Back to: O level agriculture notes uganda
What is crop protection?. Crop protection is an activity or practice aimed at providing conditions that will enable the crops to grow without pest destruction, disease infestation and weed infestation.
Weeds
A weed may be defined as a plant growing where it is not wanted or a plant out of place.
Therefore the above definition means that a bean plant in the cassava garden can be considered as a weed.
If weeds are not controlled ,they have adverse effect on the crop plants as well as the quality of the plant and the produce.
Economic Importance of Weeds
- After weeding , the weeds provide organic matter and plant nutrients when they have decomposed.
- Some are also used as vegetables for human consumption e.g pig weed (dodo) Solanum nigrum.
- Weeds also provide a good soil surface cover hence minimizing waterless or evaporation of the H2O from the soil.
- Provide a good surface soil cover that helps to control soil erosion.
- Some weeds are also a source of food for animals, both domestic and wild.
- Some are used as local medicine (herbs) for people and animals to cure some diseases e.g Aloevera (Kigaji), Sodom Apple, Mululuza, Molinga tree.
- Some are used to construct temporary houses e.g. Spear grass.
- Some weeds are also used in mulching the garden.
- Some also help in fixing Nitrogen in the soil hence improving the soil nutrients.
- They also help in preventing /controlling leaching in plant nutrients by taking them up. These are then recycled and returned to the soil when weeds die and decay.
Disadvantages
Lead to loss /reduction in crop yields because of competing with the the crops for crop nutrients.
They reduce the plant size and height which leads to less photosynthesis area for the plant.
Some are altenate hosts for some crop pests.
They lower the quality of crop produce especially when their seeds mix up the crop products.
Weeds also lower the quality of the pastures making them to become unpalatable to the animals.
Some weeds are poisonous to man and livestock when eaten tick berry fruits.
They also increase the cost of production.
Some weeds also block irrigation, navigation and drainage channels especially the water weeds.
Reduce the value of land on selling.
Lead to extra work during seedbed preparation and weeding.
Reduce market value of crops.
Aquatic weeds e.g. Water hyacinth and mile cabbage endanger the life of fish and other animals in water by suffocating them depleting O2 supply in water.
Some weeds are irritating to workers thus reducing efficiency strongly e.g. Love grass, thorn apple.
Weeds also lead to extra work during seedbed preparation.
Some weeds limit i.e choice of crops to grow in some areas.
Characteristics / Factors That Make Weeds More Successful Than Crop Plants
Weeds are more aggressive /vigorous than the crops and they are able to outcompete the crops.
They produce a lot of seeds that ensure their survival always.
Weeds also have a faster rate of growth than normal plants; therefore they are able to complete their lifecycle within short time.
They are able to grow more harder (difficult) conditions than the plants e.g. poor soils, drought. e.t.c.
Weed seeds undergo dormancy that enables them to germinate at the right time and grow.
They are more resistant to crop pests and diseases than the crops.
Some weeds have perenating organs that can sprout and grow into new plants.
Weeds also have efficiently diverse dispersal mechanism e.g. the fruits and seeds that can be dispersed by the wind , water or animal and self.
Most of the weed plants are not palatable to livestock than the crop plants and therefore cannot be grazed upon or destroyed.
Some have protective structures e.g. Thorns that protect them from damage or being destroyed by animals.
Others are parasitic e.g witch weeds that obtain their nutrients from the crop.
Some of the weeds seeds can germinate even when they are immature.
Some weeds produce toxic substances that exclude other plants from growing around them.
Some are resistant to herbicides so cannot die when sprayed.