Very general page about growing radishes from a gardening perspective. 
http://www.diynetwork.com/how-to/outdoors/gardening/fertilizer-for-radishes

Cornell extension page about radishes- typically plant traits, site characteristics, etc. 
http://www.gardening.cornell.edu/homegardening/scene341b.html#profile

Kind of a poor quality video, but here is what I was talking about to explain the negative charge of soil.  So we could either create an activity for teachers to conduct this.  OR we could even make our own video. 
https://www.youtube.com/watch?v=s4HoRtqhPOM

Also, I ordered a high school activity booklet from the Nutrients for Life Foundation, it was a free resource.  I should be able to download it soon, and I can send any more information or ideas after reading through it. Also on the page are some videos about phosphate and potash mining- maybe a good thing to teach about where fertilizers come from.
https://www.nutrientsforlife.org/for-teachers

Article about Dead Zone in the Gulf. 
https://www.sciencedaily.com/releases/2008/04/080421143836.htm

Lesson from USGS (aquarium) with adding fertilizers to pond water and observing differences in the aquatic community
http://pubs.usgs.gov/of/1998/of98-805/lessons/chpt6/act2.htm

*Along with the environmental side of things- I just remember that K-State Extension has a watershed model where you can actually show pollutant runoffs into surface waters- it's pretty cool! I look for videos of this, but I couldn't find any.  So if we want to do that, I could probably ask the extension person in charge to film a video of it.   I think it would be a great resource for teachers and students!

That's all for now, I will send more things as I come up with them!!