Two Simple Hydroponic Production Solutions That Generate Results

Two Simple Hydroponic Production Solutions That Generate Results

Hydroponic-lettuce-crop

Lettuce is one hydroponic crop for which a more direct, vertical airflow onto the crop is beneficial.

Hydroponic crop production brings a unique set of needs compared to conventional production. Addressing two often-overlooked factors can improve production and crop quality.

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The first factor relates to providing proper buffering to maintain a more constant pH in the irrigation water. The second relates to providing proper air movement over the crop to encourage transpiration and nutrient uptake.

Simple fixes for these two factors can make a big difference in the crop.

A Solution for Low-Alkalinity Water

Imagine this scenario: The pH of your fertilizer solution needs to be adjusted down with acid to reach your target pH. All is going well for a period of time until the pH suddenly drops rapidly and won’t hold in the manner you expect. What happened?

One possibility is that the continuous injection of acid eroded the alkalinity of the water. Alkalinity is a natural buffer. Waters lacking adequate buffering capacity can experience rapid pH changes in response to the addition of acid or basic materials, including fertilizers.

Envision a second scenario: You’re a grower in a warehouse production space that uses reverse osmosis (RO) water. The RO process strips all of the alkalinity, or buffering capacity, from the water. Any addition of a non-neutral fertilizer or supplements will result in a change that must be compensated. Even when fertilizer programs are well balanced, the pH of these solutions must be closely monitored. While this can be addressed, production would be more efficient if the extra management step could be avoided.

Boost Fertility With Potassium Bicarbonate

Fortunately, there’s an easy, crop-friendly way to add buffering capacity back into the water and minimize the likelihood of encountering either scenario — potassium bicarbonate. The Griffin CEA team recommends adding potassium bicarbonate to fertility programs whenever clear irrigation water has less than 50 ppm CaCO3. Potassium bicarbonate will also provide a touch of potassium to the crop. This is generally a favorable addition and easily managed in the greater fertility program.

With improved buffering capacity, you can work to build a strong fertility program for your crop that’s also forgiving. Remember to ask your supplier for help in this process.

If you’re using concentrated stock tanks, remember that potassium bicarbonate is a product that needs to be injected solo. Avoid mixing potassium carbonate with other fertilizers and supplements in concentrated form.

Calcium-Deficiency-in-Lettuce-feature

Calcium deficiency, showing as the brown, marginal burn on these lettuce leaves, can be minimized with proper airflow over the crop. Photos by Griffin

Which Crop Likes Airflow Directed Onto The Plants?

A uniform production environment produces a uniform crop. It’s normal for microclimates to develop within a production space when the only sources of airflow are greenhouse vents, fan/pad systems, or warehouse HVAC systems. These microclimates result in temperature and humidity differences across the crop. In the worst-case scenarios, dead-air zones develop where humidity can rise to levels that are conducive to disease development and/or significant temperature gradients can occur within the production space. Microclimates can be minimized by adding horizontal airflow (HAF) fans to the space, which move the air throughout the production space. Properly placed HAF fans will move the air around a crop without actually blowing air onto a crop.

With few exceptions, directing fans onto crops should be avoided. While a little airflow is a good thing, turbulent airflow over a crop resulting in visible movement of the crop can have a detrimental impact on crop growth. When airflow over a leaf surface is high, the stomates close to reduce transpiration and prevent excessive moisture loss. Stomatal closure limits carbon dioxide availability to the crop, reducing photosynthesis and growth. This is generally very evident in production — plants in the direct path of airflow are generally shorter and have less vegetative growth.

Take Care With Lettuce

There is one crop for which a more direct, vertical airflow onto the crop is beneficial. Under low light and higher humidity, lettuce crops can develop tip burn of the interior leaves. This tip burn is also known to occur under excessively high daily light integrals (DLI) in lettuce — greater than 12 mol/m2/day without good airflow and 17 mol/m2/day with good airflow.

Tip burn of the young leaves is often caused by a calcium deficiency due to low transpiration resulting from pockets of stagnant air at the growing tip. Gentle airflow in a downward direction over the crop has been shown to improve transpiration of the young leaves and reduce the incidence of tip burn. Gentle is key here: It doesn’t take a lot of airflow to improve transpiration. No gale-force winds are needed. Instead, achieve gentle airflow with vertical fans. These large paddle fans, mounted above the crop, have been shown to produce enough downward air movement to improve transpiration at the growing tips and reduce the incidence of tip burn.

Making efforts to address these two commonly overlooked factors, buffering and airflow, can go a long way to simplifying production and producing a great crop. Our simple solutions are easy to deploy and bring measurable results.