(1991) back matter (jnrlse)...george w. carver and booker t. washington, and self- development, hill...

PRO FI LES The American Society of Agronomy honors the 1890 land-grant universities for 100 years of service and research.

The Journal of Agronomic Education presents two of three Profile articles on role models who have brought diversity and excellence to a wide array of students through teaching and research at land-grant universities.

-Dr. Randall J. Miles, JAE Profile Editor

Walter Andrew Hill-Outstanding Minority and Scientist

D. Jordan*

In 1890, Congress passed the Morrill Act establishing land-grant colleges and universities to serve African- Americans. To commem- orate 100 yr of service, the American Society of Agronomy honored an outstanding minority educator and scientist, Walter An- drew Hill, at the 1990 annual national meetings in San Antonio, TX.

Hill exemplifies the researcher-educator who has dedicated his life to people. In the same spirit of George Washington Carver, Hill integrates both education and research to enhance the quality of life for all people. While researching the numerous facets of the sweet pota- toes [Zpomoea batatas (L.) Lam.] Hill has helped edu- cate a diverse group of students, both domestic and international.

Hill’s interest in science began early in his life. He knew that he loved science and people and wanted to make a contribution to both. He was not sure how his interest could be used in a meaningful way, but Hill was determined to apply himself to solving the problems and concerns of people, particularly African-Americans.

Hill grew up with a deep-seated commitment to serve his community. His father was an African Methodist Episcopal minister and his mother was a schoolteacher. During his teenage years, Hill often traveled with his father to the rural communities surrounding North Little Rock, AR. His father was instrumental in bringing many African-American youth to urban North Little Rock to

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School of Natural Resources, Univ. of Missouri, Columbia, MO 6521 1. Contribution from the Missouri Agricultural Experiment Station. Jour- nal Series Number 11335. Received 2 Jan. 1991. *Corresponding author.

published in J . Agron. Educ. 2050-52 (1991).

Educator

further their education. This strong dedication to education and people exemplified by his father later influenced many of Hill’s professional decisions.

With a scholarship to Lake Forest College in Illinois, Hill graduated in 1968 with a B.A. degree in chemistry. While teaching high school chemistry, physical science, and general science in the Chicago school system, Hill earned a M.A.T. in chemistry at the University of Chica- go. Although Hill found teaching at the high school level to be rewarding, he sensed that something was still missing in his life. He needed challenges to help him make greater contributions to society. He states that, “The question in my mind became how can I make the most impact on people, particularly Africans in this country as well as in developing countries?”

Through his own research, reading about the life of George W. Carver and Booker T. Washington, and self- development, Hill discovered he had an interest in agriculture with an emphasis in food chemistry. He called several universities to inquire about their programs. Hill was directed to a soil chemistry program instead of food chemistry at the University of Arizona. The soil chemistry program did not discourage Hill. In fact, he became even more excited because he viewed the study of soils as a medium for plant growth. Hill reasoned that if he understood the soil system then he would have a strong basis for understanding food and plant chemistry. In addition to his newly-found program, financial assistance and a receptive faculty were available in the department.

Hill enrolled as an undergraduate in soil science with Dr. H. Bohn as his advisor at the University of Arizona. Most people would have become discouraged at re- entering an undergraduate program after completing a master’s program, but Hill was excited about his new career possibilities.

Seeking knowledge with every task was a second nature for Hill. Like Booker T. Washington, Hill never missed an opportunity to prove that even in the most menial tasks one could take pride and dedication in do-

50 J. Agron. Educ., Vol. 20, no. 1, 1991

ing an excellent job. A typical task of dishwashing in alab was viewed as an opportunity to become integratedinto the lab activities. This was exactly what happened.Dr. Bohn soon realized that he was more than qualifiedto successfully complete a master's program in soilchemistry. The confidence and training Hill received atthe University of Arizona inspired him to pursue andcomplete his Ph.D, at the University of Illinois in 1978under the auspices of Dr. Toby Kurtz.

After completion of his doctoral studies, Hill had sev-eral job opportunities with industry, government, andacademia but his decision was clear when TuskegeeUniversity made him an offer. The university, located ina small rural town in Alabama, desperately needed a soilscientist on the faculty.

Hill's job neatly fit both his academic and personalneeds. The job was extremely challenging. He taught soilchemistry, soil microbiology, soil physics, soil classifi-cation, soil and water conservation, and general soilscience. In addition to teaching, he served as advisor forthe plant and soil science club, coach for the soil judgingteam (3), and conducted a full-time research programwith both graduate and undergraduate students. Hill didit all. Many wonder how Hill was able to be so success-ful with a more than full teaching load, extracurricularactivities and a research program. Hill said, "It was achallenge that I would never wish on any young newprofessor but I discovered early-on that I had some ofthe best talent in my students that one could ever hopefor. They were excited about science and were willing towork hard. So, what I did was delegate and coordinateresponsibility appropriately and trusted my students."

He added, "I allowed them to be a complete part ofmy research program. I mentored and trained themresponsibly and they trained my new students." It wasnot unusual for Hill and his students to work late intothe night. This kept his program going and growingstrong. His students have won 17 awards for outstand-ing research projects and presentations.

One of Hill's former graduate students, Edwin Mar-tinez, applauded his philosophy. Martinez said Hillcreated a positive environment for productive research.He further described him as a thorough, accessible per-son who sets high standards and gets the best out of hisstudents. He said, "Hill cares about you as a person."Hill became Martinez's role model. Martinez is nowworking on a Ph.D, in agronomy at the University ofIllinois and he credits Hill with assisting him in achievingthis goal.

Over the last 12 yr, Hill has had several researchprojects (1,2,5,6,8). Some of his earlier projects were ex-amining the fertilizer use efficiency and associativeN2-fixation of sweet potato. The association between thesweet potato and the N2-fixing microorganism maypotentially decrease the amount of fertilizer needed forsweet potato production (1). This work received thePlucknett Outstanding Research Paper Award in 1983 atthe International Society of Tropical Crops Symposiumin Lima, Peru.

Presently, his main research focus has been on sweet

potato plant environment relationships for low-inputcropping systems and for controlled ecological lifesupport systems for space missions (5,6,7,8). Hill iscoinventor of a system for growing sweet potatoeshydroponically for space missions (7).

Because of his work and that of his students andcolleagues, a center for sweet potato research has beenestablished in conjunction with the George WashingtonCarver Agricultural Experiment Station in Tuskegee. Heis truly a leader among professionals in research andteaching.

Hill's research and teaching has merited several awards:United Negro Scholarship Fund Distinguished ScholarAward, Tuskegee University Faculty AchievementAward, The White House HBCU Faculty Award forExcellence in Science and Technology, Plant and SoilScience Distinguished Faculty Achievement Award, LakeForest Distinguished Service Citation, Black EnterpriseMagazine Futurist in Science and Technology, andKellogg Fellow.

Hill's professional experiences are too numerous to listbut they range from projects organized for ruraldevelopment issues (9) to chair of International projectsfor space research.

Since 1987, Dr. Hill has served as dean of the Schoolof Agriculture and Home Economics, director of GeorgeWashington Carver Experiment Station, CSRS researchdirector, and Cooperative Extension administrator atTuskegee University.

Although Hill is no longer as active in the teachingprogram, one can easily see the impact he has made onthe Tuskegee agricultural program, the state, and otherparts of the world. It has been 100 yr since the MorrillAct of 1890 was passed. Hill is representative of manyoutstanding African-Americans who have contributed tothe development and continued progress of theagricultural industry in America. Many share the samedream of our 1990 Outstanding Minority Educator whostated:

I became a scientist to be a role model and teacherof Science for Black and minority youth to encouragethem to believe in themselves and their creativepotential, and to develop new knowledge throughresearch that contributes to providing food and healthand a better environment for all (4).

