This topic has been discussed, but not all that much, at least on RIU.

Here's the background, I've got a nl#5 about 3 weeks into flower. Generally been doing well, but I inspected it today and the dreaded purple/blue tinge of phosphorus deficiency has begun to show. My feel is with 5 weeks of flower to go, that's too soon to have this issue.

The soil used was 2 gallons of MG Organic Choice with 10% perlite. Total of 2 tbps MG Organic Bone Meal(6-9-0) and 2 tbps dolomite were mixed in soil. Appears most of the P has been sucked dry. The only feeding that has been done is with 1/2 tsp molasses in 2 quarts water.

I've added the 1/2 tsp molasses to 2 quarts water, been fermenting for 24 hours. Just added 1 tsp of the MG bone meal today. Just going to ferment another 24 hours more. I know there many that will say that is not enough time. I did find some good info that this will provide a gentle P boost. The MG meal is very fine powder, supposedly this will aid in the partial release of the P. I know that it has some extra N, but I'm planning on revegging after harvest.

So I have 24 hours before the deed. Anyone going to tell me if this is a bad idea?