How do I tell how much nutrients my plant is using or not using (testing run off)

I was wondering how to tell how much nutrients my plants are using so I can fluctuate the nutrient concentration. I imagine it is something like testing the ph of your water then testing the ph/ppm of your fert and subtracting the ph from the ppm then testing the run off. I would really appreciate it if somebody could post a tutorial on this subject. I can't seem to find a thread on this. Thanks

I run coco.
I check the ppm before I feed.
Then I check the ppm after. That is it.
If it is higher you are feeding too much.

In coco the ph in the run off is not a concern assuming the ph going in is correct.

What difference does it make?

Why would you want to "fluctuate" the nutrient concentration?

Keep 'em green and growing.

It depends entirely on your medium.

Which you've neglected to mention!!!!


I agree with TROUSERS I too grow in coco and I monitor the EC (electrical conductivity) of my feed going IN vs my 20% runoff EC. If I get more than 0.2EC swing in either direction I alter the next feed.

However with coco its inert therefore you can feed each time as long as you monitor it this way.



J

Jaguarr29 said:

I was wondering how to tell how much nutrients my plants are using so I can fluctuate the nutrient concentration. I imagine it is something like testing the ph of your water then testing the ph/ppm of your fert and subtracting the ph from the ppm then testing the run off. I would really appreciate it if somebody could post a tutorial on this subject. I can't seem to find a thread on this. Thanks

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Your imagination is pretty wild. Really though, it wouldn't be easy for the average person to figure out exactly how much of any specific nutrient a plant is absorbing like that. While you may be able to get some rough idea, and as some of the others said depending on medium... materials like coco, sphagnum, vermiculite, and especially compost\humus\clay (found in soil) have cation exchange capacity*; even microbes themselves possess exchange sites. The sites are predominately negatively charged (when pH is nearer neutral), so they attract cations (some materials to a certain degree, and some at a certain pH (acidic) possess anion exchange capacity).

*cations: positively charged ions like Ca2+ or K+ that are plant nutrients

Because I grow in soil, and to make things easier for myself, I just transplant at certain stages and if necessary slowly begin to administer liquid organic nutrients (low[er] NPK). I can tell by the existing and newer growth whether anything might be lacking at some point in the soil. But, I also make use of AACT and foliar fulvic acids when possible, which will quickly assist in the assimilation and translocation of nutrients into plant tissues.

But I'll never know exactly how much of X nutrient a plant is taking in, this is why I use microbes to mediate.

Jaguarr29 said:

It is important to know in order to keep your plant in the optimum range. So lets say you ppm was around 1250ppm and your runoff was at 725ppm. Now you know how much your plant is using.If your ppm was at 1250 and your run off was at 1100/ppm then you know then you now know that your plant isnt using as much nutrients and could be a possible red flag for nutrient lock out at the least you will know to lower the fert ppm.

I was told this method a while back and do not remember the exact method. I do know that it is a bit more complicated and specific than the method Trouser suggested.(NO OFFENSE INTENDED) You can't just check the ppm right after feeding because your roots have not had time to absorb all the nutrients. I'm pretty sure you cant test the run off until the second fert and the second watering.


Edit: @jondamon i did forget to mention the medium----->>> Soil..Happy Frog/pottingsoil

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don't forget to account for evapo transpiration.
If you reservoir holds 10 gallons, and the next day it is 7 gallons and even though the ppm of the 7 gallons is higher the plant probably still absorbed nutrients
bring it back to 10 gallons before making a conclusion on how much fertilizers the plant is absorbing.