Exploration of salt tolerance of plants native to California’s San Joaquin Valley.

The WISRD Hydroponics Lab is working to determine the maximum salinity level a plant can tolerate while simultaneously thriving in a Nutrient Film Technique hydroponic system that closely resembles the San Joaquin Valley.



Hydroponics is a subset of hydroculture which focuses on cultivating plants in nutrient solutions with or without the use of an artificial medium such as sand or gravel, but without soil. Hydroponic systems are categorized as open systems meaning the nutrient solutions delivered to the plant aren’t reused or as closed where the solution is reused. Hydroponics is groundbreaking because it can be highly productive and conserve plenty of water, land, and the overall environment. Furthermore, success in hydroponic culture only requires basic agriculture skills. Regulating the root environment is crucial to the health of the plant so hydroponic labs are set up in enclosed spaces in order to control air and root temperatures, light, water, plant nutrition, and climate (Jensen, 1997, p. 1081). There are 6 basic hydroponic systems: Wick, Water Culture, Ebb and Flow (a.k.a. Flood and Drain), Drip, Nutrient Film Technique (N.F.T.), and Aeroponic. The system used in this lab is the Nutrient Film Technique. N.F.T. systems have a constant flow of nutrient solution and a submerged pump. In these systems, the nutrient solution is pumped into a tray or tube holding the plants, flows over the roots of the plants, and then drains back into the reservoir. Typically, there are no other growing mediums other than air, making it a cost-effective system. The plants are grown in small plastic root baskets, with the roots dangling out of the bottom and into the nutrient solution. These systems are very susceptible to power outages and pump failures which interrupts the flow of nutrients and causes the roots to dry out rapidly (“Basic Hydroponic,” n.d.).

The San Joaquin Valley, located in Central California, is a densely populated agricultural region. This region is the highest producing in California, the state with the highest production of agricultural goods. The region also has the highest mean farm size and gross production per farm, while simultaneously having one of the lowest total number of farms in the state by region. That factor shows how the region has become industrialized and more of a model for agricultural efficiency rather than sustainability (Klonsky & Tourte, 1996). Apart from these agricultural factors, California is a rapidly expanding state. As the north and south parts of the state have started to become overpopulated, many people have decided to look to central California for a place to live, causing a population boom. The problem with this being: the more people, the more clean water needed, and without sufficient water in the region; the concentration of minerals increases (“Salinity in the Central,” n.d.).

Currently, the California Water Project uses the San Joaquin Delta as a liminal space for the water being transported to Central California, unfortunately, the delta is subject to salt contamination from the ocean which begins the salinity contamination process for the valley (California Environmental, 2006). Thousands of years ago, the San Joaquin Valley was part of the Pacific Ocean, which accounts for the naturally occurring high levels of salinity in the region (“Salinity in the Central,” n.d.). When water is transported through the region, the CWP often uses the underground passage for better irrigation and less evaporation. This water becomes contaminated with nitrate, oxidized, dried nitrogen, which comes from improperly discarded fertilizers. Furthermore, the salt already in the water from delta cannot be diluted into the ground due to the impermeable clay layer that covers many of the valley’s aqueducts. This water, without the proper drainage, will simply evaporate leaving behind all the salt, nitrate, and excess minerals it had picked up on its journey from the Sacramento Basin. This leaves both the surface and underground with increasingly high concentrations of salinity (California Environmental, 2006).

The rising salinity will continue to create long term damage to the land and eventually make it completely barren. Additionally, the current effects of the salinity crisis occurring in the San Joaquin Valley could spread throughout the regions surrounding the valley if the issue is not contained and fixed. This could have devastating effects for not only California but the entire United States and could potentially even lead to a food crisis in America. Overall, the effects of the salinity crisis will only intensify as time goes on until it reaches nearly irreversible effects and environmental ruin (“Salinity in the Central,” n.d.).

Research Questions

The primary research goal for the Hydroponics Lab is to determine the maximum salinity level that a plant can tolerate while simultaneously thriving in an agricultural setting. The lab is designed to control the flow of water, the nutrient level, and the amount of salt present, all while being able to observe the plant’s reaction and growth in relation to the increasing salt levels.

