Agriculture

1. Prepared By-
Mr. Ashutosh Patidar
Assistant Professor
(Vikram University)
Today Lecture

2. Types of Weed in various
Crops and its Harmful
effects in crop production
Topic

4. Weed
Weed is such an undesirable plant growth or
weed is a plant growing where it is not wanted
and grown in association with crop, which
snatches major parts of nutrient, water, light,
space & CO2 available to crop and are useless,
poisonous.

5. ✓ Weeds are unwanted and undesirable
plants that interface with the utilization
of the land, water resources and thus
adversely affect crop production and
human welfare.
✓ Weeds can also be referred as plants out of
the place.

6. ✓ Congress grass is called “king of weed”.
✓ 30,000 species of plant are categorized as weed
but only 18000 species are registered as weed.
✓ The term weed was coined by Jethrotull

7. Problems of Weed
Extent of loss in crop yield- It depends on intensity of infestation,
time of occurrence and type of weed. Yield losses due to weeds
were higher in broadcasted or direct sown, rice (27.3%) then in
transplanted rice (21.6 %), and average losses due to weeds in
different crops were 30 to 40%, in soybean, potato, vegetable, root
crops and 15 to 20 % in cereal crops.

8. Loss of Quality- Contamination of food grains with weed seeds and
weed seeds present in the produce causes odd odors to flavour.
Harbour pest and diseases- Weeds provide shelter to many pests
and diseases.
Human health- Spread of diseases in human.
Interference- It interferes with agricultural operations, ex. Sowing,
harvesting, inter-cultivation.

9. Characteristics of Weed -
1. Large number of seed production and small size of seed - Test weight
of Phalaris minor - 2 gm.
2. Dormancy - mostly weed seed have dormant and viable for many years.
Ex- Field bind weed 50 year, Goose foot 40 year.
3. Vegetative reproduction - Rhizomes, stolen, bulbs etc
4. Root systems-
✓ Monocot weed - Seminal roots
✓ Dicot weed - Tap roots

10. Type of Photosynthesis - Most of the weeds have C4 type of
photosynthesis.
Weed seed dispersion - wind, water, human, animals, farm yard manure,
and agricultural implements.
Germination and flowering at very early stage of life and they are prolific
with abundant seed Production potentialities.
Root of some weed is very deep viz. convolvulus arvensis 20 feet, and
Java grass 5-7 feet.

11. Weed Growth Stages
Early stages of weed growth are important for
weed controls.
Examples
Germination – Seedling – Tillering –
Stem elongation – Inflorescence
emergence – Milking – Dough – Maturity.

12. Crop weeds competition
Light, Nutrient,
Water, CO2.

13. Harmful Effects
of Weed

14. • Competition for mineral nutrients- Being hardy and vigorous in growth
habit; they soon outgrow the crops and consume large amount of water and
nutrients. In general, weeds removed N and K from soil in much greater
quantity than P.
• Competition for water- Weeds consume large amount of water as
compared to other crop plants For producing equal amount of dry matter,
the weeds, in general transpire more water than most crop plants e.g. wild
mustard transpires about four times more water than a crop of oat.
• Competition for Solar Energy- About 99% of dry matter in plants is made
up of organic matter that is dependent on solar energy. When plants are
mutually shaded, their production potential is greatly reduced even though
water and other nutrients are available to them in abundance. Emerging
plants are shaded by quick growing weeds

15. • Competition for space- Weeds compete for space both in the rhizo sphere and
atmosphere. In the presence of weeds, crop plants also have limited space to
develop their shoots, which amounts to reduced photosynthesis in them. More
seed production of weeds Growth habits of weeds
• reduce the crop quality- Weeds may reduce the quality of the crop produce in
many ways. Weed seed like wild mustard, sweet clover, a Mexican poppy and
bulblets of wild garlic and wild onion when threshed and ground with winter
grains can results in serious consequences besides imparting objectionable odour
to the flour.
• impair the quality of the animal produce- Many weeds in pastures and forage
crops impart undesirable flavors to milk and meat of animals. For e.g. Pivali
tilwan (Cleome viscosa) imparts undesirable flavour to milk. Gokharu or Landaga
(Xanthium strumarium) get attached to the body of sheep and seriously impair the
quality of wool.

16. • Harm animal health- Several weeds of grasslands and forage crops contain
high alkaloids, tennis, oxalates, glucosides, and other substances that prove
poisonous to animals when ingested. For e.g. Silky lupine ( Lupinus
sericeous) is responsible for crooked calf disease. Some weeds are noxious
and produce poisonous chemical which are injurious to animal health
• Harbor insect pests or diseases- Weeds either give shelter to various insect
pests and diseases or serve as alternate host. For e.g. Weed around paddy
bunds harbour the gallfly. Weeds act as a host Cause of many diseases
• Damage human health- Health, comfort and work efficiency of man are
also affected by weeds directly or indirectly. For e.g. people in U.P. are
plagued year after year with hay fever and asthma aggravated by pollens of
rag weeds. Lantana flower leaves are dangerous for humans.

17. • Contaminate water bodies- Aquatic weeds change the flavor appearance and
taste of drinking water. Aquatic weeds are a menace to fisheries too. Aquatic
weeds on decomposition gives offensive odors and pollute atmosphere.
• Himalayan balsam- Himalayan balsam grows fast and can reach two to three
meters in height. It rapidly spreads on the banks of slow-moving watercourses and
becomes dominant, stopping other plants growing.
• Quicker wear and tear to farm implements- Being hardy and deep-rooted, the
tillage implements get worn early.
• Reduce the value of the land- Agricultural lands heavily infested with perennial
weeds like Kans (Saccharum spontaneum) always fetch less price. Giant hogweed

18. • Less efficient use of land- In case of perennial weeds, the carrying capacity
of the grazing lands is reduced and cause depreciation of land value.
• Increase in cost of cultivation- In fields of crops infested with weeds, the
tillage operations require high cost.
• Disturbance in Public places- It is desirable that public places be kept
clean of weeds. Presence of weeds around our living and working places
makes the surroundings dull.

19. Herbicide

21. Thank You