Soil slurry test = pH 7.0

[ToughCall]

Hello good people,

I'm at the tail end of veg with 5 clones in 3 gallon fabric pots. I had to correct some deficiencies and get nutes dialed in, and then I did a slurry test. Each pot I dug about 2" down and then grabbed a tablespoon of soil and added straight RO water creating 5 samples of 1 part soil 2 parts RO water, stirring frequently and let it rest for 30 minutes before testing.

Each sample read 6.9 to 7.0 pH, using a reliable pH pen.

Does it make sense to try and adjust the soil to lower the pH to 6.5?
Or keep it simple and adjust my tap water (I stopped using RO to water) each watering, using alternate pH ranges - from 6.3 to 6.7 every other watering?

Thank you,

[GEORGE]

7 is neutral, so I would think not. JMO

[mpsj]

Hello good people,

I'm at the tail end of veg with 5 clones in 3 gallon fabric pots. I had to correct some deficiencies and get nutes dialed in, and then I did a slurry test. Each pot I dug about 2" down and then grabbed a tablespoon of soil and added straight RO water creating 5 samples of 1 part soil 2 parts RO water, stirring frequently and let it rest for 30 minutes before testing.

Each sample read 6.9 to 7.0 pH, using a reliable pH pen.

Does it make sense to try and adjust the soil to lower the pH to 6.5?
Or keep it simple and adjust my tap water (I stopped using RO to water) each watering, using alternate pH ranges - from 6.3 to 6.7 every other watering?

Thank you,

I don't know what soil you are using nor what you did to correst some deficiencies, but in general I would not try to adjust your soil... especially during a grow.

[CityDweller]

Hello good people,

I'm at the tail end of veg with 5 clones in 3 gallon fabric pots. I had to correct some deficiencies and get nutes dialed in, and then I did a slurry test. Each pot I dug about 2" down and then grabbed a tablespoon of soil and added straight RO water creating 5 samples of 1 part soil 2 parts RO water, stirring frequently and let it rest for 30 minutes before testing.

Each sample read 6.9 to 7.0 pH, using a reliable pH pen.

Does it make sense to try and adjust the soil to lower the pH to 6.5?
Or keep it simple and adjust my tap water (I stopped using RO to water) each watering, using alternate pH ranges - from 6.3 to 6.7 every other watering?

Thank you,

Watch out for plain RO. It has a negative effect on soil if there is no EC. I don't know the science but have experienced the issue and had it explained to me by Vermont Compost.
Option 1. Add a small amount of calmag and adjust ph to 6.0-6.5
Option 2. Mix some tap with the RO and then adjust ph to 6.0-6.5

With a soil ph that high I would try to lower it with a tiny bit of soil acidifier.

[ToughCall]

Thank you all for thr quick and helpful replies. I'll stick to pH adjustments with water while in grow. Much appreciated!

[mpsj]

[QUOTE=CityDweller;1071282065]Watch out for plain RO. It has a negative effect on soil if there is no EC. I don't know the science but have experienced the issue and had it explained to me by Vermont Compost.
Option 1. Add a small amount of calmag and adjust ph to 6.0-6.5
Option 2. Mix some tap with the RO and then adjust ph to 6.0-6.5

With a soil ph that high I would try to lower it with a tiny bit of soil acidifier.[/QUOTE

True Reverse Osmosis water is free from all minerals and dissolved solids. At first water treated via RO will stabilize to a pH of 7, but carbon dioxide in the air will dissolve in the RO water forming carbonic acid. Carbonic acid will lower the pH so RO water is often acidic. Something to consider if one is pH conscious with their grow.

[CityDweller]

[QUOTE=mpsj;1071282078]

Watch out for plain RO. It has a negative effect on soil if there is no EC. I don't know the science but have experienced the issue and had it explained to me by Vermont Compost.
Option 1. Add a small amount of calmag and adjust ph to 6.0-6.5
Option 2. Mix some tap with the RO and then adjust ph to 6.0-6.5

With a soil ph that high I would try to lower it with a tiny bit of soil acidifier.[/QUOTE

True Reverse Osmosis water is free from all minerals and dissolved solids. At first water treated via RO will stabilize to a pH of 7, but carbon dioxide in the air will dissolve in the RO water forming carbonic acid. Carbonic acid will lower the pH so RO water is often acidic. Something to consider if one is pH conscious with their grow.

I'll see if I can find the email explaining why straight RO is not good for soil. It went beyond the low PH although the low PH is definitely a consideration.

[CityDweller]

This is from Vermont Compost. They make the amazing super soil I am using.

" It’s not that RO water adsorbs to soil colloids as it is that it strips cations from bonding sites on those colloids, specifically calcium and magnesium.

RO water also tends to be acidic, as it has lost its (mostly alkaline) dissolved salts, like Ca, Mg, K, and bicarbonates. Because it is slightly stronger than a Lewis acid, it begins pulling these salts back into solution, but then reacts w them to form unavailable precipitates.

In time, the humic complexes are devoid of cations and the soil is full of nutrients in an unavailable form.

Most folks will tell you to either add a CalMag liquid back into the RO water, or adjust its pH to reduce its acidity, or blend 80% RO w 20% tap water to change its nutrient profile.

Hope this is helpful!"

[CityDweller]

Forgot it was 20% tap suggested. Gotta fix this. Was doing 50/50. Don't want the soil filling up with salts.

[mpsj]

This is from Vermont Compost. They make the amazing super soil I am using.

" It’s not that RO water adsorbs to soil colloids as it is that it strips cations from bonding sites on those colloids, specifically calcium and magnesium.

RO water also tends to be acidic, as it has lost its (mostly alkaline) dissolved salts, like Ca, Mg, K, and bicarbonates. Because it is slightly stronger than a Lewis acid, it begins pulling these salts back into solution, but then reacts w them to form unavailable precipitates.

In time, the humic complexes are devoid of cations and the soil is full of nutrients in an unavailable form.

Most folks will tell you to either add a CalMag liquid back into the RO water, or adjust its pH to reduce its acidity, or blend 80% RO w 20% tap water to change its nutrient profile.

Hope this is helpful!"

Thanks for digging--up the email. RO can play havoc that's why I don't use it.