Monday, November 26, 2007

Module 12 - CO2 Fertilization and Greenhouse Presentation, DUE Tuesday December 4.

San Remo is called the Town of Flowers where beautiful roses, sweet-smelling carnations, and colorful begonias and camellias are cultivated. With exceptional climate, the heart of Italy’s floriculture region is in San Remo. Note the HAF fans (Blue) and CO2 injectors (Red). Image Source: Dr. Sandy Wilson, University of Florida.

(see note about exam at bottom of post).


As we learned earlier in the semester, CO2 provides carbon to the growing plant when the physiological processes of photosynthesis and respiration achieve balance. Depending on the environmental control taking place in the greenhouse it can be beneficial both from a plant growth and economic standpoint to add supplemental CO2 to the greenhouse. After all, approximately 40% of the dry matter of most plant species consists of carbon.

Supplemental CO2 is most beneficial during periods when the greenhouse is not venting very regularly and supplemental light is being applied (or natural light is abundant). Conditions such as these are usually found during the winter production months. It is also important to remember that as transpiration rates increase the capacity for CO2 uptake increases for most plants with C3 photosynthesis.

  • Explain the impacts of supplemental CO2 on plant growth.
  • Discuss greenhouse environmental conditions that warrant supplemental CO2
  • List several different methods of CO2 injection.
One Type of CO2 generator. Image Source: (

non-mineral nutrients
carbon deficiency
carbon dioxide injection
CO2 generator
light sensor
LP gas
natural gas
compensation point


1. Read Chapter 11 in your textbook. Carbon Dioxide Fertilization. pages 387-396.

2. Watch the following slide show reviewing the basics of this topic.

STUDY QUESTIONS and EXERCISES (Answer each of the following in complete sentences. In most cases 2-4 sentences will suffice).
  1. Explain why sufficient carbon dioxide levels are critical to plant growth and development.

  2. If 300 ppm of atmospheric CO2 is sufficient for most plant growth, why is it hypothesized that many plants respond positively to higher levels.

  3. Describe the CO2 compensation points. What is an average level at which greenhouse crops meet the CO2 compensation point?

  4. Explain some measurable benefits of CO2 injection into the greenhouse atmosphere using at least 3 different crop examples.

  5. Describe two different methods of carbon dioxide injection used in greenhouses today.

  6. At Eurofresh Farms (you have seen several videos) they inject CO2 during the day by running the boilers. The hot water generated during the combustion process is then stored and recirculated in the greenhouse during the night. Explain why they go to the additional effort to store the hot water.

  7. Why did using compressed CO2 as a source (which works effectively) fall out of favor and become replaced with injection methods that require combustion?

  8. What are some potential problems that can occur when using combustion as the source of CO2?

I realized last week that I needed to require that your presentations be in PowerPoint or Google Presentations. This is so that they can be shared online with the other online students. The more "traditional" presentation methods are really only an option for the seated class. Please complete your presentation using Google documents or PowerPoint and turn it in. If you need help with this please contact me. I am not grading on technical ability, just information presented.

The presentation does not need to cover every detail from the past four weeks of effort. It should cover the following things:
  1. the environmental production requirements for your plant

  2. how the greenhouse design you came up with is capable of meeting the plant's environmental needs

  3. how your greenhouse design meets any additional requirements for your business plan
For example, a greenhouse designed to produce poinsettias would have to be capable of heating and cooling for the crop, but would look quite different depending on whether the market was retail (out of the same house you grew them in) or wholesale (shipping to retailer).

This exam will be in a familiar format. In order that I have time to grade it, I must receive it by Tuesday December 11th. I will e-mail it with instructions by the end of this week.

Tuesday, November 20, 2007

Exam Study Guide

The Exam Study Guide is now available. Remember the exam is cumulative. More details will be available soon. Until then, have a Happy Thanksgiving.

Monday, November 12, 2007

MODULE 11 - Light and Temperature - DUE. Tues. November 27th.


"Greenhouse growers harness the biology of photosynthesis and flowering to create a marketable product. Like other raw materials needed for plant growth (e.g., plastic, and nutrients), light is not free. We increase light levels by investing in alternative technologies such as state-of-the-art retractable roof greenhouses to maximize available sunlight, or installing high intensity discharge (HID) lights. Alternatively, we may choose to save costs and sacrifice potential yield by using older or simpler greenhouses with lower light transmission. Yet another option is to relocate production (e.g., cuttings or cut flowers) to areas with naturally high sunlight during production months. Light clearly has an economic value.

Growers can benefit from knowing how to best manage light. For example, you may be able to grow an extra production cycle of plugs or bedding plants, hasten flowering of perennials for higher out-of season prices, or make more informed decisions when purchasing new structures and equipment." ---from Lighting Up Profits: Understanding Greenhouse Lighting. 2004. (edited by Fisher and Runkle. ISBN 1-892829-10-X)

  • Explain the basic process of photosynthesis (hopefully this is somewhat of a review)
  • Discuss how light intensity affects growth
  • Describe the possible effects of day length (photoperiod) on the flowering process
  • Compare and contrast different types of supplemental lighting.
  • Explain the methods used to provide artificial long- and short-day conditions


HID lights
black cloth
cellular respiration
fluorescent lights
light quality
incandescent lamps
carbon dioxide
light compensation point
electromagnetic radiation spectrum
light saturation point
visible light
Metal Halide Lamps
inrared radiation
Short-day plants
light meters
Long-day plants

Image Source: Flickr, Bartimaeus


1. Read pages 399 - 431 of the textbook. Chapter 12. Light and Temperature

2. Read parts 1 and 1.1 of the Photosynthesis review on wikipedia.

3. Read the NGMA's Helpful Hints on Supplemental Lighting.

4. Read Evaluating Supplemental Light for Your Greenhouse by Fisher et. al.

5. Watch the following two slideshare shows after reviewing the reading assignments.


PART I. Fill in the blank (2 points each)

1. The process by which green plants convert light energy of the sun into chemical energy is called ________________. (1 pt).

