SUPER Thriving Lettuce?

The Garden Professors have previously written about the ubiquitous garden center product, SUPERthrive, here and here. The manufacturer claims a plethora of beneficial uses for SUPERthrive —everything from Christmas tree care to turf to hydroponics. They claim SUPERthrive will “revive stressed plants and produce abundant yields” and that it “encourages the natural building blocks that plants make for themselves when under the best conditions” thus “fortifying growth from the inside out,” but I know of no body of rigorous, peer-reviewed literature to support any of those claims (1, 2, 3, 4). In fact, I’m not entirely sure what those claims really mean, but I’m encouraged on their website and bottle to use it on every plant, every time I water, to receive these amazing benefits!

A test case

The hydroponics claim intrigued me because during the winter months I grow plants hydroponically under lights. One of the benefits the manufacturer claims is “restores plant vigor” and “works with all hydroponics systems.” As a plant scientist, and knowing something about the ingredients, I was skeptical to say the least, but I thought that if SUPERthrive was going to show any beneficial effect it would surely be in hydroponics since that is a more uniform environment than outdoors. So, I shelled out my $11 for 2 oz (the things we do for science!) and set off to design a simple experiment.

The hypothesis

A typical experiment like this starts with what we call the null hypothesis (denoted “H0”). The null hypothesis is defined prior to the experiment and often states that we think there will be no difference between the treatment and control. In this case, my null hypothesis is that the SUPERthrive treatment will have no effect on the mean fresh weight of the harvested lettuce relative to the control lettuce. Note that I haven’t made any hypotheses about other parameters that might be important, e.g., flavor, compactness, number of leaves, color, disease incidence, survival rate, etc. For this experiment I am interested in only one thing: total harvested weight as a signifier of healthier plants.

After the data is collected and analyzed, we decide whether to accept or reject the H0 by running an appropriate statistical test. If there is no statistically significant difference, then we cannot reject the H0—that is, we accept the H0 that there is no difference between treatment and control. If there is a statistically significant difference between treatment and control, then we say we reject the H0 and conclude that the treatment did have an effect. Keep in mind, sometimes no difference between treatment and control is a good thing, e.g., in toxicity studies.

Experimental design

With my skeptical spectacles on, I set up my experiment to test my hypothesis. I made a six-gallon batch of hydroponics nutrients suitable for leafy greens. I split the batch in half and added SUPERthrive, per the manufacturer’s dilution recommendation, to one of the three-gallon aliquots as the treatment. I then divided the control and SUPERthrive treatment each into six individual, identical, two-quart containers. I thus had six independent replicates of a treatment and a control. (See Figure 1 below for a schematic of the experimental design.)

Figure 1. Outline of experimental design

To further avoid any experimenter bias, I had my wife assign numbers randomly to each container, record which were SUPERthrive treatment and which were untreated control, and then re-sort all the containers. I had no idea which containers contained which nutrient mix. I did not open the “secret decoder envelope” until after all measurements were complete!

Figure 2. Identical 2 quart containers randomized on day 1 in the hydroponics solutions. This kind of hydroponics is called “Kratky” or passive. Enough nutrient solution is supplied at the beginning to last the plant for its entire life-cycle.

Into each of the 12 containers I placed a 12-day-old lettuce seedling, taking care to select plants that were of equal size and leaf number. The containers were then placed under my lights (cool white T8 fluorescent) for the remainder of the experiment. I rotated the rows of plants several times to try to control for any edge effects in my grow area. After 30 days in the containers, I harvested and weighed each plant.

Figure 3. Plants after 30 days of growth.

What did my experiment show?

The graph below is a box and whisker plot that shows the spread of the data and the mean for each group in grams of harvested fresh weight of the plants (roots were removed). In my experiment, the SUPERthrive treatment showed a clear drop in harvested fresh weight! In fact, the heaviest SUPERthrive plant weighed less than the smallest control plant, and the SUPERthrive set was much more variable in harvested weight. These results surprised me a bit.

Figure 4. Box and whisker plot of lettuce plant fresh weight. Master Blend: Master Blend nutrients; Master Blend + ST: Master Blend nutrients plus SUPERthrive (0.9 ml/gal.)

A standard statistical test (Student’s T-test, unpaired, two-tailed) was performed to show that that there was in fact a statistically significant difference (p<<0.01) between the two groups. Thus, we can reject the H0 (remember our null hypothesis is that there will be no treatment effect) and conclude that there is a difference between treatment and control harvested weights, with the treatment mean plant weight being significantly smaller than the control mean plant weight.

