Yeah that soil data mart is a whole other animal. Luckily I'm mostly on the agronomy side of things right now, focused on Nitrogen, so we just kinda skim the data for soil properties (such as hydrology) that we need and display the GIS plots as a visual aid for the user. Then it's just manipulating that data to show trends on the GIS plots that the user is interested in. Having that soil data sitting there in a free and consistent format makes my job a hell of a lot easier, as I'm sure you found with the nutrient db.
I've recently started playing with Json (well, Google's Gson anyway) myself for a mobile application I'm working on so this may be a nice learning experience for me, but I'll dive into your source a little more this weekend and maybe try to knock an issue or 2 off your repo's list :)
