Weed Management in Horticultural Crops

WEED CONTROL METHODS

WEED CONTROL:

Weed control includes many techniques used to limit weed infestation and minimize competition. Weed control technique attempt to achieve a balance between cost of control and crop yield loss, but weed control is used only after the problem exist.

Weed management: Weed management is an approach in which weed prevention and weed control have companion roles. Weed management is the combination of the techniques of prevention, eradication and control to manage the weed in a cropping system or --environment. or

It is defined as a system of farming, using all available knowledge and tools to produce crops which are free from economically damaging competitive vegetation

Weed Control Methods
Preventive	Curative
· Sowing of weed free seeds. · Use of clean implements. · Removal of weed along the canal and irrigation channel · Care in transplanting of seedling/plantlets. · Use of well rotten manure · Avoiding passing of cattle from weed infested area. · Crop management practices. · Enforcement of Weed Laws. · Quarantine methods and use of pre- emergence herbicides.	Eradication	Control
		Mechanical	Cultural	Biological	Chemical
		-Hoeing, -Hand weeding -Digging, -Mowing. -Burning, -Mulching	-Selection of crop, -Crop rotation, -Use of compost or manure, -Allowing the land to fallow, -Pre-sowing irrigation, -Sowing time, -Orientation of -sowing/transplanting	-Plants-parasites, -Predators and - Pathogens

WEED CONTROL METHODS:
There are two broad methods of weed control:

1. Preventive methods
2. Curative methods

i) Eradication
ii) Control measures

1. Preventive Method: Prevention of introduction and spread of weeds in an entirely new locality is termed as preventive method. It is essential to know that how weeds disseminate. By taking following measures weed spread can be prevented from entering into a new locality.

I) Sowing of weed free clean seed: The seed contaminated with weed seed is a good source of spread of weeds. It becomes hard to separate the weed-seed from the crop seed. For example, cruciferous crops like radish, cauliflower, cabbage, broccoli etc. are well mixed with the seed of Satyanashi (Argemone mexicana). Such impure seed should be discarded for sowing.

II) Use of clean implements: While operating agricultural implements like cultivator, harrow, and seed drill etc. in weed infested field, care must be taken that multiplication part of weed like rhizome, bulb, tubers, stem is not being carried along. The agricultural implements should be cleaned properly. Only then these should be used in other fields. This helps in controlling spread of the weeds.

III) Removal of weeds along canal and irrigation channel: Weed seed get transported through water and reach the field. Removal of weeds growing along the sides of canal or irrigation channel is necessary.

IV) Care in transplanting of seedling/plantlets: Many horticultural plants like all transplanted vegetables,flowers, and fruits are transplanted in the field with soil attached to their root. Infestation of soil with weed may contaminate a new field.

V) Use of well rotten manure: Weed seeds have good viability. The seed of hirankhuri (Convolvulus arvensis ) remain viable for as long as 50 years. Doob (Cynodon dactylon) and motha (Cyperus rotundus) seed viability lasts for two and five years, respectively. For making manure the cowdung is generally heaped. If the heaping period is short, the seed do not lose its viability and grows in the field wherever manure is applied. So only well rotten manure should be used.

VI) Avoiding passing of cattle from weed infested area: Grazing in weed infested field followed by allowing passage of cattle in new field favours dissemination of weed seed. The weed seeds after passing through alimentary canal of the animal come out through dung, where it gives rise to weed. Some weed seeds also stick to the legs and skin of the animals and get transported to some other place where it germinate and grow as a weed.

VII) Crop management practices. All such practices which favour the growth of main crop only disfavour the growth of weed. The following management practices have smothering effect on weed and must find place in crop land to prevent weed spread:

• Proper crop rotation prevents establishment of weeds.
• Higher plant population per unit area smothers the growth of weed.
• Proper placement of fertilizer in the root zone of the seed favours the growth of crop only. The weeds deprive of nutrients and their growth is restricted.
• Fast and vigorous growing varieties by virtue of their larger leaf canopy cause smothering effect on the growth of weed. Such crops should receive preference to prevent spread of the weed.

VIII) Enforcement of weed Laws: In India, many noxious weeds grow in the fields and pose great economic and health hazard. Noxious weeds are those perennial weeds which are reproduced by seeds,stem,roots,and other reproductive parts as well and are very difficult to control.Parthenium hysterophorus, Striga sp.,Cyperus rotundus,Cynodon dactylon etc.are noxious weeds that grow in many horticultural crops.In India , no weed laws are in force except in Karnataka where Parthenium has been declared as a noxious weed.

IX) Quarantine Laws. Quarantine laws impose legal restrictions on the movement of the agricultural material. If there were adequate quarantine laws, the Parthenium and Argemone which widely grows in vegetable and flower field may not have entered India. Creating isolation between widely weed infested area and new area is essential by enforcing and observing quarantine properly.

X) Use of pre-emergence herbicides: Herbicides which are used before the emergence of weeds either before or after planting of crop, is a good preventive measure for preventing weed infestation. Such herbicides either inhibit seed germination or kill young seedlings before they get established.