For plants grown for seed, I keep the npk about equal. I dont notice any detriment to it. When hemp was newly legalized, lots of greenhouse people got a license without any prior experience. I saw a greenhouse of tree sized hemp plants that looked great. They were getting Jacks 20 20 20 through drip. It was probably a waste of nitrogen, but the plants didnt care.
I use the same thing on outdoor plants as I do tomatoes. Calcium Nitrate when they are young and masterblend 4 18 38 when they flower. Fan leaves will turn a little yellow at the end of flower, but it doesnt seem to matter. These fertilizers are ridiculously cheap compared to anything from a hydro store.
What I’ve seen the main thing is not over supplying anything the whole way through, we’ve had issues with high nitrogen in tissue samples and even dropping the input N down it’s hard to get it out the plant by the end of flower.
I’ve gone on the path of mixing my own salts and it’s for sure been a learning experience but I think we are getting there. One thing I’ve learned is watching ph run off is very important and you cannot adjust it with your input, if you watch Daniel’s video on it he explains it well. During stretch i used to get a big ph rise then after day 30 it started to go the other way and no way could I fix it with my input ph, now I control it with the amount of nh4 in my mix. During stretch I increase nh4 and after day 30 I lower it and I’ve had complete control of run off ph doing that.
That’s what I started noticing but with limited experience, it’s sometimes tough to make the right call, let alone correctly make adjustments. Especially if the strategy chosen is more detrimental than beneficial. Then you wait months to get to the same point and try a new one. There’s no way around it experience is vital. I love the f4200 just for that reason. Everyone has years of experience here and you can tell just by reading. Yeah sometimes you do bicker with each other and we all like to be petty sometimes but through discussion or even when shit-flinging starts you can find amazing information hidden or at least an idea to try that is somehwat based in reality. Blue diamond thread has 1k+ posts and most of them are off topic but still there was plenty of good information shared let alone the entertainemnt value of community collectively descending into maddness.
At least I’m on the right track somewhere as this is the case for me. I have one of my zones in worrying range of sometimes hitting 5.4 but usually 5.5. Can you tell me in which video he’s talking about input PH that I could check? I watched the video about “Properly managing your runoff” and Daniel suggests raising the PH and decreasing K and increasing NO3-. I’m not really comfortable raising it to 6.5 and tried 6.1-6.2 with varied success in reaching 5.6 but still some days it’s between 5.4-5.5. I don’t really want to be pushing too much runoff and ruining the EC stacked in the substrate. I think with my idea of cutting N I did it too early and managed to acidify the substrate in the process with some excess K?
Regarding the Nh4 I currently use Masterblend 4-18-38 Tomato Formula which has 0.5 Ammoniacal Nitrogen so if I need more cations, I’m not in an ideal place, to say the least. In my neck of woods, I can only get Masterblend or Athena, but the price is 2.5-3x. From their guaranteed sheets I only see Nitrate in Athena. Would you recommend biting the bullet and trying it out? You’ve ran the line so any suggestions are appreciated.
In the video he also talks about managing ph with nh4, increasing your nh4 will lower your ph and decreasing your nh4 will increase your ph.
I had the same issue with Athena after day 35 that my ph would drop down to the same 5.5 but I’m running a custom mix now and can control it to some degree.
The other zone is doing fine and is between 5.7-5.8 so as is usual it’s cultivar/ environment dependant. Before changing nutrients plenty of stuff to take away from this and make notes for the next run to avoid the same mistakes. Just need to make some upgrades and will try to experiment which direction to take plants for the last weeks and dial it in.
Need to do some research as I feel week 4+ is my weakest area with making correct adjustments.
Thank you everyone for everyone’s input it gave me some ideas and some direction for improvement. Appreciate all of you <3
Note that in most cannabis formulations that are used at high EC values, increasing the pH beyond 6 will often lead to calcium phosphate precipitates in the lines. Due to the high Ca and P values used. In this case you’re very limited in what you can do with input pH, as it absolutely has to remain within the 5.5-5.8 band.
