What are the benefits of maintaining the optimum substrate oxygen level?

Increasing the oxygen level in the root zone can ensure healthy root growth and can impact crop yields.

Low oxygen levels in the growing substrate can play havoc with the health of both vegetable and ornamental plants. Shalin Khosla, greenhouse vegetable specialist at Ontario Ministry of Agriculture, Food and Rural Affairs in Harrow, Ontario, said a substrate oxygen level below 5 parts per million can have a negative effect on plant growth.

Continue reading What are the benefits of maintaining the optimum substrate oxygen level?

Be aware of the challenges of using loose substrates in hydroponic production systems

If you’re going to use a loose substrate in a hydroponic production system, you may have to change how you handle starter plants and the treatment of recycled water.

Many growers of ornamental plants including annuals and perennials traditionally use a peat-based substrate such as 70 percent peat, 30 percent perlite. The growers, who produce these crops in containers, will often use the same substrates if they expand their crop offerings to include hydroponically-grown edible crops, including lettuces and leafy greens.

Continue reading Be aware of the challenges of using loose substrates in hydroponic production systems

Grodan rockwool substrates offer growers more control

Grodan stone wool products offer the benefits of high irrigation efficiency, plant steerability and uniform crop development.

Grodan stone wool substrates are made from basalt rock that is processed at a very high temperature (over 2,900ºF). This hygienic, inert substrate offers vegetable and ornamental plant growers the opportunity to control growth from propagation to harvest.

“Grodan stone wool products are inert,” said Rens Muusers, Grodan Technical Sales Manager for the USA. “This means the grower has full control over what is happening in the substrate. Being inert, Grodan stone wool doesn’t bind nutrients and chemicals like other substrate types may do. Any fertilizers, pesticides or other chemicals, including growth regulators, that are applied to the stone wool are available to plants.

Linked to stone wool’s inert nature, Muusers stated growers have more opportunities to steer their crops.

“Other substrates that aren’t inert may bind elements, pesticides or other chemicals that are applied to enhance plant growth or health,” he said. “This may result in having to apply more of a chemical in order to have the same efficacy. The amount of chemical that will need to be applied to stone wool will be lower and it will be more effective than in non-inert substrates. This also helps growers to minimize their input costs.

“Using methods to control water content and EC (electrical conductivity) levels within the substrate allows growers to influence plant growth.”

Muusers stated by controlling the water content and EC in the stone wool, growers can influence the plant balance between vegetative and generative development.

“The steerability offered by Grodan products can result in earlier production, improved plant, fruit and flower quality and improved plant health,” he said. “All of these benefits result in better resilience to insect pests and disease pathogens.

“Also, stone wool can have a buffering impact on the pH in the nutrient solution, slightly increasing pH in the substrate. This increase is minimal compared to the impact of plant and microbial activity in the root zone on pH.”

Muusers indicated another benefit of using stone wool is crop uniformity.

“Because Grodan stone wool products are manufactured in state-of-the-art facilities with strict standards and quality controls, it is a very uniform substrate,” he said. “Depending on the Grodan product being used, this allows growers to produce very uniform crops. The uniformity of seedlings produced in stone wool plugs results in faster germination and quick crop establishment.


Grodan AO plugs and Grodan AX plugs

Grodan AO and AX stone wool plugs are ideal for starting many crops. The plugs are available in sheets that fit into 1020 trays. AO plugs are connected to each other at the top of the plugs. AX plugs are attached to each other at the bottom of the plugs. Muusers said there are also some options in regards to the seeding hole size as well as with the dimensions of the plugs.

“The properties of the AO plugs are exactly the same as the properties of the AX,” he said. “The only difference is where the plugs are attached to each other.

Grodan AX 25/40 cube with lettuce roots and stem post-harvest.

“AO plugs are ideal for NFT systems with smooth gutter surfaces and also for deep flow systems. Some NFT systems use gutters with grooves on the surface for which growers may prefer the wider base and greater bottom surface area of the AX plugs which may be more stable in these systems.”

Muusers said both plugs are used mainly for leafy greens and culinary herb production. There are also growers who are using them for aquatic plants.

Grodan Cress Plate

The Cress Plate is a fairly new product used primarily for the production of microgreens. It is the thinnest product of Grodan. It is only 1 cm thick, less than ½ inch.

Cress Plates come in two sizes. One size fits into 1020 trays. A larger size is used by some growers who need customized sizes. Growers are able to cut the Cress Plate sheet to the exact size they need.

“The Cress Plate has the same beneficial characteristics as other Grodan products,” Muusers said. “It’s inert, clean and hygienic. It’s a uniform product. It holds water evenly. The Cress Plate also provides quick, easy germination and even development of a microgreen crop.”

Muusers indicated growers use Cress Plates in a couple of ways.

“Some growers sell the microgreens with the Cress Plate, essentially selling a living product,” he said. “This allows the end consumer to use the freshest product longer, something that is valued by customers like restaurants. “Growers who produce baby greens and baby lettuce tend to harvest off of the Cress Plates. By harvesting higher up the plants, the plants continue to grow and produce for several harvests. This multiple harvest method is preferred to the uncommon practice of reusing substrates.”

Muusers stated reusing the Cress Plates is risky, just like reusing any substrate.

“There is the possibility of sterilizing the used substrate with steam or some other technique,” he said. “When a sterilizing technique like steam is used, it can have a negative impact on the properties of the substrate. I wouldn’t recommend harvesting and then resowing on top of a previously used Cress Plate because of the risk with potential disease issues and the potential negative impact on germination and growth.”

Grodan Delta Blocks

Grodan blocks come in different sizes and are ideal for both ornamental and vegetable crops.

“Depending on the crop, once a seedling is germinated in a plug it can be transferred into a block and then transplanted into a finish substrate to be grown on,” Muusers said. “Tomatoes and peppers are usually propagated in plugs and then transplanted into blocks. The final grower purchases the young plants in blocks and transplants them into the final substrate such as Grodan slabs. For cucumbers, which are a relatively quick crop, those are sometimes sown directly into blocks, instead of plugs.”

There are different size blocks for different size crops. A standard block size is 10 cm-by-10 cm-by-6.5 cm, which is referred to as a 4-inch block.

