Contents

01 April 1977
Vol 196, Issue 4285

About The Cover

Aircraft of National Aeronautics and Space Administration, carrying a thermal scanner, passes over an experimental field at the U.S. Water Conservation Laboratory in Phoenix, Arizona. The scanner maps canopy temperatures that are used to predict grain yield on the basis of a “stress degree day” concept. See page 19. [U.S. Department of Agriculture, Agricultural Research Service; Con Keyes, Tempe, Arizona]