Through the use of the Hydroponics Lab, the plan is to observe how changes in salinity levels will affect plant growth and health; and the possible methods plants use to combat this challenge. The salinity increases is the salinity threshold of San Joaquin’s crops. By testing multiple levels of salinity on crops grown in the valley in a hydroponic environment, quantitative data will be collected to understand how much salt a plant can withstand. A central concern of the salinity crisis is the future of agriculture both in the San Joaquin Valley and other locations with similar issues. Through the research achieved with the Hydroponics Lab, the lab will gain to understand how rising salinity levels will affect the types of plants that can survive and those able to thrive in the valley. The salt content of the soil may pose an adaptable environment for some plants and a deadly threat to others; the Hydroponics Lab is designed to find the plants, out of those currently being grown in the San Joaquin Valley, that can continue to be produced as the environment changes. As a clearer idea of how crops endure higher salt content becomes more evident, an understanding of what plants do to individually grow and survive in a saltier environment can be established. Understanding the survival methods of plants against rising salinity will help explore the possibility of acclimating plants to higher salinity environments. The question posed is whether or not a faster acclimation of a plant is possible.


Hydroponics Plan 2019-2020

May 15th: Publish the scientific article.

April 29: Begin writing a publication on findings and propose potential solutions as well as making plans for the future of the Hydroponic Lab.

April 28: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations.

April 21: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations.

March 31-April 14: Collect observational data of each of the grow tubes.

March 31: Follow steps 13-14 of the procedure to prepare for plant testing, changing salinity levels based upon data from the second iteration. Salinity levels should be closer to one another in an attempt to find a maximum. Transfer the sprouts to the hydroponics system.

March 24: Begin the third iteration. Germinate the same plant seeds in the germination tray following steps 1-12 of the procedure above.

March 23: Remove plants from grow tubes. Completely drain and clean the system, making sure all salt and nutrients are completely removed from the system to ensure another trial can be run without error.

March 20: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations. If needed, determine the amount of salt to increase or decrease based on the survival of the plants.

March 13: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations.

February 25-March 10: Collect observational data of each of the grow tubes.

February 25: Follow steps 13-14 of the procedure to prepare for plant testing, changing salinity levels based upon data from the first iteration. Salinity levels should be closer to one another in an attempt to find a maximum. Transfer the sprouts to the hydroponics system.

February 18: Begin the second iteration. Germinate the same plant seeds in the germination tray following steps 1-12 of the procedure above.

February 12: Remove plants from grow tubes. Completely drain and clean the system, making sure all salt and nutrients are completely removed from the system to ensure another trial can be run without error.

February 11: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations. If needed, determine the amount of salt to increase or decrease based on the survival of the plants.

February 4: Following instructions on the Vernier Salinity Probe, determine the salt intake of plants using the probe. Record data and make observations.

January 14-28: Collect observational data of each of the grow tubes.

January 14: Follow steps 13-14 of the procedure to prepare for plant testing. Transfer the sprouts to the hydroponics system.

January 7: Begin the first iteration. Germinate plant seeds in the germination tray following steps 1-12 of the procedure detailed below.

Hydroponics Plan 2018-2019

Longterm Goal: To test the salinity tolerance of plants

Begin Running Lab Monday, November 12

**Must start by above date.

  1. Caps
    1. Reprint – Wednesday, October 31 through Monday, November 5
    2. Test/ Revise – Monday, November 5
      1. **same caps we tested before, minimal testing and no revision expected
  2. Supplies
    1. Send out supplies order – Thursday, October 11
  3. Building Lab
    1. Begin Construction – Monday, November 5
    2. Check/Finalize – Wednesday, November 7
    3. Test Run Lab – Wednesday, November 7 – Thursday, November 8
      1. Split Plants (3) – Thursday, November 8
    4. Run Lab with Plants – Thursday, November 8
      1. **Above is the ideal date, can be pushed back to Monday, November 12 if necessary
  4. Website
    1. Construct Website:  Monday, October 16 – Monday, October 29
      1. Finalized Version – Wednesday, October 31

Plan 2017-2018

Step 1: Finish creating solutions and test molarities under the spectrometer
Finish Date Goal: Sunday, January 14
a. We are still waiting for a new shipment of sodium chloride to make the rest of our solutions. So far, we have done 0.5, 0.7, 1, 1.3 molarities.
Finish Date Goal: Before break (Friday, December 15), if sodium chloride does not arrive Monday, January 8.
b. When we finish making the solutions, we will test each molarity under the spectrometer and create a calibration curve.
Finish Date Goal: Friday, January 12

