Ecology program at UC Davis rated top in the U.S. by researchers:

Research Productivity and Reputational Ratings at U.S. Ecology, Evolution, and Behavior Programs.
M. T. Brett, L. Brouwer, and L. A. Brett
Bulletin of the Ecological Society of America - Vol. 80 No. 4 - October, 1999
 

Agriculture program at UC Davis rated top in the U.S.by ISI:
ISI. 1998. Exclusive citation rankings reveal America's top research universities. Science Watch, 9(5):1-3.