Subject
- Abandoned mined lands reclamation -- Social aspects -- Oregon -- Willamette River Valley1
- Acid soils -- Oregon -- Willamette River Valley2
- Aggregate industry -- Environmental aspects -- Oregon -- Willamette River Valley1
- Agricultural chemicals -- Environmental aspects -- Oregon -- Willamette River Valley1
- Agricultural conservation -- Oregon -- Willamette River Valley -- Economic aspects1
- Agricultural conservation -- Oregon -- Willamette River Valley -- Evaluation1
- Agricultural credit -- Oregon -- Willamette River Valley1
- Agricultural ecology -- Oregon -- Willamette River Valley1
- Agricultural pests -- Control -- Oregon -- Willamette River Valley4
- Agricultural pollution -- Oregon -- Willamette River Valley2
- Agricultural productivity -- Oregon -- Willamette River Valley2
- Agriculture -- Economic aspects -- Oregon -- Willamette River Valley3
- Agriculture -- Oregon1
- Agriculture -- Oregon -- Silverton1
- Agriculture -- Oregon -- Willamette River Valley4
- Agriculture and state -- Environmental aspects -- Oregon -- Willamette River Valley1
- Air -- Pollution -- Mexico, Gulf of1
- Air -- Pollution -- Oregon -- Portland1
- Air -- Pollution -- Oregon -- Willamette River Valley5
- Air -- Pollution -- Research1