weed management in cropping system

1. WEED MANAGEMENT IN CROPPING
SYSTEM
PREPARED BY
KABIRU LAWAN
2301B06102
AGRON 503- PRINCIPLES AND PRACTICES OF WEED MANAGEMENT
INCHARGE: Ms. MUTHA SRAVYA

2. CONTENTS
• INTRODUCTION
• THE NEED FOR WEED MANAGEMENT
• WEED MANAGEMENT STRATEGIES
• CONCLUSION
• REFERENCES

3. INTRODUCTION
• Weed control within the first several weeks after crops are planted is critical in order
to avoid a yield reduction from weeds.
• The effectiveness of any weed control program depends largely on timeliness of the
control.
• Preventative, cultural, mechanical, and chemical weed management methods all are
most effective if applied at the correct time.
• Fields that are kept free of weeds for the first several weeks after planting give the
crop a competitive edge that allows the crop to shade out or out compete weeds
that emerge later in the season.

4. Contd…
• Accurate weed identification is the first step to successfully managing weeds.
• Since weeds vary in their ability to compete with crops and reduce yields and
also vary in their response to different management strategies, proper
identification is essential to develop effective management plan.

6. THE NEED FOR WEED MANAGEMENT
• Reduction of crop yield is the major justification for the effort and
expense of weed management in arable crops.
• While in horticultural crops effects on crop quality are also
important.
• In most agricultural systems there has been a reduction in manual
weed removal.
• Increase production costs, interfere with harvest, and lower product
quality.

7. Contd…
• Weeds also impede irrigation water-flow, interfere with pesticide
application, and harbour disease organisms.

8. WEED MANAGEMENT STRATEGIES

9. PREVENTION
• The most important factor in overall weed control is to prevent weeds from developing seed and perpetuating the
weed problem.
• Sources of weed introduction include weedy stock, weed seeds in the growing area or nearby, or plant propagules
in manure, soil, uncomposed yard waste, or other organic matter sources.
• Many growers cultivate or treat the margins of the property with herbicides to reduce the number of windborne or
water-carried seeds that can move to the growing area.
• Screens on open-water inflow sources can be installed to keep out water-borne seeds.
• When using fine-mesh screens, increasing the surface area of the water intake and periodic debris removal may be
needed to avoid clogging of the water flow

10. CULTIVATION
• Weed management systems for field-grown crops start with mechanical cultivation.
• Begin this process by irrigating the field to induce weeds to germinate and then cultivate the new seedlings.
• Alternatively, the field can be sprayed with a postemergence herbicide after weed emergence so that the soil will not be
disturbed by cultivation before planting.
• Each time cultivation occurs, new weed seeds can be brought close to the soil surface and germinate. This method reduces
the soil seed bank so fewer weed seeds will be present to germinate when the crop is planted.
• After planting (and crop emergence if a seeded crop), preemergence herbicides can be used before weed emergence or the
field can be cultivated between rows after new weeds germinate or both.
• After harvest, cultivate again to kill emerged weeds so they do not seed and replenish the weed seed bank.

11. COVER CROPS
• Cover crops can be used between rows and at field edges to improve weed management and to allow
for another crop to grow instead of weeds.
• The cover crop selected will depend on soil type, environmental conditions, and the crop.
• The cover crop can be a living mulch that is repeatedly mowed to minimize competition, or it can be
sprayed with herbicides and used as a nonliving mulch.
• Certain cover crops can be hard to suppress with herbicides, such as white or strawberry clovers.
• An annual cover crop can be established and allowed to senesce naturally or (where freezing
temperatures occur) be killed back by exposure to frost

12. MOWING
• Mowing is used to prevent rampant growth of the weeds, reduce the formation of seed, and reduce
the spread of weed seed into cultivated areas.
• Properly timed mowing can also suppress some perennial weeds such as established
johnsongrass.
• However, repeated mowing over a period of time (seasons or years) without any other means of
weed control tends to favor the establishment of low-growing perennial grasses, which are very
competitive for water and nutrients.
• Also, species that have flower heads below the level of the blade are not effectively controlled. If
performed after seed set, mowing can spread weed seed and exacerbate weed problems

13. FLAMING
• Flaming can be used before planting or on weeds between crop rows.
• To avoid injuring the crop, direct the flame at young weeds between the rows or use shields.
• Broadleaf weeds are controlled more effectively than grasses by flaming, and young weeds are
better controlled than older ones.
• Because of the cost of fuel, the time required to pass over the beds, potential injury to workers,
and fire hazard, flaming is not a widely used method of weed control for field-grown flowers or
nurseries.

