Subject
- Herbicides32
- Soils -- Oregon21
- Industrial arts -- Study and teaching18
- Soil microbiology17
- Soils -- Analysis17
- Wheat14
- Douglas fir11
- Fertilizers11
- Soil moisture11
- Soils -- Nitrogen content11
- Forest soils9
- Subterranean clover9
- Weeds -- Control9
- Herbicides -- Testing8
- Soil mechanics8
- Soils -- Oregon -- Willamette River Valley8
- Geology -- Oregon7
- Nitrogen fertilizers7
- Plant-soil relationships7
- Submarine geology7