ACKNOWLEDGMENTS

Dr. Debrah Jefferson and Ms. Geneva Williams aregratefully acknowledged for their insightful commentsand timely review of the manuscript. I also thank Dr.Hill's former students and colleagues for their contri-bution.

J. Agron. Educ., Vol. 20, no. 1, 1991 SI

Donald Robert Wallace—A New Kind of Role Modelfor the 1990s

D. Jordan*

For more than 20 yr,Donald Robert Wallace hasworked with young, blackurban students to successful-ly motivate them into fieldsof agriculture. He has a longhistory of bringing theagricultural and biologicalsciences alive for urban stu-dents. Although he is knownfor the work he has donewith urban black youth, hisreach is by no means limitedto blacks. Over the years, he has recruited and retaineda diverse group of students, which includes both urban,rural, and students of all racial and ethnic backgrounds.Wallace describes himself as color blind, meaning thathe looks at the person as a human being with specificneeds and interests rather than stereo-typing the in-dividual.

Wallace, like many other agriculturalists, is from atraditional farm background. His grandfather was afarmer in southern Illinois and his father worked withthe USDA as a soil scientist. He received his B.S. degreein Fisheries and Wildlife at Michigan' State University in1968 and taught courses in natural resources, biologicalsciences, and agriculture for 14 yr at East St. Louis HighSchool in Illinois. He also received his M.S. and Ph.D,in agricultural and extension education from MichiganState University. During his years at East St. Louis HighSchool, he developed a successful program in agriculture,which attracted more than 1000 students. Due to a short-age of funds for the school, the program was reducedto about 400 students (the majority being urban blacks)enrolled in some aspect of agriculture. Even with this

School of Natural Resources, Univ. of Missouri, Columbia, MO 65211.Contribution from the Missouri Agricultural Experiment Station. Jour-nal Series Number 11336. Received 2 Jan. 1991. 'Corresponding author.

Published in J. Agron. Educ. 20:52-53 (1991).

reduction, he had clearly established a record that manyother recruiters cannot equal. Wallace remembers hetaught 12 classes a day including classes in the horticul-ture program he helped develop at the local junior col-lege. His day usually began at 0700 h and ended around2000 h. During the summer months, his studentsprogressed even further by working in the agriculturalbusinesses and landscape projects.

In 1982, Wallace proposed the same program on thecollege level. He returned to Michigan State University(MSU) and coordinated the Minority Apprenticeship Pro-gram (MAP). Wallace brought five minority high schoolstudents to Michigan State to work under various agricul-ture or natural resource professionals for on-site train-ing. The MAP is a special program for minority highschool sophomores, juniors, and seniors whose missionis to provide academically superior and personally out-standing minority high school students with an opportu-nity to view and experience agriculture and naturalresources. Another goal of the program is to increase theawareness of these students about agriculture by provid-ing professional work experiences in the College ofAgriculture and Natural Resources. Finally, it encouragesand supports minority high school students to enroll inthe College of Agriculture and Natural Resources andpursue professional careers in the field.

The minority high school students come to MSU cam-pus for 7 w where they live and work away from homeon their own to develop leadership skills and importantemployment skills that will set the pace for their educa-tional career in college and their professional future afterthey graduate. These students go through a rigorous selec-tion process. They are required to provide personal andacademic references, and explain in writing and in a per-sonal interview what they hope to gain through their par-ticipation.

The program grew rapidly under the auspices of Wal-lace. There were 36 students with six sponsors in 1983,and 54 students with nine sponsors in 1984 (MichiganState Univ., 1985). Not only did the program serve as


a recruiting tool for many of the best and brightestminority students from Michigan and nearby states, butit became a model that many other universities haveadopted. Wallace developed a corporate board to assistin the development and modification of the MAP as aNational Model Program. He interviewed, selected,trained, and supervised the adult staff for the program.

In addition to on-site training, seminars and careerworkshops were held for the students. These workshopsand seminars were designed to provide the student witha variety of leadership development opportunities. Fivemajor areas were concentrated upon: (i) time manage-ment—which emphasizes the importance of using sched-ules and establishing priorities to use time effectively, (ii)self-awareness—students learn how to deal with indivi-dual strengths and weaknesses, (iii) problem-solving—alternatives to handling everyday problems, (iv) assertive-ness skills—designed to allow students to know when andhow to effectively express themselves, and (v) motiva-tion—expose and stimulate students to the possibilitiesto life in general (Michigan State Univ., 1985). Severalmajor companies recruited students for internships andlater hired them as employees.

Another spin-off program from the MAP was im-plemented in 1987 by Wallace called CAREERS for theMichigan Department of Natural Resources. The pro-gram gives hands-on experience with high schools, juniorcolleges, and universities during the summer in which par-ticipants are selected for future employment. He wrotetraining materials to accompany the CAREERS programfor DNR managers. The topics were Effective Supervi-sion, People are People, Needs and Values of the Minori-ty, and Effective Assessment. He has also written aninternship program for Domino's Pizza, Inc.

One might ask, "What does the minority student thinkof a white male as a role model?" Several of Wallace'spresent and former students address this question. Theyall describe him as someone who is sincere and truly hasthe individual's best interest at heart. They each say heis fair and allows his students the opportunity to provethemselves. Even though he gives a person an opportu-nity; he expects that person to hold their end of the bar-gan as well. One student stated, "He believes in you andexpects you to do well." Many of his students have goneto major corporations, graduate school, governmentagencies, and universities, and all have retained an in-

terest in agriculture and a belief in the importance ofagriculture to humankind. One student summed up Wal-lace in the following way: "I really don't care what colorDr. Wallace is. I know he cares about us and has madethe inaccessible accessible to us." Even more important-ly, Wallace has shown hundreds of black youth the op-portunities that exist in agriculture. Many black studentsassociate agriculture with a "hard life," both in a histor-ical and present-day perspective. While this perspectiveis an understandable one, Wallace has worked to makestudents aware of the vast opportunities that exist inagriculture and related areas and that agriculture neednot be a "hard life."

Wallace's colleagues at Lincoln University also describehim in a very positive manner. Mr. Edward Taylor, Ex-tension and Placement Specialist, sees him as a creative,innovative person who is dedicated to his students. Hefeels that Wallace works exceedingly well with all studentsbut has a particularly dynamic interaction with black stu-dents. Although Taylor says that Wallace can be overlyoptimistic, he also thinks Wallace is a person with vision;a person who focuses on possibilities rather thanobstacles.

There have been, and still are, many important blackrole models and educators in agriculture. As we move intothe 1990s, a new kind of role model like Donald RobertWallace will be important in maintaining a network ofmulticultural agricultural professions for the future.

ACKNOWLEDGMENTS

I thank the students, staff, and faculty at LincolnUniversity for their input in this article. Dr. DonaldRobert Wallace is presently Director of Recruitment andRetention with the Department of Agriculture, NaturalResources, and Home Economics at Lincoln University,Jefferson City, MO. Ms. Geneva Williams and Dr.Shirley M. Jordan are acknowledged for timely and con-structive criticism of the manuscript.

J. Agron. Educ., Vol. 20, no. 1, 1991 53

James Michael Tiedje-The Man and His Vision D. Jordan*

As Jim Tiedje’s research, teaching, and service record shows, he is a man of vision and creativity. This is manifested in the range of research and many fine scholars he has produced over the years. Tiedje’s fore- sight and imagination is truly far-reaching as reflected in the projects and people he has chosen to work with. Even when his laboratory was filled to capacity with his own staff and students, he always managed to find space for the eager young scientist from Holland or Yugoslavia to the mid- career scientist who just needed to learn a new technique to carry on an effective research program. This unself- ish attitude toward promoting the growth of science and interaction of ideas has resulted in a worldwide melting pot of scientific knowledge and common need to solve the problems of the world. Tiedje’s students have taken on a range of careers from being scientists and teachers in major companies or universities to being president of a university.

