Agricultural/Bioengineering Greenhouse and Controlled Environment Agriculture 2 — Questions and Answers
Question 1: CO2 enrichment in greenhouses is used to:
- Prevent pest and disease outbreaks
- Increase photosynthesis rate and crop yield above levels supported by ambient CO2 (Correct answer)
- Reduce humidity inside the greenhouse
- Lower irrigation requirements
Correct answer: Increase photosynthesis rate and crop yield above levels supported by ambient CO2
Elevating CO2 to 800-1200 ppm in greenhouses increases the rate of photosynthesis, resulting in faster growth and higher yields compared to ambient 420 ppm.
Question 2: Integrated Pest Management (IPM) in greenhouses often uses biological control agents such as:
- Broad-spectrum chemical pesticides applied weekly
- Beneficial insects like predatory mites and parasitic wasps to control pests (Correct answer)
- UV lights that kill all insects
- High CO2 levels to suffocate insects
Correct answer: Beneficial insects like predatory mites and parasitic wasps to control pests
Greenhouse IPM uses beneficial organisms — such as Phytoseiulus persimilis for spider mites — to naturally suppress pest populations, reducing pesticide dependence.
Question 3: The growing medium perlite is widely used in greenhouse production because it:
- Provides significant plant nutrients
- Offers excellent drainage and aeration while being lightweight and inert (Correct answer)
- Acts as a buffer for pH swings in nutrient solutions
- Has high water-holding capacity similar to peat
Correct answer: Offers excellent drainage and aeration while being lightweight and inert
Perlite is a volcanic glass expanded by heat into lightweight, porous particles that provide excellent aeration and drainage while being chemically inert and disease-free.
Question 4: Heating degree days (HDD) are used in greenhouse engineering to:
- Measure crop light accumulation
- Estimate seasonal heating energy requirements for a greenhouse in a given climate (Correct answer)
- Calculate water use efficiency
- Determine optimal planting density
Correct answer: Estimate seasonal heating energy requirements for a greenhouse in a given climate
HDD quantifies the cumulative temperature difference below a base temperature over a season, used to size and estimate costs for greenhouse heating systems.
Question 5: Electrical conductivity (EC) of nutrient solutions is routinely measured in hydroponics to:
- Determine the pH of the solution
- Monitor total dissolved nutrient concentration and adjust feeding accordingly (Correct answer)
- Measure oxygen levels in the solution
- Test for microbial contamination
Correct answer: Monitor total dissolved nutrient concentration and adjust feeding accordingly
EC measures the concentration of dissolved ions in nutrient solutions, serving as a proxy for overall nutrient strength that growers monitor and adjust continuously.
Question 6: Gutter-connected greenhouse ranges are preferred for large commercial operations because:
- They are cheaper per unit to build than single-span houses only
- They share sidewalls, reducing heat loss and allowing efficient use of labor and equipment across a large, continuous growing area (Correct answer)
- They require no climate control systems
- They eliminate the need for supplemental lighting
Correct answer: They share sidewalls, reducing heat loss and allowing efficient use of labor and equipment across a large, continuous growing area
Gutter-connected ranges eliminate exterior sidewalls between bays, dramatically reducing heat loss, lowering per-unit construction costs, and enabling continuous mechanized operations.
Agricultural/Bioengineering Greenhouse and Controlled Environment Agriculture 2
CO2 enrichment in greenhouses is used to: