Chap 3. Propagation Environment and Facility Courtesy: Landis, T.D. (1993) Environmental Controls 1. 2. 3.
4. 5. 6. Light Temperature Growing Media Plant Nutrition
Humidity Carbon Dioxide 1. Environmental factors A.Light - Electromagnetic spectrum - Solar radiation vs. artificial lights
a.Quality - what wave length the light belongs to - perceived by the human eye as color. - red light and far-red light -effects plant height and development b. Quantity -intensity or brightness of light
- radiometric and photometric measurements - influence on photosynthesis c.Duration - -
influenced by longitude and season photoperiods: long-day, short-day, day-neutral Light Quality 1. What does it mean? What spectrum of light does it involve? (Red, blue, green, orange, or infrared lights, etc.)
2. Measurements a. Wave lengths: distance from peak to peak or valley to valley in units of nm or m m = 10-3 mm nm = 10-6 mm = 10-3 nm b. Wave number: number of waves per cm of light (number/cm)
c. Frequency: number of cycles per second (cycles/sec, cps) Hertz (Hz) = 1 cycle/sec Mega Hz = 1 million Hz Composition of Visible Light Red Orange Yellow
Green Blue Indigo Violet Source: NASA Light Intensity 1. What does it mean?
How much irradiated on the surface (Quantity) 2. Radiometric measurements a. Light intensity measured in terms of power of radiation on a unit surface area Power = energy/unit time Intensity = power/unit area, energy/unit area per unit time b. Measurement units: Joules cm-2 sec-1, watts cm-2, BTU ft-2 hr-1, kcal cm-2 hr-1 c. The shorter the wave length, the more the energy available.
3. Photometric measurements a. Light intensity expressed in terms of illuminance or how bright the light is (visible radiation only) b. Measurement units: Foot candles, lumens, lux, mol m-2 sec-1 c. Relationships: 1 lux = 1 lumen m-2 1 foot candle = 10.76 lux
4. Factors affecting light intensity a. Moisture in the air: No. of clear days in January: 70-80% in AZ, 30-40% in NY b. Topography: Higher the altitude, brighter the light c. Pollutants in the air: PAN, SO2, NOx, etc. Duration of Light 1. What does it mean?
How long the light was on 2. Factors that affect light duration a. Time of the year (seasonal variation) b. Latitudes (both northern and southern hemisphere) Fargo: 56.5 N 3. Photoperiod responses a. Long day plants (short night plants)
Requires days longer than 16 hours to bloom Aster, petunia, potato b. Short day plants (long night plants) Requires days shorter than 13 hours to bloom Chrysanthemum, poinsettia, kalanchoe c. Mechanism of responses
Phytochrome system P660 red light absorbing form P730 far-red light absorbing form Influence of Photoperiod on Flowering Spectral Distribution of Various Lamps
Lighting for Photosynthesis 1. Environmental factors (continued) B. Temperature Optimum temperature - For most plants: 70 oF day and 60 oF night Importance some examples - Cold-moist stratification breaks dormancy of some
seeds - Warm temperature of soil medium improves germination and rooting - Heat applied to graft union to speed callusing and tissue joining - Bottom heat on propagation bench stimulates rooting, more cost-effective than heating whole greenhouse.
Use of psychrometric chart in greenhouse cooling Pad and Fan Evaporative Cooling System High pressure fogging system Growing Media
Ideal Composition 0.45 Solid 50% 45% mineral
5% organic matter Water 25% Air 25% Soil Amendments Sand: low water-holding, low CEC, heavy, size varies
used as inert medium Vermiculite: expanded mica mineral high water-holding, good CEC, high buffering Perlite: heated, popped volcanic rock (inert) very light, no CEC, no buffering or nutrient holding Calcined Clay: baked montmorlillonite clay, aggregate particles heavy, durable, high CEC
Pumice: Crushed volcanic rock (inert) low water-holding, low CEC Peat: about 75% decomposed sphagnum peatmoss high water-holding, high CEC, low pH Using Soil in Growing Media a. Heavy Texture Soil Use: 1 part clay loam
2 parts organic matter 2 parts coarse aggregate (amendments) b. Medium Texture Soil Use: 1 part silty loam 1 part organic matter 1 part coarse aggregate (amendments) c. Light Texture Soil Use: 1 part sandy loam
1 part organic matter Adjustment of Soil pH To raise soil pH Ground limestone (CaCO3) Dolomitic lime (mixture of CaCO3 + MgCO3) Gypsum (CaSO4)
To lower soil pH Sulfur powder (S) Aluminum sulfate [Al2(SO4)3]
Rockwool used as growing media for tomato production Fertilizer Application Fertilizer Injection Fertilizer Stock Tanks
Purification of Water - Filtration - Reverse Osmosis (RO water)
- Distillation (DI water) Fluctuation of CO2 Concentration Inside a Greenhouse in One Day 2. Environmental Control Facility 1. Cold frames 2. Hotbeds
3. Greenhouses 4. Shade houses 5. Other structures Cold Frames Semi-controlled environment Used for hardening seedlings and rooted cuttings Can also be used for vernalizing herbaceous
perennials Hotbeds Small, low structures for minimum environmental control Some bottom-heated - Use of electrical cables, hot water, stream - Heat from organic waste (manure, straw) was used earlier days
Possible problems - Seedling damping-off (Pythium, Rhizoctonia) - Complete control of temperature difficult Structural Designs of Greenhouse
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