2. The green pigment in the leaf that helps convert the light energy is called ______________. (1 pt)

3. Water used in this conversion process is adsorbed by the roots. The water is the source of the ________________ ions that combine with carbon dioxide to form carbohydrates.

4. Solar energy (light) is transmitted in the form of _________________.

5. Light intensity is measured in units called _____________________.

6. Fluorescent lamps are a better source of light than incandescent lamps because the incandescent lamps give more _________ than light.

7. Excessively high light intensities in the summer may cause __________ of the flowers of chrysanthemums, hydrangeas, and geraniums.

8. Those plants that flower when the day length is longer than a critical number of hours are called _____________- day plants.

9. House plants grown near a window in winter may lean toward the light in response to a reaction called _____________.

10. The light-sensitive substance within plants that responds to day length is a soluble protein called _________.


1. What is the most economical type of lamp used for supplemental greenhouse lighting? Explain why. (10 pts).

2. What is a good rule of thumb for the minimum amount of accumulated PAR that most ornamental crops should receive? (answer should be in micromoles/m2/day). (5 pts).

3. Metal Halide lamps are expensive, but they are occassionally used because of one big advantage. What is this advantage? (5 pts).

4. Which season of the year is it usually most critical to provide supplemental lighting in North America? Why? (10 pts).

5. List at least 5 factors that are important to consider when deciding whether or not add supplemental lighting to a greenhouse production system. Briefly explain why each is important. (10 pts).

6. What are some additional challenges that might arise when supplemental lights are added to a greenhouse production system? In other words what other things will the grower have to adjust for in her/his crop production plan? (10 pts).


1. Based on the graph below answer the following two study questions. Remember your answer must be in %. Show your work. (15 pts). If your HPS lighting system provided 5 mol per day/m2 of PAR and you lived in Columbus, Ohio; What % increase in total light would you receive in January by running the supplemental lighting system? How about in July?

2. Based on the graph below answer the two study questions but for Anchorage instead of Columbus. Show your work (15 pts).

Source: Lighting Up Profits: Understanding Greenhouse Lighting. 2004. (edited by Fisher and Runkle. ISBN 1-892829-10-X)

PART IV. Greenhouse Design Project (Final Assignment Prior to Online Presentation) Complete the assignment in this PDF file.

Monday, November 5, 2007

Module 10 - Alternative Cropping Systems - DUE TUES, NOV 13th.

Hydroponic production of strawberries has many advantages. Could you name a few? (Image Source: USDA)

Up until this point we have focused primarily on 'traditional' greenhouse production. Production that involved horticultural crops being produced mostly in containers using soilless media as a root substrate.

You have been briefly exposed to hydroponic production through the EuroFresh videos, but there are several alternative production systems that are being utilized in commercial greenhouse businesses around the globe.

Some of these systems are even being further adapted by experts for extreme production locations such as the Antarctic, Moon, and Mars! You will see a few images from research in one of the slide presentations. This module will serve as a brief introduction into these systems which are growing in popularity.

  • Briefly summarize three different types of Alternative Crop Production.
  • Compare and contrast NFT with rock wool culture.
  • Describe the function of the Ebb-and-Flood production system.
  • Explain why the invention of Hoagland's solution was a breakthrough in the 1950's.
  • List the advantages of the NFT system.
  • Describe how rock wool is manufactured.
  • List the advantages of rock wool production.
  • Explain how whole firm recirculation can reduce the environmental impact of a greenhouse business.
rock wool culture
gravel culture
sand culture
In-line pasteurization

Simple recirculating plant growth system utilizing materials that could be purchased from hardware and pet stores.

  1. Chapter 10. Alternative Cropping Systems. pages 369-385. In your textbook.
  2. North American Greenhouse Tomatoes Emerge as Major Market Force. A publication by the ERS/USDA.
Review the slide presentations below. The first reviews concepts from the reading. The second introduces you to an integrated agriculture system called aquaponics.

Cartoon of an aeroponic system.

STUDY QUESTIONS (5 pts each, answer in complete sentences)
  1. Compare and contrast NFT with rock wool culture.
  2. Describe three different types of In-Line pasteurization of nutrient solutions.
  3. Briefly describe how rock wool is manufactured. How biodegradable is rock wool?
  4. How does irrigation frequency compare for traditional container systems and rock wool production?
  5. Briefly describe how whole-firm circulation might work for a greenhouse business.
  6. Based on the ERS article what percentage of tomatoes sold in grocery stores in the U.S. were produced in a greenhouse?
  7. What are some of the growing pains faced by the North American Greenhouse Tomato industry?
  8. A local greenhouse grower says that he can get ten times the yield of tomatoes from his greenhouse using the same amount of space as his competitor that grows field-grown tomatoes. Do you believe the grower or is this just hype? Support your answer.
  9. What North American country has the fastest growing production of greenhouse tomatoes and why?
  10. What North American country has seen a decline in greenhouse tomato production and why?
Continue with your greenhouse design project. Remember to contact your instructor if you have questions. The next assignment is available in PDF format here.