Midterm 1 Flashcards
Convective
- Hot temperatures make air rise, meets with cool atmosphere and moisture condenses, accumulates in clouds
- Can cause high winds (tornadoes)
- Similar to rainfall in the area
Orographic
- Moisture laden air mass meets mountain range & unloads water
- Replenishes surface water
- Found in areas like Vancouver BC
Cyclonic
- Changes in atmospheric pressure over the ocean
- Warm ocean temperatures
- Strong storms eg. hurricanes (in sub- and tropical environments, but temperate regions receive hurricane fallout)
RAINFALL PATTERNS
- Average total annual rainfall
- Distribution & periodicity
- Intensity & duration
- Availability
- Predictability
RAINFED AGROECOSYSTEMS
rainfall system that only need natural rain fall for their access to water
Long Wet Season
- Humid regions with extended rainfall
- Problem: excess water
- Problems with waterlogging
- Habitat modification to remove water for crop growing
- Solutions: Chinampa
Wet-Dry Season
- Typical in tropical regions
- Production of crops during wet & dry season
- Rain falls have: Specific period large quantity of rain and minimal rain during dry season
- Wet season: Varies in length & intensity and Crops that need water or tolerate high quantity of water are grown here
- Dry season: Varies in length & intensity, Crops that tolerate little water, Use of organic mulch, Fallow (during very dry season)
Seasonal Rainfall
- Temperate (like here) & tropical zones
- Highly variable depending on global location
- Variably adapted crops work well
DRYLAND FARMING
- Rainfall during crop season insufficient
- You could just irrigate but some places do not have the money
- Requirement of crops suited to be productive under less rainfall: No irrigation is used
- Dryland agriculture = pastoral systems
- Dryland farming requires: Cultivation system that promotes rainwater penetration & storage in soil and Frequent use of summer fallow
ATMOSPHERIC MOVEMENT
- Movement of disease & pests by wind
- Movement of salt near ocean
- Wind can have significant impact on agroecosystems
Desiccation from Wind
- No boundary layer between air and leaf surface
- Increases transpiration & overall water loss from crop
- Rate of desiccation exceeds water replacement: Impedes photosynthesis, Impedes crop productivity, and Produces low grain yield
Dwarfing from Wind
Direct correlation between wind and crop height
Deformation from Wind
- The side of the plant that the wind hits has less leaves and grows in the direction of the wind
- Constant wind from prevailing direction alter plant growth form
- Windbreaks are good indicators of direction of prevailing wind
Plant Damage & Uprooting from Wind
- Excessive winds not usual but can cause severe damage
- Crops experience wind damage when they are nearing maturity and heavy with grain/fruits
WIND EROSION
- Regions with low rainfall = prone to wind erosion
- Wind detaches & transports soil particles
BENEFICIAL EFFECTS OF WIND
- Good air circulation: maintains optimal gaseous exchange between atmosphere & crops, Disperses excess humidity (limits diseases), Cools plants (hot & humid climates), and Essential for crops relying on wind pollination
Wind Breaks
- Also called shelterbelts or hedgerows
- Composed of trees
- Reduce Erosion by wind, Protection of homesteads, Improve crop yield
- Windbreaks Reduce wind velocity by 80%
- Located perpendicular to prevailing wind
Planting Techniques and wind
- Planting of annuals that protect the main crop from wind
- Easy & fast to establish compared to windbreaks
- Provide more flexibility in day to day farming operation
- Reduce wind velocity
which improves moisture & temperature for the crop to be harvested and improves crop yield
FIRE IN NATURAL ECOSYSTEMS
- Major form of disturbance/environmental change
- Some natural ecosystems: dependent on regular fire cycle (eg. boreal forest & jack pine)
- Accumulation of sufficient fuel, dry conditions and source of ignition = cause of fire
Surface Fire
- Most common fire type
- Used to control or promote growth of weedy or invasive vegetation
- These are the ones that re produced by man to increase plant productivity
Crown fire
- Canopy of vegetation is consumed
- Mature plant species are killed
Ground/subsoil fire
- Peat or muck soil fires
- Occur under ground and smoulder for months
- Can be caused by coal
Fire Resistance
- Plants are not burned by fire
- Plants with thick bark, fire-resistant foliage, thick litter on soil that withstands frequent fire
Fire Tolerance
Re-sprout from the crown after fire
Fire Dependence
- Require fire for reproduction or long-term survival
- Seeds require fire in order to germinate and sprout
- Some plants have flowers that will not emerge until after a fire
Fire in Agroecosystems -Shifting Cultivation
- Ancient technique of agriculture
- Regular use of fire in shifting cultivation to clear vegetation that has been cut down
- Burned vegetation increases soil pH & increases nutrient mobility for growing crops
- Shifting cultivation: sustainable if populations are low
- Modern problem: population numbers increase, fallow phase decreases, agriculture becomes settled, soil becomes degraded
Fire in Agroecosystems -Land Clearing
- Easily accessible tool to clear land (forest) for agricultural conversion
- Often done unsustainably
Fire in Agroecosystems -
Nutrient Additions to Soil
- Left over products after burning add nutrients to the soil
- Ash, charcoal
Fire in Agroecosystems -Crop Residue Management
Fire used to manage crop residues
- Fire releases N from burning crop reesidues for next crop cycle
- Burning crop residues decreases requirement for tillage
- Sustainability: Is the burning of crop residues a good thing? See slide 24 on advantages/disadvantages
Fire in Agroecosystems - Weed Management
- Fire can reduce weeds in the litter or seeds in the soil
- Fire can reduce weeds shortly after they germinated
- Some weeds are perennial or fire resistant: burning may actually stimulate weed growth
Fire in Agroecosystems - Pest & Disease Management
- Fire can control arthropods (insects, mites)
- Higher temperatures created by fire control pathogens such as fungi, nematodes, bacteria
Fire in Agroecosystems - Facilitation of Crop Harvest
- Fire can help prepare crops for harvest
- Environmental consequences of burning: Particulates in air, CO2 emissions, other issues with effect of fire on soil as discussed earlier
Agroecology - Brief History
- Early concepts date back to early 20th century
- Did not achieve recognition as a field of study till 1990
- Became recognized in 1980s in tropical agriculture as a result of community based development
Agroecosystems ≠ natural ecosystems
- Human manipulation makes agroecosystems different
- Processes are the same
- Structure and function different
- Energy flow in agroecosystem: Open system with High input and high output
- Nutrient Cycling in Agroecosystem: Minimal recycling with High input and high losses
Negative Effects of Modern Farming
- Fossil fuel consumption
- GMO: does it affect human health?
