Organic weed management

Y Sanatombi Devi, M Sumarjit Singh, Priyaka Irungbam and Y Bebila Chanu
Contd from previous issue
It is probably the oldest method of controlling wees and it is still a practical and efficient method of eliminating weeds in cropped area. It is very effective against annuals, biennials and controls only upper portions of perennials. This method is useful for small-scale infestation. It is best to hand pulling wees after rain, when soil is moist.
Hand hoeing: It is a post-planting intercultural operation which stirs the soil and makes it more loosened and digging up to deeper layers so as to remove underground storage organs. It is very helpful in the case of perennial weeds and it is done with the help of pick axes.
Tillage: The objectives of tillage to provide a good seed bed and a root bed for smooth germination and better root growth and subsequent rapid seedling establishment and to reduce/control initial flushes of weeds by means of exhausting weed seed bank remain unchanged. Tillage brings about alternations in the physical chemical and biological properties of soil and thus, it favours crop growth and influences competition behaviour. Tillage breaks cuts or tears off weeds and exposes them to desiccation by sun. It reduces population of perennial weeds by exhausting food reserves of the vegetative structures.
Flooding: Flooding is successful against weed species sensitive to longer periods of submergence in water. Flooding kills weed by reducing oxygen availability for weed growth. The success of flooding depends upon complete sub- mergence of weeds for longer periods. Flooding constitutes an important mechanism/aspect of weed management in rice.
Mowing: Mowing may also play a critical role in managing weed in forage crops or non-crops area. Repeated mowing reduces weed competitive ability, depletes carbohydrates reserves in the roots, and prevents seed production. Mowing can killed or suppress perennials and biennial weeds. It can also suppress perennials and help restrict their spread thus, decreases the long term development of the weed population. A single mowing will not satisfactory for weed control, however mowing 3 or 4 times per year over several years can greatly reduce the occasionally eliminate certain weeds. Regular mowing help prevent weeds from establishing, spreading and competing with desirable forage crop.
Biological method: It involved the use of bio agent that affect the health of the weed or reduce weed population. An important aspect of biological weed control is that at a time, it is applicable to the control of only one major weed species that has spread widely. With perennial weeds the main objective of bio-control is the destruction of the existing vegetation, in the case of annual weeds prevention of their seed production is generally more important.
Allelopathy: Allelopathy is defined as any direct or indirect harm induced in one plant through toxic chemicals released into the environment. Such weed control will neither harm the environment nor increase and management costs. Allelopathy weed control may be applied as a single strategy in certain cropping systems, such as organic farming. Small seeded and slow germinating crop are more likely to be adversely affected by allelopathic cover crops than large seeded rapidly germinating crop. Under allelopathic weed management, the allelopathic potential of crop is manipulated in such a way that the allelochemical from these crops reduce weed competition. Allelochemicals can be found in different concentrations in several parts of plants (leaves, stems, roots, rhizomes, flower and even pollen). Such chemical are release from plant parts by leaching, volatilization, residue decomposition, root exudation.
Bioagent: Pests that attack part of weed can reduce the number of weed present, which in turn can reduce the size of future weed populations. This lowers the effort needed to control the remaining emerging weeds.
Bioherbicide: Herbicide listed by the Organic Materials Review Institute (OMRI) for use in organic production as of May 2004. All product listed are classified as listed
Corn gluten meal: Corn gluten meal is a by-product of corn processing. The use of corn gluten meal as herbicide was patented in 1991. It can be use as an organic herbicide. CGM displayed pre-emergence herbicide effects during a series of turfgrass and also affected the small seeded annual and perennial weed. Corn gluten meal works by inhibiting the root formation of germinating plants. It should be applied before germination of weeds. If it does not rain in 5 days of application, water it in with approximately 0.25 inches of water. Then leave a drying period after germination.
Herbicidal soap: Made from ammoniated soap of fatty acid, it is a non-selective weed killer that can be used within vegetable and flower garden, landscape areas and may be used in cultivated area. It kills moss, algae and weed. Best results are obtained with young, actively growing weeds, less than 5 inches in size. Larger weed may require second application.
Vinegar: Vinegar has proven itself an effective weed killer. It is a non-selective bioherbicide. Unlike commercial weed killers, vinegar is eco-friendly and won’t harm people, pets or the environment.
Steps for preparation:
1. Pour 1 gallon of white vinegar into a bucket.
2. Add 1 cup of table salt. Stir the solution with a long-handled spoon until all the salt dissolves.
3. Stir in 1 tablespoon of liquid dishwashing soap. This will act as a surfactant and make the    vinegar and salt solution adhere to the weeds more efficiently. Blend thoroughly.
4. Funnel the weed killer into a plastic spray bottle
5. Drench the weeds with the solution on a dry, sunny day.
6. Any plants soaked with this solution will die within several days. They won’t be back and nothing else with ever grow there.
Conclusion: Increase in chemical residue in harvested produce of crop if such type of food eaten by human being it causes harmful effect due to disturbance of food chain. To eliminate the harmful effects of chemical methods of weed control there is one option that is eco-friendly weed management for sustaining ever growing popu- lation. Maintaining appropriate crop rotation with legume and non-legume crops, and growing of cover crop helps to suppress weeds by smothering and allelopathic effects. Growing competitive cultivars, modifying in sowing and planting techniques and mulching with organic residues, and the adoption of tillage operation makes an inappropriate environment for weed seed germinations and their growth.