Step 2: Building the new hydroponics lab
Finish Date Goal: Before spring break
a. Scale down the lab design to 0.5 and create a rendering
Finish Date Goal: Friday, December 15
b. Make a list of what parts we need
Finish Date Goal: Tuesday, January 2
c. Identify what parts we have
Finish Date Goal: Friday, January 5
d. Buy parts and/or deconstruct the old lab to collect materials
Finish Date Goal: Tuesday, January 16
e. Construct the new hydroponics lab
Finish Date Goal: Monday, April 23
The above date will probably be adjusted, we don’t have experince building a lab and will revise our prediction when we begin building.

Step 3: Growing the plants
Finish Date Goal: TBD, At least after Monday, April 30
a. Finalize lab setup: 4 tubes, Tube [a] containing lowest (exact amount to be determined) salinity level, Tube [b] containing medium-low salinity level, Tube [c] containing medium-high salinity level, Tube [d] containing high salinity level, with six plants per tube. Troubleshoot if needed.
Finish Goal Date: Friday, April 27
b. Figure out number of grow days most accurately matching the number of grow days in the San Joaquin Valley.
Finish Date Goal: Monday, April 30
c. Grow plants for number of grow days in San Joaquin Vallley.
Finish Date Goal: TBD

-Dani B.

Materials and Methods


The variables controlled in the lab are water level, temperature, humidity, plant nutrients, and salinity concentration. The amount of water irrigating the growing plants needs to remain constant throughout all three systems because of the different salt concentrations being maintained in each trial. Temperature and humidity will be maintained constant for all three systems to create a sufficient control experiment. Plant nutrients are going to be controlled by having the same water level in the individual systems, in order to maintain the same nutrient concentration in each system. Each system is powered by a 396 gallons per hour pump. The lighting system of the experiment is on a 12-hour time schedule. The light is set to automatically turn on at 6:30 am and turn off at 6:30 pm every day. Salinity concentration in each individual grow tube system is the only varying variable in the experiment.


  • Smart sockets (4)
  • DHT11 Salinity/humidity sensors (2)
  • Plant nutrients solution (TBD)
  • Protoboard adaptors (2)
  • Germination Tray
  • 1 fluorescent light
  • Set of 8 fluorescent light
  • 18 3D printed root baskets (51 mm x 31 mm)
  • Clay pebbles (2lbs of preferably 9 mm balls)
  • Distilled water
  • NFT Hydroponics System (Figure 1)
  • 3 Clear plastic tubes (39 in x 3 in) with 3 holes spaced 7 inches apart
  • 3 valve systems (Figure 2)
  • Vernier Salinity Probe (3)
  • Procedure (for one iteration):

    1. Prepare a germination tray with a heating pad, clear plastic dome, and thermostat.
    2. Set up HiLetgo Humidity sensor using instructions provided by the instruction manual.
    3. Set up HiLetgo Thermometer following instructions provided by the instruction manual.
    4. Place the germination tray on a stand under one (1) fluorescent lighting system.
    5. Rinse 2lb bag of clay pebbles.
    6. Fill 18 3D printed root baskets with rinsed clay pebbles to the top.
    7. Sprinkle 6-10 seeds in each root basket.
    8. Place root baskets in the germination tray; evenly spaced.
    9. Fill the germination tray with 1 inch of distilled water.
    10. Cover the germination tray with the clear dome and close the airways.
    11. Let plant seeds germinate in the germination tray for a week until plants are 1-2 inches in height.
    12. Make daily observations of the plant’s growth twice a day (AM and PM). Record humidity, temperature, and physical observations.
    13. Set grow tubes in the hydroponics system (Figure 1) to salinity levels a, b, and c, where a is at 0.000 M (0.00 ppm), b is 0.025 M (1.50 ppm), and c is 0.600 M (35.0 ppm).
    14. Add the appropriate amount of salinity into each hydroponic system.
    15. Test the salinity using Vernier Salinity Probe.
    16. Transplant plant sprouts in root baskets into the environment and allow homeostasis for 2 weeks before gathering data.
    17. Make physical observations of the plant including height, leaf size, coloration daily.
    18. After 2 weeks, begin observing salt intake and nutrients intake weekly.
    19. Using a Vernier Salinity Probe, determine the salt intake of the plants.
    20. Following Vernier Temperature and Humidity Sensor manual, monitor temperature and humidity using Vernier Temperature and Vernier Humidity Sensors daily.
    21. Collect salinity data for 2 weeks.
    22. Adjust salinity levels based on the survival of the plants. Only adjust the salinity level if all plants in the grow tube are dead.
    23. If adjusting salinity levels, drain and rinse system before beginning a new iteration.
    24. Repeat steps 1 through 21 with different salinity levels until a maximum amount of salinity is reached. A maximum is defined as 5 values within 0.005 ppm of each other.
    25. Take notice of and record trends occurring.