The students who have worked under his tutelage represent a diverse group selected based on their promise and intellectual acumen. As one of the first faculty members to accept an African-American female graduate student, he sent an important message to the department and college. This was new ground he treaded to explore the talent in a group often ignored. Because he has vision and sensitivity that reaches out to all groups, he is able to tap into resources that are often overlooked by other people. This extends into his research and teaching activities. Tiedje has been willing to take the first steps in addressing research questions that require novel and sometimes controversial approaches to solving problems. This is obviously seen in his meritorious record.

What began as a seemingly easy task turned into a valuable learning experience. After all, Tiedje was my major professor, which I thought would give me an extra advantage in writing this article. The real advantage came from a recent interview with him when I realize how understanding someone’s personal history truly gives a greater appreciation for that person. As a student, I had a very distant but positive view of him. After surviving the rigors and high standards he sets for all of his students, I assume that he had done his job (reasonably well, I might add) and that this chapter in my life had ended.

School of Natural Resources, Univ. of Missouri, Columbia, MO 6521 1. Contribution from the Missouri Agricultural Experiment Station. Jour- nal Series Number 11337. Received 2 Jan. 1991. *Corresponding author.

Published in J. Agron. Educ. 2054-56 (1991).

As I delved into my career, he became an even greater mentor to me. He was very willing to share his wealth of knowledge on the practical details that young professionals often encounter (e.g., job interviewing skills) to using his laboratory equipment (free of charge) to finish a project at my new job.

As I talked to his former students, my former colleagues, and reflected on my own personal experiences with him as a mentor, an important quality emerges about him as a person. He first approaches all people with human concern and compassion, not just wanting and ex- pecting the best, but willing to go the extra mile to see that happen. I can remember writing my first paper for presentation at a national conference. The deadline was near and he was leaving for Christmas vacation. He gave me all the possible phone numbers for relatives where he could be reached so that we could discuss the final draft. I remember telling my friends what a “swell advisor” I had because he wanted to see me succeed.

Tiedje does not always verbalize his feelings about his students to them but he always has their best interest at heart. He seizes every opportunity to provide them with the experiences they need to grow and succeed. For example, it is common for his students to review research articles or grant proposals. Clearly this invaluable experience builds the student’s confidence and self esteem. Along with instilling self-confidence, he excites his students about the study of science. This motivates their desire to succeed and stimulates them to approach science with innovation and creativity. Most importantly, he fuels their desire to make a difference in the world we live in. I had the good fortune to spend 5 yr as a student in his laboratory, and while I am the first to admit that I am somewhat biased, I think I am qualified to present a unique perspective on why I, present and former students, colleagues, and friends value him as a person, outstanding scientist and educator with extraordinary vision and creativity.

Tiedje spent his early years as many typical agronomists on a farm (hog and dairy) in central Iowa. Active in 4-H and Future Farmers of America, he became known across the state of Iowa for his excellent oratorical skills. While teaching at Iowa State University, Roger Mitchell (currently dean at the University of Missouri), reflects on how proud he felt when “Jimmy” Tiedje had won yet another speech contest. He went to Iowa State University, majored in Agronomy, and graduated in 1964. Tiedje was interested in the scientific side of agriculture; in fact, he was intrigued by the scientific endeavor. His family was pleased with his ambition and desire to pursue these goals.

With encouragement and strong influence from Profes- sors Lloyd Frederick and Roger Mitchell, he decided to begin graduate studies at Cornel1 University with Martin Alexander. Tiedje describes his training with Alexander


as excellent, but what he appreciated most was thebreadth of topics he was exposed to and the opportunityto pursue them.

After graduating from Cornell University in 1968,Tiedje joined the faculty at Michigan State University asan assistant professor of soil microbiology. Tiedje hasalways attracted some of the best and brightest studentsboth national and international, but he struggled as anyyoung budding professor to get his program started. Hesays, "I was interested in students who loved science andwere willing to work hard. I wasn’t interested in placingunnecessary biases or prejudices on them but wanted tomake a pleasant environment where students felt com-fortable and were enthusiastic about learning." In the ear-ly days, most of his students were international, his firstgraduate student, Trom Duong, was from Vietnam.Duong is now president of the University of Cantho inVietnam. Two of his early students, Robert W. Taylor(Bahamas) and Mary K. Firestone (USA), describe as not only a creative and innovative scientist but as apleasant and kind person who was always thoughtful inhis approach to any of their concerns. Firestone furtherstates, "Even if I had run into a road-block in an experi-ment after a discussion with Jim, I always left his officewith a ’shot of enthusiasm and energy’ to go back andwork in the lab."

This comment is by no means an isolated perceptionheld only by his early students, his present and recent stu-dents describe him in an equally favorable light. AlthoughTiedje’s later students (1980s) acknowledge that he wasnot always in the lab to give them counsel and advice,they clearly felt he created a sense of family among hisstudents. By this time, the demands of his internationalreputation required that he travel a great deal. DavidMyrold, a former Ph.D. student in Tiedje’s lab, best sum-marizes the feelings of his most recent students:

Jim is an excellent teacher. His outstanding ability asa communicator allows him to present ideas clearly tostudents. In my mind, however, it is not his formalteaching that sets Jim apart, but rather the positivemanner that he taught me by example. One didn’t haveto be in Jim’s lab long to realize that he worked long,hard hours. His dedication to science was taught byprecept. Seeing him pouring over manuscripts in the weehours of the morning taught more clearly than anythingelse that success in science required lots of hard work.Along with his dedication came abundant enthusiasm.He was constantly supportive of his students, offeringencouragement and sound advice. (D.D. Myrold, 1990,personal communication).

The same feelings were echoed by his postdoctoral stu-dents as well. Peter Groffman, now at the University ofRhode Island, felt he was an extremely effective rolemodel and admired his work habits.

In addition to providing a pleasant and productivework environment, Tiedje made sure both educationaland social activities were available to bring students, labstaff, and postdoctoral and visiting scientists together.A weekly journal club to discuss recently publishednoteworthy scientific articles and weekly lab group meet-

ings focused on each student’s research project and en-couraged his students to interact. Special eveningmeetings exposed his students to guest seminar speakers(many of whom were well-known scientists), which keptthem abreast of recent developments in the field.

Some of the social activities include an annual Memori-al Day picnic and an annual Christmas party for every-one participating in his program. Tiedje usuallyencouraged his students to bring dishes that were nativeto their home state or country. This participation fostereda sense of respect for cultural differences among lab mem-bers and a sense of enjoyment and excitement for thevaried taste buds among lab members.

Tiedje has had a somewhat wide range of formal teach-ing experience. He has taught soil microbiology,microbial ecology, and given guest lectures on creativityin science and grantsmanship.

Without question, Tiedje is internationally known forhis excellence and innovative approaches in research. Heis a leader in microbial ecology and soil microbiology andbiochemistry. His lab has produced some of the mostpromising methods for detoxifying halogenate chemicalssuch as PCBs and hexachlorobenzene (4,5,7). Hisdenitrification studies (both field and laboratory) havecontributed significantly to the understanding of thispoorly understood portion of the N cycle (2). In addi-tion, his lab has used N tracers (15N and 13N) to eluci-date pathways and products in the N cycle (6). His currentresearch focuses on molecular biology of denitrification(1), "molecular ecology" using molecular biology toolsfor students of microbial communities in nature (3), andthe anaerobic metabolism of pollutants (4).

He has been described by his colleagues as one of themost creative scientists in the College of Agriculture atMichigan State. Tiedje says his interest in creativity inscience was spurred when he did a sabbatical at theUniversity of Georgia in 1975. His wife, Linda BethTiedje (also a scientist), took a course on the subject dur-ing their stay in Georgia. They began discussing how oneinfluences students through this process. From their in-vestigation and information from a national conferenceon this subject, they learned that one is best taught byrole models. Jim saw the role model~concept as a wayof inspiring his students that a pleasant environment canbe a productive environment. The idea has paid off forhim and his students.

