24.12 WEEDS

♤ Weeds are unwanted and undesirable plant that interfere with utilization of land and water resources and thus adversely affect crop production and human welfare

♤ They are gregarious in nature compared to crop plants.

Harmful effects of weeds

1. Weeds compete with main crop for space, light, mois-tire and soil nutrients thus causing reduction in yield.

2. Affect quality of farm produce, livestock products such as milk and skin

3. Act as alternate host for pests and pathogens

4. Cause health problems to human beings eg; Parthe-nium causes allergy

5. Increase cost of cultivation due to weeding problem

6. Aquatic weeds transpire large quantity of water, obstruct flow of water

7. Reduce the land value (if cynodon, parthenium are present in the land )

8. Some weeds are poisonous to livestock.

Beneficial effects of weeds

1. Weed as soil binders

2. as manure

3. as human food

4. as fodder

5. Weed as fuel

6. Weed as mats and screens

7. Weed as medicine: Many weeds have great therapeutic properties and used as medicine. Eg.

Phyllanthus niruri - Jaundice Eclipta alba - Scorpion sting

Centella asiatica - Improves memory Cynodon dactylon - Asthma, piles

Cyperus rotundus - Stimulates milk secretion

8. Weed as indicators: Weeds are useful as indicators of good and bad soils. Colonum occurs in rich soils while Cymbopogon denotes poor light soil and Sedges are found in ill-drained soils

♤ Genetically modified crops (GM crops, or biotech crops) are plants, the DNA of which has been modified using genetic engineering techniques, which are then used in agriculture.

Watershed Management

♤ A watershed is an area of land and water bounded by a drainage divide within which the surface runoff collects and flows out of the watershed through a single outlet into a lager river (or) lake.

Micro Irrigation

♤ Micro irrigation is defined as the methods in which low volume of water is applied at low pressure & high frequency. The system has extensive network of pipes at operated at low pressure. At pre-determined spacing outlets are provided for emission water generally known as emitters.