    Trial 1

    Note: These are not the desired results, so we will be re-testing until our graph appears to be in accordance with the principle’s of Behr’s Law, meaning that the graph will be linear; absorption increasing as concentration increases.

    Concentration (Molarity)                                                Absorption (%)
    H2O                                                                                     Control

    0.5 M                                                                                    0.127
    0.7 M                                                                                    0.106
    1.0 M                                                                                    0.060
    1.3 M                                                                                    0.077
    1.7 M                                                                                    0.072
    2.0 M                                                                                    0.073
    2.3 M                                                                                    0.049
    2.7 M                                                                                    0.127
    3.0 M                                                                                    0.60

    -Dani B.

    Note: This page was not updated from February-August 2020. For comprehensive Hydroponics Lab updates during this lapse, visit Sadie G.’s journal (wisrd.org/sadieg).

    November 12, 2020
    The results of salinity Trial 2 which began in September will not be published because of procedural errors, so a new salinity Trial 2 was launched at the end of October (hereafter reffered to as Trial 2B). The seeds in Trial 2B germinated on November 1, and they were transferred from their germination environment and into the lab for testing on November 9. The “Data” tab will be updated with results from this Trial as they become available.

    We are also continuing work on our research paper. Our first draft was completed in October and we are now nearing completion of a second draft. We will be meeting with Professor Moreno, who is serving as a writing consultant to us, next week to discuss next steps to prepare our paper for publication in the WISRD Journal.

    WISRD Hydroponics also presented a poster at WISRD’s Fall Poster and Lecture Series on Monday, November 9. The presentation was a success. Here is a link to our poster available for download: http://wisrd.org/wp-content/uploads/2020/11/Screen-Shot-2020-11-12-at-3.24.15-PM.png

    September 17, 2020
    We are now in the third week of salinity Trial 2. There is now a photo gallery below the log. We will be updating it weekly with new trials from Trial 2 and data once it becomes available.

    September 10, 2020
    Over the past week, the Hydroponics group has been working on our methods paper. This is first step to working towards completing a full reserach paper to be published in the WISRD research journal by the end of the year. We have been collaborating with WISRD Fellow and writing coach from the Publications department Prof. Amielle Moreno, who has been a valuable resource to us as we work on the paper.

    Additionally, we recorded our first podcast episode today for the WISRD podcast. Ximena and Sadie were interviewed by Dani (who has also joined the Hydroponics lab this year) and Ian about their progress over the past three years, day-to-day operations with Salinity Trials 1 and 2, and next steps for the project.

    Some highlights included a discussion on how they embraced the contextual learning model to develop new skillsets as they built the new Hydroponics lab, and how they cultivated a partnership with Dr. Sandhu at the USDA UC Riverside Salinity Lab, and how that collaboration has guided their data collection practices. The full episode will be available under WISRD Podcast on the Publications page within the next ten days as soon as our Editor, Ian, has finished editing it.

    September 2, 2020
    WISRD is formally back in session, but progress was made over the summer on salinity Trial 1. The lab was set up at Sadie G.’s house and she is operating it while we do not have access to the WISRD lab.

    Trial 1 ended on August 8th. The following metrics were collected as averages for each grow basket: total biomass, root biomass, shoot biomass, and root length. These measurements were taken for Tube 1 (80mM NaCl), Tube 2 (40mM NaCl), and Tube 3 (control; 0mM NaCl). Three plants were grown in individual grow baskets, meaning nine total plants were grown. A leaf sample was also taken from each plant.

    Leaf samples were dehydrated and will be sent to Dr. Sandhu at the UC Riverside Salinity Lab for an ion analysis once he has access to the necessary equipment.

