Agrometeorology PDF Notes

## AGROMETEOROLOGY ### Probability - Initial Probability: The rainfall amount at a particular probability (50 or 75%) in a week or month within a region. - Conditional Probability: The level of rainfall projected for a specific location and period. ### Rainy Days - Meteorological Rainy Day: ≥ 2....

## AGROMETEOROLOGY ### Probability - Initial Probability: The rainfall amount at a particular probability (50 or 75%) in a week or month within a region. - Conditional Probability: The level of rainfall projected for a specific location and period. ### Rainy Days - Meteorological Rainy Day: ≥ 2.5 mm rainfall in a day - Crop Rainy Day: > 5 mm rainfall in a day - Effective Rainfall: 5 mm in a day ### SOLAR RADIATION - The sun is the ultimate source of energy for the Earth's physical and biological processes. #### Sun Facts - Diameter: 1.39 x 10^6 km - Distance from Earth: 1.5 x 10^8 km - Closest to Earth: 31st December - Furthest from Earth: 1st July - Central interior temperature: 8 x 10^6°C to 40 x 10^6°C - Surface temperature: 5778°K or 5505°C - Time to reach Moon: 1.25 seconds - Time to reach Earth: 8.3 minutes or 500 seconds - Luminous Efficacy: 93 lumens per watt of radiant flux #### Solar Radiation Facts - It is received in EMR consisting of steam or flow of particles called quanta or photons. - Measured in Einstein (1 mole of photons) - SI unit of power: Watts (W) - SI unit of solar radiation: Watts/m^2 - 1W = 1 Joule/sec - 1 cal/cm²/min = 697.93 W/m²/ - 1 feet candle = 10.764 lux - Lux is the oldest unit of measuring light intensity - Energy per unit area incident on the earth concentric with the sun: 1.979 cal/cm²/min or 2 Langley/min or 1390 watt/m² - About 80% of incoming solar radiation is reflected back into the atmosphere by clouds. ### Solar Constant - The energy falling in 1 minute on a 1 cm^2 surface area at the outer boundary of the atmosphere. - 1.94 cal/cm²/min or 1.94 Langley/min or 1353 W/m². #### Equinox and Solstice - Day and night are equal on 21 March (Vernal/Spring Equinox) - Day length increases until 21 June (Summer Solstice) - Day length decreases until 23 September (Autumn Equinox) - Day length continues to shorten until 21 December (Winter Solstice) ## AGRONOMY FACTS for COMPETITIONS ### Infrared Radiation - Means "below red", longer radiation. - Sensitive to it, mostly absorbed by atmospheric water and CO2. - Ecological importance ### Ultraviolet Radiation - Means "above violet", photochemical effects, shorter radiation - UV-A: reaches the Earth's surface, less harmful - UV-B: can be harmful to skin and causes skin-burn, genetic damage, skin cancer, etc. - UV-C: very harmful to humans and completely screened out by ozone at about 35 km altitude ### Photo-synthetically Active Radiation (PAR) - Used in photosynthesis and absorbed by plant leaves ### Visible Radiation - Most effective in heating of the Earth, know as sunlight, PAR - At the Earth's surface comprises 50-60% of total solar radiation. - Strong photosynthetic radiation in red and blue bands. - Important radiation bands for photoperiodism, seed germination, flowering and fruit color development: near infrared (0.76 to 0.92 µ). - Earth absorbs shorter wave radiations and emit longer waves. - The balance between global and reflected radiation is called net radiation - 1 µ = 10^-6 m - 1 mµ = 10^-7 cm = 10^-9 m - 1 A = 10^-8 cm = 10^-10 m | Radiation | Spectral (µ) | PAR (400-700 nm or 0.4-0.7µ) | |---|---|---| | Ultraviolet | 0.1-0.4 | Violet | 390-450 nm | | UV-A | 0.4-0.315 | Blue | 450-490 nm | | UV-B | 0.315-0.28 | Green | 490-574 nm | | UV-C | 0.28-0.1 | Yellow | 574-595 nm | | PAR | 0.4-0.7 | Orange | 595-626 nm | | Near-infrared | 0.7-4.0 | Red | 626-750 nm | | Far infrared | 4.0-100 | ### Albedo - The portion of incident solar energy that is reflected back is known as albedo. - Amount of Visible Light Reflected / Total Incident Light x100 | Substance | Albedo (%) | Substance | Albedo (%) | |---|---|---|---| | Ice | 90 | Lucerne | 23-32 | | Indian Soil | 35 | Moong | 26 | | Average of Earth | 30 | Wheat | 23-25 | | Meadows | 10-20 | Pearl millet | 24 | | Grey Dry Soil | 25-30 | Potato | 19 | | Grey Moist Soil | 10-12 | Rice | 12 | | Ploughed Soil | 14-17 | Crop Plant | 15-25 | | Black Dry Soil | 14 | Coniferous Forest | 15-20 | | Black Moist Soil | 08 | Deciduous Forest | 10-20 | | Water surface at 30° latitude | 6-9 | Charcoal | 04 | ### Light Intensity - It is the minimum light intensity at which the rate of respiration is equal to the rate of photosynthesis. - Directly proportional to temperature. - Compensation point for heliophytes is 50 ft candle, for rice 600 ft candle at 16°C or 1400 ft candle at 27°C. ### Saturation Light Intensity - It is the maximum light intensity at which the rate of photosynthesis reaches a maximum. - Most of the field crops belong to sun species (heliophytes) and reach light saturation at about 2500 feet candles while shade species (sciophytes) reach a light saturation level at a maximum of 1000 feet candles. - About 112000 calories of energy are required to reduce one molecule of CO₂ to the level of carbohydrate. | Crop | Light Saturation (Feet Candle) | |---|---| | Sugarcane | 6000 | | Rice | 5000-6000 | | Wheat | 5300 | | Alfa-Alfa | 4700 | | Sugar Beet | 4400 | | Maize | 2500-3000 | | Potato | 3000 | | Apple | 4050-4400 | - Photosynthetic rate of C4 plants is about twice of C3 plants. - Light saturation of C4 plants is higher (8,000 to 10,000 ft candle) than C3 plants (2,500 to 5,000 ft candle). - Light Saturation Point - C4 > C3 - Light Compensation Point - C3 > C4 - CO2 Saturation Point - C4 > C3 - CO2 Compensation Point - C3 > C4