Why has my Ph droped?

[cwesto]

I grow in soil, righ now i am in 2 gal. pots. I have 6 plants that are about 25-26 days through veg. I have been using only growbig mixed with rested tap water. I started at 1tsp/gal after 1 week of veg have worked my way up to 2 tsp/gal. My plants look healthy and all, but today when i watered and tested runoff Ph almost all of my 6 plants tested at around a PH of 5.... Why is my Ph droping?? I was thinking possible salt build up, I heard that FoxFarm products tend to create alot of salt..

I thought of something. The runoff itself looked a little brown or orange i thought, Maybee that along with the color of the Ph testing solution showed a lower Ph that it actually was... does that sound possible or logical at all??

cwesto Reviewed by cwesto on 11-27-2007. Why has my Ph droped? I grow in soil, righ now i am in 2 gal. pots. I have 6 plants that are about 25-26 days through veg. I have been using only growbig mixed with rested tap water. I started at 1tsp/gal after 1 week of veg have worked my way up to 2 tsp/gal. My plants look healthy and all, but today when i watered and tested runoff Ph almost all of my 6 plants tested at around a PH of 5.... Why is my Ph droping?? I was thinking possible salt build up, I heard that FoxFarm products tend to create alot of Rating: 5

[whatsthatsmell]

Salt buildup from your nutes will cause your soil pH to drop. To fix this problem you should flush your plants with double the amount of water as there is soil, so if your in a 2 gallon pot your going to flush your plant with 4 gallons of water. The 4 gallons of pH adjusted water will remove alot of that salt in your soil, then you can test your soil run off again. You should be around the correct range, if not, keep flushing until you reach that magic number. IF you do not flush your plant, you will end up in a lockout and if left unattended could take you over a month to get out of.

Hope that helps.

[stinkyattic]

I'll betcha that your potting soil is peat-based and the lime buffer added at the packaging facility is used up.

What brand and type of soil is it?

Ergh I hate peat moss....

[organic_sourdiesel]

I'm using promix HP. I've only watered it twice... once with ph 6.3 for planting, then with ph 6.3, ppm 600 for the first feeding. I'm using botanicare. The runoff tests 4 days later came out at ph 5 and from 1000-1600 ppm! This is just nuts! I don't understand.

The HP is brand new, so the lime should still be in there... I didn't add any more dolomite, which could have been a mistake...

I've never seen such a drop. I'm flushing now, and I've only fed once. This is not cool. My leaf fringes are curled up, and there are some twisted leaves. Oh, and some of the lower fan leaves have rust spots.

I have two posts in the indoor growing section, explaining more about my setup and situation.

I'd appreciate any advice...
bless

[stinkyattic]

Promix is peat.
Never heard of the HP; it's the BX that cannabis growers use, so I looked it up... seems it's pre-ferted as well... 'micronutrients and macronutrients' are listed as components. pH range is listed from 5.5-6.5. That's quite a window... yikes.
You gotta get them into better medium.
That is only going to get worse.
http://www.hort.purdue.edu/hort/faci...s/proMixHP.pdf
I hate peat...
Flush with water at 7.5-8.0. Find a new soil. Repot at your earliest convenience.

[Weedhound]

You say your leaf edges are curled up? Got a pic? I'd love to see if possible...

[Sjapp]

ha sorry... i'm embarrassed. what are pH levels? all i know is that pH=-logH from my math class...

[cwesto]

SA, I am using a mixture of 3:1 ocean forest to perlite, with a layer of hydroton covering the soil to maintain moisture. That is my mix ans soil, I didnt notice peat moss on the back of the bag when i bought, but i could be wrong.

The thing is my plants look generaly healthy, heres some check out my new pics onmy grow log, which u can find in my signature..

[growbe]

The growing concensus is that most are using HP and not BX anymore due to the lack of perlite in bx and the added vermiculite. Most promix growers are adding 1 tbls of lime to to 1 gal of HP, and about 20 percent more perlite. HP also has MYCORISE.
I have seen side by side grows of bx and hp, clones nothing added at all and the hp grows better plants.
Optimum ph in promix is 5.6 to 6.2 You should adjust nutrient solution ph to about 5.8 to 6 after everything is added. This ph seems low but is necessary to make iron, manganese, zinc, copper, boron, and phosphorus available to the plant. At higher ph, these become less avail. to the plant.
Biggest problem with the promix thing is that the lime charge that provides the plant calcium and magnesium is going to run out after repeated waterings. I doubt the foxfarm nutes have alot of cal mag. I would say after a couple weeks, calcium and magnesium should be added at a low rate to water. 1/4 teaspoon of powdered gypsum or calcium nitrate + 1/4 teaspoon epsom salts per gallon of water can be used to do this. Add everytime if def. occurs such as mag def with green veins on bottom leaves but geting yellow.
If you are going to keep them in promix, keep it wet and feed every other time with small amounts of ferts.
BUT it looks like the damage is done.

[organic_sourdiesel]

Well, I took some ph/ppm tests and half of my garden read around 5.0ph/900-1000ppm, and the other half read 5.3ph/600-700ppm. The first half didn't get flushed as much as the second did. So last night I flushed them all with ph7.6 water. My res and # of plants only allows for 1 litre of water per plant, so that's all I can do, unless I use tap water that hasn't sit for 24hours... The tests I did today were only a little higher in ph, so I suppose I need to flush one more time with a high ph to try and get them back into a nice range.

The plants are looking hungry (they are pale in the new growth, and have rust spots on the older growth), and I'm worried about this progressing too far if they don't get food for another 4 days (time it will take them to dry out again after this flush). I'm sure there is still food in there, but I'm worried about the ratios after flushing like this... Maybe I'll flush them with a mild dose of calMax, or bloom/veg... I was thinking it would be a good idea to foliar feed them with a weak solution of half bloom and half veg (I'm in transition as of Monday). I am using botanicare pro veg and pro bloom soil. Does this sound like a good idea?

Optimum ph in promix is 5.6 to 6.2 You should adjust nutrient solution ph to about 5.8 to 6 after everything is added. This ph seems low but is necessary to make iron, manganese, zinc, copper, boron, and phosphorus available to the plant. At higher ph, these become less avail. to the plant.

Although stinkyattik suggested it, it is not feasible to repot my current grow into new soil now... That would be too much more of a cost. I'm guessing that I will have to feed with a higher ph to allow for the drop that seems to occur... A store owner in my town said to always feed with 6.8.... seems about right, as the ph in my runoff is always in the low 5s after 6.3 went in, for the last 3 or 4 crops. I wish I had used dolomite lime this time, and more of it in the past... I forgot that GH nutes are ph buffered... Botanicare seems to lower the ph in the peat in a MAJOR way.

I don't have a cam to show pics of my leaf fringes that are curled up. By fringes, I'm referring to the sides of the leaves...

As always, I appreciate the advice...
I'm considering switching back to buckets...

peace