Phosphorus Deficiency Or Soil Ph?

average grow · Feb 16, 2019

Anyone able to share some wisdom on this?
Nearing the start of week 3, a few days after topping the leaces are turning this colour
Currently running 18/6 and feeding every couple of days with nitrosol and a magnesium additive at pH of 6.6 in the water.

Thanks guys

Jimster · Feb 16, 2019

They are getting ready for some bigger homes, but they look pretty good to me. It's pretty early to be seeing any type of deficiencies, especially since you are feeding every few days. You didn't mention what you are growing in? The bottom most leaves often turn yellow and die off due to lack of light. If they start turning yellow and it is moving up the plant, it usually indicates a Nitrogen deficiency. In my experience, unless you are going hydro, the chances of seeing any basic deficiencies other than Nitrogen are pretty rare. Any type of solid medium...promix, foxfarm, potting soil...they all usually have enough in them to allow things to get started and finish, although not with stellar results. Promix is probably the one with the least amounts of nutrients in it. It actually takes a very small amount of nutrients to feed them. I think the stress of topping and slight rood-boundness might have caused the problems that you see, although they look pretty good to me!

crimsonecho · Feb 16, 2019

Stop the magnesium. Plants don’t need much. Especially at this stage with fresh soil. Magnesium interacts with phosphate and potassium and causes your problems probably.
Here is the Mulder’s chart that would back up my reasoning.

average grow · Feb 16, 2019

CrimsonEcho said:
Stop the magnesium. Plants don’t need much. Especially at this stage with fresh soil. Magnesium interacts with phosphate and potassium and causes your problems probably.
Here is the Mulder’s chart that would back up my reasoning.

View attachment 856985

Legend, easy done

average grow · Feb 16, 2019

Jimster said:
They are getting ready for some bigger homes, but they look pretty good to me. It's pretty early to be seeing any type of deficiencies, especially since you are feeding every few days. You didn't mention what you are growing in? The bottom most leaves often turn yellow and die off due to lack of light. If they start turning yellow and it is moving up the plant, it usually indicates a Nitrogen deficiency. In my experience, unless you are going hydro, the chances of seeing any basic deficiencies other than Nitrogen are pretty rare. Any type of solid medium...promix, foxfarm, potting soil...they all usually have enough in them to allow things to get started and finish, although not with stellar results. Promix is probably the one with the least amounts of nutrients in it. It actually takes a very small amount of nutrients to feed them. I think the stress of topping and slight rood-boundness might have caused the problems that you see, although they look pretty good to me!

Thanks for the advice it was a good read, just growing in a decent potting mix from bunnings. Yep the roots have just started leaving the pot and I'll transfer this week. I'll let ya's know how it goes

Dirtbag · Feb 17, 2019

Agree cut out mag. Dont feed any single specialty nutrients, just a good balanced base nutrient. And lower ph of your feed to 6.0-6.2.

average grow · Feb 17, 2019

I think it was a problem with the runoff pH. Was sitting around 5.1 and I believe this has caused a phosphorus deficiency. Could be wrong I guess. Anyway I've flushed and the runoff is now 6.2 so fingers crossed now.

I'll update in a few days here with some pics if anyone's interested. Cheers

Dirtbag · Feb 17, 2019

Try not to be too concerned about runoff ph from soiless mix honestly. Coco/hydro, sure, but soiless runoff ph can sometimes be very misleading. For ph just focus on what's going in. Too often people get freaked out by the numbers coming out of the pot and make drastic unnecessary adjustments when testing soiless runoff. Sometimes to the detriment of the plant.

average grow · Feb 17, 2019

Dirtbag said:
Try not to be too concerned about runoff ph from soiless mix honestly. Coco/hydro, sure, but soiless runoff ph can sometimes be very misleading. For ph just focus on what's going in. Too often people get freaked out by the numbers coming out of the pot and make drastic unnecessary adjustments when testing soiless runoff. Sometimes to the detriment of the plant.

Thanks for the help mate. I think I should flush just in case

average grow · Feb 17, 2019

Dirtbag said:
Try not to be too concerned about runoff ph from soiless mix honestly. Coco/hydro, sure, but soiless runoff ph can sometimes be very misleading.

