[Dave Coulier]

Originally Posted by stihgnobevoli

Very excellent experiment dave. But i'm afraid you original premise was a bit off. The old rule isn't "Don't feed your seedlings till after week 2" it's "Seedlings don't need food till after the cotyledons start to yellow and fall off which usually takes up to week 2."

if you look at your pics. around Day 11 seems to be when the feeding started making a difference. which would most likely be when the cotyledons ran out of food. you actually proved the old adage true.

But at the same time you have provided a wealth of information as to how much food you can start your seedlings off with.

Thanks very much for the experiment.

Thanks for stopping in Stihgn. Im glad you enjoyed the experiment. Your right it did take little awhile before the feedings to begin making a difference. It may have something to do with the cotyledons being able to provide enough food up until that point, but I still am going to be feeding before I see any yellowing of the cotyledons.

Nutrient deficiencies often are present before we ever see them, and as well all know Its better to prevent a problem from occuring than treat the problem after it occurs.

I have some future experiments going through my mind. Once I settle on one, Ill make another fun thread for us to enjoy and hopefully learn something.

Till next time folks.

[Waldgeist]

Hello Dave!

Thanks for sharing this intresting experiment.


'MEDIA: Promix Bx w/bio-fungicide. Amended with 15% Axis Regular and Bioworks Rootshield Plus were my only amendments.

FERTILIZER:
The non-control seedlings were fertigated on a near daily basis using GH 3 Part Flora series, Agsil 16h and Sequestrene 138. The control received RO water only on nearly a daily basis.'

I have some questions,

-Why do you feed RO water instead of tap to the control group?
-Did you mix the nutrient solutions also with RO water?
-Does the mentioned media in its actual amended stage contain any nutrients at all?
-Did you Ph the RO water? Did you Ph the nute solutions?
-Is the irrigation schedule for all plants in the experiment the same, or did you irrigate every plant to its individual needs?

you mentioned a 'nearly' daily basis for irrigation, judging from the pictures of the control group, the plants seem overwatered and have slight PH issues.

I like the experiment, but I think it will be much more intresting when you would repeat it with a hydroponic sterile media like rockwool or perlite and provide a minimal amount of micro nutrients to the control group. no plant grows nice with RO water only in an (almost)unfertilized (soil-type)media.
RO water is soft water. Soft water is "water with a low concentration of dissolved minerals" and since RO units can remove up to 99% of the dissolved minerals in water, then of course they make soft water. Soft water has less buffer and allows for easier manipulation of pH as well.
Never use just plain old RO water for plants as it is severaly lacking in trace elements! Always add back in the desired elements.

thx

[Dave Coulier]

Originally Posted by Waldgeist

Hello Dave!

Thanks for sharing this intresting experiment.


'MEDIA: Promix Bx w/bio-fungicide. Amended with 15% Axis Regular and Bioworks Rootshield Plus were my only amendments.

FERTILIZER:
The non-control seedlings were fertigated on a near daily basis using GH 3 Part Flora series, Agsil 16h and Sequestrene 138. The control received RO water only on nearly a daily basis.'

I have some questions,

-Why do you feed RO water instead of tap to the control group?
-Did you mix the nutrient solutions also with RO water?
-Does the mentioned media in its actual amended stage contain any nutrients at all?
-Did you Ph the RO water? Did you Ph the nute solutions?
-Is the irrigation schedule for all plants in the experiment the same, or did you irrigate every plant to its individual needs?

you mentioned a 'nearly' daily basis for irrigation, judging from the pictures of the control group, the plants seem overwatered and have slight PH issues.

I like the experiment, but I think it will be much more intresting when you would repeat it with a hydroponic sterile media like rockwool or perlite and provide a minimal amount of micro nutrients to the control group. no plant grows nice with RO water only in an (almost)unfertilized (soil-type)media.
RO water is soft water. Soft water is "water with a low concentration of dissolved minerals" and since RO units can remove up to 99% of the dissolved minerals in water, then of course they make soft water. Soft water has less buffer and allows for easier manipulation of pH as well.
Never use just plain old RO water for plants as it is severaly lacking in trace elements! Always add back in the desired elements.

thx

1.) The reason the control group got RO water over Tap is because tap would have provided nutrients to the control group, mostly Ca & Mg. I wanted to see the comparison between plants fed nutrients and those that received none, hence RO. I think giving them Tap water would have made the comparison harder to gauge.

