1. Efficient use of nitrogen in cropping systems;Bock,1984
2. Geologic nitrogen in Pleistocene loess in Nebraska;Boyce;J. Environ. Qual.,1976
3. Saline-seep diagnosis, control, and reclamation;Brown;USDA Conservation Research Report No. 30,1982
4. Moisture and nitrate relations in dry-land agriculture;Buckman,1910
5. Nitrogen in Subsurface Discharge from Agricultural Watersheds