Muusers indicated that some growers put multiple plants into one block depending on the crop.

“For tomatoes, growers are looking for a certain head density per square meter,” he said. “The head density per square meter is sometimes achieved by growing multiple plants or by pinching the plants. Tomatoes are the primary crop that growers plant more than one seedling in a block.”

Muusers stated this method of planting multiple plants is also done with cucumbers and peppers. Another reason a grower sows multiple plants into blocks is to try to save on the cost of the blocks.“Some growers use 6-inch blocks instead of 4-inch blocks and put two plants in them,” he said. “In my opinion, it is always better to put one plant in one block. There is less competition resulting in better seedling uniformity as well as a more uniform crop.”

The blocks, like the plugs, are inert and are steerable. Muusers stated the blocks are also important in regards to irrigation efficiency—how the water content and more particularly, the EC, are refreshed within the substrate.

“Grodan focuses on good root growth and uniform root growth throughout the blocks,” he said. “Also, the blocks need to be able to withstand the rigors of handling during propagation. Their structure must remain stable throughout the growing process to be able to support the plants especially when the blocks are moved around. The blocks won’t break or fall apart.”


Grodan Gro-Slabs

Muusers indicated that Grodan slabs come in different product types developed to meet the challenges and needs of different crops.

“We have different slab types for different applications,” he said. “The slabs differ in fiber orientation and fiber thickness to deliver the kind of functionality a grower is looking for. The Grodan plugs and blocks have the same fiber orientation. They are designed for quick root establishment.”

There are Grodan slabs designed for vegetable crops. These crops are usually short term, less than one year. There are slabs designed for longer horticultural ornamental crops that are grown for longer than a year. The slabs for long term crops, including cut roses and gerbera, have a stronger fiber structure to withstand the longer production period.

“Grodan slabs are very uniform,” Muusers said. “Since the substrate is inert, they offer a high degree of crop steerability. This offers a lot of options for irrigation strategies combined with the substrate to influence plant development in a vegetative or generative way.”


David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.


Substrate trials look to assist hydroponic growers avoid propagation-related issues

Substrate trials in Hort Americas’ research greenhouse are looking at conventional and organic propagation substrates along with different irrigation strategies for producing healthy starter plugs for hydroponic production systems.

Hort Americas has retrofitted a 12,000-square-foot greenhouse in Dallas, Texas, for the purpose of studying edible crop production in a variety of hydroponic production systems. The greenhouse is also being used to demonstrate products offered in the company’s online catalog.

Tyler Baras, who is the company’s special projects manager, is overseeing the trialing of conventional and organic substrates in different production systems.

Tyler Baras, special projects manager at Hort Americas, is overseeing the trialing of leafy greens and herbs propagated in conventional and organic substrates. The seedlings are transplanted into a deep water culture, NFT or vertical tower production system.
Photos courtesy of Tyler Baras, Hort Americas

“The trials I am focusing on are organic substrates vs. conventional substrates,” Baras said. “I’m primarily using stonewool or rockwool as the conventional propagation substrate. I am also starting to trial some loose substrates, including peat and perlite.

“The seedlings are never moved into another substrate. The seed is sown into plugs and then the rooted seedlings are moved into a deep water culture, NFT (nutrient film technique), or vertical tower production system. The plugs are really only useful for the first two weeks in propagation. Then it is really about getting the roots to grow outside the plugs so the roots grow directly in the water.”

For the organic production systems, Baras is working primarily with expandable coco plugs. He has also started working with some organic loose substrates including coco peat and perlite.

For the substrate studies Baras is working with two standard hydroponic crops, basil and lettuce, primarily butterhead lettuce.

“When I’m testing the lettuce I use either raw or pelleted seed,” he said. “With basil it’s all raw seed. Basil tends to germinate relatively easily, whether the seed is planted into a dibbled hole or sown on top of the substrate.”

Focused on irrigation strategies

A primary objective of the substrate trials is to determine the best irrigation strategies for both organic and conventional substrates.

“This is probably more important with some of the organic substrates than the conventional substrates because the organic substrates tend to hold more water,” Baras said. “One of the big challenges that organic hydroponic growers run into is overwatering their plugs because coco holds more water than conventional substrate plugs that growers are used to. Coco plugs hold more water than stonewool, phenolic foam and polymer-based peat plugs. These other plugs dry out faster than coco plugs.”

For the substrate trials, rooted seedling plugs are finished in a deep water culture, NFT (nutrient film technique) or vertical tower production system.

Baras said growers who are moving from conventional to organic production tend to use the same irrigation techniques they employed with their conventional propagation program.
“The growers will continue to irrigate the plugs a couple times per day,” he said. “With a lot of the organic plugs, when the seed is sown, they only need to be irrigated once every three days. If the plugs are overirrigated the roots don’t have an incentive to search out the water when they are planted into the production system. The search for water is what drives the seedling roots down to the bottom and out of the plugs.

“The goal of planting into plugs is to have the seedling roots grow outside of the plugs into the water of the deep water culture or NFT system. If the plugs are overwatered as young seedlings, the roots don’t make it down to the bottom of the plugs so it takes longer to start the seedlings and sometimes they just end up rotting because the plugs remain too wet.”

Type of irrigation system

In addition to looking at the irrigation frequency of plugs during propagation, Baras is studying the impact of different methods of irrigation during propagation, including overhead and subirrigation.

“When deciding whether to use overhead or subirrigation, it depends on whether raw or pelleted seed is being sown,” he said. “If pelleted seed is going to be used, a lot of times it’s advantageous to use overhead irrigation because it helps to dissolve the coating surrounding the seed. This helps to ensure the seed has better contact with the substrate. Sometimes it’s almost a little easier to get good germination with subirrigation if raw seed is used because of the direct contact with the substrate.

Growers need to avoid overwatering young seedling plugs or their roots may not make it down to the bottom of the plugs, which could delay transplanting into the production system.

“Smaller indoor growers often use subirrigation for germination. A lot of the large growers, especially those coming from the ornamental plant side such as bedding plants, usually have overhead irrigation systems installed. These growers have propagation areas set up with overhead irrigation, which can be used to start their hydroponic vegetable crops.”

Baras said most indoor warehouse growers are not going to be using watering wands or overhead irrigation in their operations.