What can we make of this experiment?

Well, we need to keep in mind a few things.

1) Six replicates is a very small sample size; this could be a spurious, unlucky result. There is always some distribution of growth rate, even in a uniform genotype. Did I get unlucky and happen to put six plants that would always be on the smaller end of that distribution into SUPERthrive?

2) After analyzing the data, I discovered that four of the SUPERthrive plants ended up in the same row and were the smallest heads in the experiment (sometimes you flip a coin and get four heads in a row!). Could this be the reason for the unexpected results? The other two treated plants were in the other two rows, but neither was as large as the smallest control plant.

3) I do not have a perfectly controlled environment like one would find in a lab or even in a larger growing facility. However, something marketed with such aggressive claims of amazing plant health benefits and vigor should give a noticeable effect under a variety of imperfect, real-world conditions, such as those one would find in a home garden situation, don’t you think?

4) Perhaps my plants were already growing at their maximum potential and there was nothing for SUPERthrive to “improve.” Afterall, hydroponics indoors is already a relatively stress-free environment, as the SUPERthrive manufacturer also points out. Then what do they think their product is improving in hydroponics? Would I have seen an effect under less-than-ideal or more stressful conditions then? This could certainly form the basis of other testable hypotheses.

Conclusions

What I think we can conclude is that in this experiment, with this genotype of lettuce, and under these hydroponics conditions and environment, SUPERthrive had no positive effect whatsoever and may have even had a negative effect. Under other conditions would one see a positive effect? Possibly. Would different plants or genotypes respond to the SUPERthrive differently? Possibly. We must always be careful of over-extrapolating both positive and negative results from a single experiment.

But, because the individual ingredients have not been shown to provide any beneficial effect, and no plausible mode of action is given by the manufacturer for their broad general claims, we should remain highly skeptical. As pointed out in the previous post, the SUPERthrive manufacturer has certainly had plenty of time to scientifically demonstrate efficacy of their product, since they proclaim to be “always ahead in science.”

Because the results showed a clear and unexpected negative effect, the experiment surely needs to be repeated. Repetition is a central tenet of science. I hope to share additional results with you in a post later this spring—after all, I have a whole bottle of SUPERthrive and we love salad!

References

  1. Banks, Jon & Percival, Glynn. (2012) Evaluation of Biostimulants to Control Guignardia Leaf Blotch (Guignardia aesculi) of Horsechestnut and Black Spot (Diplocarpon rosae) of Roses. Arboriculture & Urban Forestry. 38(6): 258–261
  2. Banks, Jon & Percival, Glynn. (2014) Failure of Foliar-Applied Biostimulants to Enhance Drought and Salt Tolerance in Urban Trees. Arboriculture & Urban Forestry 40(2): 78–83
  3. Chalker-Scott, Linda. (2019) The Efficacy and Environmental Consequences of Kelp-Based Garden Products.
  4. Yakhin Oleg I., Lubyanov Aleksandr A., Yakhin Ildus A., Brown Patrick H. (2017) Biostimulants in Plant Science: A Global Perspective. Front. Plant Sci., 7:249

Hydroponics for the Holidays? Home Systems are a hot holiday gift list item

Systems to grow fresh produce in your home using hydroponics or other automatic processes have been popular for several years but seem to be even more popular this year with more folks home and looking for something to do and hoping to produce their own food.  As a result, these systems are popping up on holiday wish lists and gift buying guides all over the internet.  But are they worth it?  And if so, what should you look for in a system? 

First off, what are these systems? And what is hydroponics?  Hydroponics is the process of growing plants without soil in a aqueous nutrient solution.  Basically, you provide all the nutritional needs of the plants through nutrient fertilizers dissolved in water.  These systems can grow plants faster and in a smaller space than traditional soil-based production. It also allows you to grow plants indoors and in areas where you would not normally be able to grow.

This Aerogarden (which is the previous generation) has a digital brain that controls light and water schedules for the specific growth phase of the plant and yells at you when it thinks you need to add more fertilizer solution.

As for systems, you might have seen what is probably the “oldest” one on the market – the AeroGarden.  Since it is the oldest and most common, that’s the example we’ll be staying with.  It has been around a few decades and has evolved from a basic electronic system to fully automatic, “smart”Bluetooth connected systems that you can control with your phone.  In recent years there have been many new systems come onto the market at all different sizes and price points.  A quick search of online retailers will usually provide an array of options – from DIY kits to plug-and-play enclosed systems such as “Click & Grow” and “Gardyn”. My only experience is with the Aerogarden system, so I can’t speak to any of the others (though I’d love to try them out!).

