Old Reviews Amending pro mix

[Mainemedical]

Hey everybody, I've been having a problem with my pro mix bx. When it dries out completely the ph goes up to about 7 so it's locking out cal/mag. I've been feeding more often so the ph doesn't spike but I'm wondering if I could maybe add something to my soil to keep it in the 6.2-6.5 range even when it's completely dry. Any advise would be greatly appreciated

 

[The Squid]

Sulfur works. Muddy has done some experiments with this and used to or still used a little in his mix to bring the Ph down. I haven't had huge issues with it, just don't let it dry out completely. Sorta like coco. Due to it only having some starter nutes, cal/mag is a somewhat common issue in Promix. So look for that weeks 5-6.

Also, I personally use a Ph closer to hydro with Promix as it is considered semi soil-less, so in between 5.9-6.5 really. I learned from Jackal some about that and he said he doesn't put anything over 6.3 in his ever. Bring it to around 5.9 and let it pull up through the range as it dries, but not dry all the way or yes, you'll have issues, I have seen them.

It takes some dialing in.

 

[Mainemedical]

Thanks squid how much sulfur would I add per gal of soil?

 

[The Squid]

You'll have to run some tests probably. I did some a while back, but just decided it wasn't worth it. I was a tsp or two per gallon I think.

Muddy is on, perhaps he will see this and chime in.

 

[Muddy]

I've had the same issues with Pro Mix and have been experimenting with some different things to lower the pH. So far, aluminum sulfate has worked best. Sulfur does work but it takes too long to become effective. I've got some seedlings going now where I added cottonseed meal to the mix. I've found that the starter nutes in Pro Mix either aren't sufficient for autos, or are just not the right ones. By about 14-15 days I was seeing a lack of N in the plants and slowed growth. Besides lowering the pH, cottonseed meal also adds some N to the mix. These seedlings are only 8 days old but are looking much better than in the past. I've also started feeding earlier. I've giving 1/8 strength at the first feeding, usually day 6 or 7, then upping it to 1/4 on the second feeding.

 

[Muddy]

Bear in mind that Jackal was using the AN pH Perfect nutes, which are entirely different. Using most other nutrients a pH below about 6.3 in Pro Mix will eventually lead to plant deficiencies. In my experience, 6.3 - 6.4 seems to be best.

Also, I personally use a Ph closer to hydro with Promix as it is considered semi soil-less, so in between 5.9-6.5 really. I learned from Jackal some about that and he said he doesn't put anything over 6.3 in his ever. Bring it to around 5.9 and let it pull up through the range as it dries, but not dry all the way or yes, you'll have issues, I have seen them.

 

[Mainemedical]

I also am using AN ph perfect and that is exactly how I am feeding mine now :thumbs: I read on the bag that they recommend to start feeding after 7 days in soil. I had been waiting til about week 2 previously. Thanks for the info muddy ill definitely try adding some cottonseed meal to my mix. How much would you recommend I add per gal of pro mix?

 

[Muddy]

I can't make any recommendations yet on the cottonseed meal as this is my first attempt at using it. It's 6-1-1 and I know that would be too much N for seedlings, so I used half the recommended amount, which was about 15 grams in a half gallon pot. I just spot checked a couple of the pots today, a day after giving them their first feeding at 6.3, pH is reading around 6.6, down from the starting pH of 7. I know it will lower the pH, but how much and how fast I don't yet know.

Yes, with pH Perfect, just go with whatever it automatically adjusts to. If you add any pH up or down it totally screws it up.

 

[The Squid]

Bear in mind that Jackal was using the AN pH Perfect nutes, which are entirely different. Using most other nutrients a pH below about 6.3 in Pro Mix will eventually lead to plant deficiencies. In my experience, 6.3 - 6.4 seems to be best.

Great point. Sorry about that. Seems to work ok for me. I don't go too low though. Honestly around 6.3 with feeds and it seems to drift up.

 

[Muddy]

I usually start my feeds around 6.0 and then up them to 6.3 as the soil pH starts to come down and stabilize.

Great point. Sorry about that. Seems to work ok for me. I don't go too low though. Honestly around 6.3 with feeds and it seems to drift up.