Nitrogen Deficiency Week 3 Of Flower.

[Sappy.Hour]

As the title suggests I am experiencing nitrogen deficiency at the beginning of week 3 of 12/12. A little about my grow.

Lighting: 400w mh/hps
Room: 3x5x6’
Medium: sunshine #4 with worm castings.
Nutrients: compost teas for the most part with a little fish emulsion (grow and bloom)
PH: 6-6.5 (feed and plain waterings) Run off is about the same.
All the wind and air flow a guy needs. It seems like I’m nitrogen def and I don’t understand how. 5 days ago they were green and happy to the point they almost had too much food and the tips were just beginning to burn!!

The only variable I have changed is the lighting from metal halide to hps. I always keep the mh on until the preflower stretch is complete then switch to hps.

Question #1: Do plants use/uptake nutrients differently under different lights? Eg, would a plant use more or less say, nitrogen, under a metal halide than it would under a hps?

Question 2: Is using organic amendments and nutrients in soilless mediums just plain silly?

 

[MamaBear]

I don't think so (lights) and NO, it's not silly.

I make my own soilless mix. Coir, Peat, Compost & Pearlite is what I use. No real soil in there. ​

They do need different nutes at different times though. They need extra N the beginning of flowering for the stretch.
You said you fed pretty heavy (almost burning them). They may have locked out the nutes for a bit. Flush them well and let them sit till they dry out again. Check your compost tea recipe.

I've had best results with these:

Green one for VEG, pink one for FLOWERING
I add green one to the soil in the pot in the beginning.
Top dress with the pink one when they start flowering.
I rarely need to add anything else during the whole grow. Literally, just water them and watch them do their thing.
Some plants are hogs and eat up everything in their pots pretty quick. You can also make some excellent compost tea with this stuff if they need an extra boost.
In a pinch, I use MG tomato food 1/2 strength to give them a big N boost if they need it. That doesn't happen very often though.

 

[jumpincactus]

yellowing of leaves is a normal sign of senescence/or fade of flowering cannabis nearing the end of its life cycle. cannabis will begin to use its stored nutrients as it gets closer to ripeness or death if you will. This will cause the yellowing of some of the leaves as the plant cannibalizes itself to complete the flowering cycle. :D

 

[Greenshark]

What's the run off EC compared to what's going in? I think you will find they are locked out but I have zero experience with your growing medium so take this with a pinch of salt.

 

[justiceman]

Question #1: Do plants use/uptake nutrients differently under different lights? Eg, would a plant use more or less say, nitrogen, under a metal halide than it would under a hps?

Question 2: Is using organic amendments and nutrients in soilless mediums just plain silly?

Yes plants do use/uptake nutrients differently under different lights. Most notably because of the intensity. Your HPS gives off more light than your MH at the same wattage, thus causing an increase in the plants metabolism. Not to mention 3 weeks into flower they are really gearing up to produce which takes even more energy/nutrition.

It's not silly to use organic amendments and nutrients with soilless if it's treated that way the entire time. This is just my opinion but when people try to mix hydroponic nutrients and organics together it can often become hard to figure out problems if they arise. I like to keep them separate.

 

[Nugteq]

I think everyone has given you some solid advice. If I may add to theirs, I'd say that perhaps you are having a ph issue at the rootzone. In my experience I had early yellowing of plant around week 3 when there were ph issues from the onset of flowering cycle..once this has already happened not much can be done except to insure you ph meters are correct going forward and perhaps check the runoff of your plant with a ph pen to determine what the root zone ph is. This can help you diagnose whether it is indeed a ph issue or not. Cheers.