I can recommend this soil physics script:

http://www.iup.uni-heidelberg.de/institut/forschung/groups/t...

It needs some basic math (for a physicist) and some other basics (it won't explain the many things physicists take for basic knowledge, such as the existence of electrons etc), but most concepts are explained well, IMHO.

Same for this book on isotopic tracers in the hydrological cycle:

http://www-naweb.iaea.org/napc/ih/IHS_resources_publication_...

(better if you have the basics of radioactivity etc down)

Also, here's a good book about physical oceanography:

http://oceanworld.tamu.edu/home/course_book.htm

Hm.. that's that off the top of my head.. there might be some more (also other areas); I can look if you're interested.