He has received numerous awards and honors both asresearcher and educator. Some of the most prestigioushonors are the MSU Distinguished Faculty Award (1986)and the Soil Science Research Award (1990). He is fellow of the American Society of Agronomy, SoilScience Society of America, and the American Associa-tion for the Advancement of Science. From 1988 to 1990he was chair of the Environmental Protection Agency’sAdvisory Panel. His professional and communitycontributions are too numerous to mention, but theyrange from making his laboratory available to high schoolstudents for summer programs to being editor-in-chieffor the refereed journal Applied and EnvironmentalMicrobiology.


After 22 yr in microbiology, Tiedje wears a somewhatdifferent coat these days. He has been director for theCenter for Microbial Ecology since 1989. The Science andTechnology Center, sponsored by the National ScienceFoundation, supports 27 students, 13 postdocs, and hasfaculty from 12 departments on the campus. Tiedje says,"We have people with skills from very different dis-ciplines together to address questions of how microbeslive and function in a changing environment and world."The Center for Microbial Ecology offers short courses,workshops, and seminars that benefit students, scientists,and the general public on issues related to microbial ecol-ogy. It is one of the most exciting interdisciplinary pro-grams in science. Tiedje has envisioned the Center forMicrobial Ecology as an important vehicle for educatingsociety and as a stimulus for creating interaction betweenthe university community and local community. Tiedjesays, "After all, we are concerned about maintaining asafe and healthy environment for our children's future.An understanding of microbial ecology ultimately playsan important role in that process."

The man is someone who cares about people and theworld around him. The fame and international reputa-tion his research and teaching have brought him have notaffected how he relates to others. Ask anyone who knowshim, other than a biased person like myself, and they arealmost sure to tell you that he is a humble, easygoing,caring person. Tiedje's vision goes beyond the knowledgebase he possesses and extends through the years of inter-personal relationships with students and the lives he hastouched.

ACKNOWLEDGMENTS

I thank my former colleagues and Jim Tiedje's formerprofessors and colleagues for sharing their perspective ofhis contribution with me. Dr. Shirley M. Jordan and Dr.Stephen Anderson are acknowledged for their objective,timely, and constructive criticism of the manuscript.


ERRATA James Michael Tiedje-The Man and His Vision

D. Jordan; J. Agron. Educ. 20:54-56 (1991).

The above article, which appeared in the Spring 1991 issue of JAE, contained a typo on page 5 5 . In the paragraph beginning “Without question,” the word students was printed instead of studies in the second-to-last line. The new paragraph is corrected below:

Without question, Tiedje is internationally known for his excellence and innovative approaches in research. He is a leader in microbial ecology and soil microbiology and biochemistry. His lab has produced some of the most promising methods for detoxifying halogenate chemicals such as PCBs and hexachlorobenzene (4,5,7). His denitrification studies (both field and laboratory) have contributed significantly to the understanding of this poorly understood portion of the N cycle (2). In addition, his lab has used N tracers (15N and 13N) to eluci- date pathways and products in the N cycle (6). His current research focuses on molecular biology of denitrification (l), “molecular ecology” using molecular biology tools for studies of microbial communities in nature (3), and the anaerobic metabolism of pollutants (4).


SELECTIONS FROM THE MEDIA CENTER

Publications of the International Agricul-tural Research and DevelopmentCenterswConsultative Group on Inter-

national Agricultural Research(CGIAR), International Rice ResearchInstitute (IRRI), P.O. Box 933, Mani-la, Philippines. 1989. 730 p. Paper-back. $10.00. ISBN 971-104-216-9.

"Knowledge gained through interna-tional agricultural research is useless un-less it is published and disseminated to itstarget audience of scientists, educators,extension specialists, and farmers," be-gins the Foreword in the newly releasedbook Publications of the InternationalAgricultural Research and DevelopmentCenters. This catalog is a handy referencefor locating educational materialsproduced by CGIAR and non-CGIARcenters, and would be helpful to educa-tors worldwide.

This catalog lists descriptions, prices,and ordering instructions for education-al materials published by the 13 centerssponsored by CGIAR and 10 non-CGIAR centers. The book is arranged bycenter and lists the books, periodicals,slide sets, films, and other educationalmaterials published by each. It also hasan extensive subject index, which helpsthe reader find all publications in certainfields. The catalog is also available onfloppy disk.

Libraries and reference centers at alleducational levels would be wise to con-sider this well-organized handbook.-SUSAN ERNST, American Society ofAgronomy, 677 S. Segoe Road, Madison,WI 53711.

Range Management, Principles and Prac-tices-Jerry L. Holecheck, Rex D.Pieper and Carlton H. Herbel.Prentice-Hall, Englewood Cliffs, NJ07632. 1989. Illus. 501 p. Hardcover.$48.00.

This book offers an alternative to ex-isting tests providing a comprehensiveoverview of range science. It has a con-ventional offering of subject matter thatis organized in a very logical manner.However, some of the working defini-tions used in the textbook are not consis-

tent with those accepted by the Society forRange Management. For example, range-land is defined as "uncultivated land thatwill provide the necessities of life for graz-ing and browsing animals" which leadsto the statement that "because economicand social values change constantly, theamount of rangeland in the world variesfrom year to year." This philosophy ex-cludes the more accepted definition ofrangeland as a kind of land and is basedon use rather than potential.

The textbook is well-illustrated with135 figures and contains 90 tables. Chap-ters include: "Rangeland and Man,""Rangeland Physical Characteristics,""Range Management History," "De-scription of Rangeland Types," "RangePlant Physiology," "Range Ecology,""Range Inventory and Monitoring,""Considerations Concerning StockingRate," "Selection of Grazing Methods,""Methods of Improving Livestock Dis-tribution," "Range Animal Nutrition,""Range Livestock Production," "RangeWildlife Management," "Range Manage-ment for Multiple Use," "Manipulationof Range Vegetation," "Range Manage-ment in Developing Countries" and"Computer Applications and the Fu-ture," In several instances, the reader isreferred to other texts for more specificinformation. This attempt to integratethis textbook into the existing rangemanagement literature is worthwhile. Ad-ditional reference books may be necessarydepending on the depth of the coursesthat adopt this textbook. The authors dopresent ecological and environmental con-sequences of some range managementpractices.

The text is generally well written andvery readable. Literature citations are in-corporated into the text in a manner thatis informational without complicating theprinciple. The textbook is intended for anupper level undergraduate course at theuniversity level. This does not preclude itsusefulness as a reference for range profes-sionals. However, it does presume someprevious exposure to prerequisite subjectmatter for thorough understanding. Inmany cases the principles supporting amanagement practice are reviewed ratherthan developed.

The literature cited is current, withsome 1987 citations, and is a pleasantblend of historical and recent, Often, theauthors use recent findings to establish an

evolution of change in traditional rangemanagement concepts. While this is avery important contribution, it is oftenunderstated in the text.

It emphasizes the management of therange resource and focuses on grazingmanagement. This textbook provides amuch more thorough review of theaspects of proper grazing managementcompared to previous introductory text-books. Supporting areas such as rangeplant physiology and range ecology areless extensive in providing progressive in-sights or relating principles to grazingmanagement practicums. As an example,the chapter on range plant physiologydoes not include a discussion on C3 andC4 photosynthetic pathways. The illustra-tions are only of average quality. Manyof the illustrations are reproduced fromother publications and the style changesare distracting. Some of the black andwhite photographs do not provide enoughcontrast to be useful. Many of the distri-bution maps have so many pattern codes,they are hard to distinguish.

This textbook clearly finds itsstrengths in the geographical experienceand subject matter expertise of theauthors. Other topics are discussed, withthe benefit of updated literature citations,resulting in a worthwhile addition to therange management literature.--STEVENS. WALLER, Department of Agronomy,University of Nebraska-Lincoln, Lincoln,NE 68583-0915.

Agroforestry for Soil Conservation--Anthony Young, CAB International,International Council for Research inAgroforestry, WalIingford, OxonOX10 8DE, United Kingdom. 276 p.Paperback. $27.95.