    The lab has been cleaned out, and salinity Trial 2 began on August 26, 2020. Two weeks from Trial 2 start date, September 9, salinity solutions will be introduce to Tubes 1 and 2 with Tube 3 as a control as in Trial 1.

    The page will be updated with synthesis of Trial 1 data and conclusions as they become available.

    Visit WISRD’s Twitter account for photos and updates on Trial 2 progress.

    January 22, 2020
    The two week mark was this monday, January 20. Although our procedure states that we are only letting the plants germinate for 2 weeks in the germination tray, we need to keep the plants in there for at least one more week. We need to ensure that our lights are powerful enough to similarly replicate the sunlight plants native to the San Joaquin Valley get.

    January 14, 2020
    It has been one week since the beginning of the germination of the lettuce. All 14 root baskets have sprouts, with an average of 12 per basket.

    January 7, 2020
    Today, we began the germination of our butterhead lettuce. Steps 1-12 of the procedure were followed. In total, 14 root baskets were planted.

    May 22, 2018

    Updated by: Dani B.

    Today is our last day of WISRD for the schoolyear. Sadie and Ximena will be in WISRD next year, but I won’t be returning until the 2019-2020 school year. This week we’ve gotten our caps printed, finished our second PVC pipe, cleaned up the lab, taken inventory, and written our reflections. Next year, we plan to put together the different components of our lab and start growing.

    -Dani B.

    May 21, 2018

    Updated by: Dani B.

    Our caps finished printing today! Sadie and Ximena are upstairs sanding and sealing the caps to the PVC pipe, which we drilled and sanded last week. I went down to the lab to take inventory of everything we have, and to clean up and organize the lab for next year. Here’s the list:

    Plant Bloom Nutrient (2)

    Plant Growth Nutrient (2)

    Utility Pail (6)

    Pump (2) (One is broken)

    Reservoir Tank (1)

    Reservoir Lid (1)

    Grow Tray (1)

    Lab Base (1)

    Starter Plugs (66)

    Octa-Bubbler Pump and Cord (1)

    Electric Fan (1)

    Black Cord (1)

    Sun Grip Light Hanger (1)

    Great White Premium Mycorrihaze (1)

    Grow block clips (5)

    Flora Flex Cap (5)

    Multipurpose Ties (19)

    Yard Stick (1)

    Colored Sharpies (4)

    1 tbsp (1)

    1/4 tsp (1)

    1-liter measuring cup (1)

    Pitcher (1)

    Light (1)

    Light Cord (1)

    Gray PVC Pipe (4)

    White PVC Pipe (9)

    Elbow Connector PVC (8)

    Clear PVC Pipe 3 Holes drilled and sanded + sealed caps (2)

    Also, Josie asked me to write a paper for the WISRD Journal, so I will be working on that this summer. Right now I’m looking over the publication archives to get an idea of what an article should look like.

    -Dani B.

    May 18, 2018

    Updated by: Dani B.

    Today we are starting to wrap up our work in WISRD for the year, so we uploaded scanned versions of all out documents (hard copy) from the Hydroponics lab.

    The file path on the WISRD computers is Network > dumbledore > assets > Life Sciences > Hydroponics

    Here’s our plan for the last three days in WISRD this year:

    Friday: Print caps, transfer documents on to server

    Monday: Sand and attach caps, seal caps

    Tuesday: Design and print stabilizers

    May 15, 2018

    Updated by: Dani B.

    Today we went downstairs to the lab to look at the pumps, lighting system, and structure. We also sketched out where we wanted to position the lab underneath the stairs taking into consideration the pumps and where we will need elbow connector pipes. 

    We decided that we would use the reservoir for clean water on the ground level, but not above the tubes because the stairs don’t have a lip that we can drill through. We also strategized about how to support the PVC pipes because we don’t have any way to hang them (the extension we were planning to use are part of the fire system and we can’t attach anything to them). Here’s our sketch and we will make a plan soon. (The drawing is meant to be vertical, not horizontal, but I couldn’t rotate it because of the web browser I’m writing this on.)

    We’ll have to wait until we can print these because the 3D printer is being fixed at the moment.

    -Dani B.

    May 14, 2018

    Updated by:  Dani B.

