Water Schedule For Rockwool

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4plant

4plant

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any rockwool growers have a fool proof watering schedule from start to finish? Or at least a strategy that I can follow. I was neglecting my grow over the holidays and over watered the little plants in 4” blocks so much I’ve got root rot issues now. I’ve read a lot of different opinions on frequency vs duration but can’t make up my mind as to what I should follow. I’m currently hand watering 1 litre per 4” cube every 2 days. I would like to automate my feeds with my drippers . Also the 4” blocks will be placed on uni slabs soon. Thanks
 
jumpincactus

jumpincactus

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Remember the Moisture Gradient
Rockwool propagation cubes and slabs are designed to be used together to minimize root disturbance. Excellent moisture holding capacity and good aeration of the root zone are features of rockwool substrates. Irrigation of rockwool is a little different to other solid substrates because of the way the material is manufactured to have just the right degree of moisture gradient, and because it does give quite a limited root zone for plants that eventually grow fairly large. For this reason, rockwool is best irrigated with short, frequent applications of nutrient, with just enough at each irrigation for the rockwool to reach 'field capacity'. Field capacity is a term that means the substrate has drained fully but is still holding a good level of moisture for the plant roots to access until the next irrigation. At each irrigation, there should be some drainage from the rockwool material. However, this doesn't need to be excessive. Even in closed systems where the drainage solution is being collected and reused, it pays not to over-water and not to run the irrigation continuously.

Having around 10-15% of the nutrient solution fed to the plants, drain from the slab at each irrigation is considered to be optimal. This amount of drainage of solution flushes fresh nutrient solution right through the slab without too much wastage and usually keeps the EC in the slab fairly stable. When rockwool is irrigated and allowed to drain naturally, it will then contain 80% nutrient solution, 15% air pore space and 5% rockwool fibers. A typical rockwool tomato growing slab actually holds around four gallons (about 15 liters) of nutrient solution immediately after irrigation, despite the drainage holes allowing free drainage of excess solution. Four gallons is a good reserve of moisture for four plants, so drying down to wilting point could take a long period of time for small plants.

How much solution should be given at each irrigation? Having a drainage collection tray or channel under each slab allows growers to see how much drainage they are getting after each irrigation (even if this has to be poured off and measured in a jug) and the irrigation program can be increased or decreased to keep this at the 10-15% level. By doing this, the amount of solution to be given at each irrigation can be worked through and adjusted as the plants grow. Keep cutting back the irrigation amount until only 10-15% of the solution volume applied drains from the slab, and then the amount of irrigation has been fully adjusted for. How often should nutrient be applied? Rockwool needs small frequent irrigations, particularly under hot or low humidity conditions when the plants are taking up a lot of water. However, the frequency of irrigation can be as low as once per day (or every other day) for small plants under cool conditions, to over 10 times a day for large plants in a hot or dry environment. It can be hard to judge just how much moisture the rockwool material may be holding at any one time to determine when to irrigate. Smaller propagation blocks and even larger cubes can be gently picked up - the weight will soon tell you if the cube is saturated (it will be comparatively heavy and moisture will drip from the wet base), or whether it has dried out considerably, in which case it will feel very light (compare an unused dry cube to one in use).

Rockwool is an unusual material in that, even when the slab has lost 50% of its moisture to plant uptake, the plants are still able to very easily keep extracting water until the slab is almost completely dry - so plants in rockwool can't get water stressed until the rockwool is almost completely dry, by which time the cube or slab has become much lighter in weight. For granulated rockwool in pots or containers, a similar method can be used, either by gently lifting the pot to see what the weight might be (a light pot is a dry pot) or by a light tap or kick: if the pot moves, the rockwool has become quite light and potentially too dry. Another method to try and gauge the moisture status of the rockwool and how often to irrigate is to carefully remove a small piece of the wrapper plastic and examine the moisture gradient of the slab from top to bottom.

Like all growing media, moisture in rockwool can be gauged manually. Lightly touching or pressing the rockwool at the base of the slab will soon determine if there is still a good level of nutrient held in the base of the slab or whether it has become too dry. The top and middle layers of the slab should always appear drier than the base where the reservoir of moisture is naturally held, so only the base of the slab should be checked. Even if the top of the slab appears to be dry, this is not important as the moisture gradient has been designed to give these sorts of root zone conditions - only ensure the base of the slab has sufficient moisture. This process of working out how much moisture is still in the rockwool material is not something that needs to be done for long. Growers will soon become quite skilled at working out their frequency and amount of irrigation for each stage of plant growth and may only need to do this for their first crop provided growing conditions remain stable. Other times when it might be important to have a quick check of the amount of solution drainage or amount of moisture in the slab is when conditions suddenly change - addition of more grow lamps, sudden changes in temperature or humidity, or rapid growth spurts can all change the irrigation requirements of the plants. Generally, good brands of rockwool are quite forgiving compared to other substrates - the material is naturally well aerated and doesn't suffer the compaction issues that some substrates do during the life of the crop. It does hold high levels of moisture, so the chance of drying out is not as severe as it might be with other substrates and being sterile gives young plants, seedlings and cuttings an advantage as well. The irrigation program and water holding capacity of the substrate depends on the fiber density and arrangement, which can differ from brand to brand.
 