“Most of the warehouse growers will be using subirrigation, such as flood tables,” he said. “For them it is going to be important that they select the right kind of seed to get good germination. They may have to try other techniques like using a deeper dibble or covering the seed with some kind of loose organic substrate such as perlite or vermiculite. Growers using overhead irrigation can usually sow pelleted seed without having to dibble the substrate.

“Many growers tend to have issues when they are using pelleted bibb lettuce seed with subirrigation. We are looking at ways of increasing the germination rate using dibbling with the pelleted seed or increasing the dibble size or covering the seed.”

Baras said growers who are using automation, including mechanized seeders and dibblers, prefer to use pelleted seed.

“With pelleted seed it’s easier to be more precise so that there is only one seed planted per plug cell,” he said. “I have seen automation used with raw basil seed. I have also seen organic production done where automation was used just to dibble the plug trays. Dibbling seems to be one of the biggest factors when it comes to getting good even germination.


Need for good seed-substrate contact

Baras said occasionally with tightly packed coco plugs, if the seed is not pushed down into the plug the emerging radicle may have issues penetrating the substrate.

“This helps push the radicle down so it contacts the substrate and establishes more easily,” he said. “When subirrigation is used it can be advantageous to cover the seed with vermiculite or just brush the top of the coco plug after the seed is planted to get some coverage of the seed.

“What usually affects the way that coco plugs work is the size of the coco particles. There is really fine coco. There is coco fiber, which can be mixed into the plug to help with aeration and increase drainage. We are looking at various plugs with some increased fiber content trying to aerate the plugs in order to speed up the drainage.”

Stonewool or rockwool is the primary conventional propagation substrate in the trials. Other loose substrates, including peat and perlite, are also starting to be trialed.

Baras is also looking at using loose substrates in different ratios in plugs and then transplanting them into deep water culture, NFT, and vertical tower systems.

“One of the issues with hydroponic systems and loose substrates is these substrates can enter the production system and clog up the irrigation lines,” he said. “The trick is trying to avoid having any loose substrate enter the system. We are looking at using loose substrates and allowing the seedlings to establish longer in the plug cell during propagation before transplanting them into the production system. This enables the seedlings to develop a larger root system, which can prevent loose substrate from falling into the system.”


For more: Hort Americas, (469) 532-2383; https://hortamericas.com.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.


Products being used in greenhouse trials

NG2.0 from GRODAN: The New Standard for Optimal Irrigation

Grodan NG2.0

Press Release

Precision Growing has never been so Precise

Next Generation 2.0 (NG2.0) is the latest substrate technology from GRODAN. This technology enables propagators and growers to produce more while using less water, nutrients and space. It creates optimal growing conditions for a whole season, and allows roots to make better use of the entire substrate. NG2.0 is available in plugs, blocks and slabs to help growers and propagators produce sustainable, healthy fresh produce for a growing population.

The growing world population means the demand for sustainably produced and healthy fresh produce is continuing to increase. The greatest challenge facing growers is creating the ideal conditions for growth: not just for a few weeks, but all year round. Precision Growing plays a vital role in this respect. It gives growers the opportunity to produce more using less water and nutrients.

The next step in Precision Growing

GRODAN introduced Next Generation Technology in 2007. Its introduction already signaled a giant leap forwards in crop management, plant steering and root development. NG2.0 is an exciting continuation of this technology that has been extensively trialed in practical situations over the past years. The response to NG2.0 is extremely positive. NG2.0 is the next step in Precision Growing (see video below).

NG2.0 adds new benefits to those already offered by Next Generation Technology. Water distribution is even more uniform and even better utilization of the entire substrate volume by the crop is ensured.

Continual new growth of roots in both the block and the slab results in a healthier and more vigorous crop throughout the whole growing season. These benefits translate to higher yields, improved fruit quality and reduce the sensitivity of the crop to diseases. NG2.0 creates the perfect substrate for growers and propagators of plants.

Phased transition to NG2.0 in North America

Beginning in 2016, GRODAN will implement NG2.0 starting in the Netherlands in a phased in approach.

Future launches of NG2.0 will occur in other markets in Europe and North America. For more information on your specific area, please contact GRODAN (see below).


About the GRODAN Group

The GRODAN Group supplies innovative, sustainable stone wool substrate solutions for the professional horticultural sector based on Precision Growing principles. These solutions are used in the cultivation of vegetables and flowers, such as tomatoes, cucumbers, sweet peppers, eggplants, roses and gerberas.

The Group offers stone wool substrates together with tailor-made advice and tools to support Precision Growing, facilitating the sustainable production of healthy, safe, and tasty fresh produce for consumers.

Sustainability plays a prominent role at GRODAN, from the production of stone wool substrates to end-of-life solutions.

Founded in 1969, the GRODAN Group is active in more than sixty countries worldwide. The Group’s head office is in Roermond, the Netherlands.



Grodan’s Stone Wool Substrate

As a commercial hydroponic grower, it is important to be able to promote the production of high quality vegetables, grown in a clean and sustainable environment.  Produced from pure basalt rock, Grodan’s Stone Wool Substrate (also commonly known as Rockwool) is of the highest of grades, promoting uniform wetting and providing excellent drainage. Grodan’s proprietary binder and wetting agent insure more uniform water dispersion and water holding, which leads to better root development throughout the entire substrate. Control of water and nutrients is very important to commercial growers to achieve maximum yields.  Take control with Grodan Substrates today!

  • Easy to use – 100% recyclable
  • Contains no contaminants
  • Sustainable and environmentally-friendly
  • Saves water and nutrients
  • Hort Americas Grodan Guide Click Here!




Grodan provides precision growing with a substrate that is inert and will not bind nutrients inhibiting a uniform crop development and a primary focus on the root zone. Further, steer-ability (controlling water content and electrical conductivity), irrigation efficiency and production optimization are all pillars of Grodan substrates.  

Hort Americas is an innovative leader in North America’s controlled environment agriculture industry (CEA) and strives to continually innovate in agriculture via premium technical support, professional salesmanship, unmatched customer service and outstanding products to our customers in the United States, Canada, Mexico, and the Caribbean.

For questions, support or to purchase → Click Here!


