Renfro
Well-Known Member
Checking and adjusting the pH of your root zone in soil or coco is a very important part of growing healthy plants. Often you will notice nutrient deficiencies despite the fact you know you have provided an ample feed at an appropriate pH level. When this happens it’s generally either unhealthy roots or something going on in the medium locking out the nutrients. This could be a salt buildup or it can be a pH related issue.
Runoff testing is unreliable and bad information is often worse than no information. Testing soil pH should be done with a reliable digital soil pH pen. The cheap analog meters with the long metal probe are not good for pH measurements, they are good for moisture and that it. You should test all plants as they are not always the same, do not rely on one test for all plants. I am showing an example of a correction on a plant that was off and showing signs of nutrient uptake issues.
For starters the medium is DNA Mills Coco Cork and I have found it likes to be at 6.5 (I know). The plant is a Romulan cut that I was given and was tossed into flower right at flip as an afterthought. The normal feed pH is 6.5 and each 10 gallon pot gets 2.5 gallons of water, currently every 8 hours for most plants including this one (she drinks).
I tested the coco and the starting number of 5.74 (too low for me).
6.5 minus 5.74 = 7.26. I adjusted my next feed accordingly and it measured 7.25.
5 minutes after feeding I tested again and the pH is at 6.71.
2 hours after feeding it tested at 6.62
6 hours after feeding it tested at 6.38
It generally drifts back down some and ends up a little below 6.5. The following feed is then adjusted as needed to walk it onto target range. If the situation persists then the medium may have some sort of pH buffer that’s slow release and you may have to combat this the whole grow.
The soil pH meter can also be used to detect your daily pH swings and use them to your advantage. Lets say you want 6.3 - 6.8. If you water at 6.8 and it drifts down to 6.3 between the next watering then thats great! If you started at 6.5 not so much as you end up at 6.1 (seen it happen). Not everyone's soil will have a pH swing, more beneficial bacteria seems to make the pH move around more but it's good to know if you do and use it to your advantage.
Images in the following post. FWIW I meant to put this in the General Growing section but messed up lol.
Runoff testing is unreliable and bad information is often worse than no information. Testing soil pH should be done with a reliable digital soil pH pen. The cheap analog meters with the long metal probe are not good for pH measurements, they are good for moisture and that it. You should test all plants as they are not always the same, do not rely on one test for all plants. I am showing an example of a correction on a plant that was off and showing signs of nutrient uptake issues.
For starters the medium is DNA Mills Coco Cork and I have found it likes to be at 6.5 (I know). The plant is a Romulan cut that I was given and was tossed into flower right at flip as an afterthought. The normal feed pH is 6.5 and each 10 gallon pot gets 2.5 gallons of water, currently every 8 hours for most plants including this one (she drinks).
I tested the coco and the starting number of 5.74 (too low for me).
6.5 minus 5.74 = 7.26. I adjusted my next feed accordingly and it measured 7.25.
5 minutes after feeding I tested again and the pH is at 6.71.
2 hours after feeding it tested at 6.62
6 hours after feeding it tested at 6.38
It generally drifts back down some and ends up a little below 6.5. The following feed is then adjusted as needed to walk it onto target range. If the situation persists then the medium may have some sort of pH buffer that’s slow release and you may have to combat this the whole grow.
The soil pH meter can also be used to detect your daily pH swings and use them to your advantage. Lets say you want 6.3 - 6.8. If you water at 6.8 and it drifts down to 6.3 between the next watering then thats great! If you started at 6.5 not so much as you end up at 6.1 (seen it happen). Not everyone's soil will have a pH swing, more beneficial bacteria seems to make the pH move around more but it's good to know if you do and use it to your advantage.
Images in the following post. FWIW I meant to put this in the General Growing section but messed up lol.
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