4plant

4plant

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He could write for max yield. I guess I’m trying to find out weather light frequent waterings vs less frequent drenching are preferable. In the past I’ve had to really drench promix to avoid salt build ups.
 
DieselDuds

DieselDuds

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He could write for max yield. I guess I’m trying to find out weather light frequent waterings vs less frequent drenching are preferable. In the past I’ve had to really drench promix to avoid salt build ups.

I grow with rockwool and I have a digital timer that I can set to run for 1 second to 20 seconds to and hr. Measure how many ml the pump pushes and count how many seconds it takes to fill the ml amount and you should be good
 
jumpincactus

jumpincactus

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He could write for max yield. I guess I’m trying to find out weather light frequent waterings vs less frequent drenching are preferable. In the past I’ve had to really drench promix to avoid salt build ups.
how did you know my middle name is "max yield" LOL just kidding fellas.
 
DieselDuds

DieselDuds

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Oh yeah. And no there isn't no magic number that you can start with and finish with. You have to adjust as the plant grows and each plant is different
 
4plant

4plant

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I think I’ll try for 10-15% runoff and wait until I get 75% dryback. I have some FloraFlex caps coming this week that should help water more evenly and keep that algae away.
 
jumpincactus

jumpincactus

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He could write for max yield. I guess I’m trying to find out weather light frequent waterings vs less frequent drenching are preferable. In the past I’ve had to really drench promix to avoid salt build ups.
I didn't write that. Just sharing some one elses work. I don't have a link for the source it was
Oh yeah. And no there isn't no magic number that you can start with and finish with. You have to adjust as the plant grows and each plant is different
yes sir each strain and or pheno will have different nute requirements and moisture levels. What may be too much water for one may not be enough for another.

This is one reason I profess that to be master grower level, one needs to fight the urge to pop flavors of the month and muckle on to a few favorite strains and get to know thy ladies inside and out. This with taking notes is the only good way to run multiple strains and limit your headaches with a varied strain run. Then you can run a group of genetics that you know have the same requirements and how finicky each strain is. Just sayn.
 
DieselDuds

DieselDuds

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I didn't write that. Just sharing some one elses work. I don't have a link for the source it was

yes sir each strain and or pheno will have different nute requirements and moisture levels. What may be too much water for one may not be enough for another.

This is one reason I profess that to be master grower level, one needs to fight the urge to pop flavors of the month and muckle on to a few favorite strains and get to know thy ladies inside and out. This with taking notes is the only good way to run multiple strains and limit your headaches with a varied strain run. Then you can run a group of genetics that you know have the same requirements and how finicky each strain is. Just sayn.

With what you said , how does one know if a plant likes or dislikes a certain humidity or heat. I would tend to think a northern strain can handle more water, and colder temps where a southern strain likes a drier soil and more humid climates. Does a strains lineage hint twards where it the location it originated from ? With ice cream , cake, dosi ? It's not like jamician red or afghani kush . Those names would indicate the region it originated from.
 
4plant

4plant

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Last night I hand watered to find how much it takes to achieve 10% runoff and I was surprised that it only took 1 litre. I’ll wait until I’ve hit about 50-70% dryback and away we go. Also I have the 4” blocks on unislabs now with 4 drainage slits cut in each.
 
jumpincactus

jumpincactus

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With what you said , how does one know if a plant likes or dislikes a certain humidity or heat. I would tend to think a northern strain can handle more water, and colder temps where a southern strain likes a drier soil and more humid climates. Does a strains lineage hint twards where it the location it originated from ? With ice cream , cake, dosi ? It's not like jamician red or afghani kush . Those names would indicate the region it originated from.
from a genetics standpoint, a plant will slowly alter its genetic makeup over time based on the environment it is bred in. This may take many generations to happen. So a landrace equatorial thai sativa that thrived in very moist hot conditions over time depending on where that genotype was continually bred will slowly adapt to its new environmental conditions. Now how long that takes is a mystery to me. That would be a question for a geneticist that works in botany. In closing even tho you may have say afghani based genetics, how long has the strain been worked away from its landrace origin. So if it was once used to hot dry more arid conditions after many generations of being bred either indoors or in much different environmental conditions its needs and what makes it thrive will be different. I hope that made sense.
 