Riococo Coco Coir Substrates

As an organic crop producer, you seek to optimally balance air, water and nutrients in order to attain maximum yields. Hort Americas supports your efforts by bringing you Riococo’s award-winning Coco Coir Substrates. With excellent water/nutrient retention and distribution, you can guarantee your root structure will receive the proper amount of aeration.

Riococo controls the intrusion of contaminants and salts into their coir materials during collection and processing by implementing a stringent quality control system. This aids in maintaining the product’s consistency and uniformity. Riococo maintains detailed documentation for every product from its origin to final destination.

  • Easy Propagation
  • 100% Bio-degradable Natural Coir Fiber
  • OMRI-Certified
  • Optimal chemical properties, including mineral ion concentration and pH
  • Technical Properties Chart


Riococo has obtained an ISO 9001:2008 Certificate which shows the company’s adherence to quality management practices. In becoming certified, Ricococo has been certified to satisfy requirements of ISO 9001:2008 with respect to the management system governing the service provided to organic crop growers world-wide.


Hort Americas is an innovative leader in North America’s controlled environment agriculture industry (CEA) and strives to continually innovate in agriculture via premium technical support, professional salesmanship, unmatched customer service and outstanding products to our customers in the United States, Canada, Mexico, and the Caribbean.

For questions, support or to purchase → Click Here!


An OMRI-certified option for organic and hydroponic growing

Riococo Closed Bottom Organic Plug used for Lettuce

Riococo Closed Bottom Organic Plug

For the Organic or Hydroponic grower seeking an OMRI-Certified option for fast and effective seed germination, plug and transplant production for leafy greens and culinary herbs, Hort Americas brings you the Riococo Closed Bottom Organic Plug (CBOP). Whether you grow in 1020 trays, grow bags, nutrient film technique (NFT), raft systems, aquaponics or aeroponics systems, with this CBOP you are well on your way to attaining maximum yields!

Dr. Hugh Poole, international agricultural consultant, said coconut coir is initially high in sodium, potassium and chloride salts. “Where the coconut coir originates from can have an impact on the salt levels.” He further states, “If the EC (electrical conductivity) level is below 1.0 milliSiemens (measure of electric conductance) per centimeter (mS/cm), growers should not have to leach the coir. In most cases, the coir producers have already leached the coir for the growers. It should be ready to use. If the salts level is high, then the coir producer has not done its job. A producer should be able to provide growers with the coir’s EC value, its pH value and other information, including percent moisture, as well.”

Rest assured growers, Riococo Closed Bottom Organic Plugs consistently provide all of the above!

Riococo Closed Bottom Organic Plug used for Lettuce

  • Made from Low EC, pre-washed coir
  • Available in 25mm, 32mm and 42mm
  • Custom Sizing Available for Container-Size Orders
  • Technical PropertiesClick Here!

Hort Americas is an innovative leader in North America’s controlled environment agriculture industry (CEA) and strives to continually innovate in agriculture via premium technical support, professional salesmanship, unmatched customer service and outstanding products to our customers in the United States, Canada, Mexico and the Caribbean.

For questions, support or to purchase → Click Here!

Hort Americas offers OMRI-certified Riococo coir substrates

Riococo Closed Bottom Organic Plug used for Lettuce

Riococo Closed Bottom Organic Plug used for LettuceHort Americas offers several Riococo coir substrate products. Two of those substrates recently received OMRI certification for use in organic crop production.

Riococo Coir Starter Blocks allow growers to propagate easier and faster to produce healthy plants organically. These biodegradable blocks are made from a 100 percent coir fiber compressed disc packed in biodegradable cellulose paper.

The blocks have excellent water holding capacity. Equal distribution of water throughout the blocks ensures optimum management of the air and water balance and the equal distribution of nutrient solutions.

The blocks’ natural coir fibers retain water and keep roots well-aerated. The blocks’ open structure is maintained throughout the propagation cycle until the blocks are transplanted into separate growing containers.

OMRI-certified Riococo Closed Bottom Organic Plugs work in a wide variety of production systems, including 1020 trays, grow bags, nutrient film technique (NFT), raft systems, aquaponics and aeroponics. Available in 32 mm and 42 mm sizes, these coir plugs are ideal for the production of leafy greens and culinary herbs.

For more: Hort Americas, (469) 532-2383; mluitjohan@hortamericas.com

CBOP – Hort Americas Closed Bottom Organic Plug

Hort Americas CBOP

Propagating in coco coir is a great way to establish plants. Now with the new Closed Bottom Organic Plug, CBOP, from Hort Americas you can reap the benefits of what you sow.

CBOPs are available in three sizes to fit the specifications of your production system. Whether it is nutrient film technique, raft, grow bag, or directly back into Riococo blocks/slabs, the new CBOP is easy to use and has all the benefits of using Riococo coir.

Currently, we have the 32mm (1.26 in) and 42 mm (1.65 in) size available. The 25 mm (0.98 in) size will be available in 2016.



pH & EC measurements 2:1 water extraction

To see more product information on the Hort Americas Closed Bottom Organic Plug, click here.

Starting Seeds in Grodan

The most important thing when using Grodan stone wool is that you need to saturate the product fully before using it. When you don’t fully saturate it, some of the stone wool can stay dry and will be hard to get wet at a later stage (hydrophobic). A way to check if the product is fully saturated is to weigh the product and it should be above a certain weight. As an example a Grodan Delta DM6G Grow Block of 10 x 10 x 6.5 cm (4” x 4” x 2.5”) has a volume of 650 ml, so in theory if it is completely filled with water it should weigh 650 grams. However, there will always be air in the Grodan rock wool so we take a water content (WC) of about 85% after initial saturation, meaning the Grow Block should be approximately 550 grams or slightly greater.

I recommend using nutrient solution at 5.5 pH when saturating the product so that nutrients are immediately available for the plant. For the germination itself nutrients are not needed, so some people saturate the plugs with just water and then add the nutrient solution immediately following germination. However, fairly quickly after germination nutrients are needed for further development. So to sure it is easier to saturate the plugs with nutrient solution. Most growers use 1/2 rate nutrient solution for starting then full rate at transplant.

Below are characteristics of some of the most common types of Grodan used in hydroponic production.


