passive plant killer

[delta9nxs]

I got a question for all you PPK Pros. When you install the sink tailpiece in the bottom of your media container, with the plumbers goop it ends up sticking up about 1/8-1/4" of an inch from the bottom of the container. Does this little lip create a second mini water table inside of the pot? And if so why not?

Is it beneficial to have an additional say 3/16" drain hole next to the tailpiece to eliminate any water that would collect there?

howdy! the lip on the tailpieces is less than 1/8". if the liquid did not drain the plant would suck it up very fast after the perched water table is removed.

but it does drain. the capillary action of the medium will drain most of it over the lip as the pwt is removed.

this is an aspect of this device that is often forgotten about or overlooked.

there is a continuous hydraulic hook up throughout the device. and the pwt, as it drains, actually pulls excess water out.

we are forming a siphon temporarily.

 

[delta9nxs]

hey, mcfly! air filled porosity should be tuned to mode of watering.

that 8% will not be sufficient for a heavy pulse.

i think 8% and the finer medium is ideal for space and low gravity sealed environments that are being supplied by capillary action only.

but for high growth rates with cannabis in this device you really need a much higher air filled porosity.

i currently run a 35% mix.

in my current grow i have been pulsing 45 sec every 45 min. about 56 oz's.

last week as i switched to flower the liquid began overflowing some of the containers with the 3/4" holes. same volume same medium.

so i dialed the pulse down 5 seconds. overflow stopped.

last night i got a slight overflow from one container and dialed it down another 5 seconds. again the overflow stopped.

what this tells me is that the air filled porosity is being reduced by root growth.

i feel this continues until the end of stretch, when most root growth is done.

at that point i will adjust the interval to the volume so that no overflow occurs.

i am looking forward to containers that i can run with a 5-6" medium depth with no holes.

nasa is real happy just to keep a plant alive. we need to exceed that criteria for commercial cannabis yield.

 

[delta9nxs]

Nope...

[URL=https://www.icmag.com/ic/picture.php?albumid=20719&pictureid=519722&thumb=1]View Image[/URL]

hey!

 

[real ting]

Oldone that pic is crazy :0 Where the roots that hit the reservoir rotting?

howdy! the lip on the tailpieces is less than 1/8". if the liquid did not drain the plant would suck it up very fast after the perched water table is removed.

but it does drain. the capillary action of the medium will drain most of it over the lip as the pwt is removed.

this is an aspect of this device that is often forgotten about or overlooked.

there is a continuous hydraulic hook up throughout the device. and the pwt, as it drains, actually pulls excess water out.

we are forming a siphon temporarily.

Thanks man, that clears it up. So the wicking action is working both ways, up and down?

hey, mcfly! air filled porosity should be tuned to mode of watering.

that 8% will not be sufficient for a heavy pulse.

i think 8% and the finer medium is ideal for space and low gravity sealed environments that are being supplied by capillary action only.

but for high growth rates with cannabis in this device you really need a much higher air filled porosity.

i currently run a 35% mix.

in my current grow i have been pulsing 45 sec every 45 min. about 56 oz's.

last week as i switched to flower the liquid began overflowing some of the containers with the 3/4" holes. same volume same medium.

so i dialed the pulse down 5 seconds. overflow stopped.

last night i got a slight overflow from one container and dialed it down another 5 seconds. again the overflow stopped.

what this tells me is that the air filled porosity is being reduced by root growth.

i feel this continues until the end of stretch, when most root growth is done.

at that point i will adjust the interval to the volume so that no overflow occurs.

i am looking forward to containers that i can run with a 5-6" medium depth with no holes.

nasa is real happy just to keep a plant alive. we need to exceed that criteria for commercial cannabis yield.

D9, is there an easy way to test the air porosity of your custom medium mix?

edit: on other question, do you mean overflowing over the lid of the container, or overflow coming out of the 3/4" drain holes instead of draining through the tail piece?

 

[zeke99]

D9, is there an easy way to test the air porosity of your custom medium mix?

