Thoughts, Suggestions, Tips, and Extensions

Post date: Aug 05, 2015 3:56:19 AM

1) Thought: It is important to start with clean water when growing plants hydroponically.

Suggestion: Start by getting a baseline measure of the water quality. Soft water = 0-70ppm, Medium = 70-140, Hard = 140+. Ideal is to have Soft water but medium water will do also. Hard water is where problems start to arise. Hard water tends to come from ground or well water. If the water is very hard, 200+ it may be difficult (but not impossible) to be used in a hydroponic system. Hard water can make it difficult to maintain proper pH and PPM levels. In extreme cases (~400ppm) which is the case in my classroom, a Reverse Osmosis filter is needed to reduce the amount of total dissolved solids level or PPMs.

Tip: Use a basic PPM meter to measure the total dissolved solids or TDS. There are many meters out there from portable pen styles that deliver temporary or momentary readings, to "station" styles that produce continuous or long-term readings. If hard water is used, when nutrients and pH adjuster is added, the PPM levels will likely be way above the recommended levels. Option 1: Reduce the amount of nutrients to say in the desired PPM range. This is the simplest option but likely least effective method. Option 2: use 50-100% rain water in the system. Obviously this adds a sustainability aspect but rain water collected from a roof can contain bacterial, fungus, viruses and chemicals from the roofing materials. This options needs more research to determine the best way to approach it. Option 3: Use a Reverse Osmosis (RO) filter to filter the water which will produce very low ppm readings. This option is the most recommended because it produces very clean water that can be used to make a very rich and stable nutrient solution. However, RO systems are not without their disadvantages. They are pricey and may require new filters each year (or multiple times a year depending on the amount of water that is filtered and how hard the water is. Another disadvantages is that to get 1 gallon of filtered water, it can take 2-4 gallons of water to make it; wasting 1-3 gallons that can not be used because of its high level of dissolved solids. They are also slow. It may take 1 hour to filter 3- 5 gallons. Often RO Systems are hooked up to a large reservoir (55 gallon drum) and a float valve, allowing for a large supply of RO water on demand. Though RO filters are not ideal, they may be the only option to be successful with hydroponics.

Extensions: Students can complete an analysis of the water quality of multiple sources (School, home, bottled water, distilled, etc).

For more information on water quality in hydroponics, go HERE.

For more information on the RO system I use, go HERE.

For more information about a Water Testing Kit, go HERE.

For more information on RO Systems, go HERE.

For a recommended PPM pen meter, go HERE.

For a recommended station style meter, go HERE.

2) Thought: Teaching data gathering is a natural fit when teaching Hydroponics.

Suggestion: Measure multiple variables as a hydroponic system is being maintained. Variables include PPM's, pH, Air and Water Temperature (at different points in the system), Plant height(s), Humidity, lumens (light intensity), Dissolved Oxygen, and leaf temperature just to name a few!

Tip: Start with the basics: PPMs, pH, and a temperature. Students can record the data daily via paper and pencil or through a spreadsheet program. If Google Forms is used at this step, the data analysis can be done easily!

Extensions: Gather data from multiple systems.

For a recommended PPM pen meter, go HERE.

For a recommended station style meter, go HERE.

For a recommended affordable thermometer, go HERE.

For a recommended Indoor Humidty Meter, go HERE.

For information on how to complete data gathering, watch THIS.

For a helpful Date Gathering and Analyzing app, go HERE

3) Thought: Along with data gathering comes data analysis.

Suggestion: Entering the data into a spreadsheet program such as Microsoft Excel or Google Sheets allows for many possibilities to analyze the data. It is recommended that Google Forms be used so that the data is already in a spreadsheet (Google Sheets).

Tips: Have students create charts or graphs for the different data. Allow them to identify trends and data points that bring up questions. Ask them to hypothesize the "dips and dives" of the different data. ("Why did the PPM and pH change on 9/2? What caused it? or "I think the PPM's dropped because the plants were taking in nutrients")

Extensions: Annotate the graphs to reflect the observations that where made or hypothesis that were generated.

For examples of hydroponic data and graphs, go HERE.

For a helpful Date Gathering and Analyzing app, go HERE.

For more information about how to complete Data Analysis, watch THIS.

4) Thought: Starting from seeds takes time!

Suggestions: If the plan is to start plants from seeds, most seeds will need to be started 1-4 weeks before going into a hydroponic system however some seeds will sprout very quickly. Needless to say, planning needs to be done.

Tips: Germinate seeds by preparing RockWool cubes by soaking them in water, adjusting the pH to 6.0 (for most plants), putting 2-3 seeds in each cube. Specialized germination domes are recommended because the lid helps maintain a moist atmosphere and the clear lid to allow light through. Some seeds/plants (such as peppers) may require the use of a heat mat to help jump-start the germination process.

Extension: Some plants can be "cloned" by growing plants from snipped pieces of a mature plant. The procedure is very simple. Clip plant (at appropriate place), moisten cut end, dip in rooting hormone, put clipping in a grow media such a Rockwool. Students really enjoy this procedure and find it fascinating that they get the chance to "clone a plant"; producing genetically identical plants from a mature plant. "Clones" work very well when completing experimentation so that the variable of the different seeds/plants is eliminated.

For more information on germinating seeds, go HERE

For more information on cloning, go HERE

5) Thought: The more oxygen (via air or dissolved oxygen) that can get to roots, the better!