Grodan AO cubes 25/40 10/10

AO cubes are recommended for lettuce, herbs, and other greens in a raft system as the tapered base makes it easier to fit into the raft faster.


AO 25/40 mm (0.98 x 1.58 in)
L25 x W25 x H40 mm
200 (20 x 10) cubes per pad
Grodan-ao-cubes6,000 cubes per case
30 pads per case


Top = 25 mm
Bottom = 19 mm
Height = 40 mm
Hole = 10 x 10 mm
Weight dry (1 cube) = 2 g
Weight saturated (1 cube) = 18 g
Also available:  AO 36/40 = 1.5 in; 98 cubes/pad; 2,940 cubes/case
AO 50/40 = 2 in; 50 cubes/pad; 1,500/case


Grodan AX cubes 25/40 10/10

AX cubes are recommended for lettuce, herbs, and other greens in a NFT system as the wider base gives the plug more stability in the gutter.


AX 25/40 mm (0.98 x 1.58 in)
L25 x W25 x H40 mm
200 (20 x 10) cubes per pad
AX-cube6,000 cubes per case
30 pads per case

Top = 19 mm
Bottom = 25 mm
Height = 40 mm
Hole = 8 mm (1/4)
# per pad 200 (20 x 10)
Weight dry = 2 g
Weight saturated = 18 g


Grodan Kiem Plugs in French Trays



Kiem Plugs in French Trays
# per tray = 240 (12 x 20)
Height = 2.1 cm
Dry weight = 1 g
Kiem Plugs
Height = 2.1 cm
Weight dry = 1 g
Weight saturated = 9 g


Grodan Block Delta DM4G


7.5 x 7.5 x 6.4 cm (3 x 3 x 2.5 in)
Weight dry = 25.3 g each
Weight saturated = 273 g each
Volume = 368.7 cubic centimeters
85% WC = 313.4 g


Grodan Block Delta DM6G


10.2 x 10.2 x 6.4 cm (4 x 4 x 2 1/2 in)
hole = 1.5/1.6 in (36/40 mm)
Weight dry = 45.6 g each
Weight saturated = 494 g each
Volume = 655.5 cubic centimeters
85% WC = 557.2 g


Grodan Block Delta DM9G


15 x 10 x 6.5 cm (6 x 4 x 2.5 in)
two holes
Weight dry = 67-73 g
Weight saturated = 879 g
Volume = 975 cubic centimeters
WC 85% = 828.8 g


Grodan Grotop Expert Slab


Grotop Expert
100 x 20 x 7.5 cm (39.4 x 7.9 x 3 in)
(99 x 19 x 7.8 cm)
Weight dry = 753 g


Grodan AX 25/40 cube with lettuce roots and stem post-harvest.
Grodan AX 25/40 cube with lettuce roots and stem post-harvest.

Also available from Hort Americas:

Grodan Block Delta DM9G 27 x35 top right (144/case)

Grodan Block Delta DM6G 20×15 1 hole

Grodan Block Delta DM6G 27×35 2 hole

Grodan Block Delta DM4G 20×15 (384/case)

Grodan Block Delta DM4G 27×35

Grodan Cube AO 36×40 15/15 hole

Grodan Cube AO 36×40 10/10 hole

Buffering coir not necessary if it’s processed properly

Proper processing of coir to lower its natural high salts level should eliminate the need to buffer it with calcium nitrate.

By David Kuack


Coir has become a major component of both greenhouse vegetable and container crop production. It can be used by itself, for instance in grow bags, slabs and propagation cubes, or it can be used in growing mixes with other components like sphagnum peat, perlite and bark.

Coconuts, which are produced by coconut palms (Cocos nucifera), consist of husks that surround the nuts. The nuts are consumed as food and the husks are used to
produce various types of coir growing substrates, including chips, chunks and peat. Coir peat is a by-product of the husk fibers that are used to fill cushions and car seats.


Naturally high in salts
Dr. Hugh Poole, international agricultural consultant, said coconut coir is initially high in sodium, potassium and chloride salts.
“Where the coconut coir originates from can have an impact on the salt levels,” Poole said. “Coconut palms produced inland away from the ocean may not accumulate as much sodium, potassium and chloride, but growers should assume that all coconuts will have high salt levels.
“These salts are relatively soluble and are not totally bound by the coir so they are easily leached. Most coir producers use rain water for most of the year to remove the salts. If the EC (electrical conductivity) level is below 1.0 milliSiemens per centimeter (mS/cm), growers should not have to leach the coir. In most cases, the coir producers have already leached the coir for the growers. It should be ready to use. If the salts level is high, then the coir producer has not done its job. A producer should be able to provide growers with the coir’s EC value, its pH value and other information, including percent moisture, as well.”


producers should be able to provide growers
with the coir’s EC value, its pH
value and other
information, including percent moisture.

Photos courtesy of
Poole advises growers using coir to test for soluble salts before it is combined with other mix components and before any plants are placed in the coir.


“If the level of salts is low, then a grower doesn’t need to worry about sodium, potassium and chloride,” he said. “Many growers say the soluble salts level should be less than 1.0 mS/cm. Others say the salts level should be less than 0.5 mS/cm. It really comes down to how the coir is going to be used. If Ellepots are going to be filled with coco peat for young seedling production, then the soluble salts level should be around 0.5 mS/cm. If the coco peat is being blended with sphagnum peat, perlite or some other growing mix components and plants are being transplanted into containers, the coir soluble salts level can be higher. I have seen EC values as high 3-6 mS/cm. In these instances, unless the coir is being diluted with a lot of other mix components, growers would certainly want to leach the coir before it is used.”
Poole said growers who ask their suppliers for a low EC coir is similar to asking for a low EC peat moss or compost.
“If growers have to deal with a growing mix component with an EC level that is always bouncing around, it is going to be very challenging for those growers from crop to crop and from year to year,” he said.


