Soil Vs. Hydroponics (Nutrition Edition)

First things first: your produce will NOT taste like "water" if hydroponically grown. Taste is affected by a myriad of factors, not the least include whether it was grown in one particular substrate or another (assuming a few chemicals are controlled for). We should also discuss what "soil" means. Soil is weathered rock and organic "stuff." Organic stuff can include humus, living things, twigs, dead roots, excrement--basically anything from a living thing, including itself. Dirt, however, is just weathered rock. This does mean that aquaponic growbeds are soil, but that simply shows that the definition of "soil" is too broad for our purposes. So, we should just arbitrarily exclude hydroponics.

As to the nutritional value of certain soils there are huge differences. Soils can be low in certain nutrients, have low accessibility to them, and/or the opposite for distinct nutrients. One soil may be loaded with accessible Iron (Fe) but has a pH of 7.4--around where Fe becomes largely "unusable." Therefore, the plant--which is programmed by evolution (naturally or artificially) to spread its genes--will have to make choices about reproduction. Anyone who has talked to a pregnant, or formally pregnant, (which is everyone) should know that making offspring is incredibly taxing on resources--for members of the Kingdom Plantae as well as every other kingdom. So, a deficiency in nutrients which produces say, fruits, will result in a choice being made by the plant--produce more low-quality fruits, or fewer high quality fruits. Most flowering plants will choose to lower the quality of the fruits rather than risk something not eating it. For many garden plants, we made that strategy. Because what does a subsistence-farmer want more of?--calories or "nutrition." If you said "calories", you are likely correct. Better to be missing something in your diet than dead. 

Coincidentally, if the nutrient value is high, but skewed, this effect will show up as well--for a different reason. If nitrate (NO3-) is too high in a soil/solution, then vegetative growth will not yield to flowering growth easily. As you can see, nutrient availability is a determining factor in nutritional value. In hydroponics, it is exactly the same. Without certain chemical in the soil, certain crops do not have the "correct" taste--as is the case with wine-grapes and the snobbery thereof. While hydroponics cannot replicate those chemicals if their precise formula is unknown to science, hydroponics can replicate all the nutrients necessary for individual plants to thrive, and has been able to since the 1930s.

"But wait" you say, "doesn't the soil have a wholesome, organic, natural wonderfulness of mother-earth." Uh...no. No, it does not. There is nothing different about the NO3- present in a solution of water in-between sand particles of soil than NO3- present in a solution of water in between sand particles in a hydroponic growing medium. That's the wonderful thing about physics, chemistry, and science in general: parallelism. That means that the physical forces governing one thing is the same everywhere else. If a person can tailor build their hydroponic systems nutrient solution to a specific plant, then it is likely to be more nutritional--though it is possible to do that with soil, just harder. Also, and this is a particular pet-peeve of mine, just because something is somehow "natural" it does not mean it is somehow better. You know what's naturally occurring in plants? CYANIDE. Narcotics are derived, mostly, from one plant--opium. Since when did heroin become good for you because it is natural? Uh...never... Anyway, where were we, oh right, hydroponics. The truth is, I cannot make a judgement on its nutritional quality because it is completely, and totally dependent on the situation.

What I can do is tell you which is better for the environment and is probably much healthier for you: hydroponics. Hydroponics uses significantly less pesticides, and zero herbicides--because there are no weeds. None. Pesticides are a suspected cause of Colony Collapse Disorder which threatens the entire food supply supported by bees--so basically everything. In fact, when hydroponic farms do use pesticides, it is limited and largely inside the greenhouse due to a local parasite (aphid, etc.), so it does not contaminate the bees! In fact, many greenhouses are using parasitic insects instead of pesticides. Score one point for the environment! Oh, and many of those pesticides are being shown to harm human health in minute or, historically, significant ways! The clear winner here is hydroponics.