    Since my last journal, we made a lot of progress with our PVC pipes. We worked with the 3D printing team and got two 3D printed caps for our first pipe, with the measurements listed in the journal below. Once the caps were on, we put sealant around the edges. This much we were able to present at the Spring poster session, which went really well. We got a lot of great questions on our project and people seemed to be impressed! We tested the caps with water and they work well. We also spent some time in the lab downstairs trying the figure out how we could position the pipes. We may end up hanging the pipes on a cord with a carabiner so that the grade can be adjusted. Since the frame is slightly shorter than the pipes, we are planning to 3D print a U-shaped stabilizer so that the tubes don’t slip out of the frame. We sketch up designs for those soon and put them in the journal. Next, we will start working on the sensors for the lab.

    Today, we drilled the holes in the tubes. There are three per tube, so six in total. They’re each one inch in diameter and evenly spaced. We are going to put mesh netting inside of each of the holes so that we can keep the baby plants inside. This way, the mesh will be tight enough to hold in the plant so that it’s not swept away by the current of the water, but loose enough so that the roots can grow through the mesh when the plant gets older.

    We did have one small issue with the drilling. Because the plastic is so hard, it is not easy to drill and can crack. We accidentally drilled too quickly into one of the holes and got a small crack on the top of the pipe. It shouldn’t be a big problem because there probably won’t be water in that area and we can put sealant on the crack. Once we had drilled, Sadie sanded down the holes and got the plastic out of the tube, and Ximena created the drill centers and drilled into the new pipe.

    -Dani B.

    April 24, 2018

    Updated by: Dani B.

    Yesterday we worked on the caps for the PVC tube that our plants will grow out of in the lab. We decided to make one side higher, so less water flows in, and the other side lower, so that more water flows out and into the used water reservoir. Here’s some sketches of how we want it to look: (I wasn’t able to rotate the image)

    We decided to have the PVC pipe on a slant, with the fresh water reservoir above it, underneath one of the steps, and the used water reservoir underneath it, on the ground or in the tray. This will help to prevent molding because the water will be flowing through constantly, but we can manage the amounts.

    We’ve started talking to the CAD team about having the caps 3D printed, so needed to try it out cheaply and quickly. We decided to use masking tape in the dimensions of the caps, which will be 2.737 inches on the higher side and 1.5 inches on the lower side. Here’s the water flowing through the PVC pipe, using the masking tape caps:

    In the photo, you can see that the tape “cap” on the other end of the tube is higher, while the cap end in the foreground is lower, so only the necessary water stays in the tube, and the rest flows over the top of the cap, preventing molding and keeping the water in the tube at a constant salinity at all times.

    Last Friday, I researched how the AC (alternating current) power supply works and how we will use it to measure the charge of our solutions. Here’s the notes I took:


    Objective: Measure the charge of the salinity solutions (unit of measure of amps), using an AC (alternating current power supply)

    Why AC Power Supply?: With the DC (direct current) power supply, the positive probes were clogged with negative chlorine ions and the negative probes were clogged with positive sodium ions. Because the negative and positive probes were direct current, they were continuously attracted the same opposite charge ions over an extended period, causing the probes to become blocked. By using the AC power supply, there won’t be time for the probes to become clogged because the probes will constantly alternate between negative and positive charges.

    AC Power Supply: Current flows one way from a source, reverses, flows the other way. Occurs multiple times per second at a rate determined by the frequency which is typically 50 or 60 hertz.

    AC Power Measurements- Current:

      • AC power supply measurements are equivalent to DC
      • NOT average readings, AC current readings are Root Mean Square (RMS)
      • Power can be measured by observing waveform, breaking up into tiny time slices. For each moment, determine power dissipation using (P=12xR)
        • R = resistance
      • R is constant, since it’s internal resistance, can be removed from final equation
      • Equation for effective power = Ieff = √(I12 + I22 + …. + In2 ) / n
        • n = number of time slices in waveform
      • Figure 1: Visual representation of waveform/time slices
          • Image: Amtek Programmable Power
      • Effective equivalent of DC calculation
    • To find the RMS current value, transfer value from a sum to an integration

    Integrations and Derivatives:

      • To find a function’s derivative, use the slope formula: ∆X / ∆Y = slope
      • Translates to: Δy / Δx =  f(x+Δx) − f(x) / Δx
      • Simplify, and then push ∆x as close to zero as possible
      • Example for function f(x) = x^2
      • Or, the slope at x is 2x
      • The integral of a function is the opposite of the derivative: if the derivative of f(x) = x^2 is 2x, then the integral is x^2
    • The integral symbol is ∫, the “s” signifying the summing of slices

    What are ions?