To buffer or not to buffer
Poole said some growers are asking suppliers to buffer their coir with calcium nitrate.
“These growers are thinking that the cation exchange sites are loaded with potassium and sodium ions and if the coir isn’t buffered with calcium nitrate then their crops may suffer a calcium or magnesium deficiency,” he said. “These types of deficiency problems are more commonly encountered with hydroponic systems. If a substrate is being used, then this usually isn’t a concern.
“Most of the coir’s exchange sites are tied up with sodium and potassium. These ions are readily replaced by calcium. If calcium is applied, much of that calcium is going to be tied up in the exchange capacity taking out sodium and potassium. Therefore calcium is not in the substrate solution for utilization by the plants. There is a lag before the cation exchange capacity can be fully charged with calcium, potassium and magnesium. If a grower isn’t cognizant of this lag and doesn’t address it, it can cause deficiency problems. When 50 ppm calcium is incorporated in the fertilizer solution, the leachate may only contain 10 ppm calcium. Not that the plants utilized the other 40 ppm. Much of that 40 ppm was tied up at the exchange sites and will be available later.”


Avoiding deficiency problems
Poole said if the coir’s EC level is initially low and growers apply a Cal-Mag fertilizer at the beginning of a crop, there shouldn’t be deficiency problems. He said growers using reverse osmosis water, in which there is no calcium or magnesium, should make adjustments in fertility especially if they are producing a fast growing crop. Although no deficiency problems might occur, Poole said growers should be diligent in monitoring fertility levels.
“Once the cation exchange sites are charged with calcium and magnesium, then there is free exchange and there shouldn’t be any problems,” he said. “In the first two to four weeks, growers should probably start out with higher calcium and magnesium levels if they’re growing with coir. They should try to favor calcium and magnesium absorption at the exchange sites. This
is a precautionary step.”


If the coir’s EC level is initially low and growers
apply a Cal-Mag fertilizer at the beginning of a
crop, there shouldn’t be deficiency problems.
Poole said growers, who are using coir and are planning to use a 20-10-20 fertilizer, need to be aware that this fertilizer does not contain any calcium, magnesium or sulfur.

“The growers are going to have to add these nutrients,” he said. “If growers are using coir they have to recognize that the exchange sites need to be filled or charged with calcium and magnesium before there starts to be a free exchange of nutrients back and forth.

“With coir where the exchange sites are filled with sodium and potassium, the only way of removing these ions is by reducing them with leaching with water or by overcompensating with calcium and magnesium.”

Poole said initially, the natural salts found in coir must be leached with water. The remaining salts will be exchanged with calcium and magnesium by a buffering treatment or with elevated levels in the fertility program. He said buffering is not an option for organic growers.

“If coir is washed well and its EC is below 0.5 mS/cm or lower, then the coir shouldn’t have to be buffered for most crops. If calcium nitrate is used to buffer the coir, magnesium has to be provided as well.”

Poole recommends growers should review both their water analysis and their fertilizer analysis to know what nutrients they are applying and to confirm nutrient levels.

“Young plants and bare-root plants are more sensitive to high salts than to short-term nutrient imbalances,” he said. Long-term crops should be monitored using tissue analyses to optimize plant nutrition and crop productivity.

For more: Hugh
Poole, FloraSynergy; (864) 359-7090; hapoole@Interact2Day.com.


David Kuack is a freelance technical writer in Fort
Worth, Texas; dkuack@gmail.com.

Using Grodan for Lettuce and Herbs

Using Grodan for Lettuce and Herbs 

In recent years there has been
a worldwide increase
in the consumption
of lettuce and fresh herbs. Naturally this has led to an increase in production.  More and more growers are now opting to use GRODAN
as their substrate.
The benefits of
using GRODAN in the production process are:
  • It is an
    inert and hygienic substrate
  • The speed and
    uniformity of germination and growth.
  • There is
    sufficient substrate volume to propagate to the
    desired plant size.
  • Once it is
    placed in the gutter or raft system the
    propagation blocks provide further stability.
Inert and clean
GRODAN stone wool
is an inert and hygienic
substrate, so it provides your crop with a clean,
disease free start. Furthermore, stone wool retains its structure throughout the cultivation
cycle. Filters remain clean and free from blockages, cleaning between crops is
easier and more importantly, faster, allowing less downtime between crops. The
fact that it is also inert means that all applied nutrients and
water are directly available for the growing crop. The combination of faster turnaround
and faster growth adds to the possibility of extra cultivation cycles during
the year.
Uniformity and speed of germination and growth
One of the most critical
stages of cultivation is germination. Seed holes cut into the stone wool plugs provide
the perfect air/water ratio around the seed which facilitates a high
germination percentage. More importantly, as the stone wool substrate is
uniformly saturated, each seed has the same germination environment, which provides uniformity in
emergence and initial growth. The speed and uniformity of growth which
follows results in a higher quality end product. It also provides a crucial opportunity
for additional cultivation cycles during the year.
Substrate volume to propagate the desired plant size
There are two distinguishable
stages in the production process; propagation and final production.
With the propagation of lettuce, a favorable microclimate is required. This is partly achieved
by retaining a high plant density. 
In GRODAN trials, we have seen that when the propagation period
is extended (21-24 days), the microclimate created results in more speed in
final production. Also, as larger plants are used, the production cycle is shortened,
once again providing an opportunity for additional cultivation cycles during
the year.
In order to extend the propagation
period you also require a larger substrate volume (i.e. AO
36/40 or MM40/40). This larger volume allows more root growth and
more stability.  Crucially, it also
allows irrigation to be managed. Often in propagation, too much water is given.
This results in weaker plants with greater susceptibility to disease.
Having the right irrigation strategy with the right substrate volume will give
you the possibility to be critical to the moment of irrigation. Having a precise irrigation
strategy will also retain the roots within the plug and therefore result in less
damage during transplanting.
To improve the irrigation strategy, we would suggest that you weigh
the blocks or AO sheets to decide if irrigation is needed (table 1).
Table 1. Indicative weights to irrigate the
blocks or AO sheets.
Grodan product
Approximate substrate volume
Indicative weight to base irrigation on (±60% WC)
MM 40/40
64 ml per block
40 gram per block
AO 36/40
40 ml per plug
3926ml per sheet
24 gram per plug
2.4 kg per sheet

Stability during use in gutter or raft system

Depending on the production system
which is used, the
GRODAN propagation component provides a certain degree of stability. For plants in
gutter systems, suitable products are MM blocks or the AX
plugs (figure 1). For plants in a raft system an AO plug is recommended, as its tapered
base makes planting
into the raft faster.
Figure 1. Left picture showing Grodan AX  plugs with basil seedlings, middle Grodan MM
blocks with lettuce during propagation stage, right picture showing Grodan AO
GRODAN stone wool
will give you an inert, clean substrate which provides fast, uniform
germination and growth. Whether you have a raft or gutter system, we have a plug or block that
will fit your needs.