- Contributed to environmental pollution
- decreased crop diversity
Fertilizer to environmental pollution
- 50% of N fertilizer applied taken up by crops
- 30% of p fertilizer applies taken up by crops
decreased crop diversity
98% of global population relies on only 50 different types of crops
Intensive Tillage
- Complete, deep, and regular manipulation of soil
- Loosens soil: better drainage, aeration, fasten root growth, increased soil temperature
Mono-culture
- Mono-culture = simple agroecosystems
- Forms moved from producing a high diversity of crops to growing only a few crops
- Simple agroecosystems: Efficient use of form machinery, Minimal labour costs, Maximal technology inputs, and Intensive agriculture practices
- Monoculture vs sole crops
Macronutrients Access
- Oldways: animal and human manure
- Today: increased demand for cheap food: created by the Development of fertilizer industry
Nitrogen
- Legumes: convert N2 to plant available N: Insufficient in N for industrial agriculture
Phosphorous
Come from Natural rock deposits
Potassium
Come from potassium desposits
Agrochemicals
- Insecticides, pesticides, herbicides, fungicides
- Removes organisms that threaten crop productivity
- Agrochemicals treadmill: Once you got on it you cannot get off it
- Agrochemicals are like steroids
- Chemicals remove beneficial and unbeneficial consequences
Why is industrial Agriculture not sustainable?
- Soil degradation
- Overuse of water
- Pollution
- Destruction of natural habitat
- Dependence on external inputs
- Production of GHG
- Loss of genetic diversity
No Control in Industrial Agriculture
- Few farms controlled by large corporations
- Is modern crop and food production healthy: Global obesity issues
- Food waste issues
- Unequal food distribution
Soil
- Soil is not dirt
- The interface between living (biotic) and non-living (abiotic)
Pedosphere
- The interface between living (biotic) and non-living (abiotic)
5 main factors contributing to Soil Formation
- Climate: Temperature and precipitation influences weathering rates
- Topography: Slope steepness
- Biology: Plants and animals that contribute and decompose organic matter, addition of nutrients
- Geology: Type of rocks broken down
- Time: Takes a while to form soil
Takes a while to form soil
1cm soil/ 178 years
Elluviated and Illuviated
Elluviated : leached soil horizon
Illuviated: receives leached materials
Soil Texture
- Also referred to as soil separates
o Sand = 2 to 0.05mm
o Silt = 0.05 to 0.002
o Clay = smaller than 0.002
Soil Structure
- The arrangement of soil particles based on Particle size, Shape, and Soil texture also influences structure
What contributes to different soil structure?
