Experimenting with hydroponic lettuce cultivation to achieve the best quality yield and accelerate harvest time
In an era where people are starting to care about quality products, agriculture remains the same. Few people see the value and are dedicated to producing the best quality yield, which differs from growing to achieve the highest yield at the lowest cost.
In this test, we experimented with growing five types of hydroponic lettuce using LED grow lights and a hydroponic system involving water circulation in the same tank. The variables were the intensity of light at different points, to see to what extent light intensity affects quality. This includes density, size, weight, freshness, and color intensity, etc.
From tiny baby stage to today, exactly 24 days, we have recorded our cultivation process for the information of all the farmers reading this article. Meanwhile, our team couldn't resist and has already prepared the korean BBQ grilled pork.
And here are the results from the experiment within 24 days.
The average harvest time for most hydroponic lettuce is around 30 days. If it's a head-forming lettuce like butterhead or baby cos, it's approximately 45 days.
Planting position.
Hydroponic water circulation system is a method of growing lettuce with water and a water storage tank. It's convenient for checking and adjusting water conditions, including acidity-alkalinity (pH) and fertilizer concentration (EC), as we don't have to expose the roots to light frequently.
The list of hydroponic lettuce in this experiment was grown using the water circulation system with King Whale fertilizer. Given the limited space, we arranged the plants to receive light appropriately at various levels.
Green Oak Lettuce = GO
Butterhead Lettuce or Bibb = BH
Red Oak Lettuce = RO
Green Coral Lettuce = GC
Baby Cos Lettuce = BC
Controlling factors.
The entire system contains 50 liters of water. We used a 3-part fertilizer formula CoreX (Core), EldeX (Grow), FloreX (Bloom) in a ratio of 0.5:0.5:0.5 grams per 1 liter of water (for 50 liters, use 25 grams per formula once in 30 days) to get an EC of 1.5~1.6 and pH of 6.5. In this experiment, we did not use pH Down to adjust the pH of the water because,The fertilizer automatically adjusts and maintains the pH over time, so there's no need to worry about pH changes or invest in an expensive automatic water adjustment system. A suitable and stable pH helps plants absorb nutrients all the time.
- Provide light 24 hours a day.
(This is to test the stress on plants if they receive light 24 hours a day. It's recommended to provide light for 18 hours a day as the night period is crucial for root development of plants.) - PPFD: 74 - 270
- DLI: 6.4 - 23.3
- pH: 6.52
- EC: 1.55
- Water volume: 50 liters per tank.
- Fertilizer: King Whale, 3-part formula, 0.5:0.5:0.5 grams per 1 liter of water.
- Water temperature: 27.5°C.
- Number of plants: 30 plants.
The amount of light received by the plants.
The key difference in this experiment is the amount of light, and the quantity of light is an important indicator of the quality of the harvest yield. It determines whether the produce will be crisp, dense, and brightly colored.
When growing plants, fruits, or hydroponic lettuce, a challenging aspect to consider and control is the amount of light the plant should receive each day (DLI, Daily Light Integral) and the intensity of the light (PPFD, Photosynthetic Photon Flux Density; PAR, Photosynthetically Active Radiation).
Try imagining a country like Thailand that receives light for only about 12 hours a day, and from 11:00 AM to 1:00 PM, The light can be so intense that if you don't provide shading, growing lettuce would be quite challenging. This is in contrast to countries in Europe, which are cooler and can receive up to 18 hours of light per day during the summer season.
As mentioned before, in this experiment we provided 24 hours of light to test the plant's stress levels. Personally, I believe that if we provided only 18 hours of light, the results might have been better (with more leaf elongation). We used a BEARLED grow light with a power of 240W, operating at only 60% efficiency (144 Watts), covering a planting area of 150 x 60 cm.
PPFD = The intensity of light that plants can photosynthesize, similar to brightness.
DLI = The amount of light that plants should receive in 1 day. If the plants receive strong or intense light, they should not be exposed to light for too long to allow the plants to rest and extend their roots at night, which will yield the best results (but it shouldn't be so intense that the leaves burn; it needs to be controlled within an appropriate range). If the plants receive soft light or have a low light intensity, they should be exposed to light for longer periods. The DLI quantity is more important than resting the plants to extend their roots at night. Therefore, adhering to DLI is most important. For example,
- If PPFD is 200 and the light is provided for 12 hours, the DLI value is 8.64.
