By Karla Garcia and Deidre Hughes
Plant nutrition is a key factor in growth and yield. But how can we know which nutrient is missing? Or which is the best fertilizer for our crop?
In learning about plant nutrition, we first need to know there are nutrients required in greater quantities than others. The nutrients that are essential for plant growth are called “macronutrients”. The rest of the nutrients also essential for plant growth but in lower quantities are called “micronutrients”.Continue reading The importance of knowing basics of plant nutrition
It’s not that hard to do once you understand some fertilizer basics.
By Deidre Hughes
Mixing your own fertilizer solutions might seem like a daunting task at first. But once you understand some fertilizer basics you’ll realize it’s not that hard to do. One of the biggest benefits of mixing your own fertilizer solutions is the amount of money you’ll save. Another benefit of mixing your own solutions from dry fertilizers is that it requires less storage space than pre-mixed fertilizers which are often in liquid form.
The 17 Essential Plant Elements include nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, iron, manganese, zinc, copper, molybdenum, and nickel.
The non-mineral essential plant elements include hydrogen, oxygen, and carbon. These are either taken up as a gas or water.
There are 4 elements that are beneficial to promote plant growth but are not considered to be necessary for completion of the plant life cycle. They are silicon, sodium, cobalt, and selenium.
Figure 1 illustrates the essential and beneficial elements location on the periodic table. You can see that there are three clusters of elements within the periodic table.
These elements can be further divided into either macro- or micronutrients based on the relative concentrations typically found in plant tissues. The macronutrients include nitrogen, potassium, calcium, magnesium, phosphorus, and sulfur. The micronutrients are chloride, iron, boron, manganese, zinc, copper, molybdenum, and nickel.
The 17 essential plant elements can be remembered using a clever Mnemonic device that my botany professor Dr. Max Bell taught me in my undergraduate days at Truman State University. Here is the mnemonic device to remember the 17 essential plant nutrients of higher plants:
- HOPKNS Ca Fe is Mighty good and Clean. The owner is my Cu Zn Mo B the Nickel Miner.
The beneficial mineral elements can be remembered as a “Cozy Sinner” (Co Se Si Na).
Figure 1. Periodic table of the elements illustrating the essential and beneficial elements in higher plants.
In hydroponics, these mineral elements come from either the fertilizer salts you add to your source water or are already present in your source water. The macronutrients carbon, hydrogen, and oxygen come from either water or gases in the air.
Our Hort Americas Hydroponic fertilizer (9-7-37) was specifically designed to meet the unique needs of hydroponic plant production. Please contact us at to find our why Hort Americas Hydroponic Fertilizer is the perfect fertilizer for your hydroponic system.
Growers have affordable options for ensuring plants receive sufficient oxygen in hydroponic production systems to maximize growth and to reduce the chances of disease.
Oxygen is critical in the development and growth of edible crops grown in hydroponic systems such as nutrient film technique (NFT) and deep water raft culture. Tyler Baras, special projects manager at Hort Americas, is studying methods of adding oxygen to both conventional and organic hydroponic production systems in the company’s 12,000-square-foot research and demonstration greenhouse in Dallas, Texas.
“One of the big differences is how growers add oxygen,” Baras said. “A lot of times in conventional hydroponics, growers use air pumps and air stones to add oxygen. In organic systems these tend to be hot spots for biofilm development. We have removed all air pumps and air stones from the organic systems we are trialing.
In the conventional production systems Baras is studying he has installed water pumps with a Venturi attachment to add oxygen to the nutrient solution reservoir.
“The pumps aren’t injecting air into the irrigation lines, but simply into the reservoir to circulate the water and to create a circular flow within the fertilizer reservoir,” he said. “As the pumps operate they draw in air through a ¼-inch emitter. There is the benefit of moving around the solution and the air being drawn in increases the level of dissolved oxygen.”
A method that organic growers use to increase oxygen levels is cascading the water when it returns to the reservoir. As water returns it is allowed to fall and break the surface of the reservoir so that the water can pull in oxygen.
“This can also be done in vertical farms where the water will fall down large return pipes to the reservoir,” Baras said. “This can happen in multiple stages where the water will drop several times. This is an effective method for increasing dissolved oxygen.
