds on vegetation and soil:
- The use of machine and farm implements e.g tractor and plough, destroys soil structure.
- It encourages soil erosion.
- It causes air pollution and soil compaction
Effects of Biological Control of Weeds on Vegetation and Soil
The following are the effects of biological control of weeds on vegetation and soil:
- Predator may feed on crop rather than weeds
- Introduced plant may be difficult to control.
- Overgrazing can result to soil erosion.
Adverse Effects of Weeds/Problems Posed by Weeds in Agriculture/Economic Importance of Weeds
The harm done by weeds is due mainly to their competition with crops. These are some of the reasons why weed pose challenge to farmers, hence a need for them to be controlled. The effects or economic importance of weeds include:
- Weeds compete with crops for space.
- Weeds compete. With crops for sunlight.
- Weeds compete with crops for nutrients.
- Weeds harbour crop pests and diseases.
- Weeds compete with crops for soil moisture.
- Weeds result in loss of crop yield.
- Weeds compete with crops for oxygen.
- Weeds reduce the palatability of some pasture grasses.
- Weeds reduce the quality of crops.
- Weeds increase farmers cost of production.
- Some weeds are toxic to farm animals.
The topic is presented step by step
The class teacher revises the previous topics
He introduces the new topic
The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
- Mention two examples of the following: (i) Perennial weeds (ii) Annual weeds (iii) Biennial weeds
- Explain the following with three examples each: (i) Monocotyledonous weeds (ii) Dicotyledonous weeds
- State five effects of weeds on crops.
- Enumerate five effects of weeds control methods on vegetation and soil.
The class teacher wraps up or conclude the lesson by giving out short note to summarize the topic that he or she has just taught.
The class teacher also goes round to make sure that the notes are well copied or well written by the pupils.
He or she does the necessary corrections when and where the needs arise.
Prepare for the next lesson by reading about
DISPERSAL OF WEEDS (WEED DISSEMINATION)