Home > Flashcards > Print Preview
The flashcards below were created by user
on FreezingBlue Flashcards. What would you like to do?
Who was known as the "Father of Soil Conservation" in the US?
Hugh Hammond Bennett
How many square feet are there in an acre?
How do you calculate the amount of nitrogen from a square foot of (biomass) dry weight?
- Using Dr. Peet's method:
- dry weight x 43,560 = lbs per acre
- lbs per acre x amount given (.0362 for Austrian winter pea) - amount given (9.2 for winter pea)
The interaction of Rhizobium bacteria with legume crops such as bean or soybean is an example of what kind of mutualism?
A cover crop that is allowed to grow within the crop is called
According to the Hoyt (2005) data, corn yields were higher at most levels of fertilization following
A hairy vetch cover crop
- Is an effect of one species on another through chemicals
- Can be used to suppress the germination and growth of weeds
- Effectivenes has been observed to change with the plant's stage of growth
A way to increase genetic and species diversity within a cropped field:
- Strip cropping
- Cover cropping
T/F In terms of agro-ecosystem diversity, an example of undesirable "simplification" of the system would be the loss of predatory insects through indiscriminate use of a broad-spectrum insecticide
T/F Living mulches can keep soil coooler, reduce weeeds and erosion, but they might also compete with the crop for soil moisture
T/F In the USA, water erosion is typically a bigger problem in western states
False (eastern states because they have more rainfall)
T/F Beneficial use of cover crops is restricted to providing cover during late fall, winter and early spring seasons
T/F Island biogeography theory has been applied to pest and beneficial insects in agricultural fields to better understand how they are distributed into a crop such as soybean or a vineyard
Human-accelerated erosion can increase geological erosion by how much?
10 to 1000 times
Land equivalent ratio
provides an all-other-things-equal measurement of the yield advantage obtained by growing two or more crops as an intercrop compared to growing the same crops as a collection of separate monocultures
occur in same place every year
what type of slope is good for farm land?
- 0-2 good
- 2-5 okay
- 6 - you're on the edge of good farm land
How likely is Greene County to get 3 inches of rainfall in a 24 hour period?
About once every two years (based on probablility)
T/F In one large rainfall event, you could see 70-80 percent of rain-caused erosion for an entire year
- removal of thin layers over time
- think of the pages in a book being removed one by one
too big to be smoothed over or crossed with equipment
usually follows crop rows
where does wind erosion occur?
vegetative cover is critical to prevent wind or water erosion?
Why was Hugh Hammond Bennett considered a visionary?
He realized the value of land cover, realized we could not continue farming the way we were and he organized research
How much cover is needed to begin to get into conservation tillage levels?
- At least 30%
- Conventional tillage is usually around 3-5% cover
- No till - about 90% cover
- Low-residue - about 25-30% cover
- Buffer - 90-100% cover
Wind breaks offer crops shelter from wind erosion/damage. If you have a 10 foot tall tree, how many feet of cover will you provide?
100 feet (10 times)
In "The Cattle Vote", how did the cattle vote?
- 1 month in: equal
- 2 months in: 3/4 cattle preferred treated side
- 3 months in: 84% treated
- 4 months in: 73%
- overall: 74% treated
In "The Cattle Vote", what would the weed component of the yield be on the untreated side?
What problem can arise with grazing fescue only?
- fescue toxicosis (or endophyte toxicosis)
- summer slump - reduced food intake, head down, mouth open, coronary band (swelling, redness, necrosis)
- onset usually 1-6 weeks after grazing stockpiled fescue begins
what months would it be best to avoid grazing fescue pasture?
- November - when flowering is at its peak
- end of May, early September (when concentrations are higher near the base of plants)
If you're looking for weed control but don't want to use a herbicide, what else might you consider?
- Mixing in some goats
- 20% reduction in woody vegetation in 8 weeks, 94% after four growing seasons
Planting in different seasons - using winter-planted crops in spring as a cover crop, for example
In crop communities, what are characteristics which exist only at the community level called?
How does conventional agriculture differ from an agroecological approach when it comes to the crop community?
- Conventional - simplifies (reduce to a single crop population growing in an otherwise sterile abiotic environment)
- Agroecological - understand species interactions in the conext of the larger community (beneficial species interactions, some complexity desirable)
organism-organism interactions can be conceptualized as interferences. what does this mean?
an organism has some kind of impact on its environment, and through this impact, another organism is affected
the removal of some resource by one or both of the interacting organisms
one or both organisms add some substance or structure to the environment
Interferences can have beneficial, detrimental or neutral effects on neighboring organisms. Does it matter the interference is a removal interference or an addition interference?
No. Either can have those types of effects
What does competitive exclusion suggest?
- That two species with similar needs cannot occupy the same niche or place in the environment
- This doesn't fully apply in many communities
What is an important way that agroecosystems allow for the coexistence of species in a multiple cropping community?
by combining species with slightly different physiological characteristics
T/F Species with a mutualistic relationship are not only able to coexist, but are dependent on each other for optimal development
- One mutualist lives wholly or partly inside the other
- ex: Rhizobium bacteria and leguminous plants
- The organisms involved are relatively independent physically, but interact directly
- Ex: the relationship between a flowering plant and its pollinating insect
- The interactions among a set of species modify the environment in which they all live to the benefit of the mixture.