This book presents the results of an In-ternational Council for Research inAgroforestry (ICRAF) review of thepotential of agroforestry for soil conser-vation, treated in its wider sense to in-clude both control of erosion andmaintenance of fertility. It is intendedprimarily for research scientists engagedin agroforestry research and provides anextensive reference section. A second in-tended audience consists of those con-


cerned with planning agroforestrydevelopment in national and internationaldevelopment organizations and aid agen-cies. With the intended audiences, thebook serves as an excellent reference andwould provide strong supplemental read-ing material for the classroom. Upperlevel-undergraduate and graduate stu-dents interested in agroforestry wouldfind this book useful as a source of newideas and methodologies and as areference.

A possible limitation is an emphasis onthe tropical regions; however, there areexamples and suggested applications forother climatic zones. A second potentiallimitation is the book does not take intoaccount availability of soil water whichcan be a limiting factor for plant estab-lishment and growth.

The objectives of Agroforestryfor SoilConservation are: (i) To summarize thepresent state of knowledge on agrofores-try in soil conservation, including bothknown capacity and apparent potential;and, (ii) To indicate needs for research this potential is to be filled. To meet theseobjectives, the book is organized into fourparts. Part I, "Soil Conservation andAgroforestry," lays the groundwork forthe text and includes previous reviews ofsoil conservation in agroforestry andbasic definitions. Soil conservation, sus-tainable land use, and the range ofagroforestry practices are also discussedin Part I.

Part II, "Agroforestry for Control ofSoil Erosion," is based on the premisethat erosion control is a prerequisite forother forms of conservation. Topicscovered in this part include: trends in soilconservation research and policy, barri-er and cover approaches to erosion con-trol, and agroforestry practices forerosion control. The discussions concern-ing the various practices for erosion con-trol are excellent and present descriptions,examples, drawings and photographs ofexisting systems that have been successful.

Part III, "Agroforestry for Main-tenance of Soil Fertility," details method-ologies where erosion is not a seriousproblem or where it has been broughtunder control. In these cases, soil conser-vation consists of preventing physical,chemical, and biological degradation ofthe soil. The role and potential ofagroforestry for this is the basis for PartIII. Subjects included in this section in-clude: soil fertility and degradation, ef-fects of trees on soils, soil organic matter,plant nutrients, soil properties andprocesses, the role of roots, agroforestrypractices for soil fertility, and a listing oftrees and shrubs for soil improvement.

The fourth part, "Agroforestry for Soil

Conservation," includes modeling soilchanges under agroforestry, researchneeds, and a conclusion section. Themodeling section involves an in-depth dis-cussion of a computer model that inte-grates and predicts erosion control andfertility maintenance. A summary followsthe main text and provides a quick walkthrough the book and summary ofresults.

Agroforestry for Soil Conservation iswell-written in a logical sequence withmany useful tables, illustrations, andphotographs. This text expands the cur-rent level of knowledge and understand-ing of the potential for agroforestry andindicates additional research needs. Itwould serve as a strong reference bookfor anyone involved in agroforestry.--THOMAS L. SCHMIDT, NebraskaForest Service, Department of Forestry,Fisheries, and Wildlife, University ofNebraska, Lincoln, NE 68583.

AGROECOLOGY--Edited by C.RonaM Carroll, John H. Vandermeer,and Peter M. Rosset. McGraw-HillPublishing Company, 11 West 19thStreet, New York, NY 10011. 641 p.Hardcover. $89.95.

AGROECOLOGY is a multidiscipli-nary book which attempts to integrate in-formation from agriculture, ecology,anthropology, and rural sociology. DuetO the diversity of topics included, thebook consists of 23 chapters authored orcoauthored by 32 different professionals.The book is organized into four sections:"General Background to Agroecology,""Ecological Background to Agroecolo-gy," "Some Management Questions,"and "On Agriculture Research."

The "General Background to Agro-ecology" section consists of six chaptersdealing with world hunger, climate andgeography of agriculture, origin ofagriculture, and social relations, energyuse, and ecological impact of modernagricultural systems. Although all thesechapters make interesting reading, thechapter on energy use is outstanding anddiscusses an important issue often neglect-ed. The authors have determined that be-tween 1700 and 1983 energy use perhectare increased fifteenfold while yieldsincreased 3.5 times. I did find the portionof the chapter on climate describing at-mosphere circulation and physical prin-ciples to be tedious reading due to thedetailed nature of the informationpresented.

The "Ecology Background to Agrooecology" section contains six chaptersdealing with crop physiology (light,water, and temperature), population ecol-ogy, disease and insect dynamics, benefi-cial soil organisms, and the broaderecological community. The third sectionentitled "Some Management Questions"has seven chapters on interfaces withnatural areas, nitrogen, integrated pestmanagement, nutrition and agriculturalchange, intercropping, and geneticresources. These two sections provide agood general discussion of the verydiverse topics included. Faculty and stu-dents specializing in these areas are like-ly to find the discussions to be verygeneral, while students not specializing inthese areas will find some of the chaptersto be difficult reading.

The last section "On AgriculturalResearch" has four chapters dealing withreasons to study traditional agriculture,agricultural research in developed and de-veloping countries, and a case study onhybrid corn (Zea mays L.) to illustrate thepolitical economy of agriculturalresearch. These chapters are very thought-provoking, and in general are very criti-cal of the direction of agriculturalresearch. I find these chapters to very elo-quently demonstrate the limitations andproblems of present research efforts.However, I also find them to be verybiased as little discussion of the positiveresults evolving from research efforts isincluded. The case study on hybrid cornhas many technical errors and takes previ-ous research results out of context. Theauthor’s view that heterosis does not ex-ist and that corn breeding of hybridsrather than mass selection is used todaysolely due to private industry’s profitpotential is not consistent with the bulkof genetic research findings. The un-balanced presentation in chapters in thissection reduces the effectiveness of criti-cisms presented, and could lead to incor-rect information transfer to those withlimited agricultural research experience.

The efforts to draw upon the expertiseof many professionals in this book is bothits major strength and weakness. Thelarge quantity of multidisplinary informa-tion makes it a valuable reference bookfor upper level courses in agriculture,especially those that deal with agriculturein tropical countries. Each chapter has anextensive list of references adding to itsvalue as a reference. However, the multi-author, multidisciplinary approach alsoleads to a lack of continuity, and non-uniform complexity, writing style, andphilosophical perspective across chapterslimiting its usefulness as a textbook. Thebiased nature of the information present-


ed in the last section ("On AgriculturalResearch") is also a serious liability ofthis book.--STEPHEN C. MASON, De-partment of Agronomy, University ofNebraska, Lincoln, NE 68583-0914.

Crop and Plant Protection: The Practi-cal Foundations--Rudolph tteitefuss,Jacquie Welch (translator), J.L. Fran-cis (translation ed.). John Wiley &Sons, Inc., 605 Third Avenue, NewYork, NY 10158. 1989. 261 p. Hard-cover. $87.95.

Dr. Heitefuss’s objective was to writea comprehensive introduction to thefundamental concepts in the field of plantprotection, and he has succeeded. Thecoverage is complete and has just the rightamount of detail. It would serve well asa textbook for advanced undergraduates,and I believe professional agronomistsand others interested in plant productionand protection would find it interestingand useful reading. I have only two com-plaints. First, there are minor flaws in thedelivery of the text, figures, and tables insome of the early chapters. And second,most of the bibliography is in German sothat many English readers will havedifficulty using this book as a reference.This book is a translation of Pflanzen-schutz (2nd ed.) published by GeorgThieme Verlag in 1987.

