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CROP PRODUCTION Unit 4: Climate Climate (p. 97) Weather – Short term status of atmospheric conditions – Processes involved in establishing weather/weather patterns = meteorology Climate – Average weather and variations over time – Study of climate = climatology Climate (97) Eight major factors in determining crop distribution: 1. Temperature Influenced by latitude, elevation, and water bodies Determine temperature extremes and number of frost free days 2. Humidity 3. Precipitation – 4. 5. 6. 7. 8. Examples: snow, sleet, rain, hail Weather Patterns Solar radiation Wind Topographic features Social/political factors (First three determine moisture availability and heat/moisture stress on crops) Profile of the Atmosphere (p. 98) Layer Depth Actions Troposphere 0-10 miles Weather events, clouds, jet stream Stratosphere 10-31 miles Ozone layer protects from UV rays Mesosphere 31-53 miles Temperature decreases w/height Thermosphere 53-310 miles Warmest layer Exosphere >310 miles Atoms/molecules escape earth’s gravity into space Ionosphere 37-620 miles Electrified, reflects radio waves back to earth Troposphere (99) Air will move upward if: – Temperature increases – Air pressure decreases – Air has more water vapor Rising air cools at the rate of 1° C per 100 meters – As air cools, water vapor condenses – If humidity is high, condensation will begin at higher temperatures Troposphere (99) Air will move downward if: – Temperature decreases – Air pressure increases – Air has less water vapor Descending air warms at the rate of 1° C per 100 meters Warmer air holds more moisture than cooler air Precipitation (99) Distribution patterns – Geographic cropping regions: Arid (0-25 cm/yr) Semiarid (25-50 cm/yr) Sub-humid (50-75 cm/yr) Humid (75-100 cm/yr) Per-humid (100+ cm/yr) Precipitation (99) Distribution patterns – Monthly – look at: Precipitation vs. crop water needs Soil-saturated moisture Transpiration rate – Monthly—consider: 12” precipitation will grow wheat in ND and sparse grazing in TX – Increase production by fallowing in arid/semiarid regions World Climate Temperature (p. 101) Inversion – Air near the ground is cooler than the air above Cardinal temperatures – Varies for different crops – Minimum Lowest temp required for growth or process – Optimum Temp required for best growth/process – Maximum Highest temp limit for growth/process – Within range, growth rate doubles for every 10° C increase in temperature (see chart p. 102) Temperature (p. 103) Hopkins Bioclimatic Law – Events such as planting, harvesting, etc. are delayed 4 days for one degree latitude north, 5 degrees longitude east, and 400 feet in altitude Growing season requirements for major crops: – – – – – Corn—120 days Oats—90 days Barley—80 days Sugarcane—450 days Cotton—180 days Temperature (103) Heat Units – Used to measure plant development H.U. = daily min. temp. + daily max temp – base temp 2 Base temp for major crops – Corn: 50° F – Soybeans: 50° F – Sorghum & Cotton: 60° F – Small Grains: 40° F Temperature (103) Growing Degree Days (GDD) – Place minimum and maximum daily temperature limits; provides a “calendar” for physiological maturity GDD = daily min. + daily max. – critical min. temp. 2 – Critical max for corn is 86° F – Critical min for corn is 50° F – GDD can never be negative – Used especially in vegetables, hybrid seed production, and crop scouting (insects & weeds) Sample Calculations Day Min temp Max temp 1 45 62 2 50 65 3 54 68 4 55 74 5 60 80 Totals: GDDs HUs More Sample Calculations Day Min temp Max temp 1 49 62 2 52 72 3 56 81 4 60 82 5 64 89 Totals: GDDs HUs Temperature (103) Other types of degree days… – Cooling Degree Days Measure air conditioning bill – Heating Degree Days Measure heating costs – Stress Degree Days Same as GDD, but 86° F is base Humidity (104) Evapotranspiration Relative Humidity – Amount of water in the air compared to the total water the air could hold at a given temperature Vapor Pressure – Pressure caused by presence of water vapor molecules in the air Vapor Pressure Deficit – Drying power of the air Weather Patterns (105) High Pressure Cells “Anticyclonic” Low Pressure Cells Movement “Cyclonic” Clockwise Circulation Sinking & away from center Air Movement CounterClockwise Rising & towards center Few Cloud Cover Many Little Precipitation Much Weather Patterns (106) Air mass – Large body of air essentially uniform in horizontal directions Four major masses are described by origin: 1. 2. 3. 4. c – originate over land = continental m – originate over water = maritime P – cool or cold = polar T – warm or hot = tropical Weather Patterns (106) So…how would you describe each of the following air masses? – cP Dry, cool – mP Moist, cool – cT Dry, warm – mT Moist, warm Weather Patterns (107) Weather front – Two or more air masses with different properties collide and create an area of instability in the boundary zone – Cold Front When a cold air mass replaces warm air, pushing it upwards; thunderstorms and showers result – Warm Front When a warm air mass replaces cold air and moves higher; if air is moist, widespread precipitation results – Occluded Front A composite of two fronts; usually result in cool, drizzly weather Weather Patterns (108) Surface features affect weather – One example Mountains forcing air to rise, resulting in precipitation on the windward (upwind) side and drier climate on the leeward (downwind) side – Northern Hemisphere Usually find dry/arid regions on the east side of the mountain because weather patterns move west to east Climatic Change (109) Microclimate – Crop environment Macroclimate – Can also be affected by human activity – Greenhouse Effect Four gases have increased due to human activity 1. 2. 3. 4. Carbon dioxide Methane Nitrous oxide Chloroflourocarbons Climatic Change (110) Effects of greenhouse gases/human activity – Acid rain Resulting from sulfur pollution – Desertification Expansion of deserts due to mis-use of land – Deforestation Greed of ag producers Cirrus Clouds Occurring at elevations of 20,000-40,000 feet Cirrostratus or cirrocumulus Cumulous Clouds Clouds that are vertically developed Causes severe weather Cumulonimbus Website resources – http://ww2010.atmos.uiuc.edu/(Gh)/home.rxml – http://en.wikipedia.org – http://www.geographic.org/maps/maps.html Chapter 4 – Review Questions (p. 112-113) – Thinker