Plant nutrition in greenhouse cultivation differs in many essential aspects from field crops and justified the development of a special publication on this subject. The high productions realised and the specific produce quality requirements ensure high uptakes of nutrients and a careful tuning...
books.google.com
This is a good read on the reasoning behind (and usually the source quoted in most papers dealing with Si and horticulture) adding Si first and PH adjusting or taking the approach
@Dirtbag does and you need to PH the prediluted form. You can still run into problems adding it after other nutes unless you have a real good understanding of interactions with your specific nute regiment. You could nerd out 100% and do the math if you like.
Now, in practice, I run Si at 34 ppm. Add it to the plain water in a rez and let it sit overnight. PH in the morning and then mix the nutes. I was having S precipitate out of my solution over the span of a flower cycle (buildup in the rez) and this cured a lot of that problem.
If you want the easy way follow what GH says about it. As a bonus the reasoning behind adding
Calmg (containing Fe) before a nutrient that contains micros is Fe. Fe is another one of those things that's a real bitch in nutrient solutions and is very sensitive to O2 and PH. Depending on the type of chelate used for the Fe up to 50% of it becomes unavailable above 6.5 and above that starts to precipitate out and bond with other ions.. Also the reasoning behind hitting Si first ---> Ph down ---> then so on. It's mainly to control the PH of the solution before trying to dissolve other nutes into the mix, like Fe, since it is usually in the highest concentration of all micros by a long shot.
