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.

Monday, October 29, 2007

MODULE 9 - Next Step in the Greenhouse Exercise - DUE Tues. NOV 6th

Hi all,

As some of you know, I am teaching a seated section of this course this semester as well. The seated course has fallen about a week behind the online section. In order to re-synchronize the courses, the distance learners get a light week. You only need to complete Part II of the greenhouse assignment this week. You may mail the assignment to me if it is easier to handle the calculations that way. Just make sure it is postmarked by November 6th.

Let me know if you have any questions,


Tuesday, October 23, 2007

Module 8 - Fertilization, DUE Oct. 30th, 2007

Boron Deficiency on Hydroponically Produced Melon.

Fresh plant material is usually made up of between 80 and 95% water. So far, 16 elements have been identified as essential for plant growth. The plant cannot complete its life cycle without the element. Action of the element must be specific - no other element can take its place. The element must be directly involved (structure, constituent, enzyme activator, etc.)

Optimum plant growth is a function of nutrient concentration in the plant. There is a critical nutrient concentration below which growth is reduced/terminated. The adequate zone is above the critical concentration and provides maximum growth. The toxic zone is above the adequate zone, again resulting in reduced growth or death. THEREFORE, MORE IS NOT ALWAYS BETTER!

---Dr. Pat A. Rorabaugh, Controlled Environment Agricultural Center, Department of Plant Science, University of Arizona

  • List the major and trace elements needed for plant growth
  • Recognize common symptoms of essential element deficiencies
  • Evaluate deficiency symptoms to determine if the element is mobile or immobile
  • Explain the importance of pH in terms of nutrient availability.
  • Explain how soluble salts can be used to infer nutrient concentrations from a media solution
  • List and describe the general forms of fertilizers.
  • Explain the advantages of chelated micronutrients
nonfertilizer (non-mineral) nutrients
primary macronutrient
secondary macronutrient
pre-plant fertilization
post-plant fertilization
rule of 75
backflow preventer
liming materials
dolomitic limestone
sulfur, iron sulfate, aluminum sulfate
slow-release fertilizer
polymer encapsulated fertilizers
slowly soluble fertilizers
sulfur-coated fertilizer
chelated micronutrients
PourThru method
Press Extraction method
Foliar analysis

  1. Read Chapter 9 in your textbook. pages 303-366; this chapter is a long and detailed, so allow yourself extra time to complete the reading.
  1. Watch all the videos at the end of this section, you have seen a couple of these before. (THERE IS NO AUDIO LECTURE THIS WEEK because I think the growers tell this story best).

  2. Compare and contrast the plant nutrition program of Eurofresh, Kraft Farm, and Crossroad Farm in a few paragraphs. (20 pts).

  3. Choose the nutrition system from the greenhouse operation you liked best. Explain what it is about their nutrition plan that appeals to you in 4-6 answers. Back up your choice with information you have learned from the course. (10 pts). There is no right or wrong choice here. All these growers or businesses were selected for their knowledge and economically successful operations.

STUDY QUESTIONS (2 pts each)
  1. What is the purpose of a back flow preventer.

  2. Which essential elements come from the air and water?

  3. Explain what essential nutrients (elements) are impacted by the Cation Exchange Capacity of a soilless media.

  4. What essential nutrients are usually available in anionic forms that are easily washed out of the root substrate along with excess water?

  5. Explain the differences in nutrient availability caused by pH in soil and soilless media

  6. A purple color on the underside of the seedling leaves of marigolds and tomatoes is a sign of what two production problems.

  7. Describe the difference between a slow release fertilizer and a slowly soluble fertilizer.

  8. Name the essential nutrient at the center of every chlorophyll molecule.

  9. Fluorinated water can be a problem if you are producing members of a certain plant family. What is that family? You are probably very familiar with the ornamental members of this family. For extra credit name a commercially important vegetable crop member of this plant family that is sensitive to Fluorine.

  10. A petunia grower notices some purple discoloration on the underside of older leaves. Some leaves are brown and papery. What nutrient is likely deficient?