      • Look at periodic table to determine the amount of protons and electrons it takes to balance the element.
      • For an atom to be stable they must have eight electrons.
      • Through chemical reactions atoms gain and lose their electrons to make sure they have eight electrons.
      • Those elements who have eight electrons or multiples of eight, are not susceptible to chemical reactions.
      • Elements who have eight electrons in a single ring as well as two or three electrons are highly unstable and are able to react with other elements.  

    AC Power Supply Background

    In a switch mode power supply (SMPS), the AC mains input is directly rectified and then filtered to obtain a DC voltage. The resulting DC voltage is then switched on and off at a high frequency by electronic switching circuitry, thus producing an AC current that will pass through a high frequency transformer or inductor. Switched-mode power supplies are usually regulated, and to keep the output voltage constant the power supply employs a feedback controller that monitors current drawn by the load.

    -Dani B.

    April 13, 2018

    Updated by: Dani B.

    Today we finished our poster for the WISRD Poster Presentation and Lecture on April 30. Yesterday, we were downstairs in  the lab space, working on our lab model. We could see that in order to minimize unnecessary energy use, it would be best to use a water-flow model instead of using a pump. That means we would have the clean water resevoir at the top of the lab, most likely mounted to the underside of the stairs. Then the water would flow into the tube and through a hole in the bottom cap to change the concentration. I’ll attach a picture of our sketches next week.

    -Dani B.

    March 20, 2018

    Updated by: Dani B.

    Today Sadie and Ximena went downstairs to get an estimate of how the new lab will fit in the space we have under the stairs. They looked at the drafts, and are starting on a Sketchup of the lab. I (Dani) worked on the poster for the Spring Poster Presentation today. We’re using the same format, but rewriting the background and current research, as well as connecting each of the things we have worked on or run into in our research proccess to content that can be extrapolated from the context. We are also still working on compiling a list of all our materials for the lab, but we’re getting ready to cut our PVC pipe!

    -Dani B.

    March 16, 2018

    Updated by: Dani B.

    We’re now using the DC Power supply to collect data on the amp of each molar solution, which is represented by dq/dt.

    Yesterday, we had a negative and positive probe and the probes ended up corroding. There were sodium ions and chlorine ions, and the chlorine went to positive and sodium to negative probes, so the probes got clogged and corroded. In order to finish getting the amps, we have to figure out what is clogging up the probes and how to counteract this. Here’s a drawing of the circuit with the DC power supply:

    Seven fundamental laws of physics: Length, mass, charge, time, stuff, temperature, luminosity

    Everything can be described in seven fundamental concepts. Time is used as seconds but can also be the time takes light to travel or in similar more specific contexts, temperature is in kelvin scale (with absolute zero as zero) mass is kg, g, etc., stuff (given the unit of a mole- which is 6.02 x 10 to the 23), luminosity is lumen; candles. Amps is not fundamental, so it must be a relationships between of the fundamentals, charge to time. Represented as dq/dt, delta charge over delta time.

    So later in the class we figured out that in order to get rid of the sodium clogging up the negative probes, then we can switch the positive and negative probes. Then, the sodium would just go to the other side, and we would have to keep switching. This is the purpose fulfilled by the AC, alternating current, power supply, which Joe has ordered for us. Our plan is to start with the AC power supply doing a few zero mole solutions and then making sure that we have a straight line. After that we could start running all the rest of our solutions through and see if we have a linear relationship.

    -Dani B.

    February 27, 2018

    Updated by: Dani B.

    Today we finally finished our calibration curve using copper 2 sulfate. We used the 0.20, 0.14, 0.08 mol solutions. We used the PASCO Spectrometer to identify and create a calibration curve. Our calibration curve looked great! Our absorbance rate had a steady increase as we increased the concentration of copper 2 sulfate. Next, I made an unknown concentration of copper 2 sulfate in the lab, I knew it had a concentration 0.17, but Ximena did not. She placed the cuvette of this ‘unknown’ solution into the Spectrometer and turned it on. The spectrometer gave her an absorption reading of 0.41 (shown at the bottom left hand corner.) Using the calibration curve, which is the strait horizontal line running through the graph, Ximena was able to approximate the exact concentration of the ‘unknown’ solution. She guessed 0.168 mols. The software that we used gave Ximena a green dot where she approximated the consecration because she had a very good approximation. The software would have given her an orange square if she was any further away.

