Running tests on various phytochemicals can be quite expensive. Many phytochemcials have not even been discovered yet. Simply put, the research costs quite a bit of cash. I have not seen a whole lot of incentive for this to be done so that we know about all of them in our food. Despite these challenges, the data I have come upon indicates nutrient dense farmed crops do have a different markedly different properties with respect to these nutrients.
First of all, phytochemicals consist of different mineral elements, as does all matter. This implies that if we take a hig brix nutrient dense carrot that has double the average calcium and trace mineral content of your average organic or conventional carrot, by definition, we will have different phytochemical concentrations. Hence, I consider analyzing the mineral content to be more important than the phytochemicals because if the mineral tests prove to be disappointing then I know the plant could not have made its full complement of phytonutrients.
For example, take the case of the missing phytochemical in pineapple thanks to depleted soils. See http://webcache.googleusercontent.com/search?q=cache:GkSiCKJMPpUJ:www.ralphmoss.com/html/cach379.shtml+noni+pineapple+depleted&cd=1&hl=en&ct=clnk&gl=us.
Research on microbiology products shows that various vitamin content goes up with their use. For example, vitamin C content increases. See http://www.infrc.or.jp/english/KNF_Data_Base_Web/PDF%20KNF%20Conf%20Data/C6-1-216.pdf. My experience tells me that a decline in soil life makes minerals less available to the plants, which means vitamin content.
Vitamin content has gone down, following mineral declines. See http://www.scientificamerican.com/article.cfm?id=soil-depletion-and-nutrition-loss. My experience tells me that these declines in part come from dying soil life that has a harder and harder time making minerals savable to the plants. Fortunately, using quality microbiology products restores the soil life addresses this problem, putting back the important phytochemicals into our so we can have foods that promote health, rather those that drain it.