The answer to “are they worth it” is up to you, really.  Most home based hydroponic or aeroponic systems offer convenience, but at a cost.  Most cost several hundred dollars and are small, so they produce a small amount of produce (or other plants) at any one time. So you have to determine what goals you, or your intended giftee, have with the system. 

“Baby” lettuce, 18 days after sowing. The current version of this 9-plant Aerogarden system, called the “Bounty”, retails for $300 but you can usually get it for under $200 on sale.

The benefit of the “plug-and-play” enclosed systems like the AeroGarden is that basically you can take it out of the box, set it up in less than 10 minutes, and have some fresh lettuce or herbs in a few weeks.  It controls the water cycles, lighting, and all other conditions for growth.  You just drop in pods that contain the seeds suspended in a spongy-material.  The smallest system, that holds 3 plants, retails for $100.  As an additional expense comes from buying refill kits to replant. The mid-size systems are the most common and range from $150-$300.  The largest system, the “XL Farm” retails for $600. But these systems are commonly on sale at pretty significant discounts. 

For many systems, you typically buy a new set of pods (there are different plant variety selections), but there are pods you can buy to assemble your own using your own seeds.  For the AeroGarden, the pod kits range from $15 up to $30 to grow up to 9 individual plants. There are other plug-and-play systems on the market, as well as some kits that are more build-your-own and less automated. 

No matter which systems you buy (or gift), keeping these costs in mind is important.  If you’re looking for a fun and easy activity with the benefit of a little fresh produce and aren’t as concerned with production costs these systems may be for you – and if you are giving or getting them as a gift that definitely makes it more economical. But given the cost of the plug-and-play systems and the refill pods, they will never be an “economical” option for producing your own food.  If you are wanting to produce food on a budget and you’re interested in home hydroponics, look for plans to build your own or buy a DIY kit. 

DIY Hydroponics: Going soil-less at home and abroad

It seems that as interest in gardening grows, especially among younger generations, interest in different techniques that home gardeners use and different plants they grow are also on the increase.  You see the old standbys like straw bales and containers emerge.  Terraria, succulents, and air plants are having their moment.  And all kinds of technology driven indoor growing systems are all over the web, mostly hydroponic, but some aeroponic and aquaponic as well (we’ll talk about the difference in a bit – if you’re just here for that, skip the first 2/3 of the article).

I had been thinking about getting one of those new techno aeroponic growing systems as a demo for my office as a discussion starter for those interested in controlled environment growing whether on the homework commercial scale.  There is a general interest and need for basic education for hydroponics and aquaponics in the area that I hope to build extension programming around, so having something at the office could provide some interest from walk-in and social media clients.   I had dusted off a first generation AeroGarden that I found in the storage shelves in the office storage catacombs and set it up in my office.  It is a far cry from the new models I saw in those online ads that are outside of my budget for “toys to show off at the office.” It doesn’t have nice LED lights or connect to my phone via Bluetooth like the fancy new models.  Given its age, it produces more noise and heat than the lettuce and herbs I’ve tried to grow in it.  Maybe I’ll be able to get one of the fancy models one day.

Then I remembered a book that an urban ag friend of mine had written on building DIY hydroponic systems from common building materials and resolved to not only build a system, but incorporate it into my programming somehow.  The book, appropriately titled “DIY Hydroponic Gardens: How to Design and Build an Inexpensive System for Growing Plants in Water” by Tyler Baras shares plans for building a variety of types of hydroponic systems using basic building materials like gutters and lumber, drip irrigation tubing and fittings, and various other bits and bobs.  Tyler had been a featured speaker for the West Virginia Urban Agriculture Conference that I started and hosted when I worked for WVU Extension, so the book was on my radar – I placed an order.  (Note: I don’t get a kickback for sharing the book – just sharing a good resource that happens to be from a friend.)

Teaching Hydroponics to an Unlikely Audience

Image may contain: 3 people, including John Porter, people sitting, outdoor and nature
Learning traditional weaving methods using banana leaves. Banana leaf weaving is a common industry in rural Rwandan villages that allows women to provide modest incomes for their families.

