Negative, harmful and Positive, Beneficial effects of weeds in agriculture.
Effects of weeds in agriculture.
Negative/harmful effects of weed:
1. Weeds compete with the crop plant for light, nutrients, water, space and other growth requirements and reduce the crop yield.
2. Increase the cost of production by increasing the cost of labour.
3. Reduce the quality of crop products.
4. Exude inhibitors from the roots reduce the growth of the crop plants (allelopathy).
5. Serve as alternate hosts for insects and pathogens.
6. Reduce the efficiency of farm implements.
7. Harbour birds and rodents.
8. Reduce the sales value of the land.
9. Reduce fertility status of the soil.
10. Limit the choice of crop for a land. Some crops may not complete effectively against heavy weed growth and some weeds are parasite on crops.
11. Cause root and another crop damage may occur from weed control operation.
12. Cause enormous loss of water by growing in the irrigation channel.
13. Cause serious illness or death of farm animals by their poisonous constituents.
14. Interfere with navigation.
15. Injure the cattle body by their spines.
16. Increase the cost of maintenance of sports and recreation, highways, railways and other public utilities. 17. Cause annoyance to human being by plugging in cloths.
18. Aquatic weeds contaminate water bodies and on decomposition spread the odours and pollute the atmosphere.
Positive/Beneficial effects of weeds:
1. Add organic matter to the soil when incorporate into the soil.
2. Increase soil fertility when incorporated.
3. Induce soil formation by rapid weathering.
4. Improve soil structure spreading of weed roots change the soil structure and improve the physical condition of soil due to proper percolation water logging will be prevented.
5. Serve as food (Bothua, Shaknotey, Amrul etc.), feed (Durba, Mutha, Chapra etc.) and medicine (Thankuni, Durba etc).
6. Serve as raw materials for public utilities as fuel, fencing and roofing materials.
7. Help in controlling soil erosion.
8. Serve as water purifier. Eg. Water hyacinth.
9. Serve as a source of genetic materials.
10. Some weeds can be used as indicators of air pollution. Eg. Wild mustard is an extremely sensitive indicator of NH 3, NO 2 present in air.
11. Help in soil reclamation. Eg. Durba and Shialkata, when incorporate into the soil may reclaim alkaline soil.
12. Valued as religious and ritual purposes.
13. Valued as ornamental plant.
14. Act as a host for predatory insect.
15. Leguminous weed can be used as green manure before they set seeds.
16. Some weeds fix atmospheric nitrogen in paddy soil. Eg. BGA