I've been waiting for an opportunity to post this. It may or may not be the same method that Delta9 uses.

It's Greenhouse Grower mag. with another fantastic article.

Predicting Plant Water Uptake

Find out exactly how plants take up water from substrates and which factors affect water uptake most.

March 6, 2012
By Stephanie Burnett, Marc Van Iersel, Jongyun Kim

• To calculate the container capacity of your substrate, fill a container with dry substrate and seal the container holes. Once you measure the amount of water you need to add to completely fill the container, place the container over a catch basin and remove the seals. Allow the container to drain for one hour and measure the amount of water that drained from the substrate. The container capacity is: (volume to saturate-drainage) divided by volume of container. Then, multiply that figure by 100 percent.
• The total pore space can be calculated by dividing the amount of water needed to fill the container by the total container volume.
• Finally, air space can be calculated as total porosity minus container capacity...

air space = air filled porosity

 

[Snook]

D9, yure still the man. I feel like the last few pages are dejavu, posts from much earlier in this thread... I've given up on the rice hulls and going with straight NAPA 8822... it's easier, cheaper and I feel like the juice passes thru quicker.... Working on the environment. I tried verticle w cooltube again, had a hard time controlling temps ??? dono why.. took off the intake, from outside the tent, from the cooltube and temps droped back into line. Once you go 'Jacks' you'll never go backs..

 

[oldone]

Oldone that pic is crazy :0 Where the roots that hit the reservoir rotting?

It didnt stink and the plant looked good. The prevailing opinion was that it was FNB sludge.

OO

 

[mcfly420]

well about that 8%
Mercury porosimetry yielded total porosities of 73% for 0.25-1mm and 75% for 1-2mm aggregate. These were similiar to those calculated from the bulk and particle density. Saturated volumetric water contents (water filled porosity) were 65-67% for both particle distributions, somewhat less than the total porosity. This resulted in an air filled porosity at saturation of 8-9% for 0.25-1mm and 6-8% for 1-2mm.
but 6cm of medium+drip watering, Profile has 13% air filled porosity and Turface has 20%.

I know there are many reasons you chose your medium for pulsing. My new containers are 17cm high though and the combo of height/watering onceaday makes Profile look like a good option. I´ve never had a plant suddenly wilt in turface and the few times I did let a plant dry out it took days. The charts do show transpiration rates dropping after only a few hours (no wicks/water table). Im also hoping the smaller particles wont get trapped in the dense roots and a quick dip in water will produce a clean, intact, not dry rootball. At least I got high...umm...hopes

Making them overflow out the top is alot more impressive than the side.

 

[real ting]

I've been waiting for an opportunity to post this. It may or may not be the same method that Delta9 uses.

It's Greenhouse Grower mag. with another fantastic article.

Predicting Plant Water Uptake

Find out exactly how plants take up water from substrates and which factors affect water uptake most.

March 6, 2012
By Stephanie Burnett, Marc Van Iersel, Jongyun Kim

• To calculate the container capacity of your substrate, fill a container with dry substrate and seal the container holes. Once you measure the amount of water you need to add to completely fill the container, place the container over a catch basin and remove the seals. Allow the container to drain for one hour and measure the amount of water that drained from the substrate. The container capacity is: (volume to saturate-drainage) divided by volume of container. Then, multiply that figure by 100 percent.
• The total pore space can be calculated by dividing the amount of water needed to fill the container by the total container volume.
• Finally, air space can be calculated as total porosity minus container capacity...

air space = air filled porosity

Great post, I'm definitely gonna try this out before filling up my final flowering ppks. I'm thinking I will continue with a perlite/coco mix, about 3/1. This method will help me tweak it to the desired 35% air space. I'll try turface/rice hulls next round when I can have plants that were in it start to finish, as I don't believe I'd get as much of the benefit(mainly insect and fungus gnat resistance) with coco cored turface/ricehull plants.

One question I have about this method, the ppks effectively have a higher air percentage in the medium than regular pots, right? Basically what I'm saying is if you quote a medium as having 35% air space, it would not achieve that in a traditional drip setup, due to the perched water table taking up more of the air space, is that correct?

