Substrates are a key element in hydroponic systems. As growers, we must learn the needs of our hydroponic systems and crops. Crops and hydroponic systems demand particular characteristics from growing substrates. Substrates, along with all environmental variables managed at the root zone level, will have a strong effect on plant growth, development, product quantity, and quality.
Continue reading Free Download: Substrates and Rootzone GuideTag: substrates
Mastering the use of Substrates in Hydroponics
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 launches the award-winning e-Gro software platform in North America
Empowering growers to make data-driven decisions for peak crop performance
Continue reading Grodan launches the award-winning e-Gro software platform in North AmericaWhat 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.
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.
“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.
“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.”
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.
“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.”
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
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!
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
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
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
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
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 = 27 mm
Diameter: 20 & 22 mm
Weight dry = 1 g
Weight saturated = 9 g
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
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
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
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.
Dr. Hugh Poole, international agricultural consultant, said coconut coir is initially high in sodium, potassium and chloride salts.
Poole said some growers are asking suppliers to buffer their coir with calcium nitrate.
“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.
Poole, FloraSynergy; (864) 359-7090; hapoole@Interact2Day.com.
Using Grodan for Lettuce and Herbs
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.
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.
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.
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.
stages in the production process; propagation and final production.
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.
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.
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
|
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.
blocks with lettuce during propagation stage, right picture showing Grodan AO
plug.
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
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.
cubes
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.
(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.
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.
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.
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.
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.
capacity
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.
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.
media should not be allowed to go completely dry between waterings.
stay moist during the course of germination.
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
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.
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.
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.
seedlings
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.
individual cubes. The easiest way is to break the individual cubes from the top
down along the scoring.
and harvest
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.
with the root system intact. Leaving the root system intact can help to extend
the shelf life of the lettuce.
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
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