DieselDuds

DieselDuds

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from a genetics standpoint, a plant will slowly alter its genetic makeup over time based on the environment it is bred in. This may take many generations to happen. So a landrace equatorial thai sativa that thrived in very moist hot conditions over time depending on where that genotype was continually bred will slowly adapt to its new environmental conditions. Now how long that takes is a mystery to me. That would be a question for a geneticist that works in botany. In closing even tho you may have say afghani based genetics, how long has the strain been worked away from its landrace origin. So if it was once used to hot dry more arid conditions after many generations of being bred either indoors or in much different environmental conditions its needs and what makes it thrive will be different. I hope that made sense.


Good point. Thank you
 
4plant

4plant

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Have you ever noticed in your own rooms certain conditions may bring out different tendencies in plants as well?I’ve grown plants advertised as 100% Indica End up with more of a hybrid look and results to them. even growing 80% sativa’s directly beside 80% Indicas i have noticed they kind of end up quite similar although you can tell the difference It’s not as dramatic as I was expecting
 
jumpincactus

jumpincactus

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Have you ever noticed in your own rooms certain conditions may bring out different tendencies in plants as well?I’ve grown plants advertised as 100% Indica End up with more of a hybrid look and results to them. even growing 80% sativa’s directly beside 80% Indicas i have noticed they kind of end up quite similar although you can tell the difference It’s not as dramatic as I was expecting
indeed.
 
S

SUNHOUSE

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I hope this helps: Our drip system basically goes:
In Veg we like to get to roughly 70% wc and dry back to 50% (Start watering 1-2 hours after lights turn on & last feed 2-3 hours before lights turn off)
In Flower we get to about 60% wc and dry back to 35-40% (Start 1-2 hours after lights turn on & last feed 3-4 hours before lights turn off)
- approx. 100 - 105ml shots but depends on the number and length of feeds you prefer.

The chart below shows how the block water content should look. I always check mid day for a small run off.
1559317152257
 
Joeguy1010

Joeguy1010

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I hope this helps: Our drip system basically goes:
In Veg we like to get to roughly 70% wc and dry back to 50% (Start watering 1-2 hours after lights turn on & last feed 2-3 hours before lights turn off)
In Flower we get to about 60% wc and dry back to 35-40% (Start 1-2 hours after lights turn on & last feed 3-4 hours before lights turn off)
- approx. 100 - 105ml shots but depends on the number and length of feeds you prefer.

The chart below shows how the block water content should look. I always check mid day for a small run off.
View attachment 873179
What benifits do u see with this method vs just waiting until your desired WC. Then watering until runoff? Also, where did you come up with 100ml seems calculated
 
nicolajanjak

nicolajanjak

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What benifits do u see with this method vs just waiting until your desired WC. Then watering until runoff? Also, where did you come up with 100ml seems calculated

100ml correspond to 3% of the volume of a 6x6 block .. "dose size" from 2% to 6% must be used

2% in veg, 3% stretch, flower 4% and 6 % near the end .. bigger the dose size bigger the drydowns between the feeds (not the same as night dryback, during the day the medium is kept wetter )

if you work with slabs it's easy to calculate it too ..

it's part of the steering

60 % Water content at saturation for bloom ..with 20/25% dryback during night .. which make around 35-40% water content the morning before first irrigation
(for those who dont have meters 35% WC is pretty light, not dry but light)

if everything is well tuned first irrigation will happen 2/3 hours afters lights on, and first runoof will happen around midday, not before ( too early)
 
MrMackey

MrMackey

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Digging up an old thread here but seems some very knowledgeable people on the matter (hope your still around to comment) I’m looking at doing a small rock wall grow I’ve only got experience in nft and coco so far I want to try my hand at top fed 6” cubes in my small space 2.3m x 1.5m ground space only 1.6m height from floor to led I’m looking for a recommendation on how many plants I should run? And what sort of setup to sit them in like do they need some kind of root matting in a tray or just sit the cubes straight in? I plan on doing run to waste for less chance of nute/salt issues any pointers will be greatly appreciated
 
PpmOver9000

PpmOver9000

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I hope this helps: Our drip system basically goes:
In Veg we like to get to roughly 70% wc and dry back to 50% (Start watering 1-2 hours after lights turn on & last feed 2-3 hours before lights turn off)
In Flower we get to about 60% wc and dry back to 35-40% (Start 1-2 hours after lights turn on & last feed 3-4 hours before lights turn off)
- approx. 100 - 105ml shots but depends on the number and length of feeds you prefer.

The chart below shows how the block water content should look. I always check mid day for a small run off.
View attachment 873179

What are those grids underneath the rockwool cubes? Seems like a great addition considering the root mat that always happens in rockwool.
 
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