Crop and Plant Protection opens withtwo chapters about the importance ofplant protection. The first chapter re-minds the reader that 20 to 50% of theworld’s potential crop production is an-nually lost to weeds, insects, diseases, andother pests. The second chapter discussesthe importance of plant protection fromthe farmer’s economic perspective. Theexamples used in this chapter andthroughout the book to illustrate certainconcepts are from the cropping systemsof the Federal Republic of Germany. Be-cause this book is about fundamentalconcepts rather than technical details andbecause the crops and pests used as ex-amples should be familiar to most read-ers from temperate regions, the use ofGerman examples is not a problem.

Following these introductory chaptersare two short chapters, one coveringepidemiology and the population dynam-ics of pests and a second about forecast-ing pest populations and damage levels.These two chapters and the precedingchapter on the economic importance ofplant protection are the most difficult ofthe 11 chapters of this book to read and

are where the flaws in delivery are mostnoticeable. The language in these chap-ters is occasionally awkward or obtuseand the figures and tables, though help-ful once they are deciphered, are oftendifficult to understand. I can envisionmost of my students putting the bookaside in despair as they struggle throughthese three chapters, which would be ashame because the concepts presentedthere and in subsequent chapters are im-portant and well worth the trouble. Thesechapters comprise only 30 of the 261pages of the book.

The heart of the book resides in fivechapters that comprehensively cover theavailable methods for prevention or con-trol of pest problems. These chapters donot suffer the flaws of the earlier three;they are very well written and translated.Here the reader will find discussions ofhow choice of location, crop rotation, soiltillage, manuring and fertilizing, plantingdate, cultivation, crop variety, clean seed,and harvesting and storing methods in-fluence the likelihood of pest problems.Here also are chapters and sections cover-ing physical, chemical, and biologicalcontrol measures. Here also is a chapteron integrated crop and pest management.The chapter titled "Biological plant pro-tection" presents perhaps the best in-troduction to this topic that I have seen.In the chapter on chemical controls, thereare sections covering modes of action, thecauses of selectivity, formulations, fungi-cides, antibiotics, insecticides, acaricides,nematicides, and herbicides.

Dr. Heitefuss provides two chaptersabout the interaction of pesticides withthe environment and society. One of theseis an objective discussion of the risks andconsequences of pesticide use. This chap-ter is most interesting but noticeably lacksa section on the problem of pesticideresidues in ground and surface waters(though there are sections dealing withresidues in food and soil). The final chap-ter of the book covers pesticide legisla-tion with sections devoted to the keylegislation in the Federal Republic of Ger-many, the United Kingdom, and theUSA.

In sum, Crop and Plant Protection isfor the most part a finely written bookthat accomplishes its goal of being a com-prehensive introduction to the field ofplant protection. Dr. Heitefuss has donea great job of pulling together and balanc-ing information from weed science, en-tomology, and plant pathology. The earlychapters are difficult reading, but wellworth the effort, and the later chapters,the main part of the book, are excellent.There are eighty-six figures and twenty-two tables and many examples to help the

reader understand the fundamental con-cepts Dr. Heitefuss has included.--DUANE MERLIN FORD, Science Divi-sion, Northeast Missouri State Universi-ty, Kirksville, MO 63501.

Discovering the Future: The Business ofParadigms--Joel Arthur Barker. ILIPress, 8311 Windbreak Trail, LakeElmo, MN 55042-9521. 1988. Illus. 143p. Hardcover. $17.95.

Practical and fast-paced, this shortvolume by Joel Barker outlines a methodfor dealing effectively with change andthe future. Taken from his in-person con-sulting lectures and popular videotape bythe same title, Discovering the Future ex-plains to the reader the importance ofparadigms, or ways of looking at theworld. Barker defines a paradigm as "Aset of rules and regulations that 1) definesboundaries, and 2) tells you what to doto be successful within those bound-aries." He further suggests that much ofsociety’s turbulence over the past twodecades has been due to changes inboundaries and in the sets of rules bywhich we operate.

Barker traces the roots of his interestin paradigms to Thomas Kuhn’s bookThe Structure of Scientific Revolution(1973), which outlined how technical dis-ciplines have changed their rules or fieldsof reference over the past four centuries.Kuhn claimed that such paradigms couldexist only in science, where rules andmeasurements are precise. Barker extendsthis concept to potential changes in soci-ety at large.

We make these changes or adjust ouroutlook in agronomy, for example, asmore information becomes available, asinstrumentation and computers give usmore power to analyze current systems,and as we adjust our goals for the longterm. The changing importance of nitratein groundwater or pesticide residues onfood products is due in part to our abili-ty to detect smaller amounts of these com-pounds, and in part to new understandingof health-related effects of such com-pounds in the human diet. In a dynamicindustry such as agriculture, it is impor-tant to look at potential major changesin boundaries and rules as well as minormodifications in cropping or livestockproduction practices.

Barker’s book explores the questions ofwhat conditions spark the creation of anew paradigm and what types of peopleare willing to explore these frontiers.


There are always some unsolved questionsin any discipline, and often the solutionscan come only when there is a shift in theway of thinking about the challenge. In-terestingly, those who offer the most via-ble alternatives may come from outsidethe discipline or from the margin of thatfield. They bring new thinking about theworld, or have an ability to apply ideasfrom outside the discipline. Early adop-ters of a new approach are analogous tothose who first use a new hybrid or cul-tural practice. They are people willing totake a risk, as well as capitalize on newopportunities. They are willing to fail,and to try again.

After presenting a number of specificexamples of innovations that requiredmajor shifts in viewing the world, Barkeroutlines the key characteristics ofparadigms. He disagrees with Kuhn that

paradigms occur only in science--Barkerthinks they abound in the real world inmany fields. He considers paradigms bothimportant and functional, a way to evalu-ate what is important in an informationoverload society. Barker insists that thereis almost always more than one rightanswer, if we are willing to search. Suc-cess in an uncertain future will be en-hanced by avoiding "paradigm paralysis,a terminal disease of certainty," and de-veloping a "paradigm pliancy, or pur-poseful seeking out of new ways of doingthings." Finally, Barker is optimisticabout the future because humans arecapable of changing their paradigms,given new information and an environ-ment that embraces change.

Many agronomists have seen the videotape on paradigms. This book by Joel

Barker will further stimulate the thought-ful educator or researcher to explore newfrontiers in each discipline. It will en-courage each reader to look outside of theborders or boundaries that often con-strain our thinking about specificchallenges in our areas of expertise. Thebook would be an invaluable stimulus tothe person who has been teaching a givencourse for many years and who is look-ing for new teaching methods or ways ofintegrating materials. Most important, itchallenges each reader to approach the fu-ture in a proactive and positive way. Dis-covering the Future provides a creativealternative to those who think we arelocked into certain patterns in agricultureor other fields.--C.A. FRANCIS, De-partment of Agronomy, University ofNebraska, Lincoln, NE 68583-0910.


STUDENT ESSAYSThe following three articles are the winning essays from the 1990 American Society of Agronomy Student Essay

Contest. This marks the third year the essays appear in the Journal of Agronomic Education. The JAE Editorial Boardagreed to publish the essays here with the understanding that the students’ advisors or other departmental facultywould be asked to make editorial corrections. In fact all our professional journals have the proofreading and editorialassistance of secretaries, colleagues, peer reviewers, and staff editors at ASA Headquarters.

First Place

Sudden Death Syndrome: A Spreading ProblemSam Eathington

ABSTRACT SYMPTOMS

Sudden death syndrome (SDS) is capable of causing yieldreductions that result in major economic losses to farmers. Thisyield reduction is due to soybean [Glycine max (L.) Merr.] podabortion before seeds can be formed. As of yet, no effectivecontrol measure has been incorporated into the farming com-munity. The best control method is a high management levelthat prevents unnecessary stress to the soybean. By keepingplants healthy, the severity of SDS may be decreased. Asresearch continues, disease resistance will be discovered and uti-lized in soybean varieties.