- If PPFD is 100 and the light is provided for 24 hours, the DLI value is also 8.64.
When growing in a greenhouse, it's necessary to have a tool to measure light intensity, a PPFD (Photosynthetic Photon Flux Density) spectrometer, so you know how much light your plants are receiving each day. If the plants are not getting enough light, you should consider installing additional grow lights in the greenhouse to ensure the plants produce the best quality yield.
Green Coral lettuce, position D4
- Received 22.8 DLI (264 PPFD / 24 Hr)
- Width: 25 cm
- Height 15 cm.
- The leaf tips are red.
- The bunch is dense.
Green Coral lettuce at position F2
- Received 15.4 DLI (178 PPFD / 24 Hr).
- Width 17 cm.
- Height 8 cm.
- Pure green in color.
- The cluster is loose.
Red oak lettuce, position C4
- Received light of 23.3 DLI (270 PPFD / 24 Hr).
- Width 22 cm.
- Height 10 cm.
- Very bright red color, lots of red, no green speckles.
- The bunch is dense.
Red Oak lettuce, position A3
- Receives 11.0 DLI (127 PPFD / 24 Hr) of light.
- Width 21 cm.
- Height 8 cm.
- The color is dull red with many green specks mixed in.
- The cluster is loose.
From the above four examples, it is clear that when plants receive less light than the DLI they should receive each day, it will result in less-than-optimal and inefficient growth. The produce is smaller, the clusters are less dense, and it is lighter in weight. The crispiness, fullness, and freshness of the color are greatly different.
Controlling the DLI to achieve the desired level may result in increased costs, such as adding LED grow lights for a greenhouse. If grown indoors, increasing light to achieve an appropriate DLI will be more expensive than providing a small amount of light.
In the case of greenhouse cultivation, if heat can be well managed and more sunlight can be received, it may not always be necessary to use LED grow lights. This depends on the area and the amount of light in each season.
Hydroponic lettuce is just Level 1 of plant cultivation, compared to cannabis, which is at Level 4. Cannabis requires light of 1,200 - 2,000 PPFD and can tolerate a fertilizer concentration up to an EC of 4.0. The difficulty level is much higher (like comparing F-1 racing to amateur racing).
Below is a table of the average DLI (Daily Light Integral) values that are appropriate, obtained from observation in the experiment of growing lettuce with a recirculating hydroponic system, in this instance.
Average DLI values from experiments that have yielded good results and the highest quality production.
|
Grow lettuce at its highest quality. |
DLI |
PPFD |
EC |
pH |
The planting duration. |
|---|---|---|---|---|---|
|
Green Oak Lettuce. |
20 |
235 |
1.55 |
6.52 |
24 |
|
Green Coral Lettuce. |
20 |
235 |
1.55 |
6.52 |
24 |
|
Green Oak Lettuce. |
20 |
235 |
1.55 |
6.52 |
24 |
|
Butterhead Lettuce. |
12 |
140 |
1.55 |
6.52 |
24 |
|
Baby Cos Lettuce. |
12 |
140 |
1.55 |
6.52 |
24 |
Average DLI from experiments that yielded average to low-quality produce.
Note: If there are no numbers, it means conclusions cannot yet be drawn because they are outside the scope of the experiment.
|
Growing lettuce with medium to low quality. |
DLI |
PPFD |
EC |
pH |
The planting duration. |
|---|---|---|---|---|---|
|
Green Oak Lettuce. |
12.5 |
150 |
1.55 |
6.52 |
24 |
|
Green Coral Lettuce. |
12.5 |
150 |
1.55 |
6.52 |
24 |
|
Green Oak Lettuce. |
12.5 |
150 |
1.55 |
6.52 |
24 |
|
Butterhead Lettuce. |
- |
- |
1.55 |
6.52 |
24 |
|
Baby Cos Lettuce. |
- |
- |
1.55 |
6.52 |
24 |
For the next experiment, please feel free to comment on what plant you would like us to grow. Customers who want to order fertilizers can place orders on our Shopee website and you can ask our admin via Line: @growstuffshop. We are ready to provide professional advice on all types of plant cultivation and can solve any issues with your plants.
Finally, let me recommend our King fertilizer. For growing hydroponic lettuce, you only need 0.5 grams per 1 liter of water. It comes with pH Perfect which helps keep the water pH stable at 5.5-6.5 for up to 30 days without the need for pH adjustment. The result is fully grown, non-bitter, and deliciously sweet lettuce.