“For NFT, it appears more oxygen can be delivered to plant roots when the flow rate is increased per channel. As the flow rate increases, more oxygen is delivered to the roots so water isn’t sitting in the channel as long. This allows freshly oxygenated water to be delivered quickly to the roots. In conventional hydroponic NFT systems the flow rate is about ½ liter per minute. In our hydroponic NFT system I have been aiming for about 1-2 liters per minute.”
Adequate oxygen levels
Baras said oxygen is necessary for plant roots to perform metabolic processes.
“Most of the water uptake in plants is passive,” he said. “But there is a stage where the plants use energy to actively pull up water through the roots. This requires oxygen. If there isn’t any oxygen in the root zone no water will make it up through the roots to the top of the plant. Low oxygen in the root zone can appear as wilting at the top of the plants. This can seem counterintuitive in a hydroponic system because the roots are sitting in water, but the tops of the plants look like their wilting if there isn’t any oxygen in that water.”
Baras said the need for oxygen in an organic hydroponic system is even more important because of the presence of living microbes in the fertilizer solution reservoir.
“These microbes also require oxygen,” he said. “The oxygen demand is often higher in organic systems than conventional systems because not only do the plant roots need oxygen, but the microbes need oxygen as well. In an organic hydroponic system one of the best ways of keeping biofilm in check is to keep the beneficial microbes happy.”
Baras said most of the oxygen measurements he has been taking in his research have been showing very similar oxygen levels for both conventional and organic production systems when the crops are performing well.
“I have been aiming for a level of 7-12 parts per million (ppm) dissolved oxygen, but generally the readings fall between 7-9 ppm,” he said. “I’m using a ProODO meter from YSI that is a very sensitive piece of equipment that accurately measures dissolved oxygen.”
Although most hydroponic growers are concerned with maintaining adequate oxygen levels, Baras said if too much oxygen is added to the solution it can cause root stunting.
“I haven’t reached that threshold yet in my trials,” he said. “It’s crop dependent on what that level is. When there is too much oxygen the roots have less motivation to grow larger because they are getting everything they need with a smaller surface area. That can then translate to the plants producing less biomass resulting in less leaf tissue. So at some point too much oxygen can actually cause less growth. For crops like tomatoes, peppers and cucumbers the whole plant would be stunted.
“The only way growers could reach excessive oxygen levels that damage the plants are when liquid oxygen or possibly ozone is used. Using air pumps or air stones to add oxygen, the levels won’t be high enough to stunt plant growth. To reach higher oxygen levels of 15-16 ppm, a grower would have to use other methods like liquid oxygen and ozone. It’s very difficult to reach high oxygen levels above 10 ppm unless an alternative method is used beyond air pumps, Venturis and cascades. I haven’t seen any growers go much higher than 8-9 ppm using the conventional methods.”
Baras said growers using a deep water raft system could try increasing turbulence in the pond to increase oxygen level. However, too much turbulence can sometimes cause damage to the roots.
“The roots in the turbulent areas are the ones that often times grow poorly,” he said. “The plants that are near the irrigation outlets where the currents are stronger, they have the poorest root growth. Sometimes growers will use air pumps in their ponds and those plants directly above where the air stones are located grow poorly.”
For more: Hort Americas, (469) 532-2383; https://hortamericas.com.
David Kuack is a freelance technical writer in Fort Worth, Texas; firstname.lastname@example.org.
If you missed the e-GRO webinar “Managing Nutrient Solutions for Hydroponic Leafy Greens and Herbs” on Jan. 22, 2016, which was sponsored by Hort Americas, you can still view the webinar on YouTube.
Hydroponic greens and herbs are produced in systems with recirculating nutrient solutions. In order to maintain productive and quality crops, it is important to know how to properly maintain the nutrient solutions. Dr. Chris Currey at Iowa State University and Dr. Neil Mattson at Cornell University discuss strategies for managing pH and EC, formulating nutrient solutions and identifying common nutrient disorders.
Part 1: Common production systems, pH and EC management
Presented by Dr. Chris Currey, Iowa State University
Part 2: Nutrient solution recipes, common nutrient disorders
Present by Dr. Neil Mattson, Cornell University