I'm indoor with Earthboxes right now, but I'm looking into cover crops for my outdoor grow this summer.
I think that my boron is high on top of sodium and potassium. I blended in more rock dust(azomite, greensand, oyster shell flour, and basalt) but after reading some benefits of gypsum, I think that I will use some to leach with. I didn't believe in gypsum, but everything that I have been reading about Na and Boron toxicity has said to use gypsum. I have some on hand and I was about to flush it through the soil... My phosphorus input is compost and that is basically all of my macros in this mix, everything else is rock dust and Mn sulfate. I don't even use kelp anymore.
Right now, I am using a comfrey FPE from build a soil. I'm also using EM-1 in the reservoir of the Earthbox. From the reading that I did last night, I might start making my own FPE out of acid loving plants because plants with lower Ph will have more Mn in the plant tissue. My wife recently made a ferment out of bananas that smelled just like banana bread. I made this FPJ out of a tomato plant in my garden and I was able to harvest a lot of liquid from them, but I haven't had luck with any other plant material. If you know of a good one, let me know. I haven't used comfrey yet.
I came across a couple of articles that said that adding chelates to micronutrients will make iron more available, which makes Mn less available. So, when dealing with Mn deficiency issues, it's not a good idea to use chelates. I found out the hard way. I'm pretty sure that Amino acids and Humic acids are chelators. For the life of me I couldn't figure out where the extra iron was coming from on the soil tests because I was using Big-6 which didn't have iron, but it did have humic acid for a chelate. It was a complicated lesson that I learned a couple of weeks ago and I often ask myself and my wife if I am making this too complicated. I'm under the impression that the only way to combat Mn def is by foliar feeding.
I would also recommend checking out soluble gypsum - something like Diamond K. Otherwise, it takes some time to break down. Gypsum will strip cations (Ca) and anions (S.) Ca has the strongest charge of all cations, so it breaks apart bonds with Mg, K, etc when flushing. S does the same with Na, nitrates, sulfates. This is an agricultural application, and it is very effective at stripping K and Na. Some people actually "dump" their mix by flushing with say, several tbsp soluble gypsum. This is a sort of reset to flood out excesses and build to a more balanced profile. It's also a tiedjens/albrecht method where you saturate soil with Ca carbonate to 60%+, and then finish with gypsum (up to 85% according to albrecht.) In this system K and P are throttled to the minimum, to ensure calcium is always "available." The analogy I like for this is that your nutrients are basically stored on shelves. The higher your CEC, the deeper the shelf. Deep shelves hold a lot of stuff, but it's not always so easy to get to the stuff in the back. So if 80% of the stuff is calcium, you always have calcium. Then it's just a matter of reading your plants, or applying a known program with known results.
FWIW I came up with this macros formula in my research (this is aimed toward field scale agriculture
The heavier the mix, the less you need Mg/K
Ca 80-85%, Mg 8-12%, K 4-6%
S=P=K 4-6%
Definitely make your own FPJ/FPE. There are a few ways, cut or mash material first:
1. the old "stick some comfrey in a bucket of water and make diarrhea juice" works well. Some frown on the "pathogenic" microbes involved, but they're acid loving decomposers that prefer a body of water, so in a healthy soil mix they'll be food in no time.
2. em1/AEM(home made em1,) water, and plant material. This is exactly the same as the first, but will have very little if any smell. There will be a large population of LABS, which again will mostly be food.
3. traditional KNF: 1:1 mix of sugar and plant material. The high sugar content suspends the microbes and makes them go to "sleep." Best shelf life, and if you like adding a bit of sugar at certain times it's an added bonus. Ferments made with sugar will be much more acidic. The alcohol formed from the sugar and plant material will extract the water (chlorophyll) from the plants, along with a cocktail of the auxins that were present at the time of extraction (take your material at sunrise, when there's still dew.)
I've been making my own LABS (rice wash,) then you strain and mix the wash with whole milk. This will yield pure LABS, and some free cheese that's kinda like feta to boot. You can then stretch this pure LABS into Activated Essential Microorganisms (AEM,) which has a shorter shelf life but is a brewed up version that will multiple your supply several thousandfold. Good for ~3 months room temp. Highly recommend growing your own comfrey and nettle for these purposes. Use leaves to make growth formulas, and blooms/fruits for flowering/fruiting. Check out Hyroot's guide on here. These are typically used more as soil stimulant and hormone regulators.
So chelates... Yes, chelation will favor certain elements over other, however all organic nitrogen will break down into amino acids and ultimately be chelating. In fact, in organic soil, chelation is occurring basically all of the time. The high amounts of OM we run lends itself to high S, which binds with metals to form saltes. All sulfate form metals are in salt form. We also generally have very high humic/fulvic levels in our mixes. I would definitely avoid overly concentrated sources of chelation, like you are. Those are intended for field production. The aminos I refer to are home made from fish. It's another KNF formula. Mn is highly unavailable in high OM soils, and especially if PH isn't staying on the low side. I think the foliar Mn should be a good short term solution. Just go easy on it, and watch closely.
If you're interested in some good reads, check out JADAM(KNF) and The Intelligent Gardener(soil science.) The methods I've presented are mostly borrowed from KNF/JADAM and high brix gardening.
www.kisorganics.com