I'm not sure if I'm confused or you are lol. They are in a soil mix mate

Dirtbag · Feb 17, 2019

average grow said:
I'm not sure if I'm confused or you are lol. They are in a soil mix mate

Lol, I'm saying I would only bother to check runoff ph in a hydro setup or coco grow. Since you are In a soiless mix i wouldn't bother because the runoff ph can be very misleading, and often cause growers to chase a red herring trying to fix a problem that doesnt need fixing. Of all the soiless growers I know, we all check input ph and ppm, and runoff ppm. That's it. Making changes to the feeding based on runoff ph can often cause more problems than it solves in soiless mix.

If you really want to know what's going on in the profile do a slurry test.

Jimster · Feb 17, 2019

I always considered Promix to be a soilless medium. I always thought Coco was pretty much the same thing, substituting coco fiber for the peat/perlite mix of Promix. I just looked up the ingredients and it is mostly peat/vermiculite, which I guess holds nutrients better than coco. For the last 35 years or so I always thought Promix was soilless, but I guess it's a hybrid. FWIW, I haven't had any types of meters or other concerns about things getting messed up. I guess that's because they weren't affordable to most growers unless you had a big setup.
I always compared growing to drag racing. Both get to the end line and both are faster than most other cars...but one typically has every advanced options on it, but only beat the stripped down competition by a little bit. Growing with a basic and easily repeatable process might not get you the greatest buds ever made/grown, but they can get you 95%+ of the way. As I like to say...whatever works best for you!

Dirtbag · Feb 17, 2019

Right, pro-mix is a mix of peat, perlite, surfactant and fungus gnats. Some come with added Mycos too. It has a fair bit higher of a CEC than coco which besides its potassium content, is so well washed usually that its relatively inert, giving up its nutrients much more freely. Coco is somewhere inbetween Rockwool which is totally Inert, and pro-mix which has a higher CEC.

Dirtbag · Feb 18, 2019

average grow said:
I'm not sure if I'm confused or you are lol. They are in a soil mix mate

Haha, fuk it was me who was confused man. I had way too many beers and Doobies tonight lol. I got this thread and another one confused, my bad... you are in soil lol. Gotcha.

In that case there is even less reason to check runoff ph than soiless. It is absolutely pointless testing soil based runoff.

Kepp89 · Feb 18, 2019

ive heard the viable method for ph in soil is to do the slurry method. takes about 20 minutes to complete. slurry test i was .4 lower than the runoff test -- same water both times

or buy the $130+ soil ph pen

Jimster · Feb 18, 2019

Kepp89 said:
ive heard the viable method for ph in soil is to do the slurry method. takes about 20 minutes to complete. slurry test i was .4 lower than the runoff test -- same water both times

or buy the $130+ soil ph pen

The most accurate test I had for testing the soil ph, not the runoff ph, was a liquid test tube setup, you just added a soil sample, a few drops of reagent, and you got a pretty precise ph reading. It was pretty cheap, similar to a pool test kit except for soil instead of water.

.

CaliRooted · Feb 18, 2019

Deficiencies and generally correctable with a simple PH adjustment and not by dumping more food at them..

average grow · Feb 18, 2019

CaliRooted said:
Deficiencies and generally correctable with a simple PH adjustment and not by dumping more food at them..

That's what i have hopefully done, they are looking a little healthier after getting the ph back to normal

average grow · Feb 18, 2019

Kepp89 said:
ive heard the viable method for ph in soil is to do the slurry method. takes about 20 minutes to complete. slurry test i was .4 lower than the runoff test -- same water both times

or buy the $130+ soil ph pen

Yeah ill be doing that this arvo after work to confirm the ph. Cheers !

alexwolve · Jul 21, 2024

average grow said:
I think it was a problem with the runoff pH. Was sitting around 5.1 and I believe this has caused a phosphorus deficiency. Could be wrong I guess. Anyway I've flushed and the runoff is now 6.2 so fingers crossed now.

I'll update in a few days here with some pics if anyone's interested. Cheers

that’s right , phosphorus will absorb just between 5.8-6.2 , low soil ph one of the certain reason for P deficiency , try use calmag extra for raise the ph of bedsoil

Phosphorus Deficiency Or Soil Ph?

Phosphorus Deficiency Or Soil Ph?

average grow

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Phosphorus Deficiency Or Soil Ph?

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