    With all this discovered, Ximena and I are hoping to make a calibration curve like the one below using NaCl instead of copper 2 sulfate. If we have a calibration curve like this using NaCl, we could determine the concentration of our water used in the hydroponics lab!

    February 13, 2018

    Updated by: Dani B.

    Today Sadie and Ximena put the spectrometer graphs on the server, so they will be adding them to this page when they journal today. Dani worked on creating a preliminary list of the materials we will need to build a new lab. Some, or many, of them we could repurpose from the old lab, so we will be taking inventory of what we have already and seeing how we can reuse parts. From there, we’ll finalize what we need to purchase and get everything gathered so we can begin building. The list is attached below and will be updated as we get a better sense of what we’ll need along with lab extensions like resevoir tank valves and lighting system materials.

    Item: Clear piping

    Dimensions: 39 in L, 3 in Diameter

    Quantity: 4

    Item: Plastic tray

    Dimensions: 39 in L, 38 in W, 3 in Depth

    Quantity: 1

    Item: Resevoir tank

    Dimensions: 9.5 in L, 19.5 in W, 20 in Depth

    Quantity: 8

    Item: Structural tubing

    Dimensions: 38 in L

    Quantity: 4

    Item: Structural tubing

    Dimensions: 28 in L

    Quantity: 4

    Item: Structural tubing

    Dimensions: 39 in L

    Quantity: 4

    Item: 90 degree tubing connectors

    Dimensions: TBD, circumference uniform with structural tubing circumference

    Quantity: 8

    -Dani B.

    February 7, 2018

    Updated by: Dani B.

    Yesterday we ran all the solutions through the spectrometer. We’re creating a calibration curve for each solution of the absorption levels of each. Last time we ran into an issue because when running the solutions through the spectrometer, we were supposed the go from least to greatest molarity, but accidentally we went out of order of molarity, which altered the curve. To run the spectrometer, we’re using Behr’s Law, so there are going to be two axes, Absorption and Concentration. According to Behr’s law, we should have a linear graph because the absorption increases as the concentration increases. However, we’re getting a very different graph that isn’t anywhere near linear.Since the graph on this test wasn’t what we were expecting, we thought that the problem may be re-occurring and decided to take new samples of the each molarity solution and re-run all the tests. Hydroponics team member Sadie G. will have the graphs for today’s tests by the end of this class period, so we will update the page and add those images when we have run the tests again. Once we’ve gotten a linear graph, we will identify a slope. Until then, we are going to document each trial and will probably get in touch with Pasco via email to rule out whether the issue is with our use of the spectrometer.

    -Dani B.

    December 11, 2017

    Updated by: Dani B.

    Set up Hydroponics page, added dropdowns
    Set goal, created step-by-step plan
    Set timeframe to complete each step

    -Dani B.

    Trial 2 Photo Gallery

    (Last Updated 9/17/20)


    Bailey, P. (2005, October). Salinity Threatens Sustainability of Irrigated Agriculture in California’s Heartland, Study Finds.

    Basic Hydroponic Systems and How They Work. (n.d.). Retrieved from Simply Hydroponics LLC website: https://www.simplyhydro.com/system/

    California Environmental Protection Agency, Salinity in the Central Valley, A. , at 1-133 (Cal. May, 2006).

    Jensen, M. H. (1997). Hydroponics. In Hort Science (6th ed., Vol. 32, pp.1018-1021).

    Klonsky, K. M., & Tourte, L. (1996). Vegetables, Fruits and Nuts Account for 95% of Organic Sales in California. California Agriculture, 50(6). https://doi.org/10.3733/ca.v050n06p9

    Nitrates Poison Water in California’s Central Valley. (2016, September 20). Retrieved December 4, 2019, from Community Water Center website: https://www.communitywatercenter.org/nitrates_poison_water

    Salinity in the Central Valley: A Critical Problem. (n.d.). Retrieved December 4, 2019, from Water Education website: https://www.watereducation.org/post/salinity-central-valley-critical-problem

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