I think, given the cost of ingredients, it warrants the use of a control. Plants lend themselves to this quite well, in fact, the very nature of container growing isolates each from the other and makes such tests not only easy but kinda fun. Grow one container with and one without, it's really that simple. But to be sure your results are somewhat fair you can do things to make the playing field somewhat even ie. pot size, medium, light and use clones plant the same time/way etc. Why? Because these days it seems it's all about the money. Plant product manufacturers make all kinds of fancy claims and don't tell you how they came to the conclusion it really does as intended. Because of the lack of regulation regarding most of these products there is little or no requirement for honest disclosure. We fall victim to wicked artwork or hearsay, maybe a test on Yoo toob that is so unscientific or impractical that you wonder why they bothered to post it? The best way is to set up a simple test and do it yourself. When it comes to growing plants you can't have enough shit except for bull shit!