Phosphorus deficiency but high PPM

Alctrz8849

Well-Known Member
I have some plants that are 9 weeks old that seem to be extremely vigorous in their nutrient needs. I record the PPM and the PH daily and have done some deep dives on this and everything I find is confirming that this is a phosphorus deficiency as I have some purpling of the stems, bluing of the leaves, brown spots followed by more intense leaf curling. The fan leaves most exposed to the light have the most symptoms though some newer leaves that are lower due to LST and receive less light show the same symptoms just less severe. Whenever I have increased my P nutes, the plants respond positively and the problem appears to stop for half a week after I religiously change the water (using RO water with GH nutes, Hydroguard and CalMag). Last nutrient dose of N & P was 9ml/gal in a 5 gallon DWC and 6ml/gal of K, CalMag & Hydroguard. I've considered that this could be root rot but have examined the roots and they are not slimy and only appear to match pictures of being slightly tinted from nutrient water color. Root ends aren't as white tipped as I'd like but just at the far ends of the roots so I added another air pump with additional stones for more aeration despite each of the two DWC setups having a dedicated pump. It now holds 6 air stones in each bucket and is producing far more air bubbles for 3 days now.

Godfather OG - Plant with extreme leaf curling
PH: 5.51
PPM: 2,360
Water Temp: 67F
Air Temp: 70-75F
RH: 30-50%

Chiquita Banana - Better looking of two plants
PH: 5.51
PPM 1,990
Water Temp: 66F
Air Temp: 70-75F
RH: 30-50%


I feel like this could potentially be a salt build up simply due to the high PPM but every time I add another dose of phosphorus mid-week by 5ml/gal, both plants respond positively. Several days will go by and I will run into this problem again. It has been re-occurring for several weeks now and I don't want to harm my plant by flushing it if it's already deficient. Have prior hydroponic experience but it's been many YEARS and I could use some advice! Thanks!
 

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bernie344

Well-Known Member
I have some plants that are 9 weeks old that seem to be extremely vigorous in their nutrient needs. I record the PPM and the PH daily and have done some deep dives on this and everything I find is confirming that this is a phosphorus deficiency as I have some purpling of the stems, bluing of the leaves, brown spots followed by more intense leaf curling. The fan leaves most exposed to the light have the most symptoms though some newer leaves that are lower due to LST and receive less light show the same symptoms just less severe. Whenever I have increased my P nutes, the plants respond positively and the problem appears to stop for half a week after I religiously change the water (using RO water with GH nutes, Hydroguard and CalMag). Last nutrient dose of N & P was 9ml/gal in a 5 gallon DWC and 6ml/gal of K, CalMag & Hydroguard. I've considered that this could be root rot but have examined the roots and they are not slimy and only appear to match pictures of being slightly tinted from nutrient water color. Root ends aren't as white tipped as I'd like but just at the far ends of the roots so I added another air pump with additional stones for more aeration despite each of the two DWC setups having a dedicated pump. It now holds 6 air stones in each bucket and is producing far more air bubbles for 3 days now.

Godfather OG - Plant with extreme leaf curling
PH: 5.51
PPM: 2,360
Water Temp: 67F
Air Temp: 70-75F
RH: 30-50%

Chiquita Banana - Better looking of two plants
PH: 5.51
PPM 1,990
Water Temp: 66F
Air Temp: 70-75F
RH: 30-50%


I feel like this could potentially be a salt build up simply due to the high PPM but every time I add another dose of phosphorus mid-week by 5ml/gal, both plants respond positively. Several days will go by and I will run into this problem again. It has been re-occurring for several weeks now and I don't want to harm my plant by flushing it if it's already deficient. Have prior hydroponic experience but it's been many YEARS and I could use some advice! Thanks!
I get slight tip burn and curl at 1450 ppm,1550 made it much worse in 24 hours, dialed it back to 1350.
 

myke

Well-Known Member
Ive never hurt a hydro plant by flushing,12 hours of clean water up high so the root ball get a fresh drink.Then tone it down,i assume your locking it up by over ferts.
 

ricman

Well-Known Member
you may have already figured this out,,,,phosphorus in hydro is not readily absorbed at 5.5.......but much better at 5.9 to 6.0
when I had a similar issues i raised the PH to 6.0 and had good results.

Nutrient_Chart2.gif
 

Alctrz8849

Well-Known Member
And flush I did! It worked out just fine and the plants are doing great again!! I keep the PH between 5.8 to 6.2 which it naturally fluctuates from high to low in my nutrient change! I'm now flowering and on day 11! Just can't wait to see actual buds instead of pistils!!
 

bernie344

Well-Known Member
And flush I did! It worked out just fine and the plants are doing great again!! I keep the PH between 5.8 to 6.2 which it naturally fluctuates from high to low in my nutrient change! I'm now flowering and on day 11! Just can't wait to see actual buds instead of pistils!!
Good for you taking action and learning from your experience.
Charts and numbers are only useful to a point.
 
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