My own fault mate. I'd had three previous runs of Sensi Seeds beans and they were all shit apart from the Shiva Skunk. The White cheese was so bad I just binned it. Got bit three times and thought, fuck it, letsntry a forth The Bird I was sure would be OK since it's a collab with Humboldt seed company. Well I was wrong :)
The other reason was I'm new to this level of detail. I know lots about the products, but not about the chemistry required to manufacture your own nutrients. I could probably knock up something coherent, but not really know what I was doing and just follow the recipe.
I've learnt so much since starting this experiment. I didn't even know what a pycnometer was or how to calculate estimated elemental values based on the guarenteed analysis or solution density. I'm now at a point where I have a tool that I can plug in the ml/L of each solution and confidently say that plant has enough of everything. Just waiting for my lab results back to confirm everything is sweet. I can also print out graphs to visualise ramp up and down of macros etc. And cut things down to the bare minimum! I like growing hydroponics, but I don't want to be contributing to environmental issues by slinging P down the drain when I don't need it. And wasting money :)
I'm quite confident after doing a shit ton of research that we simply don't need PK for cannabis. And all we're doing is throwing money away and damaging the environment. And only so the MDs of these nutrient companies get rich. The more I've researched things, the more it has become clear that a lot of the shit we thrown in is simply not required. I may do a detailed post about it in the future, but tolerance to overfeeding is a lot higher than you think. Microelement toxicity is more likely due to them being chelated and can be taken up easily. That and they're not needed in large quantities. N, P and K have a much wider tolerance band. For example, I've read several detailed studies around nutrient requirements specifically for cannabis. They all differ slightly, but cover a wide array of cultivars. Based on their research, I've set my tolerance bands to the following.
K: 100-170PPM (can go way above 300ppm without issue)
Mg: 35-100PPM (15-150ppm without too many issues)
You can also checkout the standard recipes like Hoagland vs LARS. They differ quite a bit, but I'd bet my left testicle both would grow a green weed plant
I'm pretty confident that most base nutrients sold in hydro ships are just smoke and mirrors. Take calmag for example. If you know the density and full GA of the brand of fertiliser you're using, you could just up the a or b a little depending on the composition split. Of course there will be differences in quality etc due to the quality of ingredients etc and some will have slightly different ratios of NH4+/NO3- depending on what the target market is. Cannabis doesn't like NH4+ a lot. In soil, bacteria will convert it to NO3- but in hydroponics, if you don't add the nitrofying bacteria, it won't be present and will cause problems. Terra Aquatica can do both soil and hydro, but the NH4+/NO3- ratio is pushing the limits for hydroponics I think. Suppose that's the trade-off when you're trying to cover a wide variety of species.
Anyway, talk about a tangent! I shall be back soon :)