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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.

 

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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-lettuce-and-herbs

 

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!

 

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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-cubes

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.

Grodan-ax-cubes

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

Grodan-kiem-plugs-in-french-trays

Grodan-kiem-plugs-in-french-trays-individual

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

Grodan-block-delta-dm4g

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

Grodan-block-delta-dm6g

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

Grodan-block-delta-dm9g

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

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

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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
plug.
Conclusion
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://www.hortamericas.com

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Hydroponic Lettuce Production in Phenolic Foam

By
David Kuack and Vijay Rapaka
Inorganic
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
cubes
The
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
percent.
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
saturated.
Water-holding
capacity
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.
Watering
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.
Transplanting
seedlings
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.
Production
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.
David
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://www.hortamericas.com