  11. The new buds of petunia plants are dying, but the new leaves near the bud look green and healthy although slightly misshapen. What nutrient is likely deficient?

  12. A petunia grower notices interveinal chlorosis on newly emerging leaves. What nutrient is likely deficient?

NEW THIS WEEK ONGOING Greenhouse Design Project (46 points). There will be new components of this project due each week. You can print off the handout for week one in PDF format here. NOTE: for 1.b. The hard copies will help you later on. You can turn in the links on your homework assignment.

Greenhouse Image by Kamoda (Japan)

Monday, October 8, 2007

Module 7 - Watering (Irrigation) DUE Tuesday, Oct. 23

Automatic Irrigation System for Hanging Baskets

This module consists of three subject areas that overlap. First, by reading the textbook you should develop an understanding of the importance of irrigation and the biological functions that water drives in plant growth and development.

Second, you will take a look at the many different types of irrigation systems that are now available for greenhouse growers to choose from. These range from the trusty watering wand to high-tech automated watering systems like the one shown in the image here that combines a hanging basket conveyor with a two tiered water water delivery system.

Finally, you will examine the impact of automation on the greenhouse industry.

  • Explain why a plant needs water
  • Understand how water is taken up and moved through plant structures
  • List the effects of too much water on the growth of plants
  • Discuss how moisture stress affects plants
  • Describe several ways that water may be applied to crops
  • Discuss the current trends in greenhouse automation and speculate on what the future may hold.
Ebb and Flow benches can help reduce foliar diseases, but create other management issues.

reverse osmosis
Moisture Probes
hard water
hose watering
softened water
low volume watering
acidifying water
trickle irrigation
drip tube
moisture stress
spray stakes
wetting agents
soluble salts
boom irrigation
ebb and flood irrigation
capillary mat

  1. Read Chapter 8: Watering in your text. pages 257-301
Ebb and Flow system adapted to the entire floor of a greenhouse.

  1. Watch Audio PowerPoint Lecture on Greenhouse Irrigation (approx. 40 minutes). Depending on your Internet Connection Speed this may take some time to download.

  2. Search the Digital Greenhouse Repository using the keyword "irrigation"; study the pictures and read the abstracts when available.

  3. Watch the short video clips showing automated hanging basket and boom irrigation on display at a trade show. Write a paragraph explaining how these systems would not only save labor but could improve plant uniformity, quality, and health. (20 pts).

  4. Briefly explain (based on plant biology) why transpiration rate directly correlates with the rate of photosynthesis in a plant. (10 pts). You may have to do a little searching to answer this one.

  5. Choose 5 "irrigation" images from your search in #2 that show 5 different irrigation methods/systems and describe the advantages and disadvantages of each one. (20 pts). Create a new Google Document Presentation to answer this question. (It's like using PowerPoint, contact your instructor if you need assistance)
Poinsettias on sale in a small-scale production/retail center. Note all the drip tubes, during peak production times there are just as many poinsettias hanging from the frame as are on the benches.

STUDY QUESTIONS (Answer in complete sentences)
  1. Discuss the three rules of irrigation as covered in your textbook. For each rule explain its significance and give an example of what can go wrong if the rule is not followed (10 pts).

  2. Compare and contrast pH and alkalinity. Which is arguably more important for greenhouse crop production? Give two examples of how alkalinity and pH can interact to present special challenges for greenhouse crop production. What corrective steps can be taken to correct for water with high alkalinity? (10 pts)

  3. What is water harness actually a measure of? How does water hardness come into play when trying to maintain the proper balance between calcium and magnesium? What are some general rules of thumb to maintain the balance between these two nutrients? (10 pts)

  4. Compare and contrast 3 different containerized plant watering systems (you can choose). Make sure you indicate the advantages and disadvantages of each. (10 pts)

  5. Some growers insist on hand watering to save costs and maintain irrigation control. Support or argue against this practice with information you learned during this module. (10 pts).
Extra Credit (5 pts). Develop a summer and winter production calendar (dates to transplant) for the hydroponic lettuce system highlighted in the video below.