References

Comparison of Land, Water, and Energy Requirements of Lettuce Grown Using Hydroponic vs. Conventional Agricultural Methods

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The challenges of controlled environment hydroponic farming: a life cycle assessment of lettuce

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Slides

Goals

See how viable growing lettuce on campus is​.

What is Hydroponics

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Kratky Method

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The Food Pantry

The current food pantry is small, and hot.

Total Materials

$17/25 3" Net Cup​

$15/6 64-oz Mason Jar​

$25/565 Fertilizer​

68¢ 3" Net Cup​

$2.50 64-oz Mason Jar​

One Jar Cost

30¢ for a single head of lettuce.

<5¢ Fertilizer​

~10¢ for vermiculite.

15¢ for a lettuce seed.

Upfront Cost

$100 total.

$17 for 25 3" Net Cup​

$15x3 for 6x3 64-oz Mason Jar​s

$20 for fertilizer.

$10 for vermiculite​

$8 for Lettuce Seed

Grocery Store Cost

Schnucks Organic Lettuce – 4$​

Gardyn Studio Growing System

Retails $549 for 16 slots.

Membership sends 5 plants a month for $25.

AeroGarden

6-Pod system costs around $100 (too many models).

Utilizes pre-built seed pods. A pack of 5 costs $18.

Fun Names​

• Mr. Green, in the Hall, with the Jar​

• Lettuce Bee Bold​
• Romaine Calm​
• Chop Chop Real Smooth​
• Look Out And-Grow!​
• Duck Duck Produce​
• You're the best! A crown!​
• Breakfast and Move Things​
• Leaf Quickly​
• Toss Boss​
• Dressed for Success​
• Dancing on my Shelf​
• Green Queen​
• Home Sill Home​
• My Cat Ate My Lettuce​
• Buddy​
• These are a few of my favorite things​

Lettuce is Very Forgiving

Native lettuce grows in USDA hardiness zones 2-11.

• That is a very, very broad range.

The type of lettuce I'm growing is originally found in west asia, from the mediterranean, all the way up to siberia.

Growing Medium

Purpose - nutrients, moisture and anchorage for plants.​

Vermiculite​, Perlite​

Fertilizers

The Big Three

N – Nitrogen​

P – Phosphorus​

K - Potassium​

Nitrogen makes plants green and helps them grow.​

Phosphorus is key for energy production, which your plant uses for root growth and flower, fruit and seed development.​

Enter potassium, which is involved in processes like photosynthesis, protein synthesis, moving water and nutrients inside the plant, building strong cell walls, cell expansion and opening and closing pores that let carbon dioxide in and oxygen out (essentially plant "breathing").​

Micronutrients

Plants require 14 essential elements in the root zone, including the macronutrients (needed in relatively large quantities) of nitrogen, phosphorus, potassium, sulfur, calcium and magnesium; and the micronutrients (needed in relatively small quantities) of iron, manganese, zinc, boron, copper, molybdenum, chloride and nickel. - A Recipe for Hydroponic Success​

Fertilizer Labels

Fertilizer labels use numbers like 10-10-10 to show the percentage of each nutrient in the product.

Jack's 12-4-16 RO contains 12% nitrogen, 4% phosphorus, and 16% potassium.

Lettuce Ratio

You want to harvest lettuce before it bolts, or blooms, or else it tastes bad.

Phosphorus is the least important for hydroponic lettuce.

Organic vs Synthetic Fertilizer

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Calculating Your Fertilizer

Find your target concentration (PPM) of nitrogen.

mg of fertilizer = target ppm (mg L) / % of desire element in compound​ = mg of fertilizer in 1 liter of water to supply target ppm​

For most hydroponic crops, you are looking at a PPM N range of 100 - 175.

Again, lettuce is very forgiving. Study looking at lettuce in 50ppm N found...

125 ppm N in 1.7 L of distilled water​.

125 ppm / .12 % N * 1.7 L​

• 1.771 g of nutrient in 1.7 L​

Nutrient Formulas

1 Part

• These are the easiest to work with. Everything is included in one formula.

• This also makes it the hardest to adjust if you need to make adjustments.

• Luckily, this works perfectly for kratky lettuce.

2 Part​

3 Part​

Growing

​Making the Jars​

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Seeding the Seeds​

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Seed Scarification

This involves degrading the coat of a seed to hasten germination.

I sprayed 3% hydrogen peroxide to scar the seeds and quicken germination.

Two Schools of Thought

Promote Beneficial Bacteria.

• This increases cost.

• Organic fertilizer smells bad.

Sterilize your Nutrient Solution.