- Involve more than two species and can include both inhabitational and exhabitational mutualsims
- Ex: polyculture agroecosystem (can affect microclimate, attract beneficial arthropods)
How do mutualisms in agroecosystems increase the resistance of the entire system to the negative impacts of pests, diseases and weeds?
By contributing beneficial interactions
plant species (usually grasses or legumes) grown in pure or mixed stands to cover the soil of the crop community for part or all of the year.
When cover crops are tilled into the soil, the organic matter added to the soil is called
When cover crops are grown directly in association with other crops they are called
Benefits to the crop community from cover crops:
- reduced soil erosion
- improved soil structure
- enhanced soil fertility
- supression of weeds, insects and pathogens
What are some problems that can occur from poorly planned cover crop systems?
- If resources are limiting, the could be competitive interference
- If allowed to become too dense, some cover crop may be alleopathic to the crop
- Damaging herbivores or disease organisms may find the cover crop species to be an ideal alternate hoste, later moving onto the crop
- Crop residue may interfere with cultivation, weeding, harvesting or other farming activities
How can weeds be beneficial?
- They can protect the soil surface from erosion through root and foliar cover
- Take up nutrients that might otherwise be leached from the system
- Add organic matter to the soil
- Selectively inhibit the development of more noxious species through allelopathy
What conditions are weeds especially well-adapted to?
Simplified, disturbed habitats
- When two or more crops are planted together in the same cropping system
- corn-bean-squash polyculture
In a series of studies of the corn-bean-squash polyculture done in Tabasco, Mexico, it was shown that corn yields could be stimulated as much as 50% beyond monoculture yields when planted with beans and squash. What happened to the yield of the other two crops?
There was significant yield reduction for the other two species, but the total yields for the three crops together were higher than what would have been obtained in an equivalent area planted to monocultures of the three crops
- a broadened and complexified concept of diversity, it includes dimmensions such as:
Once diversity is generated, it tends to be self-reinforcing. Explain?
Greater species diversity leads to greater differentiation of habitats and greater productivity, which in turn allow even greater diversity
species diversity in a single location
species diversity across communities or habitats
a measurement of the species diversity of a region such as a mountain range or river valley
T/F Studies of natural ecosystems in early stages of development or following disturbance have shown that all of the dimensions of diversity tend to decrease over time.
False. They increase
- the ecosystem's recovery process after a disturbance
- the system begins to restore the diversity of species, interactions and processes that existed before disturbance
- the successional condition in which the full potential for energy flow, nutrient cycling and population dynamics in that physical environment can be realized
- the structural and functional diversity of the ecosystem at maturity provides resistance to change in the face of further minor disturbance
In what stage does an ecosystem reach its highest level of species diversity?
- As a system approaches maturity
- biomass continues to increase at maturity, though at a slower rate
Why are agroecosytems considered ecologically unstable?
- Loss of diversity weakens the functional links between species that characterize natural ecosystems
- Nutrient cycling rates and efficiency change
- energy flow is altered
- dependence on human interference and inputs increase
What are some options and alternatives available for adding the benefits of diversity to the agricultural landscape?
- 1. adding new species to existing cropping systems
- 2. reorganizing or restructuring species already present
- 3. adding diversity-enhancing practices or inputs
- 4. eliminating dieversity-reducing or diversity-restricting inputs or practices
A primary and direct way of increasing alpha diversity of an agroecosystem
- grow two or more crops together in mixtures that allow interaction between the individuals of the different crops
- Intercropping is a form of multiple cropping - adds temporal diversity through sequential planting of different crops during the same season, the presence of more than one crop adds horizontal, vertical, structural and functional diversity
- plant different crops in adjacent strips
- creates a "polyculture of monocultures"
- increases beta diversity instead of alpha diversity
- presents fewer management and harvest challenges than multiple cropping
What are some benefits from planting trees or shrubs around the perimeter of fields, along pathways of a farm or to mark boundaries?
- protection from wind
- exclude or enclose animals
- produce tree products (firewood, construction materials, fruit, etc.)
a noncrop species planted in a field to provide soil cover, usually in between cropping cycles
- usually involve planting different crops in succession or in a recurring sequence
- the greater the differences between the rotated crops in their ecological impact on the soil, the greater the benefits of the method
- a variation on the rotation practice
- leave the land uncultivated or fallow
- allows soil to "rest" - involves secondary succession and recovery of diversity in many parts of the system (esp. the soil)
What impact can animal activity have on the agricultural landscape?
activity such as grazing, crop residue consumption and manure deposition can alter aspects of structural divesity, species dominance and system function
What are the two components of species diversity?
- Species richness - the number of species
- Species evenness - the evenness of the distribution of the indviduals in the system among different species
What are some examples of importance values for a particular species?
- number of individuals
Margalef's index of diversity
- Measures number of species in terms of number of individuals
- diversity= (s-1)/logN
- (S is number of species, N is number of indviduals)
- limited because it can't distinguish the varying diversity of systems with the same s and N
an application of information theory, based on the idea that greater diversity corresponds to greater uncertainty in picking at random an individual of a particular species
Simpson index of diversity
- the inverse of an index of community dominance
- Based on the principle that a system is most diverse when none of its component species can be considered any more dominant than any of the others