classification of weeds

WELCOM

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TOPIC:

CLASSIFICATION OF WEEDS

SUBMITTED TO:Dr . Shankarnarayan sirDepartment of AgronomySericulture college Chintamani

Submitted by:Anil Kumar. G.NI BSc (Agri)ID.No: ALC3004Sericulture College Chintamani

CONTENTS: INTRODUCTION. DEFINATION OF WEEDS. CLASSIFICATION OF WEEDS.

INTRODUCTION: The definition of weeds is predicated on human

perception , desire and needs.  A weed is a plant which interferes with human

activity or welfare. It is also defined as plant growing in a place

where it is not desired at a particular point in time.

CLASSIFICATION OFWEEDS:

Classification according to habitat. weeds occur in crop lands ,

orchards , forests. They may be aquatic , terrestrial and subterranean.

Aquatic: These weeds grows in water. Ex: masilea guadrifolia, and some

convolvulaceous plants are water hyacinth, hydrilla, algae, reed grass etc.

Terrestrial: All mesophytic weeds.

Roots of these weeds remain concentrated in 20-30 cm depth from surface.

Subterranean: These weeds are not fully subterranean , their roots , rhizomes , remain underground and multiply.

Aquatic weeds

Terrestrial weeds

Classification according to life cycle.

These may be annual , biennial or perennial.

Annuals : They may mostly complete their life cycle in a season.

Biennials : These weeds complete their life cycle in 2 seasons/years.

Perennials: These weeds are found almost every where in cultivated lands , uncultivated lands , waste lands.

Classification according to cotyledon. According to cotyledons weeds are classified

as monocotyledon or dicotyledon species. The monocots are narrow leaved weeds of

grass family , dicots are broad leaved.

Classification according to bark tissue.

On this basis weeds may be woody , semi woody , and herbaceous.

Herbaceous weeds are more common than others. Ex : lantana camara, acacia arabica, are common woody species.

Classification according to association with crops

Weeds flora and their characteristics are different in different types of crops . some may be common.

According to their association they may be upland rice association weeds , low land rice association weeds , wheat association weeds, pulse association weeds. Etc

Ex: In mustard-cleome viscosa and cleome menaphylla. In horse gram- tephrosia purpurea. In rice- O.sativavar fatua .

Classification according to relative position of weeds

These may be absolute weeds , relative weeds, rogues .

Rogues means mixture of other variety in a variety grown.

Classification according to parasitization.

Some weeds grow as parasites on other crops.

They may be considered as loaders. These are cuscuta , orobanchae , striga,

etc.