Which would mean to get the right numbers for that test I'll have to include a wick to drain out the water when doing the 1 hour drain.

 

[delta9nxs]

Oldone that pic is crazy :0 Where the roots that hit the reservoir rotting?



Thanks man, that clears it up. So the wicking action is working both ways, up and down?



D9, is there an easy way to test the air porosity of your custom medium mix?

edit: on other question, do you mean overflowing over the lid of the container, or overflow coming out of the 3/4" drain holes instead of draining through the tail piece?

yes, the wicking action works both ways. it can both feed and drain depending on how you operate it.

i personally like to see at least some drip from the float valve resume before the next pulse hits.

this is in addition to the drip that occurs immediately following a pulse. you will get a drip until equilibrium occurs. then it will stop for a while. if you wait long enough a drip will start again as the plants resume pulling moisture from the reservoirs.

and yes, by overflow i mean the sidewall holes. my next grow won't have them as i will run a more shallow medium.

 

[delta9nxs]

D9, yure still the man. I feel like the last few pages are dejavu, posts from much earlier in this thread... I've given up on the rice hulls and going with straight NAPA 8822... it's easier, cheaper and I feel like the juice passes thru quicker.... Working on the environment. I tried verticle w cooltube again, had a hard time controlling temps ??? dono why.. took off the intake, from outside the tent, from the cooltube and temps droped back into line. Once you go 'Jacks' you'll never go backs..

hey, whatever works for you! i still haven't tried the napa stuff but i will someday. it probably will turn out to be more stable chemically than turface if we can ever get an analysis.

i grew a lot of plants hand watered in straight turface and it was great for once per day watering.

later

 

[delta9nxs]

well about that 8%
Mercury porosimetry yielded total porosities of 73% for 0.25-1mm and 75% for 1-2mm aggregate. These were similiar to those calculated from the bulk and particle density. Saturated volumetric water contents (water filled porosity) were 65-67% for both particle distributions, somewhat less than the total porosity. This resulted in an air filled porosity at saturation of 8-9% for 0.25-1mm and 6-8% for 1-2mm.
but 6cm of medium+drip watering, Profile has 13% air filled porosity and Turface has 20%.

I know there are many reasons you chose your medium for pulsing. My new containers are 17cm high though and the combo of height/watering onceaday makes Profile look like a good option. I´ve never had a plant suddenly wilt in turface and the few times I did let a plant dry out it took days. The charts do show transpiration rates dropping after only a few hours (no wicks/water table). Im also hoping the smaller particles wont get trapped in the dense roots and a quick dip in water will produce a clean, intact, not dry rootball. At least I got high...umm...hopes

Making them overflow out the top is alot more impressive than the side.

hey, mcfly, for some reason i thought you were talking about pulsing, sorry. turface or profile will hold a lot of water for a long time. it's has a great safety margin if used alone and is unbeatable for reliability used as a media wick.

i've got some clones in turface that i decided to eliminate and just pulled them aside and quit watering them. it's been about a week and they are finally going down.

 

[delta9nxs]

Great post, I'm definitely gonna try this out before filling up my final flowering ppks. I'm thinking I will continue with a perlite/coco mix, about 3/1. This method will help me tweak it to the desired 35% air space. I'll try turface/rice hulls next round when I can have plants that were in it start to finish, as I don't believe I'd get as much of the benefit(mainly insect and fungus gnat resistance) with coco cored turface/ricehull plants.

One question I have about this method, the ppks effectively have a higher air percentage in the medium than regular pots, right? Basically what I'm saying is if you quote a medium as having 35% air space, it would not achieve that in a traditional drip setup, due to the perched water table taking up more of the air space, is that correct?

Which would mean to get the right numbers for that test I'll have to include a wick to drain out the water when doing the 1 hour drain.

yes, if your test container retains the perched water table it is not a valid test. try tilting the container and sticking a toothpick up into the hole. you can get enough to run out to get a fast general idea.

