Subject
- Agricultural pests -- Control -- Congresses34
- Forage plants17
- Forage plants -- Oregon8
- Hazelnuts -- Varieties5
- Mineral industries -- Oregon5
- Geology -- Oregon -- Field work4
- Geothermal resources -- Oregon4
- Natural gas -- Prospecting -- Oregon4
- Petroleum -- Prospecting -- Oregon4
- Apples -- Diseases and pests3
- Metallurgy -- Oregon3
- Rhizobium3
- Vegetable gardening -- Oregon3
- Alfalfa -- Seeds -- Inoculation2
- American wood2
- Clover -- Seeds -- Inoculation2
- Codling moth -- Control2
- Conifers -- West (U.S.) -- Ecology2
- Fisheries -- Economic aspects -- Congresses2
- Forest ecology -- West (U.S.)2