For more information
contact Hort Americas at 469-532-2383 or customerservice@hortamericas.com 

Visit our corporate website at https://hortamericas.com

Using coir as a growing substrate

Provided by Shan Halamba
Edited by David Kuack

Coir is a natural, and renewable resource produced from mature coconut husks. Coir fiber is a coarse material obtained from the husk surrounding the coconut seed.
Coconut palms (Cocos nucifera) yield coconuts, which are harvested in 45-day cycles. The husks are separated from the nuts, which are consumed as food. The husks are used to produce growing substrates. The husk fiber is spun into a wide range of textured yarns. These yarns are used to produce a variety of products including colorful woven floor coverings.
Sri Lankan coir
Sri Lanka is the largest exporter of coir in the world. The coir industry began in Sri Lanka in the 1860s. Over the years, piles of coir gradually grew around coir mills and the country faced a major disposal problem. In the late 1970s, coir fiber products started to be exported to many different countries. European customers realized that the coir from Sri Lanka had desirable horticultural properties.

RIOCOCO coir substrates
RIOCOCO coir substrate products originate from Kurunegala in the heart of Sri Lanka’s coconut triangle. Here the coconut palms flourish in the region’s rich soil and humid tropical climate.
RIOCOCO coir was introduced in 2004 after many years of extensive testing, research and development combined with customer feedback. Carefully selected raw materials are blended together to produce high quality coir substrates in different formats. RIOCOCO owns eight production facilities in Sri Lanka. These operations have the capacity to produce 4 million greenhouse grow bags per year along with other growing medium products.
RIOCOCO coir characteristics
RIOCOCO coir is lightweight and can be compressed into a variety of shapes. It decomposes slowly due to its high lignin content. It is uniform and consistent because of the production process that uses various sieving systems and mixes different particle grades.
RIOCOCO coir is widely available and doesn’t create any environmental problems during the production process like other inorganic growing media. RIOCOCO is the first North American-based company to obtain the OMRI listing for coconut fiber.
RIOCOCO coir has excellent porosity and water holding capacity, which can be changed according to crop requirements by blending different grades of coir. It has ideal chemical characteristics for plant production. It can be reused for several crop cycles and can be easily disposed of without any environmental concerns.
RIOCOCO is conducting research to develop the next generation of products that will be suitable for different and new growing techniques. Each product is tested under different greenhouse conditions in temperate countries including the United States, Mexico and Japan.
Hydroponic production in coir
Currently, tomatoes, cucumbers, bell and chili peppers, egg plants and strawberries are grown hydroponically in custom blended RIOCOCO coir grow bags. These production systems include low-tech and high-tech greenhouses and nursery container systems.
RIOCOCO products consist of different blends based on the requirements of specific crops and the duration of the crop cycle.
Every crop has a specific air fill porosity and water-holding capacity. When the water-holding capacity of a growing medium is too high, root diseases such as Pythium and Phytophthora can occur. A growing medium with a water-holding capacity that is too low causes water stress and results in poor plant development.
Another important characteristic of a growing medium is stability. Growing media consisting of smaller particles are decomposed faster by micro-organisms. Many of the coir substrates on the market contain smaller particles that will decompose in the slab or pot after a couple of years in production.
Crops like bell peppers that have a long cropping period require a more stable substrate such as a blend of coconut husk and coir. RIOCOCO has developed a special mix for bell peppers that contains different particle sizes of husk chips and natural materials. This open mix has a higher water-holding capacity and air fill porosity.
Different mixes are also available for container-grown plants. A major consideration is the method of irrigation. For container plants produced with ebb-and-flood irrigation a more open substrate that holds enough water is needed.

Coir adjustments
RIOCOCO coir is washed and dried to remove excess sodium before it is blended and manufactured into slabs and blocks. These coir products are not pre-buffered with calcium which enables growers to make this adjustment depending on the crops’ requirements.
Buffering coir prior to use is necessary and can be done by applying additional calcium nitrate and less potassium nitrate to the nutrient solution when expanding the slabs and during the first two weeks of production. After this period standard nutrient formulations can be used.
The root activity in coir slabs is higher than in other organic and inorganic substrates resulting in a higher pH. This increase in pH can lead to a poor uptake of iron.
For growers who normally apply Fe-EDTA, a part or even all of the iron has to be applied as Fe-DTPA, Fe-EDDHA or Fe-EDDHMA. The reason is the high pH has an impact on the stability of the iron chelate. Once the iron chelate is unstable, plants cannot take up the iron. Fe–EDTA is stable until a growing medium of pH 6.7 while Fe–DTPA, Fe-EDDHA and Fe-EDDHMA are stable to a growing medium pH of 10
The electrical conductivity (EC) or conductivity factor (CF) of RIOCOCCO coir is comparable to other substrates.
Watering coir
There are no differences in fertilization for plants grown in RIOCOCO coir products compared to other growing media apart from the nutrient adjustments previously mentioned. Since coir holds water much better than other inorganic substrates, less water needs to be applied and it is readily available to the plants.
In general, during the summer drain percentages of 20 to 30 percent are obtained. During the winter less water has to be applied as coir can be easily over watered. A good method of controlling irrigation is to use a weight scale and work with a dry down of 10 percent for the coir slabs. In most cases a drain percentage of 10 to 20 percent is obtained.
RIOCOCO coir products
RIOCOCO coir products include slabs, trays, bags and containers. The slabs can be produced at any length, width and height to match any production system and crop. Special orders are possible such as layered slabs in which layers of different grades of coir are placed on top of each other. RIOCOCO can also make special blends for crops with different water-holding capacities and for long term crops.
For long term crops an important factor is the stability of the plastic wrapping around the slabs. Wrapping that is not UV-stable can deteriorate causing the slabs to fall apart and allowing weeds to grow in the coir. Upon request RIOCOCO slabs can be wrapped in UV-resistant plastic that is guaranteed to last for at least a year.

