Weeds and weed control - Agriculture Form 3
Suggested Learning activities
1. Learners to go round the school farm and collect and identify at least twenty (20) common weeds found.
2. Dry the collected weeds in a controlled environment to preserve their colour then mount them on full scarps or manila papers to make a herbarium.
3. Note the details of each of the weeds mounted on the papers as follows; i) Common and scientific name
ii) Short description of the weed.
iii) Habitat (area commonly found )
iv) Control measures 4. Classify the weeds according to their morphological characteristics. 5. Practice application of herbicides in a crop of carrots to control weeds.
One of the limiting factors in crops productions is the infestation of the plants which grow where they are not required. The presence of these plants that are out of place contribute, significantly to production costs in any farming enterprise.
Glossary on weeds and weed control
Allelopathic weeds- weeds that produce poisonous substances that suppress growth or germination of plants, for example,Cyperus rotundus (nut grass/ sedge). Noxious weeds-weeds whose cultivation is prohibited by law for example mathenge, and Cannabis sativa. Annual weeds- weeds that complete their life cycle within one year/season or less, for example black jack. Biennial weeds- weeds that complete their life cycle within two years / seasons, for example Spear thistle. Perennial weeds- those weeds that take more than two years to complete their life cycle, for example Couch Grass. Aquatic weeds- weeds that grow in water, for example salvinia. Leguminous weeds- weeds that are capable of fixing free nitrogen into the soil, for example Crotolaria spp. Wettable powders - Finely ground particles that are used in chemical control of weeds, for example. Atrazines and Duron Selectivity- Ability of a chemical to injure one plant while allowing another to escape. Contact herbicides- Herbicides that kill only part of the plant it comes in contact with. Translocated/ Systemic herbicides- Herbicides that kill the whole plant even if a small part of the plant gets in contact with the herbicide. Propagation - A process of production of new plants.
Galls- swellings on plant parts. Plant morphology- form or structure of something. Plant Anatomy- arrangements 0f tissues within the plant. Rogueing - uprooting a plant or weed. Mowing - Mechanical removal of shoots from weeds. Quarantine - Keeping away from other produce that may be carrying some dangerous weeds
By the end of this lesson you should be able to
- Define a weed
- Identify weeds
- Classify weeds
- Explain the characteristics which make weeds competitive
- State harmful effects of weeds
- Control weeds
- Exercise safety measures to oneself, to crops and to the environment while controlling weeds.
Weeds and weed control
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