Every situation is different, environmental conditions and grow style highly influence what is going to be ideal.
You do not necessarily need to reduce or increase any ions. For example, in my grow right now today (bright greenhouse due to summer), 190ppm N delivers about 4.2% in a veg tissue analysis. That same 190ppm N in flower gives a 3.0% tissue analysis on day 30 of flower and continues to decrease as flower progresses. The same thing happens with Ca and Mg, their tissue accumulation decreases as flower progresses.
Listen to emdub before anything I say. Itās going to depend on the intensity of your light. I run about 1100 ppfd in flower. This last flower run starting in week 3, it was 130 total nitrates, 55 P, 300 K, 160 Ca and 2.8 Fe and there were no issues with tissue sampling.
Why is this? Does the plant naturally stop taking up N, Ca, and Mg as flowering progresses because they are no longer required in such concentrations? And this is in regardless of the absolute ionic concentration of my mix? I guess that is a stupid question since this is what they would do in soil or outside in general correct? I worry about over supplying elements and luxury consumption contributing to a bland tasting final product.
I also get confused when it is suggested to lower my Ec when my run off Ec is to high. I know weāve touched on this before @emdub27. I thought diluting my Ec changes my elemental profile and ratio?
Can I ask what you were running Mg at for that last run? I still canāt get my brix past 5% on this Purple Poison Cookies Iāve ran twice now. Idk if I just have a dud pheno or, if itās my nutrient profile contributing to itās lack of flavor?
I donāt have my notebook handy, but I think it was 40 ppm Mg.
Even though I am using my fulvic acid at 0.5ml/gallon constant feed, it shouldnāt change the nutrient profile dramatically except for a slight bump in micros and chelated/unbound iron sulfate, which I accounted for.
EDIT: Taking cues from Athena nutes, EMDub and Dr. Fernandez, I always try to drive calcium as much as possible. Itās the metabolism engine of the plant. Getting that Ca value over nitrates changed how my garden performed.
The plant has adapted to take what it needs. Think no till beds, the NPK of the soil doesnāt change drastically over the life of the plant. The tissue concentration of those elements does change. IME The only thing that really kills flavor is excess nitrates. The nitrate needs to be balanced to the light level, I have to run significantly less N in the fall. That being said, cutting down to 100ppm total N is likely to be detrimental unless your light level is very low.
Iām not sure how high your runoff is, but you control that with watering frequency and volume of runoff.
If you take a mix that performs well and gives healthy at 3ec input and dilute it down to half, 1.5ec youāre going to see problems. The antagonism change based on concentration and there are some pretty hard minimums for things like the micros and Ca that I would never want to go under.
Thanks @emdub27. Appreciate your help as always. I have a pretty small setup right now. A 250 watt Timber with Cree cobs in a 3x3 tent. Not sure how many umols that gives me. My day/night temps and RH are 83/68, 78/60. That is all the way through veg and the first 3 weeks of flower. Then I like to bring my temps and RH to about 80/55 daytime and, 75/50 for nighttime. With a few minor fluctuations here and there. Can you give me a good starting point for N? Would you suggest bringing my N down to about 150 ppm based on my lower light levels?
Hello everyone. I have another question maybe someone can help me out with. Yesterday I mixed a batch of nutrients with a K : N ratio of 1.4 : 1. Elemental ppm is 162 N, and 226 K. After running this feed yesterday, this morning when I first encountered the plants, they bolted at least an inch in height in under 10 hours. Mind you this is still in veg under 18 hrs light. My question is would increasing the K : N ratio help cut back on excessive, stretchy growth? Thank in advance everyone!
Magnesium will alleviate excessive nitrogen, particularly nitrate. That is one of Bruce Tainioās findings with foliar sprays to correct toxicity and deficiency. Iāve found it to be true via foliar or root application. IME potassium has very little influence on nitrogen accumulation in tissue.
How often and how drastic of changes are you making? As a general rule unless we are starting from scratch we only change nutrient solutions a few percent per week, verify what happened via tissue analysis and go from there. The plants can do some very odd stuff during the transition periods when drastic changes are made. It also takes about a week to see the results of the changes youāve made. For instance if I increase potassiun 25% tomorrow, Iāll see a huge bump in it if I pull tissue 24 hours later, by the end of the week it will decrease and Iāll be able to get a true reading.
Thanks @emdub27. I have been running the same veg mix for 2 weeks now. 162 N, 40 P, 226 K, 165 Ca, 65 Mg. I thought about reducing the Nitrate to around 155-150 for my lower light setup. I found a college study online saying 160 ppm of N was optimal for cannabis so, thatās where I set it at. Maybe that high of N is contributing to the stretchiness and lackluster flavor?
That particular study is a bit flawed. They ran Mg at roughly 44ppm and Ca at 45 ppm. (Rough conversions from molarity to ppm.) The 1:1 ratio of Ca to Mg isnāt something Iāve ever done in the real world, but Jackās 321 is similar. The study also had a very strong dose of Na. That study was done at lowish light, 400 umol.
Greenhouse grade cal nitrate will typically deliver Ca higher than N in tissue when used as a sole nitrogen source. Ca is also fickle, more in solution doesnāt necessarily equal more in tissue. Itās not uncommon to see less Ca in tissue at 200ppm than at say 160ppm.