Shan Halamba is chief executive officer, Ceyhinz Link International Inc., Irving, Texas; (214) 492-0803; http://www.riococo.com/
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

Growing media considerations
A growing medium should provide support for the plant root system. The medium should also allow the roots to penetrate easily in search of water and nutrients. This means a medium should be able to provide ample pore space for oxygen and to hold water and nutrients.
The following are basic considerations when choosing a growing medium:
* Availability
* Weight
* Uniformity and consistency
* Optimal physical properties, including porosity and water-holding capacity
* Optimal chemical properties, including mineral ion concentration and pH
* Low decomposition
* Reusable and ease of disposal
* Cost
* Organic certification

Visit our corporate website at https://hortamericas.com/

Hydroponic Lettuce Production in Phenolic Foam

David Kuack and Vijay Rapaka
growing substrate materials that have been used for hydroponic crop production
include rockwool, perlite, vermiculite, expanded clay and pea gravel. Phenolic
foam is a relatively new inorganic substrate that offers many desirable
production properties.
Phenolic foam
Oasis Horticube Growing Medium is a sterile phenolic foam. Like rockwool,
Horticubes have no cation exchange capacity, no
buffering capacity and no initial fertilizer charge.
Horticubes come in a variety of sizes, including: 1-inch Thin-Cut
(276 cubes/sheet), 1-inch (162 cubes/sheet), 1¼-inch (104 cubes/sheet) and 1½-inch
(50 cubes/sheet). All of the sheets measure 10- by 20-inches and fit into
standard 1020 trays. Each sheet is pre-scored on the bottom and top to allow
for easy separation of the cubes at transplant.
The 1-inch Thin-Cut Horticube was developed primarily for
hydroponic lettuce production. This high density configuration accommodates 276
seeds in a standard 1020 tray. Each cube is pre-punched with a dibble hole that
is uniform in depth and has center to center spacing. This allows for the use
of automated seed sowing equipment. Horticubes work equally well with both nutrient
film technique (NFT) and a raft (float) growing system.
Using the North Carolina State University porometer, the 1-inch
Thin-Cut Horticube has a water-holding capacity of 80 percent and air porosity
of 20 percent. A comparable rockwool product, which has grooves at the bottom
of the sheet, has a water-holding capacity of 60 percent and air porosity of 40
Sowing the seed
Horticubes can be seeded dry and do not need to be watered prior
to sowing the seed. Seed can be sown using a vacuum seeder or manually by
placing the seed in the dibble holes. The specially designed hole is tapered to
ensure the seed sets properly in each cube.
After the seed is sown irrigation can be done manually with a hose
and water breaker (i.e., wide fan nozzle) or automatically by passing the
Horticube sheets through a watering tunnel. The sheets should be thoroughly
A single Horticube sheet holds about 4 liters (1 gallon) of water.
However, it takes more than 4 liters of water to ensure total saturation of the
foam because of water channeling through the dibble holes and grooves on the Horticube
sheet. To ensure thorough saturation about 10 liters (2.6 gallons) should be
applied so that the water pours through the bottom of the sheet. As rule of
thumb, water each sheet for 2 minutes at regular tap water pressure.
If the seedlings are going to be irrigated/fertigated by overhead
irrigation, place the Horticube sheets in solid bottom trays with drain holes. Never
use a solid bottom tray without drain holes. If sub-irrigation is going to be
used, place the Horticube sheets in trays that have solid sides and web bottoms.
Like rockwool, the Horticube sheets can be rewetted. Both of these
media should not be allowed to go completely dry between waterings.
Once the Horticubes are thoroughly saturated, the cubes should
stay moist during the course of germination.
Lettuce seed sown in Horticubes does not have to be topdressed
with vermiculite. The seed also does not require a dark treatment for germination.
The best germination usually occurs when the Horticube temperature is below
70°F. The seed usually germinates in two to three days.
and fertilizing seedlings
Generally lettuce seedlings in Horticubes do not require misting
or watering during germination. However, on bright hot summer days consider a
brief misting (5 seconds once a day) on Day 2 and Day 3. Apply clear tap water
with no fertilizer.
Once the lettuce seed has germinated the mist frequency needs to
be adjusted. A typical misting program consists of starting from Day 4 to Day
7, three times a day for 10 seconds. From Day 7 to finish, mist four times a
day for 10 seconds. If the seedlings are going to be either hand-watered or on
a sub-irrigation system, irrigate only once a day.
Start fertilizing the seedlings on Day 4. All of the different
nutrient formulations developed for lettuce production will work with
Horticubes. Growers should customize their specific formulations depending on
water supply, lettuce cultivars, production system, climate and season. The
nutrient solution pH should range from 5.5 to 6. The recommended electrical
conductivity during propagation is 1.0 mS/cm. The recommended electrical
conductivity during production is 1.2 to 2.2 mS/cm.
Lettuce seedlings should be ready to transplant 10 to 14 days
after sowing depending on seasonal climate conditions. During summer months it
takes about 10 days from sowing to transplant and during winter months it takes
about14 days. The criteria for transplant are development of two true leaves
and root penetration through the bottom of the Horticubes.
At transplant the pre-scored sheets can be easily separated into
individual cubes. The easiest way is to break the individual cubes from the top
down along the scoring.
and harvest
Lettuce seedlings in Horticubes transplanted into a NFT or raft
system perform equally well. During production the recommended electrical
conductivity of the nutrient solution should be 1.2 to 2.2 mS/cm. With a NFT
system the water flow rate should be 1 to 1.2 liters per minute. Analysis of
the nutrient solution should be done on a regular basis in order to make
formulation adjustments.
Hydroponically-grown lettuce produced in Horticubes can be harvested
with the root system intact. Leaving the root system intact can help to extend
the shelf life of the lettuce.
For more: Smithers-Oasis
North America; (800) 321-8286; www.oasisgrower.com or Hort Americas, LLC at +1 469 532 2383.
Kuack is a freelance technical writer in Fort Worth, Texas, dkuack@gmail.com.
Dr. Vijay Rapaka is Manager—Grower Research, Smithers-Oasis Co., Kent, Ohio, vrapaka@smithersoasis.com.

Visit our corporate website at https://hortamericas.com