Exam 2 Flashcards
What are the 6 different methods of seed dispersal?
- Mechanical
- Wind
- Water
- Human-aided
- Animal-aided
- Machinery
What is mechanical seed dispersion?
What are two example plants?
The spreading of seeds through “latching” using burs.
- Cockleburs
- Burdock
What is wind seed dispersion?
What are two example plants?
Spreading of seeds by being blown by the wind because they are attached to a pappus.
- Dandelion
- Canada Thistle
What is water seed dispersion?
What is an example plant?
Spreading of seeds by water. They have some manner of flotation like a bladder.
1. Curly Dock
What is human-aided seed dispersion?
What has reduced this?
- Spreading of seeds by humans. This is due to seed contamination during planting.
- The availability of certified seed.
What is animal-aided seed dispersion?
Spreading of seeds by animals primarily through their digestive tracts.
What is machinery seed dispersion?
Spreading of seeds by being on machinery and falling off of it during moving and use.
What is the “cardinal” rule of weed management?
Always buy and plant clean seed.
(T/F) If a seed passes through an animal’s digestive tract, it reduces but does not eliminate that seed’s viability.
True
What are the 6 (causes/contributors) (of/to) seed dormancy?
- Light
- Immature Embryo
- Impermeable seed coat
- Inhibitors
- Oxygen
- After-Ripening
What is the metabolic switch that activates seed germination in some weeds through light exposure?
Phytochrome
What is the given ratio-equation given to explain how light exposure activates germination?
(favors far-red)Pr->
What red light/far red light ratio favors germination?
Higher amount of red light than far red light.
(T/F)Tillage can expose enough light to weed seed to induce germination.
True
How was light exposure caused by tillage remedied?
Night time tillage
___ out of ____ species of weeds exposed to light during tillage germinated because of the exposure.
13 out of 17
How does immature embryos cause seed dormancy?
Some weeds drop their seed embryo immaturely and they slowly develop while in a state of dormancy.
How does impermeable seed coat cause seed dormancy?
Some weed seeds do not allow water or oxygen into it initially. The seed must be scratched or worn/weathered down 1st.
What plants are impermeable seed coats common in?
Clovers
What process does is required for crops that have impermeable seed coats before they can be planted and will germinate?
Scarification
How do inhibitors cause seed dormancy?
They form a chemical/mechanical combination that prevent germination until they’re weathered out of the seed.
How does oxygen cause seed dormancy?
Some seeds are too far from the soil surface to recieve enough oxygen for them to germinate. Once they become close enough to recieve the required amount, they will germinate.
How does after-ripening cause seed dormancy?
Some embryos (seeds) are mature but must “ripen” before they germinate.
What crop was an example of after-ripening where it caused issue?
Hard-white wheat
What were the 3 classes of seed dormancy?
- Innate
- Enforced
- Induced
Define Innate Dormancy.
The initial dormancy of a seed (all plants have)
Define Enforced Dormancy.
Seed has:
- no water
- temperature is incorrect
Define Induced Dormancy
Variances caused by the seeds living condition like:
- seed is buried too deep
- co2 levels in soil is too high
(T/F)Forms of dormancy can change many times before seed germination.
True
What was one example plant that switches dormancy forms?
What changes as it changes forms?
Buckhorn Plantain
It needs no light in it’s Innate form but needs light in Induced form
What is stratification?
When an imbibed seed is exposed to chilly temperatures for various periods of time.
Give an example of a plant changing through all 3 forms of dormancy.
Buckhorn Plantain:
Plant was just harvested: Innate
Seed over-winters and temp. is too cold: Enforced
Seed is buried too deep via tillage: Induced
What plant survived and germinated 120 years after being exposed to dormancy?
Moth Mullein
What are the 5 forms of weed control?
- Preventative
- Mechanical
- Cultural
- Biological
- Chemical
What is the recommended form of weed control?
No single one, but a combination of many is recommended.
How does preventative weed control work?
By not allowing the establishment of certain types of weeds on your farm to begin with.
What is a couple examples of attempts at preventative weed control on large-scales bases?
- Federal Noxious Weed Act
- State Seed Laws
What did the Federal Noxious Weed Act do?
was enacted to prevent weeds of foreign origin from entering the U.S.
What do state seed laws do?
Establish list of prohibited weeds for each state. Are set individually by state. Contaminted seed batches containing “banned” weeds on these lists cannot be sold within the governing state.
What are 5 weeds on the KY State Noxious Weed list?
- Canada Thistle
- Johnsongrass
- Balloonvine
- Quackgrass
- Purple Moonflower
(T/F) You can petition the KY Ag Council to force your county to control weeds on private property?
