Carbon dioxide (CO2) enrichment
· Improves plant growth in fall, winter, spring
o Due to ventilation it is not worth doing in the summer
· Effective only in daylight hours or when lights are on
· Best time: sunrise to one hour before sunset
· Exhaust fans off & vents closed
· Used only when no air circulation (with outside air)
Methods of CO2 injection
1. CO2 generators
· Use propane or natural gas
· Open flame burner
· Each pound of propane yields:
o 3 pounds of CO2 and 1.6 pounds of water
· Burning gas may yield ethylene as well, which is a plant toxin
· Gas purity
o Sulfur may also be a problem in impure gases
§ When burned yields sulfur dioxide
§ Sulfur dioxide in a damp or humid environment yields sulfuric acid
§ Natural gas: you want less than 1 grain per 100 cubic feet (7,000 grains per pound)
§ Propane: H. D. grade 5 (ie high quality propane)
o Oxygen is needed for combustion
§ Outside air inlet required
§ 1 square inch opening for every 2,500 BTU/hour of burner capacity
2. Liquid CO2 under pressure
· Bottled gas
· Distributed through 1/8-1/4 inch tubing
· Needle holes in tubing
· No combustion
· No detrimental pollutants like ethylene and sulfur dioxide
3. Organic mulches
· Microorganisms decay mulch and release CO2
· No control over concentration
· Must be replaced often
· Good in ground beds
· High CO2 day and night
o Wasted at night
· Especially good for greenhouse
o Roses
o Tomatoes
o Cucumbers
· Must be replaced/refreshed often
· Can get bursts of CO2 as decay peaks
Ethylene and
carbon monoxide
· Exhaust fumes
· Pollutants from burners
· Industrial pollution
· Plant parts, etc (ethylene only)
o Fruit, bacteria, fungi
Indicator plants for ethylene
· Tomatoes
· African marigolds
· Castor beans
· Sunflowers
· Cucumbers
· Peas
· Peppers
First symptom for these plants is epinasty, which is a severe curling of the leaves
How to use indicator plants
· Plant 4-8 pots of indicator plants
· Wait until first true leaves have appeared
· Put half the pots in suspect greenhouse
· Put other half in a clean house
Symptoms of ethylene and carbon monoxide
· Flower senescence (death)
· Petal abscission (falls off)
· Leaf drop
· Epinasty - severe curling of the leaves
· Few flowers
· Shortened internodes
· Increased branching (eg in snapdragons)
· Distored flowers
Controlling ethylene
· Maintain burners
· Use best quality fuels
· Use adequate exhaust systems and outside air source
· Avoid gas powered motors in greenhouse
o Rototillers, sprayers
· Don't burn trash close to the greenhouse
· Don't let vehicles idle outside greenhouse vents
· No smoking
Water
Water quality evaluation in terms of
· Amount and types of salts
· Salt tolerance of crop
· Frequency, rate and method of watering
· Substrate drainage (medium type)
· Other uses
· Pesticide sprays
· fertilizers
It is very complex to put a water regime into practice.
Water analysis
· pH - degree of acidity/alkalinity
· E.C. = electrical conductivity
o Index of total dissolved salts
o < 0.8 mmhos/cm: good, no restrictions
o 0.81-2.2 mmhos/cm: fair, some changes in management
o >2.2 mmhos/cm: poor; avoid
o Affected by P, K, Ca, Mg, Mn, Fe, Cu, B, Zn, Mo, Al, Na, pH
· See handout #4
Handouts
1. Suggested radiant energy (foot-candles) and daily lighting cycles for supplemental lighting in greenhouses
2. Georgeson Botanical Garden: Annual Flower Plant Evaluations 1999
3.
Perennial Plant Trials at the Georgeson Botanical
Garden
4. Fairbanks Municipal Utilities System water spec sheet
5. Chena Hot Springs water analysis
6. Recommended leaching methods, based on EC of water
o Also with a graph on th eeffect of addition of acid on pH of water
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