Tag: improved methods of agriculture

Weeds can be defined as the unwanted plants that are grown in the field and harm the desired crops. Cyperinus is the most invasive weed found throughout the world. It is the weed of rice field. This is the weed which is commonly found in the temperate regions. 

When the invasive species prickly pear was introduced it possessed a threat to the native species. The growth Opuntia is then controlled by the introduction of the species of the cochineal insect.

A carbamate is an organic compound which is derived from carbamic acid (NH$ _{2}$COOH). 

Weeds are unwanted plants in the cultivated field. They compete with the crop plants for food, space and light. They take up the nutrients and reduce the growth of the  crop.

Parthenium is most common weed which grows anywhere on the land like roadsides, war footings etc.  It releases chemicals to supress the growth of plants and allergents toxic to other livestock. Thus it is important to supress  this weed first. Thus the correct answer is 'Parthenium'. 

Eichhornia crassipes also known with the common name of water hyacinth is a free-floating aquatic plant native to America. It is often considered a highly problematic invasive species outside its native range. E. crassipes reproduces both vegetatively and sexually, but the vegetative reproduction is responsible for the plant’s rapid spread and colonization of water bodies. It occurs through the formation of stolons, which produce daughter plants. This is generally very rapid, if the temperature is high and nutrients are available, it often invades bodies of water that have been impacted by human activities as they often receive large amounts of nutrients. One plant can multiply to cover one acre in a single growing season forming a dense strand. So, with the combination of its free-floating habit, rapid vegetative propagation, and ability to survive on mud during periods of low water levels, E. crassipes has been able to naturalize in a wide variety of aquatic habitats.

Weeds are nothing but unwanted crops that grow along with the main crop. Thus, they compete with the main crop for sunlight, water, nutrients, and space and thus reduce the resources available to them. In this way, they hamper the growth of the main crop.

• Rotating crops with ones that kill weeds by choking them out, such as hemp and other crops, can be a very effective method of weed control. 
• It is a way to avoid the use of herbicides and to gain the benefits of crop rotation.