 

[mcfly420]

 

[real ting]

yes, the wicking action works both ways. it can both feed and drain depending on how you operate it.

i personally like to see at least some drip from the float valve resume before the next pulse hits.

this is in addition to the drip that occurs immediately following a pulse. you will get a drip until equilibrium occurs. then it will stop for a while. if you wait long enough a drip will start again as the plants resume pulling moisture from the reservoirs.

and yes, by overflow i mean the sidewall holes. my next grow won't have them as i will run a more shallow medium.

Thanks again, all the tips are invaluable.

Interesting. I've just built a few ppks out of these 10 gal rugged totes available at lowes. http://centrexplastics.com/2011/10/10-gallon-rugged-tote/
If you ran these with around 5" or less of medium it would most likely be around 3.5-5 gallons of medium, and you'd have a really low profile ppk, especially if you cut the top container down.

Now I'm thinking about plugging up the 3/4" air holes and trying out a saturation pulse.

 

[zeke99]

Great post, I'm definitely gonna try this out before filling up my final flowering ppks. I'm thinking I will continue with a perlite/coco mix, about 3/1. This method will help me tweak it to the desired 35% air space. I'll try turface/rice hulls next round when I can have plants that were in it start to finish, as I don't believe I'd get as much of the benefit(mainly insect and fungus gnat resistance) with coco cored turface/ricehull plants.

One question I have about this method, the ppks effectively have a higher air percentage in the medium than regular pots, right? Basically what I'm saying is if you quote a medium as having 35% air space, it would not achieve that in a traditional drip setup, due to the perched water table taking up more of the air space, is that correct?

Which would mean to get the right numbers for that test I'll have to include a wick to drain out the water when doing the 1 hour drain.

3:1 is a good place to start, depending on the coco and the perlite, you might end up at 2:1.

yes, if your test container retains the perched water table it is not a valid test. try tilting the container and sticking a toothpick up into the hole. you can get enough to run out to get a fast general idea.

Styrofoam coffee cup!

 

[delta9nxs]

[URL=https://www.icmag.com/ic/picture.php?albumid=34789&pictureid=935939]View Image[/URL]

View Image

good morning! could you please post a comment with these so i can better understand your point?

thank you!

 

[delta9nxs]

Thanks again, all the tips are invaluable.

Interesting. I've just built a few ppks out of these 10 gal rugged totes available at lowes. http://centrexplastics.com/2011/10/10-gallon-rugged-tote/
If you ran these with around 5" or less of medium it would most likely be around 3.5-5 gallons of medium, and you'd have a really low profile ppk, especially if you cut the top container down.

Now I'm thinking about plugging up the 3/4" air holes and trying out a saturation pulse.

using their inside dimensions i get 5.7 gals at 5". that's a lot of medium! sufficient for an 8 week veg or more.

 

[mcfly420]

Good morning indeed, finally had some rain/flood and the big fish were hungry

Porosity of the material ≈74% for both 0.25 – 1 mm and 1 – 2 mm aggregates, ~50% of which is intra-aggregate micropores and ~50% is inter-aggregate pores. Ceramic media has been intensively modeled for physical and hydraulic properties. Soil physical models suggest retention of plant-available water in ceramic media up to heights of approximately 20 cm, with high water retention low in the root-zone and abrupt shifts to dry conditions occurring at heights related to particle-size distribution. This characteristic may lead to a narrow range in which air to water ratios are optimal for plant growth within the root-zone. The models suggest that the abruptness of this shift to dry conditions may be lessened by broadening particle-size distribution. While much research has been done to characterize and model the physical and hydraulic properties of ceramic media, plant growth studies in the media to verify the models have been limited. The media was put into containers with an approximate volume of 2700 cm3 (19 cm x 16 cm x 9cm (lwh)). Four radishes were planted per container and grown to a harvestable size. To begin measurements, the containers were sub-irrigated by maintaining a depth of 1 cm of water in the bottom of each container, allowing the media to come to a water content equilibrium. This watering method allowed for differences in plant-available water to be apparent based on the unique level of capillary rise active in each media, in a container of typical to shallow height for plant growth (9 cm). Once watered, the containers were drained, bringing them to “container capacity” water contents. Each container was placed on a balance which output to a Campbell’s Scientific CR1000 datalogger. A datalogger program was written which calculated a rate of transpiration from changes in mass recorded by the balances over time ((massinitial – massfinal) / (timeinitial – timefinal). Values of transpiration in units of g min-1 were converted to units of ml min-1 (1.0 g water = 1.0 ml). Plant-available water was determined by summing the water use by the plants until transpiration fell to 33% of its maximum rate during each dry down. 33% was chosen because this was a point observed to immediately precede plant wilting. The rate of transpiration was monitored instantaneously on a computer screen and the plants were removed from the balances and watered near their wilting points for a second dry-down, following the same procedure.