- Organic matter content and presence of microorganisms
- Chemical reactions
- Wetting and drying
Soil Colour
- Different soil colours occur:
~ Mineral composition (Iron = red colour)
~ Organic matter content (Black or dark brown)
~ Drainage (Green or blue = poor aeration) - Munsell Soil Color Chart
~ Determines soil colour
Cation Exchange Capacity in Soil
- Complex chemical reaction between soil particle and plant roots and nutrient in soil solution/water
- Caution exchange (northern atmosphere): Occurs when soil pH is greater that 5.2
- Anion Exchange (tropical soil): Occurs when pH is lower than 5.2
Acidity and pH
- Occurs in soils with more than 500mm rainfall/year
- Low pH causes decrease in crop yield
Low PH can be amended by adding…
Lime, Biochar, ash
Saline Soil
- Common in soils of arid and semi-arid regions
- Excessive irrigation: salt (Na, Cl) build-up in soil
- Excessive use of salt-based fertilizers
- Problem with the soil solution
Sodic (Alkaline) Soil
- pH of 8.5 or higher
- contain neutral salts
- caused by SOM dispersion and Difficult water infiltration
- Problem with the soil of itself
Soil Organic Matter to Soil Organic Carbon
- SOM -> SOC (divide by 1.724)
- SOC -> SOM (Multiple by 1.724)
Crop Residues
- Industrial agriculture: lower residue input than natural ecosystems
- Therefore Important source of OM for Soil and should not be removed
Cover Crops
- Plant cover specifically grown to produce plant matter for incorporated into soil or left on surface
- Usually grown in rotation
Manure
- Adds Organic matter and nutrients
- Addition of fresh manure requires compositing and stabilization time in field
and Takes time until nutrients become available
Compost
- Optimal Carbon/Nitrogen ratio
- Optimal particle size
- Generally free of weed seeds (which is good)
- Soil diseases oppressed by compost application
- Issues: Inconsistent product and May contain contaminants
Biosolids
- Solid material removed from wastewater
- Can be applied only every 5 years Because it can contains heavy metals
Conventional Tillage
- Controls weeds, pests, prepares seed bed
- Decreases soil structure, and a lot of other bad stuff
Crop System Complexity
Diversifying our crops
Movement of water in Soil
- Infiltration
- Percolation
- Evaporation
Annual Crop Roots have…
Majority of roots in the top 30cm of soil
Perennial Crop Roots have…
Deep rooted systems
Wet Spring vs Dry Summer (not good)
- Shallow root system
- Water efficiency issues in summer
Dry spring vs wet Summer (kinda good)
- Deep root system
- No water deficiency issues (even if summer is dry
Excess Water in the Soil
- Causes water logging: Poor drainage
- Waterlogged soil found globally
Negative Effects of Too Much Water
- Anaerobic environment (without oxygen)
o Different microbes
o Limit plant production
Seasonal drought
- Reduces build-up of diseases and pests
- Acts as frost in northern climates
- acts as flooding in wet/tropical areas
Evapotranspiration
the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants
Reducing Evapotranspiration
- Crop Choice and Agroecosystem Design (Using crops with low water needs, Increasing vegetative cover, Using fallow periods, Increasing crop diversity)
- Organic Mulch
- Inorganic Mulch
Photosynthesis
plants capture CO2 from atmosphere and convert it into energy (C fixation)
C3 Photosynthesis
- Use the Calvin cycle to fix C
- Most widespread form of C fixation
- Plants thrive in cool conditions
- Examples: wheat, oats, beans, tomatoes, woody plants (trees, shrubs)
C4 Photosynthesis
- Use a hatch-slack pathway to fix C
- C fixation occurs at a lower concentration of CO2
- C4 plants use less moisture under warm and dry conditions: Common in tropical areas and Higher biomass accumulation in tropical areas
- Examples: Sorghum, Sugarcane
CAM Photosynthesis
- Crassulacean Acid Metabolism
- Similar to C4 Pathway
- CAM plants common in hot and dry environmental
- Plants minimize photorespiration and save water by separating these steps in time, between night and day
- Example: cacti, pineapple, succulents, other bromelaids
Sink
Harvestable product
Nitrogen
- Most limiting nutrient in temperate agriculture
- Added in large quantities
- Uptake from soil by roots as NO3 and NH4
Phosphorus
- Most limiting nutrient in tropical agriculture on acidic soil
- Plant available P low
- Plant acquisition via uptake from soil by roots
Potassium
- Important in metabolic processes
- K deficiency creates a uneven plant water balance
- K abundant in soil
- Excessive removal via harvest
- K leaches easily from soil
- Plants get it through their roots
Light Variation in the environment influenced by…
- Seasons – the time
- Latitude –closer to the equator the more even the day light period is
- Shade (canopy structure)
- Topography
- Air quality
Light Variation - Seasonality and Latitude
- Angle of sun controls daylight hours and intensity
- Equator vs the poles
Light Variation - Altitude
- Increase in light intensity with increasing height
- Plants have adapted to control the amount of light reaching leaves
Light Variation - Topography and Air Quality
- Topography
~ Slope and direction of soil surface
~ Slope orientation (north vs south facing) - Air Quality
~ Suspended particles decrease amount of light reaching plants
~ Limits plant growth and productivity
Light Variation - Canopy Structure
- Simple vs complex agroecosystems (has more vertical complexity)
Temperature Influenced by
- Latitude (angle of sun)
- Altitude
- Seasonal variation (northern hemisphere)
- Topography (slope orientation)
- Water bodies (maritime): Large bodies of water moderate temperature fluctuations therefore Warmer winter, cooler summers
Response of Plants to Temperature (what plants need to adapt to)
- Higher temperature causes greater evaporation
- Diurnal temperature variation extremes
- Vernalization: Some Plants require period of cold (Herbaceous species need cold spells)
Canopy Vegetation
Trees and tall plants
- Provide shade and change temperature
- Agroforestry practices
Non-Living Canopies
Crops not grown under agroforestry practices
- Use of nonliving canopy
- Strawberry production in California
- Soil surface cover
- Increases soil temperature and microclimate
- Greenhouses, hoop houses
