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Cultural weed control
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- 2. Defination Cultural weedmanagement is defined as any practice or effort adopted by the farmer in crop production which minimizes weed interference problem but such methods are not necessarily directed or aimed at weed control Cultural weed control includes non-chemical crop management practices ranging from variety selection to land preparation to harvest and postharvest processing. Cultural weed control is a part of integrated weed management which involves the integrated use of cultural, manual, and/or mechanical control methods.
- 3. Cont.. Several culturalpractices like tillage, planting, fertilizer application, irrigation etc., are employed for creating favourable condition for the crop. These practices if used properly, help in controlling weeds. Cultural methods, alone cannot control weeds, but help in reducing weed population
- 4. Field Preparation Thefield has to be kept weed free. Flowering of weeds should not be allowed. This helps in prevention of build up of weed seed population in the fields. Irrigation channels are the important sources of spreading weed seeds. It is essential, therefore, to keep irrigation channels clean. Deep ploughing in summer, exposes underground parts like rhizomes and tubers of perennial and noxious weeds to scorching summer sun and kills them. Conventional tillage which includes 2 to 3 ploughings followed by harrowing decreases the weed problem. Running blade harrows cuts weeds and kills them. In lowland rice, puddling operation incorporates all the weeds in the soil which would decompose in course of time.
- 5. PIanting Method Sowingof clean crop seeds without weed seeds should be done. It is a preventive method against introduction of weeds. Sowings are taken up one to three days after rainfall or irrigation depending on soil type. Weeds already present in the soil start geminating within two or three days. Sowing operation with seed drill removes some of the germinating weeds. Transplanting is another operation which reduces weed population. Since, the crop has an additional advantage due to its age
- 6. Planting Density Plantsof one type do not generally allow germination of other plants near their vicinity. Closer planting of crops suppresses germination and growth of weeds. Wider planting should be avoided. The principle is that the greater the amount of space taken up by the crop in the rows, the less space there is available for the weeds to invade. However, it should be borne in mind that closely spaced crop plants compete with each other
- 7. Fertilizer Application Plantsdiffer in their capacity to respond to fertiliser application. Crops like sorghum, maize, pearl millet and rice grow at a faster rate when nitrogenous fertilisers are applied and cover the soil earlier. Weeds like Cynodon dactylon, Cyperus rotundus do not respond to nitrogen application and they are suppressed by fast growing crops method of application(spot application,Banding,Fertigation using drip irrigation,Foliar application or Dolloping)
- 8. Crop-weed competition: Cropgenotype choice :Select a weed-competitive variety with early seedling vigor, and high tillering to suppress weeds. Transplanted crops tend to have fewer weeds and less yield loss than direct seeded crops. Transplant healthy, vigorous seedlings that can better compete with weeds in early stages. Maintain an adequate plant population that closes its canopy by maximum tillering to shade out weeds. Apply Nitrogen (N) fertilizer just after weeding to minimize rice-weed competition for N. Short statured, erect leaved varieties permit more light compared to tall and leafy traditional varieties. Weeds continue to germinate for long time in 'dwarf varieties resulting in high weed growth
- 9. Mulching: the weedsfind it difficult to receive enough light to grow and may not be able to pass through the mulch layer. Dry, hardy material, that decomposes slowly, keeps its effect longer than fresh mulch material.
- 10. Crop rotation: Croprotations lead to the use of different tillage systems, herbicides and general management because there are different selection pressures that are imposed on the weeds under different crops. Rotation of crops is the most efficient measure to regulate seed and root weeds. Changing the conditions of the crop interrupts the living conditions of the weeds thus inhibiting their growth and spread
- 11. intercropping (mixed croppingand under-sowing): Intercropping with fast growing weed- suppressive species (‘smoother crop’ or ‘living mulch’) between rows of main crop species is effective in weed control. There are different examples known to work in Africa, for example, pumpkins as intercrops in cassava to reduce weed occurrence.
- 12. Intercropping Intercropping isthe growing of two or more crops in the same field at the same time. It changes light spectral quality that gets to the ground It leads to quicker coverage of the ground. Light penetration to the ground is reduced hence the competitiveness of weeds is reduced. Common crop combinations for Zimbabwe are maize/pumpkin, maize/cowpea, maize/groundnut
- 13. Water management: flooding Water is the best control for weeds. Many weeds cannot germinate or grow under flooded conditions (e.g. most grasses and some sedges). Maintain a 2-5 cm water level in the field to minimize weed emergence and lower weed pressure. If water is sufficient, fields can be continuously flooded from the time of transplanting to when crop canopy covers the soil completely. Good land leveling is critical to avoid high spots where weeds can become established
- 14. Why Use CulturalControl of Weeds? Cost effective and easy to practice: Acceptable and accessible to small & large farmers Non-chemical and ecologically sound Prevention is better than cure
- 15. Limitations: Needs goodknowledge and understanding of various cultural practices that can reduce weed pressure Continuous vigilance and monitoring are essential to control weeds by cultural methods Some practices are labor intensive.