As luck would have it, I had an opportunity to put the book, and my DIY hydroponic skills, to the test.  Our university does quite a bit of work with and in Rwanda and in May I had the opportunity to travel to Rwanda as part of a study abroad program with my Ph.D. advisor.    Rwanda is a very small country, just under the size of Massachussets, with a very big population by comparison – 12 million vs 7 million!  Feeding that many people is a struggle, and even though Rwanda produces a lot of produce (and more lucrative export crops like coffee and tea), it still imports a lot of its fruits and vegetables.  We were studying how innovation spreads in rural areas, and just before our trip I found a news article sharing that there would be an upcoming $8M USD ($8B RWF) investment in hydroponics in the country in order to increase production on the limited amount of land available.

In June I was scheduled to teach a group of Rwandan exchange students that are part of a sponsored program at the university, and remembering the planned investment in hydroponics I planned to add DIY hydroponics to the curriculum.  This is fitting, since most small-scale operations would rely on finding what materials would be locally available.  While the operations started by the investment would likely bring in “real” hydroponic systems, if small scale producers want to use the technology or if individuals want to build skills, they’re going to have to use what is at hand.

UNL CUSP Scholars students from Rwanda build a DIY Hydroponic System

Planting leafy greens and strawberries in the hydroponic system.

 

 

 

 

 

 

 

 

It was interesting teaching an audience who were interested in learning about the new technology, but have little experience or general knowledge on the subject.  Even more interesting was the fact that many of the students had not used or even seen some of the basic power tools we used in building the system.  I’m no shop teacher, but in the end the students not only learned a little bit about hydroponics and hydroponic systems, but also some skills using tools that they can apply in other applications.

Proudly showing off the team’s vertical hydroponic system.

 

 

 

 

 

Hydroponics, Aeroponics, & Aquaponics – Oh My!

Earlier I mentioned that there are differences between hydroponics, aeroponics, and aquaponics.  In some ways, they use similar basic setups.  All are based on soil-less growing using an inert media to support plants, supplying nutrients and water directly to the plant roots, and providing light to the plants using either natural sunlight or supplemental lighting.  Differences come from the source of plant nutrients and from how they are delivered to the plant.  I thought I’d take a few minutes to talk about the basics of each of the techniques so you can understand the differences just in case you want to buy or build your own system.  If there’s interest, I hope to focus on hydroponics and controlled environment agriculture over my next few blog posts – tell me what you’re interested in learning.

Most people are familiar with the concept of hydroponics.  This technique relies on roots being submerged in a nutrient-rich solution where the nutrient content is engineered from a variety of mineral sources.  There are a variety of different systems (that will hopefully be the subject of an upcoming blog) where the root zone interacts directly with the solution.  In some cases, roots are submerged in a large volume of solution while in others a film or shallow stream of water flows through the root zone.  Systems where roots are submerged in the solution may simply be a large reservoir where the plants float on top where systems relying on flow may involve a pump.  Movement of water adds another plant need -oxygen, which is required for respiration by the roots.  In systems where there is no flow, air is often pumped in to provide oxygen.

Most flowing systems are recirculating, where the solution returns to a reservoir and is pumped back into a reservoir to be reused.  While it may seem counterintuitive, these recirculating water based growing systems have been touted as production methods that conserve water.  That’s why some of the leading hydroponic production and research comes from areas of the world where water is scarce. Less common are flow through systems where water and nutrients are not recaptured but discarded after initial use.

Aeroponic systems have much of the same basic setup but instead of the roots interfacing directly with water solution it is applied as a pressurized mist.  These systems generally use a much smaller volume of water, but there are some drawbacks.  Failure of the system, such as an electric outage or clogging of the nozzles that pressurize the mist (which is a common occurrence) can quickly result in plant failure since roots can dry out quickly.  Several systems that are sold commercially that market themselves as aeroponic, such as the AeroGarden or Tower Gardens, are more similar to a flowing hydroponic system than a pressurized mist aeroponic system.

The plant growing structures of aquaponics are similar to those of hydroponics, with the addition of larger reservoirs to accommodate the addition of aquatic livestock such as fish (or sometimes crustaceans).  The waste produced by the stock provide the nutrients needed by the plants rather than an engineered nutrient solution.  These systems require having the technical knowledge to meet the needs of the aquatic stock and balancing those with the needs of the plants.  The addition of the aquatic stock also introduces a microbiome of bacteria and fungi, many of which are required for animal health but can also introduce pathogens that can negatively affect human health.

Are you interested in learning more about these systems?  What do you want learn about in hydroponic or other systems? Let me know in the comments and I’ll try to base some future articles on what our readers are interested in.