SODDE~r DEATH SYNDRO~m (SDS) is becoming a signifi-cant problem to soybean [Glycine max (L.) Merr.]

producers in the Mississippi Valley. The disease, whichreceived its name because of the quickness at which soy-bean plants die, was first reported in the early 1970s ineast-central Arkansas (Hirrel, 1987). Sudden death syn-drome entered southern Illinois in 1979, and is currentlyseen in Arkansas, Illinois, Indiana, Kentucky, Mississip-pi, Missouri, and Tennessee. All of these areas havereported that 1 to 5%0 of their crop acreage has shownSDS (Myers, 1989). An estimate of the SDS distributionin 1987 is given in Fig. 1.

The yield reduction caused by this disease varies withthe incidence and severity of the infected fields. In 1982and 1984, SDS infection was severe enough to cause a75 to 80% reduction in yield in Arkansas (Hirrel, 1987).A mere 1% rate of infection in Illinois, resulting in a 10%yield loss, would mean 200 000 to 300 000 bushels of lostsoybean (Myers, 1989).

Dep. of Agronomy, 1102 S. Goodwin Ave., AE-120 Turner Hall, Ur-bana, IL 61801.


The foliar symptoms of SDS are very noticeable onplants and usually appear at flowering to early pod set.The first visual symptom is a yellowing of the interveinaltissue of the leaves. This chlorotic symptom turns to anecrotic (dead) area in about 5 to 10 d. The leaf tissuearound the main veins remains green, as the rest of theleaf tissue dies. After this premature death, the leafletsdrop off, leaving the petioles attached to the plant. Podand flower abortion can occur, which is responsible forthe majority of the yield loss (Myers, 1989).

The root system of the plant usually has a significantamount of root rot associated with it. Some of this rot-ting may be caused by secondary pathogens that invadethe roots after the initial infection. Splitting open thelower stem and upper root area will reveal a brownishdiscoloration of the vascular tissue, especially around thebuds. The pith (inner part) of the stem will remain white,which is characteristic of the disease (Hirrel, 1987).

Usually, symptoms of SDS first appear in a 10 to 15foot circular patch in the field (Coop. Ext. Service, 1987).The disease seems to favor high soil moisture levels andsubnormal temperatures. A dry period before this cool,wet period seems to increase the amount of SDSsymptoms seen (Hines, 1986).

Other soybean diseases can give similar foliarsymptoms and may accidentally be mistaken for SDS.These include brown stem rot and stem canker. Brownstem rot typically occurs in a cooler climate, but thenorthward movement of SDS may cause some misdiagonosis of the disease. Brown stem rot can easily be distin-guished from SDS by splitting open the lower stem, whichwill reveal a brownish-black pith area. With SDS, thispith area remains white. Stem canker can also be distin-guished from SDS by the lack of canker growth on thelower stem (Hirrel, 1987).


IOWA

MISSOURI

KENTUCKY

TENNESSEE~ARKANSAS

t LOUISIANA

piled by Snsao Rosebr~ek-Ke~d~g, Un|~. of M|ssu-N-Coln~b~a; ~a~regenerated by author.)

RESEARCH

Currently, researchers are working intensively to solvethe mysteries of SDS. One major inhibitor of this researchis the exact identification of the causal organism. Mostresearchers now favor a blue Fusarium solani as thecausal agent. It is difficult to determine ifF. solani is thecausal organism because of its slow growth rate anddifficulty in isolating from plants (Rupe, 1989). With thelarge number of organisms associated with the roots,finding and isolating the correct one can be difficult. Mostresearch now points to a number of strains of F. solani,which makes it even harder to identify the correctpathogen.

Another major problem researchers face is the sporadicnature of the disease’s appearance in fields. A field maybe severely damaged in 1 yr and then not show symptomsfor the next 2 yr. This makes it hard to screen for diseaseresistance in the field. Work is now being done to de-velop a laboratory procedure to accurately test for dis-ease resistance in soybean lines. A simple and accuratelaboratory screening procedure will greatly help in find-ing resistance for SDS.

Since F. solani is a soil-borne organism, some infor-mation about the life cycle of SDS can be theorized. Thedisease probably over-winters in debris in the soil. As thesoybean grows, the production of lateral roots causeswounds on the main root stem, which allows the patho-

62 J. Agron. Educ., Voi. 20, no. 1, 1991

gen to enter the roots. Inside the roots, it can grow andproduce toxins that travel up the xylem tissue and causethe foliar symptoms (D.G. White, 1989, personal com-munication). These foliar symptoms become more severeas root damage increases. If other root rot pathogens orsoybean cyst nematodes (SCN) begin feeding on the roots,foliar symptoms become even worse and probably in-crease the yield loss.

Research is being done on all aspects of possible con-trol measures, yet no positive control measure has beenfound. Soybean cyst nematode resistant lines, fungicides,rotation, tillage, disease resistance, and managementpractices have all been investigated for controlling SDS.

CONTROL METHODS

It was once thought that soybean cyst nematodesplayed a role in the disease cycle, but for the most part,this theory has been ruled out. Some researchers thoughtthat SCN resistant lines showed better tolerance to SDS,yet field studies have both strengthened and weakenedthis hypothesis (Smith and Judd, 1988).

Fungicides have been used to try to control SDS, butno practical compound has been found. A soil fumigantlike methyl bromide will control the disease, but this com-pound is too expensive and not practical to use in a large-scale operation (Coop. Ext. Service, 1987).

Rotation away from soybean might be a possibility.Some data show that two or more years out of soybeanare needed to get control, whereas other data show noresponse to rotation (Smith and Judd, 1988). Since theorganism is a soil-borne pathogen, it can survive in thesoil for 5 or 6 yr, which suggests little promise of suffi-cient control by rotation (D.G. White, 1989, personalcommunication).

Tillage systems have been studied, yet no research sup-ports this as an effective control measure. There is someresearch that suggest no-till soybeans have more diseaseseverity than chisel or conventional systems, but addi-tional work is still needed (Smith and Judd, 1988).

Resistance to SDS is believed to exist in the soybeangermplasm and will probably be the effective controlmeasure. It is still very hard to select accurately forresistance because of the sporadic nature of the disease.If a laboratory procedure is developed to allow for selec-tion, resistance will probably be found and bred intovarieties. Since F. solani is a single-cycle disease, has nosexual reproduction, and is not an obligate parasite, dis-ease resistance controlled by a single gene should last along period of time (D.G. White, 1989, personal com-munication). A single gene resistance system is easier toincorporate into soybean varieties; therefore, resistantvarieties should be quickly brought to the soybeanmarket.

Finally, the management for healthy plants may helpprevent major losses incurred by SDS. It is true that SDSusually attacks fields that are managed for optimumyields, but healthier plants usually mean more diseasetolerance and higher yields.

CONCLUSION

Sudden death syndrome is a spreading problem in theMississippi Valley. The nature of this disease makes itdifficult to work with and find effective control measures.Resistance to SDS is apparent in the soybean germplasmand will eventually be incorporated into soybean varie-ties. Disease resistance will probably be the most effec-tive control for SDS, but until it is available to thefarmers, keeping plants healthy and reducing the chancesof getting SDS is all that can be done. By not plantingcontinuous soybean or planting the same soybean varietyin a field damaged the previous year, the risk of develop-ing SDS will be reduced. The prevention of increased rootdamage from soybean cyst namatode and root rot patho-gens like phytophthora will help decrease the severity ofsymptoms if the disease develops. Finally, by spreadingout the maturity range of the soybean planted, the riskof getting SDS in all fields will decrease. So until tech-

nology catches up with the disease, wise managementpractices and a little luck is all one can do.

Second Place

Herbicide Resistance in WeedsDean Riechers

ABSTRACT

Herbicide resistance in weeds develops because certain weed bi-otypes can survive herbicide applications that kill susceptiblebiotypes of the same species. Resistant biotypes can become aproblem if repeated applications of a herbicide are used in acontinuous cropping sequence, allowing resistant biotypes toproduce seed and become established. S-triazine herbicides areextremely effective, persistent in the soil, and provide season-long control of a wide range of weed species. These factors en-hance resistant weed development. Crop and herbicide rotationare very effective in preventing resistant weed development. Us-ing herbicides from different chemical classes with differentmodes of action can control existing populations of resistantweeds.

