Is there scientific proof that growing on mineral wool is more efficient in use of fertilizers than in soil or in organic substrates?
Continue reading Grodan new whitepaper on mineral wool efficiency
Continue reading Grodan new whitepaper on mineral wool efficiency
By Karla Garcia and Deidre Hughes
Substrates are a key element in hydroponic systems. As growers, we must learn the needs of the hydroponic system and crop. Crops and hydroponic systems demand particular characteristics from growing substrates.
Continue reading Mastering the use of Substrates in HydroponicsGrodan 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.
“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.
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!
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.
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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.
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
6,000 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
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
6,000 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
Kiem Plugs in French Trays
# per tray = 240 (12 x 20)
Height = 2.1 cm
Dry weight = 1 g
Kiem Plugs
Height = 27 mm
Diameter: 20 & 22 mm
Weight dry = 1 g
Weight saturated = 9 g
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
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
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
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 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
Table 1. Indicative weights to irrigate the
blocks or AO sheets. |
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Grodan product
|
Approximate substrate volume
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Indicative weight to base irrigation on (±60% WC)
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MM 40/40
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64 ml per block
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40 gram per block
|
AO 36/40
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40 ml per plug
3926ml per sheet
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24 gram per plug
2.4 kg per sheet
|
For more information
contact Hort Americas at 469-532-2383 or customerservice@hortamericas.com
Visit our corporate website at https://hortamericas.com
Visit our corporate website at https://hortamericas.com
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