Lectures 1 & 2: Introduction to weeds Seed ecology Weed management methods

Flashcards on Introduction to Weeds, Seed Ecology, and Weed Management Methods.

Weeds

Unwanted and undesirable plants, plants out of place, or any plant interfering with human activities or welfare.

Characteristics of Weeds

Long seed life in soil, quick emergence, ability to survive in disturbed conditions, rapid early growth, and no special environmental requirements for seed germination.

Losses Due to Weeds

Losses caused by weeds are the highest among agricultural pests. Weeds cause 45% of losses, insects 30%, disease 20%, and other pests 5%.

Harmful Effects of Weeds

Includes reducing crop yield, increasing production cost, reducing quality, harboring other pests, reducing land value, limiting crop choice, and reducing labor efficiency.

How Weeds Reduce Crop Yield

Competition for sunlight, nutrients, water, and space, with intensity depending on weed species, density, time of emergence, duration of infestation, crop competitive ability, and climatic conditions.

How Weeds Increase Crop Production Cost

Include herbicide use, number of tillage/weeding operations, farm equipment depreciation, and cost of harvesting.

How Weeds Reduce Quality

Animal products (wool, milk), leafy vegetables (wild onion), oil (Mexican poppy), and contamination of crop grain (weedy rice, wild oats).

How Weeds Harbour Other Pests

Alternate hosts of insects (rice stem borer, tomato stalk borer), diseases (black stem rust, rice blast, cucumber mosaic virus), and nematodes.

How Weeds Reduce Land Value

Heavy infestation can make land unsuitable (nutgrass, parthenium weed), reduce economic value of lakes (water hyacinth), and block irrigation channels and drains (water hyacinth).

How Weeds Limit Crop Choice and Reduce Human Efficiency

Presence of a particular weed limits the choice of crops and reduces human efficiency through physical discomfort caused by allergy, poisoning, or spines.

Weed Life Cycle Classification

Annual, biennial, and perennial.

Weed Growth Character Classification

Broadleaf, grass, and sedge.

Weed Reproductive Propagules Classification

Seed (sexual) and vegetative (asexual).

Weed Photosynthetic Pathways Classification

C3 and C4.

Weed Photoperiod Classification

Short day, long day, and day neutral.

Weed Plant Architecture Classification

Herbaceous, semi-woody, and woody.

Weed Origin Classification

Native and introduced.

Weed Seed Dispersal Methods

Wind, water, animals, birds, and humans.

Weed Seed Bank Components

Seed rain + seed dispersal, decay, predation, and germination.

Seed Dormancy

A state in which a viable seed fails to germinate under conditions favorable for plant growth.

Factors Affecting Seed Germination

Light, temperature, seed scarification and fire, burial depth, and crop residue.

Temperature Effects on Seed Germination

Constant and fluctuating temperatures affect seed germination.

Seed Coat Impact on Germination

Hard seeds require scarification (physical/chemical) to enhance germination.

Seed Burial Depth

Affects vertical seed distribution.

Crop Residue Impact

Provides a physical barrier to emerging weeds, reducing and delaying emergence.

Preventive Weed Management Measures

Plant crop in weed-free conditions, reduce weed seed input, increase seed losses, and reduce the probability that residual seeds establish.

Fallow-Focused Weed Management

Weed control in the fallow phase is very important.

Cover Cropping

Growing a crop during a fallow period to create ground cover that helps increase water infiltration, slow evaporation, and manage weeds.

Strategic Tillage Use

Bury the seeds below their maximum depth of emergence.

Narrow Row Spacing

Gives advantages to the crop by developing faster canopy closure and less light penetration.

High Seeding Rates

Used to suppress weeds where weed control is expected to be poor.

Weed-Competitive Cultivars

Taller genotypes and early crop vigor were both closely associated with suppressed weed seed production and tolerance to weed competition

Harvest Weed Seed Control

Weed seed control at harvest (e.g., Harrington Seed Destructor).

Rotations (Crop, Herbicide, Tillage)

The best way to manage weeds, allowing the use of different management practices.