14. HAND REMOVAL
• Hand-pulling of weeds is always a part of crop management because cultivation
does not remove all of the weeds.
• In some crops there may not be any other method of control.
• By removing the few remaining weeds in the crop, not only will there be less
competition, but fewer weed seeds will be produced.

15. MULCHING
• Various kinds of bark, composted yardwaste, and other organic material can be used to help
suppress annual weeds by covering the soil surface and preventing weed seed germination and
establishment.
• Only 2 to 3 inches of fine organic mulch (finished yardwaste) may be required to totally eliminate
light on the soil and suppress the growth of weeds.
• An advantage of the fine mulches is that after the crop is harvested, the mulch can be worked into
the soil to improve drainage, soil structure, and water-holding capacity of the soil.
• A disadvantage of fine mulch is that weed seeds that fall on it will germinate and grow

16. SOIL POLARIZATION
• Heating soil to high temperatures can kill many weed seeds.
• Solarization is done by covering bare, moist soil with clear plastic during periods of high solar radiation and
temperature.
• Before placing the plastic on the site to be treated, cultivate or closely mow any established plants and remove the
clippings, then smooth the soil surface and irrigate the area well.
• Place clear polyethylene that is ultraviolet (UV) resistant over the area and extend it about 2 feet beyond the
infested area on all sides and pull it tightly so it is close to the soil.
• The plastic must be left in place and maintained intact for 4 to 6 weeks for control of weeds.
• Many annual weeds can be controlled using this method. Weeds not well controlled include clovers, field bindweed,
and purple and yellow nutsedge.

17. HERBICIDE
• Herbicides are used in many ornamental and arable crop production areas as an economical option to control
weeds.
• By using herbicides before weeds emerge, weed competition with the crop can be reduced or eliminated, resulting
in higher quality plants and less labor costs.
• Herbicides are generally classified according to when they are used in relation to crop and weed growth stage.
• Preplant herbicides are applied before planting, These herbicides are used before the desirable plants are present
because some can control both germinating seedlings and established plants.
• Preemergence herbicides kill weeds at the seed germination stage, These herbicides are applied before weeds
emerge. Postemergence herbicides are applied after the weeds have emerged. Preemergence and postemergence
herbicides may be applied before or after the crop is planted depending on the crop and the herbicide selected

18. Contd…
• Postemergence herbicides are applied after the weeds have emerged.
• Preemergence and postemergence herbicides may be applied before or after the
crop is planted depending on the crop and the herbicide selected.

19. CONCLUSION
• Weeds pose severe competition with the crops for various growth resources.
• Besides reduction in grain yield, weeds also reduce the quality of produce and act
as alternate host for disease causing organisms and insect-pests.
• Hence, various weed management practices need to be integrated in an appropriate
manner during critical period of crop-weed competition
• Research on herbicide mixtures, post-emergence herbicides in pulses and oilseeds,
management of parasitic weeds, weedy rice, weed competitive crop cultivars with
acceptable yield potential, weed management in changing climate scenario and
conservation agriculture, effect of herbicides on soil microorganisms, etc. need to be
strengthened.
• Considering the several advantages of using the herbicide resistant crops, it is
worthwhile exploring their possible use under specific environmental conditions.

20. REFERENCES
• Altieri, M. A. and M. Liebman. 1986. Insect, weed and plant disease management in multiple cropping
systems. Pp. 183–218 in C. A. Francis (Ed.), Multiple Cropping Systems. Macmillan, New York.
• Altieri, M. A. and M. Liebman (Eds.). 1988. Weed Management in Agroecosystems: Ecological Approaches.
CRC Press.
• Boca Raton, FL. Altieri, M. A. and P. Rosset. 1999. Ten reasons why biotechnology will not ensure food
security, protect the environment and reduce poverty in the developing world. Mindful Organization.
Available: http://www.Mindful.org/GE/Ten-Reasons-Why-Not.
• Altieri, M. A., A. van Schoonhoven, and J. A. Doll. 1977. The ecological role of weeds in insect pest
management systems: A review illustrated by bean (Phaseolus vulgaris) cropping systems. PANS (Pest Artic.
News Summ.) 23:195.
• Altom, J. D. and J. F. Stritzke. 1973. Degradation of dicamba, picloram, and four phenoxy herbicides in soils.
Weed Sci. 21:556–560.