2.) Yes, I always use RO water as my base for adding my nutrients too.

3.) The medium didn't have any extra added nutrients to it, and that goes back to #1. Having nutrients beyond the starter charge provided by Promix, would again have made it more difficult to gauge any results.

4.) I start with RO water, add my fertilizers and if ph isn't 5.5-6.0 Ill adjust.

5.) Irrigation schedule at first was pretty much exactly the same between all 3 groups for the first 7-10 days. After the differences in growth became apparent, the control group did require less water to meet their needs.

As for pH issues, Ive never encountered a pH issue within the first 3 weeks. If there is an issue with pH its always been later in flowering. 3 weeks is too early to experience issues with pH when RO water is used(no alkalinity to increase media pH), no fertilizer to cause reactions in the media that would affect pH. So I believe the pH of the media was likely to be the same or very close from day one to day 21 of the control group. The other's would be more likely to experience any pH shift as they received fertilizer.

Also Calcined DE along with Calcined Clays do an good job of helping buffer media pH. So to sum it up, I dont think theres any way pH shift lead to the decline of the control group.

As for over-watering, quite frankly Im kinda offended by that. I utitize pulse watering when I water by hand, and there is NO chance of over-watering if done correctly. Over-watering generally requires at least some leaching to occur. None of these plants in any group ever experienced run-off. Even at container capacity, I have faith in my media's properties to ensure enough air porosity.

I think to most people its clear those plants are stunted because they never received any N let alone any nutrients, rather than it being a ph shift and over-watering issue. After 3 weeks and no nutrients, the EC level in the media was at such a low level no vigorous growth was possible.

I hate rockwool, and perlite is only used because its in Promix. Id much rather not use it either. Any experiments I do will always be in a soil-less media. If someone else would like to replicate this with rockwool I would gladly tune in, but it wont be me doing that experiment.

One thing I wish I had done during this was to take weekly EC and pH measurements, but my suction lysimeters are too tall to fit under the T5. I think that data would quell any concerns you may have over this experiment. In the future I will try and make that a reality.

Ive reconsidered doing this same experiment but starting with nutrients provided even earlier to see if I can coax out some faster growth. Day 1 or 2. My GN Thai Sticks had no problems being fed 160N on Day 1 or 2 from seed, and they took off quickly.

I do appreciate the post and feedback. No experiment should be exempt from criticism, but its up each individual reader to determine If I have demonstrated/proved my original hypothesis to the point of credibility.

[stihgnobevoli]

Originally Posted by Dave Coulier

Nutrient deficiencies often are present before we ever see them, and as well all know Its better to prevent a problem from occuring than treat the problem after it occurs.

I have some future experiments going through my mind. Once I settle on one, Ill make another fun thread for us to enjoy and hopefully learn something.

Till next time folks.

very true, look forward to your future experiments fellow scientist.

[Waldgeist]

Thanks for your answer Dave.

It Wasn't meant to offend you in any way, nor meant to criticize you.
I didn't understand your intentions with that experiment before your detailed explanation to me, thats all.

I thought a tad of Mg and Ca can/could accellerate the plants internal processes when using their stored nutrients, thats what was behind my questions.

best regards

[Dave Coulier]

Originally Posted by Waldgeist

Thanks for your answer Dave.

It Wasn't meant to offend you in any way, nor meant to criticize you.
I didn't understand your intentions with that experiment before your detailed explanation to me, thats all.

I thought a tad of Mg and Ca can/could accellerate the plants internal processes when using their stored nutrients, thats what was behind my questions.

best regards

Im sure you didn't mean to offend, and maybe I took it too personally, but I got over it pretty quickly. Criticism is always welcome here, so please dont be afraid to express yourself, but know I will answer back.

Im glad I was able to clear up the intentions of the experiment. I hope you'll follow along with the next one I do.

[Dave Coulier]

Hey guys, update time. Ive decided Im going to repeat this same experiment again. This will further confirm what I already believe to be true, and hopefully put to rest any doubts readers may have. Also I will be monitoring EC, PPM and pH levels of the soil solution from day 1 - 21. Those values along with picture updates will tale a pretty strong tale by themselves.

