- Ralph U. Cotter, C. A. Magoon, Charles Brooks, Charles Faye Sarle, Charles Otis Johnston, Curtis Paul Clausen, Elmer Ottis Wooton, Floyd Franklin Smith, Fred W. Miller, Harvey Leroy Westover, Howard E. Middleton, Irvin Cecil Brown, Irvine Theodore Haig, James Thorp, Lester Henry Reineke, Lyle Thomas Alexander, Millard Peck, Orator Fuller Cook, Ronald Floyd Luxford, Samuel Augustus Jones, V. L. Wildermuth, Walter Chapin Holmes, William Hobson Rowe, William John Nolan, Willis James Nolan, Bernard Frank, Charles W. Culpepper, Clarence Sheldon Slater, Donald Bruce, Edwin Butterworth Mains, Elmer Valentine Walter, Horace Greeley Byers, John Thomas Scanlan, Johnson Thatcher Sarvis, Lorraine Joseph Markwardt, Paul A. Berry, R. R. Graves, Theodore Roosevelt Gardner, Anis Rae Peterson, Kaku Sato, Leroy Moomaw, Paul Axel Clarence Eke, George W. Morgan, John Carl Thysell, M. A. Bell
· 1932
- Alexander Campbell Martin, Arthur Henry Senner, C. C. Plummer, C. H. Hadley, Chalmers Jackson King, Curtis Paul Clausen, David A. Savage, Ernest Victor Abbott, Frederick Charles Lincoln, Glenn Gardner Hahn, Harold Francis Scholz, Harold Glenn Meginnis, J. Clark Salyer, James Herbert Beattie, Jenkin William Jones, Mayne Reid Coe, Paul William Miller, Ralph P. Hotis, Robert J. Sim, United States. Department of Agriculture, Walter Ernest Fleming, Wilbur Clifford Edmundson, Wilbur Magruder Hurst, Claude Hope, Frederick William Metzger, Ira Myron Hawley, James Robert McCalmont, John Walter Taylor, Victor Rickman Boswell, Walter Raymond Humphries, William Ernest Stone, E. E. Hall, Max Raymond Osburn, Roland McKee
· 1934
- A. D. McNair, Curtis Paul Clausen, Dalton Giles Miller, Dan Hansen, Dean Humboldt Rose, Duncan Dunning, Edward Florince McCarthy, Erasmus Manford Nighbert, Erval Jackson Newcomer, Eubanks Carsner, Frederick Vernon Rand, Harold Andrus Jaynes, James Robert Dawson, L. P. Rockwood, Ned Royce Ellis, Oris Vernon Wells, Paul Oman, Perez Simmons, Philip Lindsey Gile, R. D. Garver, Stephen Harold Hastings, William Albert Hartman, Arthur Edgerton Seamans, Edward Gantt Noble, George Wilburn Ellington, J. W. Connelly, Jacob Martin Lutz, Lester Henry Reineke, Lillian Claire Cash, Max Moore Reeher, Philip W. Manson, R. R. Graves, Raymond Herbert Miller, Roland McKee, Roscoe Harrison Carter, Archie Glenn Van Horn, David Victor Kopland, Theodore Roosevelt Gardner
· 1933
- Arthur Henry Senner, Auton William Skuderna, Benjamin Ralph Stauber, Charles Brooks, Clarence Elbert Clement, Curtis Paul Clausen, Edmund Lambert, Edward E. Clayton, Erval Jackson Newcomer, George McMillan Darrow, Glenn Arthur Cumings, Glenn Marsh Smith, James Herbert Beattie, James Robert Dawson, James Warren Hubbard, L. H. Patch, M. McPhail, Marion Bertice McKay, Ralph Edwin Beckett, Rosemary Laughlin Marsh, Rosemary Loughlin, Theodore Bergen Manny, Victor Rickman Boswell, William Doyle Reed, United States. Department of Agriculture, Archie Glenn Van Horn, Charles Evans Cormany, Chester Ihner Bliss, Erskine McFarlane Livingstone, Eugene Taylor Batten, Frederick Wulling Herbert, George Fordyce Waldo, John Gordon Gaines, Austin W. Morrill (Jr.), Lewis Alexander Hurst
· 1932
- Carl S. Scofield, H. S. Swingle, Alfred Edward Fivaz, Arthur John Ackerman, Brice Edwards, Carl Rohwer, Clarence Ferdinand Korstian, Conde Balcom McCullough, Cornelius Lott Shear, Curtis Paul Clausen, Dow Vawter Baxter, Eloise Gerry, Ernest William Laake, Frank Heidtman Lathrop, Frederick David Richey, Frederick Storrs Baker, Helen Hart, J. R. Holbert, John Clymer Dunegan, M. A. Yothers, Robert Claude Wright, Roger Dearborn Marsden, Thornton Taft Munger, Walter Ernest Fleming, Wells Aleck Hutchins, Albin Leroy Gemeny, Benjamin Koehler, Clarence Bobo Nickels, Dwight Isely, E. R. Van Leeuwen, Francis Everett Baker, George Frederick Sprague, James William Park, L. V. Wilcox, Lake S. Gill, Neil E. Stevens, Oliver I. Snapp, Ruthford Henry Westveld, Warren David Brush, Henry F. Bain, William Roy Wickerham
· 1931