Suggestion: There are multiple ways to get air to roots in a hydroponic system. An "air gap" between the top of the water and the base of the plant is the simplest but least effective method. Circulating water with pump and gravity will aerate the water to throughout the system. Forcing water out of nozzles in the form of a spray or mist allows a larger water to air surface area, such is the case in aeroponic style systems. A fine mist or even fog is very effective at delivering both the water /nutrient solution and air to the roots. Air pumps and airstones like the ones commonly found in aquariums are great at aerating the water and adding more dissolved oxygen to the water. The more air the better but also the more diffused (smaller bubbles) the air is the better. Running the water over aggregate can help increase the turbulence in the water, thus resulting in more aeration. Allowing growing media to absorb water and slowly dry or drain also will allow the roots access to air. Delivering the water through a drip system delivers a small amount of water to the media, which again acts like a sponge that can drain or dry slowly, allowing the roots to be exposed to air and not be totally submerged in water. Regardless of the method used to aerate the water/nutrient solution, it is important to no agitate the roots to the points that they constantly moving and risk being damaged. Some of the best hydroponic systems have multiple methods to provide air to the roots. For example, an aeroponic system uses nozzles to spray water into the air, on and around the roots of the plant, a thin film of water may sit in the bottom of the growing chamber, the turbulence ins the water is created as the water drains back into the reservoir. All that being said, there is a maximum dissolved oxygen level which is ~8ppm; however it is not likely that this level will be reached with just basic aquarium style pumps.

Tip: Try to combine methods. Adding an air pump to the system and putting the airstone in the reservoir can greatly increase the dissolved oxygen levels in the system. Gravity is used to help drain the water back into the reservoir. The higher the fall of the water, the more it can agitate the water in the reservoir. Cutting the drain back pipes or hoses so that there is a gap above the water can help also with this.

Extension: Using a dissolved Oxygen meter, measure, graph, and analyze the dissolved oxygen levels throughout the system/ at different points in the system. Make adjustments and modifications to system to increase the readings and increase productivity.

For more information on the importance of dissolved oxygen, go HERE or HERE

6) Thought: Maintaining a system is important to be successful.

Suggestion: Maintaining a system is rather easy but each system is different. When a system is in full operation, in general, the water/nutrient solution should be changed out once a week. During that week, the reservoir can be topped off with just water. When the plants are young and not taking up much water and nutrients, the system can likely be changed every 2 weeks. There are a few other things that go into maintaining a system. Monitoring and adjusting the pH is very important. In short, plants can not absorb or utilize the nutrients if the pH is not in the proper range. Maintaining proper nutrient level is also important by using a simple total dissolved solids (TDS) meter to monitor the PPMs or EC's. Each plant has different recommended pH and nutrient levels. Improper pH and nutrient levels can cause a number of problems from discoloration, poor growth, bad taste, and can very easily the kill plant. Other maintenance that may need done in a system include pruning, adjusting of light height, "training" climbing plants, and occasionally flushing the system with clean water are just a few things that need to be done to maintain a hydroponic system.

Tip: If attempting to grow multiple species of plants in 1 system, try to pick plants that have similar pH and Nutrient level recommendations. When in doubt a weaker nutrient solution is better than too much nutrients, which can lead to what is called "burning the plant".

Extension: In industry, automation is very commonly used to maintain a hydroponic system. Developing some method of automation in the system is a great extension! The use of sensors and meters to better monitor a system can help with maintains a system also.

For more information on maintaining a system, go HERE or HERE

For more information on pH and adjusting it, go HERE

For a recommended PPM pen meter, go HERE.

For a recommended station style meter, go HERE.

7) Thought: Every plant has different optimal environmental growing conditions.

Suggestion: Every plant has different environmental growing conditions that are considered optimal. The following basic variables need to be considered with each plant. pH range, Nutrient level, Light timing, Air Temperature, Root Temperature, and humidity. Some variables may not be easy to control in a classroom such as humidity and air & root temperature.

Tip: Bookmark websites or keep some charts on hand while growing to make sure the variables are in their proper range.

Extension: Perform an experiment to test the growing conditions and help optimize the system.

For a quick growing chart for growing vegetables, go HERE.

For a quick growing chart for growing herbs, go HERE.

For information on temperature and humidity, go HERE.

For a recommended PPM pen meter, go HERE.

For a recommended station style meter, go HERE.

8) Thought: Measuring the nutrient level is important and easy!

Suggestion: Nutrient concentration levels are measured with a device that measure the total dissolved solids (TDS) in the water. Nutrient levels can be measured in Parts Per Millions (PPMs) or Electrical Conductivity (EC). The industry and experts tend to use ECs. How one chooses which unit to measure will typically be determined by which meter is used. The most basic meters will use PPM. Higher end meters will read in both PPM and EC. Each brand of nutrients and each plant will provide optimal ranges for the nutrient levels. Some companies give ECs others will give PPMs.

Tip: For the classroom setting, using PPM is recommended. PPM has a wider range of scale (0-2000+) rather than ECs (0-3.0+) making PPM easier to graph and analyze because of the range.

Extension: Use a PPM meter to measure multiple different solutions (soda, juice, bottled water, etc). Graph the readings to help expand students understanding of PPM and give perspective of the hydroponics systems PPM levels.

For more information about the different PPM Scales, go HERE.

For more information on measuring nutrient levels, go HERE.

For more information on monitoring nutrient solution, go HERE.

For a recommended PPM pen meter, go HERE.

For a recommended station style meter, go HERE.

For a great list of tips on...

• • Nutrients for Hydroponic Systems

• Why and when to test and adjust pH in hydroponics

• pH test kits versus electronic pH test meters

• Using pH adjusters

• Pump timers

• When you need to use timer for the water pump

• How often to water the plants in your hydroponic systems

• Water level in your hydroponic system

• What size reservoir to use in your hydroponic system

• Water quality

• Artificial lighting used for hydroponics

• Water Temperatures and Oxygen for the roots

Thought: There are advantages and disadvantages to every design of grow light.

Thought: Hydroponics is full of mini-lessons!

Thought: Different nutrients = tradeoffs