Weeds are indirectly responsible for crop cultivation, but for them cultivated crops may not receive much attention
Weeds as fodder – Useful as good fodder for milch animals. Most weeds are preferred by cattle and weeds like Rynchosia aurea, R. capitata and Clitoria terneata are very good fodder legumes and also Hariyali and filed bind weed (Convolvulus arvensis).
Weeds as vegetables – Used as green vegetables and weeds serve as human food e.g., Amaranthus viridis and Digera arvensis used as greens.
Weed as soil binders – Panicum repense is an excellent soil binder; keeps bunds in position and prevents soil erosion in high rainfall regions and hilly slopes. Hariyali, kikuyu grass, kollukattai grass (Cenchrus sp.) etc., can be used as soil binders.
Weeds as manure – When weeds are ploughed in, they add to the soil plenty of humus. Excellent compost can be made out of many weed plants. E.g., Calotropis gigantea, Croton sparsiflorus and Tephrosia purpurea are used as green leaf manure for rice. In wetlands, weeds are said to form a sort of rotation with paddy and are valuable in preventing loss of nitrates. Datura sp. contains 3% N on dry weight basis, Kolingi (Tephrosia purpurea) fix N @ 50-75 kg/ha.
Weed as fuel – Prosopis juliflora very invasive in nature and notorious tree weed commonly used as fire wood. People make charcoal out of it and are marketed.
Weeds have medicinal values – Many weeds have great therapeutic properties and used as medicine.
• Phyllanthus niruri – Jaundice
• Eclipta alba – Scorpion sting
• Centella asiatica – Improves memory
• Cynodon dactylon – Asthma, piles
• Cyperus rotundus – Stimulates milk secretion
• Leucas aspera – Snake bite
• Calotropis procera – Gastric trouble
• Abutilon indicum – Piles
Weed as mats and screens – Stems of Cyperus pangorei and Cyperus corymbosus are used for mat making while Typha angustata is used for making screens.
Weed as indicators – Weeds are useful as indicators of good and bad soils. E. colonum occurs in rich soils while Cymbopogon denotes poor light soil and Sedges are found in ill-drained soils.
Other economic uses
• Useful in manufacturing of agarbattis) e.g., Cyperus rotundus
• Cymbopogon citrates (Citronella oil) and C. martinii (Palmrosa) are used for manufacturing aromatic oil.
• Argemone mexicana is used to reclaim alkali soils.
• Ornamental flowers–Lantana camera is used for interior decoration.
• Used for fencing purposes. Example–Cactus, Agave sp. Saccharum squarrosus, etc.
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