To help accomplish this I purchased four 6" Hanna Suction Lysimeters. They will fit nicely underneath my HOT5's, where my 12" ones are too tall to use previously.

My nutrient profile will be changing to incorporate UREA once more to help maintain media pH closer to a 5.8-6.2 range. Urea will supply 46% of my total N needs, while fed at 150 total N. So 70ppm Urea, and 80 Nitrate N. I intend to get the fertilzer mix tested so I can verify numbers or at least make any corrections necessary before beginning this next trial.

One experiment Ive considered is using different %'s of UREA to control media pH and discern what works best for my plants and medium, but that's for another day.

And whats an update without some pictures. Here's a lovely Shit Haze in my garden. I can already tell she's going to be the largest producer out of the one's flowering. I hope she ends up fat and juicy like the one in my avatar.

[Dave Coulier]

Originally Posted by Dave Coulier

Which one here was fed nutrients?

It was also on day 21 that plants began showing sex under 12/12 Lighting. All of the plants fed 160N showed sex by days 21-23. With 4/5 being female. The plants fed 80N showed sex by days 24-28. With 3/4 being female. The control plants were so stunted, sex was impossible to determine. I culled them at this point and started some GN Thai Stick in their place.

View Image

Waldgeist, I wanted to say thank you. You've helped a lightbulb go off in my head . You noticed the control group looked over-watered, and I was and still am adamant they werent. It had me scratching my head why they lacked the same turgor of other plants in the group.

Obviously it was related to the lack of nutrients, but I never really put 2 and 2 together until tonight. EC levels have a huge impact on plant turgor within the plants. Its very clear in the picture seen above.

I decided to go do some googling to see if I could find anything to back up what had to be true, and I found it. This could be a useful symptom to be aware when diagnosing problems in our gardens for some of us.

Tomato plants (Lycopersicon esculentum Mill. cv. Capello) were grown in peat bags, rockwool slabs, and NFT in a greenhouse to examine the effects of nutrient solution electrical conductivity (EC) and potential evapotranspiration (PET)-dependent EC variation on plant water relations. Peat bags were irrigated by a PET-dependent irrigation system. EC was varied from 1 to 4 mS·cm-1 according to PET under –5 and –9 kPa of substrate water potential setpoints (SWPS). The plants in rockwool and NFT were treated with ECs of 2.5, 4, and 5.5 mS·cm-1. Peat bags and rockwool slabs were overwatered once a week to wash out the accumulated salts. Leaf water potential (ψ1) and relative water content (θ) were measured before and after plants were overwatered. Turgor (P) and osmotic π potentials were estimated from the pressure-volume method. Before plants were overwatered, ψ1 was significantly lower in the plants with high EC and low SWPS treatments and also lower in variable EC-treated plants, but P maintained close to the control value. After plants were overwatered, ψ1 recovered close to the control level and P became higher because of the lower π in the treatments of high EC, variable EC, and/or low SWPS. At a given ψ1 the plants with high EC, variable EC, and/or low SWPS maintained higher θ. The analysis of the pressure-volume curve showed that the leaves treated with high EC, variable EC, and/or low SWPS had higher turgid water content, higher symplasmic (osmotically active) water content, lower apoplasmic (osmotically inactive) water content, and lower θ point of zero turgor (incipient plasmolysis). Maintenance of P after overwatering was directly proportional to photosynthetic capacity. We suggest that osmotic adjustment occurs in response to high EC, low SWPS, or both and that overwatering substrates and varying EC can not only avoid salinity stress, but also improve turgor maintenance.

Xu, Hui-lian, Laurent Gauthier, and André Gosselin. "EFFECTS OF FERTIGATION MANAGEMENT ON WATER RELATIONS OF TOMATO PLANTS GROWN IN PEAT, ROCKWOOL, AND NFT." HortScience 29.4 (1994): 252-253.

[Waldgeist]

thanks to you, thats very intresting.

[Dropped Cat]

Thanks DC. This information has proved timely and useful.

My short test was four seedlings. Three with a light feed and
one without, just water.

The one without feed is now being fed, although now is behind
in its growth compared to the other three.

Took four days to see the marked difference.

Yup, feed the seedlings. facepalm.