TY  - RPRT
TI  - Essential elements and soil amendments for plants; sources and use for agriculture
AU  - R. C. Severson
AU  - Hansford T. Shacklette
PY  - 1988
DO  - 10.3133/cir1017
UR  - https://pubs.usgs.gov/publication/cir1017
ID  - cir1017
ER  -