रानी लक्ी बाई के ंी् कृ षि षिशषिवाल्, झाँसी

Rani Lakshmi Bai Central Agricultural University

HFS 202 Lecture Notes

By: Dr Sandeep Upadhyay(TRA)

COA, Rani Lakshmi Bai Central Agricultural University
Jhansi, Uttar Pradesh INDIA
 Weeds
 Based on life cycle weeds are classified as annuals, biennials and perennials.
The Term 'weed' was firstly used by Jethrotull.
 Weed is such undesirable plant grown in association with crop which snatches major parts of
nutrients, water, light, place and CO2 available to the crop. Due to tough competition crop
suffers adversely and the production is reduced.
 Followings are the main points-
(i) Unwanted plant
(ii) Plant growing where it is not required i.e. a plant out of place.
(iii) Extremely noxious, useless, unwanted or poisonous plant
(iv) Any plant or vegetation excluding fungi interfering with the objectives or requirements of
people. Thus weed may be defined as unwanted and undesirable plant which interfere with
the utilisation of land and water resources and adversely affect human welfare.

Criteria of to be a weed:
Whether a plant is weed or not, depends upon
(1) Characteristics and habit of plant
(2) Relative position
(3) Time of occurrence of plant. Therefore all plants may become weeds in a particular
situation.
A. On the basis of site of predominance:
A1 Obligate weeds: such weeds are grown only in association with man and his agriculture. It is
never found in wild form e.g. Chenopodium. Anagallis etc.
A2 Facultative weeds: such weeds are grown both as wild and in cultivated habitats e.g.
Argemone mexicana, Euphorbia hirta
B. On the basis of Dependence on Host:
B1 Total Root parasite/Holo root parasite e.g. Orobanche also caaled Broomrape (on tobacco)
B2 Total stem parasite/Holo stem parasite e.g. Cuscuta also called Amarbel/dodder (found on
tomato, tobacco as well as on trees)
B3 Semi-root parasite e.g. Striga (on maize, millet, sorghum, rice, Sugarcane, pearl millet, cowpea,
barley and wheat)
B4 Semi-stem parasite e.g. Loranthus also called birdvine (on Litchi, mango trees)
Chenopodium Euphorbia hirta Argemone mexicana
Anagallis
BADI DOODHI SATYANASHI / MAXICCAN PRICKLY POPPY
KRISHNA NIL

Orobanche Cuscutta Striga Lorenthus

TOTAL ROOT PARASITE TOTAL STEM PARASITE SEMI-ROOT PARASITE SEMI-STEM PARASITE
Q: Write some harmful and beneficial effects of weeds.

Weeds, as unwanted and often invasive plants, can

have both harmful and beneficial effects. Here are
some examples of each:
 Competition for Resources: Weeds compete with
cultivated crops or desirable plants for essential
resources such as water, nutrients, sunlight, and
space. This competition can reduce crop yields and
hinder the growth and development of desired
plants.
 Economic Impact: Weeds can cause significant
economic losses in agriculture by reducing crop
productivity, increasing production costs (e.g., for
weed control measures), and decreasing the quality
of harvested crops. (Weeds cause annual crop loss
of $11 billion in India, says study New Delhi,
Hindustan Times; Feb 06, 2018 09:09AM IST)
Q: Write some harmful and beneficial effects of weeds.

 Ecological Disruption: In natural ecosystems, invasive weeds can

disrupt native plant communities, alter ecological processes, and
reduce biodiversity. They can outcompete native plants, leading to
changes in species composition and ecosystem dynamics.

 Habitat Modification: Certain weed species can modify habitats,

altering soil characteristics, water availability, and microclimate.
These changes can negatively impact native plants, animals, and
microorganisms, affecting overall ecosystem health.

 Pest and Disease Hosts: Some weeds can act as hosts for pests,
diseases, or plant pathogens, providing them with a favorable
environment for reproduction and spread. This can increase the risk of
pest and disease outbreaks in agricultural and natural systems.
See: Horticulture crops like cucurbit, radish potato,
cabbage, amarantus Insect Host on weeds
See: Horticulture crops like Banana and Citrus Insect Host on weeds
Alternate hosts of some important pests and diseases
Crop Pest Alternate host (weeds)
1 Red gram Green caterpillar Amaranthus, datura

2 Castor Hairy caterpillar Crotalaria sp.

3 Rice Stem borar Echinochaloa, panicum

4 Wheat Black rust Agropyron repens

5 Maize Downey mildew Sacharuns pontaneum

6 Pearlmillet Ergot Cenchrus cillaris

 Beneficial Effects of Weeds:
 Soil Stabilization: Weeds can help stabilize soil, especially in disturbed or bare areas. Their root systems can help prevent
erosion, improve soil structure, and enhance water infiltration.