• H202 breaks down easily in water and donates an oxygen to the plant.

Lettuce Varieties

Head Lettuce

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Baby Leaf Lettuce

Harvested early.

One-Cut Lettuce

This is a type of lettuce grown to it's full size, but when cut the leaves fall apart instead of forming a single head.

Can be harvested using the Cut-and-Come-Again or Single-Harvest methods.

Harvesting

Two Methods

Cut-and-Come-Again

• You leave the crown of lettuce intact - these are the small baby leaves that grow from the center of the head.

• The lettuce has enough energy to grow a second time essentially.

• This is best for loose leaf lettuce.

NEED A PICTURE OF THE BABY CROWN LEAVES!

Single Cut?

• You harvest the entire lettuce plant at once.

• This is best for heads of lettuce.

Storing Lettuce

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Can't Call it Organic

What's interesting is that I can't call this lettuce organic.

The USDA maintains an allow list of approved synthetic substances for an organic certification.

Jack's Nutrients uses mineral salts, most of which are considered synthetic substances and are not on the USDA allow list.

What Next?

Continuing

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AcKNOWLEDGEments​ ​: Dr. Miller-Struttmann​

Dr. Preuss​

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Backstory

Community food projects help ensure communities have access to healthy food that is grown locally and sustainably.

The Webster Environmentalist Coalition grows food with the goal of building food security on campus via a community garden behind the Pearson house.

However, there exists a void surrounding the summer growing season when outdoor plants don't grow.

My goal is to experiment with a low-cost and distributable method of hydroponics to fill that void and further develop food security on campus.

What is Hydroponics?

Hydroponics is a soil-less growing technique where crops, usually vegetables, are grown suspended over nutrient-rich water.

Plants absorb the majority of the nutrients they need from the nutrient-rich water, with the rest being made from the sun via photosynthesis.

Because the plants are not grown in soil, they are generally protected from soil-bourne pests and diseases and can be grown without environmentally-harmful pesticides.[1][2]

In a 2024 suburban sample from China, only 30% of hydroponic crops carried pesticide residue, compared with 84% of crops grown using conventional methods.[3]

The Kratky Method

There are several well-established methods to grow hydroponic crops. Most systems sit plants in a series of pipes and use pumps to circulate water through to the roots.

However, those systems are less suitable at Webster due of their large size, high cost, and maintenance burden. Our method of choice, the Kratky method, doesn't have these limitations, and was chosen for its simplicity and affordability.

Named after Dr. Bernard Kratky, this hydroponic technique involves passively growing crops in a container setup with everything the plant will need throughout its lifecycle.[4][5]

No electricity or pumps are required!

In the Kratky method, plants are seeded or transplanted into a net-cup above a container of nutrient-rich water.

The seeds or seedlings are supported by a porous medium, usually clay pebbles or rock wool, though many options exist.

Enough water wicks up the porous medium to provide a moist environment for germination and development before the plants' roots fully extend down into the water.

As the plants develop and absorb the nutrient-rich water, air flows through the porous medium to fill in the gap left by the water.

Because the water does not circulate and is quickly deprived of oxygen, the plants utilize this air-gap to acquire additional oxygen to sustain cellular respiration in their roots.

With a large enough container, there exists enough nutrient-rich water to sustain a plant until maturity without having to maintain or refill the container.

In fact, watering a plant halfway through could cause it to drown![6]

Our System

Food-safety is a valid concern for any home-grown hydroponics setup.

Here, we suspend plants in a food-safe, BPA-free, polypropylene plastic net cup inside of a glass mason jar.

Seedlings are started in peat moss, rock wool, or 100% pure cotton balls, and held in place by clay pebbles.

The brown paper bag is being used to block out light to limit algae growth, and to maintain a cool water temperature.

To manage bacterial growth, a diluted solution of 3% hydrogen peroxide may be used to clean plant roots and the medium.

No pesticides will be used in the cultivation of our plants.

A model for growing leafy lettuce using Kratky hydroponic method in a non-controlled environment [7]

Future Plans

The Kratky method was selected for its low-cost, low-tech materials, and low-footprint. This summer, we plan to see how viable growing hydroponic lettuce is on campus using this method.

In the future, there is potential to expand and distribute hydroponic growing kits around campus.

If you are interested in growing your own leafy greens or herbs, send an email to grahamscanlon@webster.edu. If you have any questions, comments, or concerns, please contact grahamscanlon@webster.edu or Dr. Miller-Struttmann.

If you are interested in helping out with the Webster community garden, please reach out to the Webster Environmentalist Coalition at websterenvironmentalists@gmail.com.