weeds stress on crops

1. Name
Ihsan Ullah
Class no 148
Topic of
presentation:
Weeds stress
The university of
Agriculture
Peshawar

2. Weeds stress
What is weed…?
1)Un wanted plants
2)Grow with out cultivation
3)Grow out of its place
4)More harmful effects
5)Compete or interfere with other crops life cycle.
6)Exhaustive in nature.
*A cotton plant in a corn is a weed*

3. Characteristics of weeds
 Longevity of seeds of e.g. ( cheno podium seeds live in soil for 30 to 40 year)
 Fast to grow / early emergence e.g. (sorghum helephense )
 Produce more seeds e.g. ( portulaca olaracea , parthenium )
 Multiple approach to produce e.g. Rhizomes , Bulbs seed cutting
 Deep rooted e.g. ( Alhajai mrale 30 to 40 m)
 Highly competitive and highly adaptive under adverse climate.
 Mature flower earlier ahead of the crop
 Creeping nature
 Most weeds are C4 pathways
 Change morphology according to the climate.

4. Common weeds
1

5. Common weeds
2

6. Losses due to weeds
 Weeds decrease production of wheat 42 %.
 Also play a major role for damaging quality of the grains.
 41% percent loss in cotton crop.
 35 % percent loss sugar can.
 39 % percent loss in rice.
 47 % percent loss in maize.

7. Losses….
 55 % percent losses in pulses.
 45 % percent losses in oil seeds crops.
 89 % percent production losses in vegetables.
 Weeds also provide suitable environment to pests which cause injurious to the
crop production.
 Weeds also absorb nutrients of the crops.

9. Rice crop weeds
1

10. weeds in onion and spinach

11. pulses
soybean

12. Weeds provide space to plants pests and nematods

13. Weeds crop competition
 Critical period of competition cpc
 during the crop period there is certain time when crop plant are most sensitive to
competition by weeds . This time is called CPC
 Critical threshold level ctl
A weed density capable of causing significant damage to a crop is termed critical
threshold level.
Threshold level are different for different weed species
The philosophy of weed control should always be to keep the weed density below the
CTL

14. Components of competition
a. Competition for nutrients
 weeds compete with crops for nutrients.
N the major common element needed in large amounts both by weeds and crops . for
example AMARANTHUS SPINISUS takes (ca and K )very quickly.
 In the rice crop ZINC deficiency cause due to weeds which takes the Zn
vigorously

15. Competition for moisture
a. Most weeds have not a god root system but have also more tolerant to drought
than crop
b. Competition for moisture weeds cause serious damage to crops . Particularly in
rain fed areas.
c. CONVOIVULUS ARVENSIS & SORGHUM HALEPENSE have very deep root
system can extract moisture from deeper zones of soil
d. VICE SATIVA due to its leaf morphology have low transpiration than crops which
compete with drought easily than crop .

16. Competition for light
a. Light is an essential requirement for p.s
b. Weeds and crop compete for light
c. Different weeds respond differently to reduced as well as natural sunlight.
d. The growth of the many plants suffers very badly due to un availability of sufficient
light.

17. Competition for co2
a. Co2 serves is a substrate for photosynthesis
b. At normal co2 level competition take place among plants for co2
c. Most weeds belong to the C4 group . because of the characteristically low CO2
compensation points of C4 plant,weeds usualy outcompete crop plants which
mostly belongs to C3 group In C2 utilization from the atmosphere.
d. Competition for co2 are the one factor in yield loses caused by weeds.

18. Competition for space
a. Plants require space to accommodate their physical body structures.
b. Weeds share the space b/w the plants as a un-invited guests
c. Under such condition when there is no enough space for both weeds and crop
plants competition for space take place
d. Since the weeds grow faster and outcompete the crop plants and reduce their
tillering and branching and ultimately the crop yield.

19. Harmful effect of weeds
 Weeds compete with crop for space light moisture and in soil nutrients thus
causing reducing in yield
 Effect quality of form produce live stoke products such is milk and skin (euphorbia
helioscopia lift pungent smell in milk)
 Animal dead due to eating poisonous weeds such is datura stramonium
 Cause health problems to humans e.g cynodon dactylon , eleusine indicia cause
allergy problems.
 Increase the cost of cultivation due to weeding operation.
 Reduce land value
 Act is a alternate source of pests insects and disease.

20. Beneficial effect of weeds
 Use is a fodder
 Use is a vegetable (amarnthus viridis and digra arvensis)
 Use is a soil binder
 Use is a manure ( when weeds are ploghed in the green stage, they add many
nutrients to the soil)
 Use is a fuel (prosopis juliflora)
 Weeds have medicinal value ( eclipta alba used for scorpion sting curing . Leuccas
aspera used for caring of snake biting)
 Ornamental purpose
 Soil erosion control
 Construction

21. Weeds management

22. Weeds management
 Manually (by hand) through sickle hand hoe etc.
 Mechanical or physical control use of physical force( tillage mowing water
management field burning)
 Chemically (NACL 2 4 D bordeux mixture)
 Culturally control (planting time, planting density, crop rotation mulching )

23. Others practices
1. Flooding
2. Pre and post tillage
3. Crop rotation
4. Burning
5. Cover crop
6. Resistant verities
7. Clean and good seeds.

24. Weeds management
1 2

25. Mulching & tillage

26. Cover crop with maize and mulching brocoll

27. Burning control

28. References
 Crop production (shafi nazir , elena bashir robyn bentel)
 manalo et al 1971
 Mercado 1979
 Agriculture the basics
 Google and UNIVERSITY OF FAISAL ABAD
 Science direct