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30 Cards in this Set
- Front
- Back
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What is an agroecosystem?
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Dynamic Association of:
Crops Pastures Livestock Flora/Fauna Atmosphere Soils and Water |
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What are the main differences between Agroecosystems and Natural systems?
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Higher productivity
More human control Simpler structure Low Species Diversity Low Habitat Heterogeneity Open biogeochemical cycles Unstable Immature successional state |
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What are the energy inputs to a agroecosystem?
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Sunlight
Human,animal, mechanical labor Fossil Fuel Chemical inputs Plant/animal detritus |
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What are the energy outputs of a agroecosystem?
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Vegetable and animal products
Loss of energy through tropic level skipping |
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What are the nutrient inputs of an agroeosystem?
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Preexisting soil nutrients
Nitrogen fixation by legumes (Nutrients that plants add) Fertilizers (Nutrients that we add) Manure, compost (Nutrients that animals add) |
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What are the nutrient outputs of an agroecosystem?
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Nutrients in food produced
Also those lost in: Leaching, runoff, volatilization Burning of vegetation Soil Erosion |
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What are the modes of nutrient storage in agroecosystems?
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Standing crops and livestock
Nutrients in the soil |
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What is the equation for water balance?
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Precipitation = Runoff + Evapotranspiration + changes in water storage in soil (leaching etc.)
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For how long must Precipitation be greater than evapotranspiration for crop cultivation to succeed?
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Precipitation must exceed evapotranspiration for more than 130 days for crop cultivation
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What is the natural tendency in terms of successional dynamics
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Natural systems press towards states of higher complexity
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How does modern agriculture affect the complexity of the system?
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It maintains it in a simple state
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How does modern agriculture maintain a simple biological system?
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Plowing/tilling
Chemical inputs Monoculture Periodical harvest |
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What are some of the major problems in maintaining continuity in crop production?
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Plant competition (crops vs. weeds)
Herbivory Disease |
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What are the main ways of controlling threats to agricultural production?
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1) Preventative Measures
2) Successive Measures 3) Integrated Pest Management |
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What are preventative measures to control pests?
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Resistant crops
Intercropping Crop rotation in time and space Crop diversification |
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What is successive pest management?
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Chemical pesticides, biotic control
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What is integrated pest management?
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Monitoring, mechanical control (promote beneficial insects), chemical control
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What are the Natural resources of a farm?
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Size of the farm
Topography of the farm Location with respect to markets Soil depth, chemistry,properties Availability of water Natural flora and fauna |
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What are Human resources and how can they affect Agroecosystems?
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People who live and work on the farm
Knowledge,creativity Values - what they think is right about landuse and ethical Social organization Workforce and work ethic, flexibility |
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What are captial resources of agroecosystems?
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Goods and services created, purchased or borrowed to facilitate natural resource exploitation
Buildings, irrigation systems, consumable products, lines of credit |
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What are the production resources of agroecosystems?
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Agricultural output of the farm, may be sold (becoming captial resources) or reinvesting in the farm (becoming nutrient inputs)
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What is meant by the concept of "coevolution" in agroecosystems?
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The development and adoption of farming systems and technologies are the result of interactions between the farmers, their knowledge and their biophysical and socioeconomic environments.
Thus,disturbing the "coevolutionary equilibrium" can throw the system out of balance and impact it |
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What are some of the positive aspects of modern agriculture?
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High-yield plants have been producing 2-5 times more than traditional varieties
World grain production tripled in 40 years Modern agriculture has saved 9-31 million square kilometers of wildlands from cultivation |
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What are the negative aspects of modern agriculture?
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Use of fossil fuels increased 4-fold
Use of commercial fertilizers has increased 10-fold Use of pesticides has increased 30-fold They have become highly unstable Biodiversity loss, soil degradation, air pollution, water contamination |
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What are the efficiency of old agricultural systems compared to new ones?
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Pre-industrial Mexico= 30%
Semi-industrial Mexico = 15% Full-industrial USA = 3% Modern systems are less efficient |
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What are some of the indicators of sustainable agriculture?
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Crop productivity
Soil productivity Irrigation water quantity and quality Abundance and diversity of beneficial organisms Agricultural chemical use Genetic diversity |
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What are some of the characteristics of sustainable agroecology?
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Socioeconomic stability
Equitability: benefits (income and products) evenly distributed among local producers and consumers Tradeoff between stability and production: Farmers often place a higher value on reducing risks than on maximizing productivity |
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What about polycultures?
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On small farms, polyculture yields are 20-60% higher than in monocultures with the same level of development
This strategy aims to minimize risk by planting several species: reduces losses due to pests, more efficient use of natural resources due to intercropping of compatible crops Polycultures also produce more organic matter that can be plowed into the soil |
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Why do large monoculture farms predominate now?
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People don't want to work by hand
Agricultural policies, prices and government services favor large-scale producers Globalization and free-trade agreements Inundation of developed countries with food from developed countries that subsidize agricultural production food from developed countries marketed at prices below the real cost of production |
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What are steps that can be taken to get closer to sustainable agricultural practices?
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Increase crop diversity: especially perrenial crops that are good for intercropping, leaf litter, use legumes as nitrogen fixers
Make the biogeochemical cycles more closed, less dependent on outside sources Emphasize local knowledge, especially for complex, locally adapted systems Integrated pest management instead of either extreme |