 Biodiversity Support: In some cases, certain weed species can provide habitat, food sources, or shelter for native
wildlife, insects, and pollinators. They can contribute to overall biodiversity and ecosystem resilience.

 Soil Improvement: Some weed species have deep taproots or fibrous root systems that can help break up
compacted soil layers and improve soil aeration and drainage. They can also accumulate nutrients and organic
matter, enriching the soil.

 Succession Facilitation: Weeds often play a role in early successional stages of ecosystem development, helping
to prepare the ground for the establishment of other plant species and the eventual restoration of more diverse
vegetation.

 Medicinal and Nutritional Uses: Certain weed species have traditional or contemporary uses in herbal medicine,
providing medicinal benefits. Additionally, some edible weeds can be a source of nutrition and may have
cultural or culinary value.

 It's important to note that the harmful or beneficial effects of weeds can vary depending on the specific weed
species, the context (agricultural, natural, or urban), and the management goals. Effective weed management
strategies aim to minimize the harmful impacts while considering the potential benefits or ecological functions
that certain weeds may provide.
Based on soil type
 Weeds have affinity to grow under black cotton soil, red/light soil and laterite
soil.

 Weeds of black cotton soil : Aristolachia bracteata , Digera arvensis ,

Amaranthus viridis, Abutilon indicum, Cynotis axillaris, Celosia argentia,Dinebra
retroflexa , Cynodon dactylon , Ranunculus repens , Plantago spp., Rumex
dentatus, and Sorghum halepense.

 Weeds of light/ red soil:

 Commelina benghalensis, Cyperus rotundus, Digitaria sanguinalis, Dactyloctenium aegyptium,

Xanthium strumarium, Cenchrus spp., Leucas aspera, Tribulus terrestris and Euphorbia hirta.

 Weeds of laterite soil:

 Laterite soil : Laterite is a soil and rock type rich in iron and aluminium and is commonly
considered to have formed in hot and wet tropical areas.

 Ex : Chrolaena odorata, Lantana camara and Hyptis suaveolens.

 Weeds of black cotton soil

Fig:1Aristolachia bracteata, 2.Digera arvensis, 3.Amaranthus viridis,

Fig:1 Abutilon indicum (Indian mallow), 2. Cynotis axillaris, 3.Celosia argentia (Safed murg)
Fig:1 Dinebra retroflexa (Viper grass), 2.Cynodon dactylon (Doob), 3.Ranunculus repens (Creeping buttercup)
Fig:1.Plantago , 2.Rumex dentatus (Jangli Palak), 3.Sorghum halepense (Johnson grass)
 Weeds of light/red soil

Fig:1 Commelina benghalensis, 2.Cyperus rotundus (Nutgrass), 3.Digitaria sanguinalis (crabgrass),

 Weeds of laterite soil

Fig:1 Chrolaena odorata, 2. Lantana camara and 3.Hyptis suaveolens.

Based on Origin
(a) Indigenous weeds: All the native weeds of the country come under this
group and most of the weeds are indigenous.e.g. Acalypha indica, Abutilon
indicum
(b) Introduced or Exotic weeds: These are the weeds introduced from other
countries. These weeds are normally troublesome and control becomes difficult.
e.g. Parthenium hysterophorus, Phalaris minor, Acanthospermum hispidum

Based on soil reaction :

 Acidophile : Weeds thrive on acidic soil, e.g. Rumex acetocella, Ranunculus spp.,
Polygonum persicaria, Sonchus spp., Spergulla arvensis and Taraxacum officinale.
 Basophile :
 Weeds thrive on saline and alkaline soil, e.g. Daucas carota, Chenopodium spp,
Anagallis arvensis and Brassica hirta (white mustard).
 Neutrophile : Weeds thrive on neutral soil, e.g. Acalypha indica, Chenopodium album,
Senecio vulgaris, Cichorium intybus, Amaranthus spp. And Portulaca oleracea.
 Indigenous weeds

Fig:1. Acalypha indica, 2. Abutilon indicum

 Introduced or Exotic weeds

Fig: 1.Parthenium hysterophorus, 2.Phalaris minor, 3.Acanthospermum hispidum

 Acidophile Weeds

Fig.1. Rumex acetocella, 2. Ranunculus spp., 3.Polygonum persicaria, 4. Sonchus spp.,

5.Spergulla arvensis 6.Taraxacum officinale.

Basophile :

Fig. 1.Daucas carota, 2. Brassica hirta (white mustard).

Neutrophile:

Fig. 1. Acalypha indica, 2. Portulaca oleracea.