What’s your thoughts on using a small amount of polyphosphate (haifa grow clean) to help keep the system clean, they claim using even 15ppm P from the grow clean can keep it clean.
Although polyphosphates can help, they will still not be able to keep everything soluble at a pH of 6.2 if your Ca and P concentrations are high. Especially if you have any sort of warm temperature in the lines.
Hey can you explain a little bit about how it works using tissue samples?
How do you know whether to take samples from young or old foliage?
How long does it take you to get a sample back from the lab you’re using? I image it has to be pretty quick in order to make the test results useful.
How do you know what standard to compare your results with? (For example, how do you know the reading in your tissue sample is high?)
Hey I was wondering if you by any chance listened to the latest episode of “We the Growers” podcast?
If you haven’t heard of it it’s a podcast put out by the company Athena, usually just talking about their products.
On the latest episode they had Dr. Bruce Bugbee on talking about various subjects. One of the things he says is that he is starting to recommend a pH of around 6.5 for cannabis. I believe he said that they are finding that cannabis does not have much sensitivity to excess iron, which he says is a main issue with higher pH. The higher pH prevents issues with micro nutrients he says.
He also said that if what you’re doing currently with your pH is working then there’s no need to change, so maybe it’s not the biggest deal in the world.
There was more that he mentioned (something about manganese being mobile?) in the podcast and I am going to give it another listen and make some notes to share here.
Cannabis has a tendency to decrease the pH in the media during mid to late flower, which is the reason why Bruce is recommending a feed at 6.5. This is so that you can compensate for this drop. Since the Fe uptake is not affected very much at this point, there are not likely going to be any uptake problems from going in this direction. This is probably feasible at the EC values Bruce generally grows at, which are in the 1.5-1.8mS/cm range (except when he has tested high EC levels).
With that said, with the P and Ca concentrations generally used in most commercial formulations, an increase of pH to 6.5 on the lines will almost inevitably lead to clogging of the lines with probably disastrous results. For most formulations, feeding at a pH of 6.5 is going to be very problematic, especially if the EC values are >2.5 mS/cm. Not because of uptake issues but because of chemical issues inside the lines.
While I was scanning over Dr. Fernandez’s paper “Principles of Nutrient and Water Management for Indoor Agriculture” I think I stumbled onto the answers to one of my questions about where to take tissue samples from.
" The most definitive method for determining optimal nutrition is analysis of leaf tissue combined with crop yield, but leaves vary based on their position and age of the plant. Standardized sampling techniques are reviewed in the Handbook of Reference Methods for Plant Analysis [82]. The uppermost fully expanded leaves are a standard for analysis because they are actively growing tissue. These leaves provide a good indication of whole-plant nutrient status. Lower leaves are less representative because they can have low concentrations of mobile nutrients such as N, P, and K (especially when these nutrients are in limited supply) and high concentrations for immobile nutrients such as calcium and boron [75]. Tissue analysis of upper leaves may not reveal deficiencies in lower leaves. Upper and lower leaves should be analyzed if there are visible nutrient deficiencies or toxicities."
The book mentioned (Handbook of Reference Methods for Plant Analysis) is also available online and has sample-taking methods outlined for various types of plants but not cannabis.
We have the flower mix down pretty good but to be honest we’ve had issues with veg and up until about day 14 of flower, when I started this I was supposed to be getting a hand from someone with lots of knowledge but at basically day 1 he went mia unfortunately.
For the last 6 months I’ve been trying a bunch of different things in veg and the last month has been the best it’s been, I think I’ve been over feeding N and with the high Transpiration rate from the hps they are just sucking the N right up.
All the agronomists I have been studying lately seem to suggest that this is pretty much mandatory when troubleshooting plant nutrition issues because certain problems can look like each other making it hard to tell what’s what and toxicities can look like deficiencies adding to the confusion.
