Weed management in Organic Agriculture

Manjunatha, G.A

Tools for prevention

Avoid the entry of weed seeds onto the farm through

• Manures

• Mulching material

• Intercultivation equipments

• Animals

• Water etc.

Instead of using manure - Use compost.

Different practices to control

• Cultural

• Mechanical

• Biological

• Chemical (organically approved)

Liebman and Gallandt, 1997

Cultural Practices

Improve crop competitiveness

• Increase crop density through narrow row

spacing and increased seeding rate .

• Use transplants, rather than seed.

• Choose competitive crop cultivars.

• Manage fertility according to crop needs; avoid

excess application.

• Spot application of fertilizers.

Intercropping

• Having different plant types growing together enhances weed

control by increasing shade and increasing crop competition

with weeds through closer crop spacing.

Ex:

• soybean +wheat

• Sugarcane + finger millet

• Sunflower + groundnut

Sugarcane+finger millet

Sunflower+groundnut

Crop Rotations

• Weeds tend to infest crops with similar life cycles

• Crop rotations limit the buildup of weed populations and

prevent major weed species.

• Altering, narrowly spaced crops with closely spaced crops,

shallow rooted with deep rooted crops, cold with warm season

crops.

Allelopathy

• Allelopathy crops are especially useful because they have the ability

to suppress other plants that attempt to grow around them.

• Rye is one of the most useful allelopathic cover crops which kills

weeds like ragweed (by 43%), pigweed (95%), and common

purslane (100%).

• North Carolina researchers investigated combinations of herbicide

use and cover crop plantings on weed control and reported Rye and

clover showed the highest weed control without herbicides.

Smother Crops

• Prevent seeds from germinating by blocking light, can smother

out some weeds.

• In northern states, oats are commonly planted as a “nurse

crop” for alfalfa, clover. The oats grow between in the place of

weeds and avoid weed emergence.

• Ex: Mustard as cover crop in Ragi.

mustard as cover crop in ragi

Weeding manually

• Hand weeding

• Removing of weeds manually before the flowering of weeds to

avoid weed establishment.

Diff hand Tools

Irrigation

• Drip irrigation is more water efficient .

• Also by directing water to the crop it minimizes weed

germination and reduces need to cultivate.

Mulching

• Covering the surface of soil to avoid the entry of sunlight by

using locally available materials like straw, plastic, papers,

wood pieces, dry leaves etc.

• Prevent seeds from germinating by blocking light, can smother

out some weeds.

Wood chips Dry Leaves

Biodegradable paper piecesStraw

Straw as mulching material in onion crop

Mechanical methods

• Cultivation of the soil with a variety of different tools can

control emerged weeds and disrupt weed reproduction cycles.

• Cost effective

• Time consuming

High-tech tools

Field cultivator High residue cultivator

High-residue cultivator Flex-tine weeder

Flexible spider weeder Badger weeder

Torsion weederRolling weeder

Basket Weeder

Flame weeding

• Burning of weeds by flame.

• Intense heat causing the cell sap to expand and disrupt cell

walls.

• Pre-emergent, and post-emergent flame weeding has been

successful in a number of crops.

• Flaming has generally proved most successful on young

broadleaf weeds.

• It is reportedly less successful on grasses.

Flame weeder

Solarizing the soil

Steps:

• Cultivate soil properly

• Irrigate soil completely

• Put plastic over the soil

– Weed get cooked

Breeding for Crop Competitiveness and Weed

Suppression

• Plant breeding is one way to improve weed management in

organic systems.

• Development of crops with increased competitive ability and

enhanced weed suppressive qualities .

• Crop qualities that promote crop competitiveness include early,

rapid establishment in less favorable conditions, crop structures

that limit weed access to light and nutrients ,increased plant

hardiness etc.

Bio Herbicide

Corn gluten meal (WeedBan and Corn Weed Blocker)

• It has been used successfully on lawns and high-value crops.

• pre-emergent herbicide.

Commonly based vinegar or lemon juice or clove oil ingredients

• Burnout : 23% acetic acid.

• Bioganic: 10% acetic acid plus clove oil and thyme oil.

• MATRAN & Weed Bye Bye etc

• post-emergent herbicides.

Weeder Geese(ducks)

They are particularly used as grass weeders

in a variety of crops.

Crops: cotton, strawberries, tree nurseries,

corn , fruit orchards, tobacco, potatoes,

onions, sugar beets etc.

Thank you….