Work by Heinse et al. (2007) shows the differences in water retention in ceramic media as particle size distribution is altered as a function of height or matric potential. Figure 5 – 2 shows how height is of central importance to the use of ceramic media for plant growth. Wet conditions exist at low heights in the media and rapid losses in water content occur at heights uniquely related to particle size distribution. As the height of the system is increased and water in the macropore network has drained away, it is increasingly difficult to sustain productive plant growth. Heinse’s data shows an approximately 37% decease in water contents under the narrow matric potential ranges of 0 to 10 cm for 1 – 2 mm ceramic media, and 0 to 20 cm for 0.25 – 1 mm and 0.25 – 2 mm ceramic media. Matric potentials of 0 to 20 cm are far below the permanent wilting point (-1.5 MPa or -15,000 cm) at which plants cannot extract water. Since total media porosity has been shown to be ~74%, 50% of which (37%) inter-aggregate macropores, this result suggests that plant-available water is only found in the inter-aggregate macropores, with minimal micropore water plant-available. The result found in this study of 37% plant-available water in 0.25 – 1 mm ceramic media seems to substantiate this conclusion and the results of Heinse’s work. The values found in this study of 19% plant-available water for 1 – 2 mm and 29% for 0.25 – 2 mm ceramic suggest that, even at the shallow root-zone height of 9 cm, plant-available water was diminished by limited capillary rise in these coarser media. With the assumption that no intra-aggregate micropore water is plant-available, if the areas under the curves from Figure 5 – 2 (from saturation to the point at which matric potential rapidly increases with little change in volumetric water content) are integrated over heights of interest, a value for plant-available water may be obtained. To compare with the results of our test, the curves were integrated from 0 to 9 cm heights (Table 5 –1). In general, values of plant-available water determined in our procedure were intermediate between predicted values obtained from the wetting and draining water retention curves of Figure 5 – 2, the exception being 0.25 – 1 mm ceramic, which matched the water retention curve value for draining. This result suggests that Heinse’s water retention curves may be used to predict ceramic media plant-available water with varying root-zone height, with the margin of error being the values determined by wetting and draining curves.

should be able to help people make height/particle decisions for wick/handwater, pulsing is another thing

 

[real ting]

using their inside dimensions i get 5.7 gals at 5". that's a lot of medium! sufficient for an 8 week veg or more.

Yes, that sounds about right. The containers are sloped inwards towards the bottom so maybe just slightly less. Luckily (or not so luckily as things might be) this round has been delayed, so the plants I'm using will have been vegging for more like 12 weeks by the time they are flipped. But since there is a separate veg setup, and I'm going for 4 trees in a 5 bulb diamond room, 8 weeks may be a good length of time for turnover in the long run.

One of the reasons I went with the totes is for the lower profile, I wanted to do 3.5 gal buckets but the height was just too much for the space I'm working with. I'm curious to see how the ppks will do in a KBS/heath style room. Any one of you talented growers in here can and have pushed the idea much further, but I'm still stoked to give it a go

When you cite your veg times are you talking about time from when the plant is a rooted clone to flipping, or do you mean 8 weeks time vegging in the flowering room before flip? I'm asking because I noticed in your wicked pulse thread you have vegged the plants in place to fill out the screen.