True
What were 3 types of mechanical control mentioned?
- Tillage
- Mowing
- Handhoeing
What 2 types of weeds are better controlled by tillage?
- Biennials
- Simple Perennials
What 2 types of weeds are made worse by tillage?
- annuals
- creeping perennials
The soil should be _______ for tillage to be the most efficient.
dry
_____ is critical for tillage to be successful in weed control of creeping perennials.
timing
What is an example of timing being critical for controlling creeping perennials?
Johnsongrass
(T/F) Repeat tillage is often needed.
True
What is the “ideal sequence of events” for tillage?
- There is a period of warmth and moisture
- Weed emergence
- Till
- Dry Period
- Warmth and moisture
- more weed emergence
- till
- dry period
Total dependence on tillage reduces chances for _______.
early planting
____________ can be an effective addition to weed control practices where tillage has been conducted.
Selective cultivation
What is tillage?
The mechanical mixing of soil.
What is mowing?
The trimming of plants growing mechanically.
What are the 2 ways mowing aims to control weeds?
- prevents seed formation
- depletes underground food sources
____ mowing is required.
repeat
Canada thistle seed is viable ___ days after pollination. Shattercane seed is viable ____ days after pollination.
- 8
- 10-15
Mowing is most effective when combined with a ___________.
competitive crop
What is the most economical system of weed control?
Tillage combined with chemical control.
(T/F) Tillage is essential to crop production.
False as proven through no-till/min-till
What is no-till?
Planting into chemically eradicated cover crop.
What is primary tillage?
How deep is it?
the initial breaking and disturbance of the soil.
6”
What are 3 implements of primary tillage?
Which is the most and which is the least common currently?
- moldboard plow-least common
- chisel plow-most common
- heavy disk plow
What is secondary tillage?
Is follow-up tillage after primary tillage has been performed. It is done to prepare the seed bed.
What are 5 implements of secondary tillage?
- field cultivator
- disk harrow
- rotary hoe
- spring tooth harrow
- cultipacker
What is interrow cultivation?
Happens in this example crop:
light tillage between crop rows to control weeds.
Tobacco
What is nighttime tillage most effect against?
What were the 3 specific example plants?
Small broadleaf weed species
- Pigweed
- Smartweed
- Wild Mustard
Is nighttime more fitting as a primary or secondary tillage?
Secondary
What is conservation tillage?
Any type of tillage that leaves at least 30% of the soil surface covered with crop residue after harvest.
What are 3 examples of conservation tillage?
- No-till
- Minimum-till
- Strip-till
What is the issue with night tillage?
Is expensive because of glasses required and doesn’t help with all weeds.
What were the 4 “other” types of mechanical weed control?
- Mulch
- Flooding
- Fire and heat
- harrington seed destructor
How does the harrington weed destructor work? How effective is it?
Catches chaff out of back of combine and turns everything that passes through to powder including weed seed. Is very effective.
What is downside to seed destructor?
extremely expensive
What are some advantages of no/min. till?
- prevents soil erosion
- improves soil structure
- better water infiltration rates
- less limitations due to soil moisture (b/c it holds moisture better)
- lower cost because of lower energy needs to utilize
What are some disadvantages of no/min. till?
- increased problems with perrenial weeds
- lower average soil temps in spring delay planting
- more insect/disease pressure
- greater management skills needed
What are some disadvantages of tillage?
- causes soil erosion
- untimely rainfall can delay
- deleterious effects on soil when worked wet (clodding, ruts, etc.)
What are some advantages of tillage?
- easier (skill-wise) than no-till
- Better control of simple perennials
- warms soil quicker in spring
What are 3 methods of cultural weed control?
- planting smother crops
- planting competitive crops
- utilizing crop rotation
What is a smother crop?
What are 2 examples?
a solid-seeded crop that is vigorous and thick and can inhibit weed growth.
- Wheat
- Alfalfa
What are competitive crops? What are 2 determining factors of competitive crops?
Crops that canopy quickly.
- plant pop.
- row width
How does crop rotation help control weeds?
Every crop has characteristic weeds that grow along with it. Rotation can help control buildup of these weeds.
What is allelopathy?
It is when one plants produces toxins and puts them into the ground around it to injure or kill surrounding plants and reduce its competition.
What are two plants that are allelopathic:
- Walnut Trees
- Quackgrass
What are two cover crops that have shown to be allelopathic:
- Wheat
- Rye
What herbicide was isolated from an allelopathic plant?
Mesotrione (callisto)