HERBICIDE RESISTANCE in weeds is a relatively recentphenomenon. It involves the ability of a biotype,

or an individual of a given species with slightly differentgenetic makeup, to survive herbicide treatments to whichthe species is normally susceptible. Herbicide-resistantweeds usually occur in fields of continuous corn (Zeamays L.) and grain sorghum [Sorghum bicolor (L.)Moench], but are also found in soybean [Glycine max

Dep. of Agronomy, 1102 S. Goodwin Ave., AE-120 Turner Hall, Ur-bana, IL 61801.


(L.) Mill.] and alfalfa (Medicago saliva L.) fields and infields next to railroad right of ways, equipment lots, andfencerows. These fields all have one factor in common— they all have had constant doses of the same herbi-cide year after year.

Herbicides that have caused resistant weeds to surfaceinclude the triazines, paraquat, 2,4-D, trifluralin(Treflan), and the sulfonylureas. This paper will deal withweeds resistant to the s-triazine chemical family of herb-icides, including atrazine, simazine (Princep), and cyana-zine (Bladex). Triazine herbicides account for 40% of theherbicides applied to U.S. corn acreage and 24% of allherbicides used in the USA (Bretches, 1989).

HISTORY OF WEED RESISTANCE

From the first use of herbicides it was apparent thatsome plants were naturally resistant to some chemicals.This became evident with the introduction of 2,4-D inthe 1940s, which controls broadleaf weeds but not grasses.Since then, many new herbicides have been developed thatselectively kill different weed species in different crops.

The first report of triazine resistance in an initially sus-ceptible weed species in North America occurred in 1970by G.L. Ryan for common groundsel (Senecio vulgarisL.) in Washington State. He reported that the s-triazineherbicides atrazine and simazine failed to control theweeds in a nursery near Olympia, WA, where control hadpreviously been obtained (LeBaron and Gressel, 1982).As of 1986 there were 48 weed species that were previ-


ously susceptible and have developed s-triazine resistanceworldwide (Vencill et. al., 1987).

The most dominant resistant weeds are common lambs-quarters (Chenopodium album L.) and smooth pigweed(Amaranthus hybridus L.). Resistant weeds spreadthroughout the Pacific Northwest, and reports of resis-tant weeds have been documented in Maryland, Virginia,and other Atlantic coast states.

DEVELOPMENT OF RESISTANT WEED SPECIES

Normal populations of weeds contain a few weeds that,as a result of a genetic mutation, can withstand chemicalapplications at a rate that would kill the majority of thepopulation. Application of the herbicides acts as a selec-tion pressure and increases the frequency of resistant bi-otypes that continue to survive and reproduce, eventuallybecoming numerous enough to be noticed and cause theherbicide to fail. Weed populations become resistant toherbicides because the herbicide kills the susceptible plantsleaving the resistant biotypes behind to produce seed andflourish (Gressel, 1979).

S-triazine herbicides kill weeds by interrupting photo-synthesis. In resistant weeds, the triazine compound nolonger binds to a protein (Qb protein of photosystem II)that affects photosynthesis, so plants keep growing. Tri-azine herbicides are persistent in the soil and provide sea-son long control of germinating seeds. They are extremelyactive and effective in killing a wide range of weed spe-cies. These factors, along with frequent applications ofthe herbicide over several growing seasons without rotat-ing, alternating, or combining with other types of herbi-cides contribute to the development of triazine-resistantweed species (H.M. LeBaron, 1986, personal communi-cation).

It has been observed that weed biotypes resistant to s-triazine herbicides have several disadvantageous traits ab-sent from susceptible weeds of the same species. They areless productive, vigorous, and competitive than the sus-ceptible species (Havaux, 1989). These less competitivespecies are normally diluted by the more aggressive sus-ceptible biotypes. Because of herbicide selectivity, sus-ceptible plants are killed off leaving the resistant biotypesbehind to survive and produce seed that builds up in thesoil reservoir (Gressel, 1979).

Weed biotypes that are resistant to a particular herbi-cidal mode of action are most likely resistant to other her-bicides that have the same mode of action. Herbicidemode of action refers to the chemical interaction that in-terrupts a biological process necessary for plant growthand development. Weed biotypes that are resistant to her-bicides with similar modes of action are referred to asbeing cross-resistant. Weed biotypes that have developedresistance to one herbicide may simultaneously showresistance to other herbicides with similar modes of ac-tion to which they have never been exposed. This occurswith s-triazine herbicides because they inhibit photosyn-thesis at a similar protein binding site (Fuerst et al., 1986).In contrast, resistant biotypes seem to have an evengreater degree of sensitivity than the susceptible biotypes


of the same species to herbicides having other modes ofaction (H.M. LeBaron, 1986, personal communication).An example is the control of triazine-resistant lambsquar-ters and pigweed species with 2,4-D or other phenoxyacetic acid herbicides, which mimic plant growthhormones.

PREVENTION AND CONTROL OFRESISTANT WEEDS

Crops grown in monoculture, such as continuous corn,favor the development of resistant weed biotypes if a sin-gle herbicide is used year after year. No-till or reducedtillage systems will also tend to encourage resistant weedproblems (H.M. LeBaron, 1986, personal communica-tion). Once the resistant weed biotypes have establishedthemselves, they are very hard to control or eradicate.

Where possible, it is also beneficial to use herbicidecombinations, rotations, or sequential and alternatingtreatments involving herbicides from different classes ormodes of action. Other herbicides, including glyphosate(Round-Up), alachlor (Lasso), dicamba (Banvel), and butylate (Sutan), are not persistent in the soil andare much less likely to promote weed resistance than s-triazines. Control of triazine-resistant smooth pigweedand common lambsquarters in corn is excellent whendicamba is applied postemergence following preemer-gence treatment with alachlor, metolachlor (Dual), pendimethalin (Prowl) (Hagood, 1989). Cultivation other tillage also tends to delay or prevent resistant weedsfrom developing.

CONCLUSION

Resistant weed biotypes existing in natural weed popu-lations in the field are being selected for by herbicides.Where herbicide resistance evolves, untreated weed popu-lations have a very low frequency of resistant biotypes(resulting from genetic mutations) capable of survivingherbicide treatments that kill the majority of the popu-lation. Herbicide applications act as a selection pressureand increase the frequency of the resistant biotypes thatsurvive and produce seed for future generations. Use ofpersistent and extremely effective herbicides, such as thes-triazines, favors resistant weed development because theselection pressure is intense and lasts most of the grow-ing season, allowing the less vigorous resistant weed bio-types to become established and produce seed. Biotypesthat are resistant to a herbicide are usually resistant toother herbicides within the same chemical class and withsimilar modes of action, even at high rates of herbicideapplication.

It is much easier to avoid resistant weeds than to tryto control them after they develop, reproduce, and in-fest an area. Crop and herbicide rotation is the easiestand most effective way to prevent weed resistance to aherbicide, along with conventional tillage practices. Theuse of herbicides with differing modes of action and from

different classes is effective once a weed population hasbecome resistant to a particular herbicide.

Third Place

The Effect of Rye Cover Crop and Nitrogen Fertilizer Rateon Yield of Irrigated Corn and Residual Soil Nitrogen

B. A. Kliewer

ABSTRACT

This study was conducted to determine how different ratesof N fertilizer applied to the soil and the use of a rye (Secalecereale L.) winter cover crop affect irrigated corn (Zea maysL.) yield and grain protein content. The study consisted of fourreplications of seven fertilizer N treatments applied in a ran-domized manner. Plant available N and potentially mineraliz-able N in the soil were measured before the experiment wasinitiated. Grain yield and total N uptake was determined at har-vest. A rye cover crop was planted postharvest. Statistical ana-lyses were conducted to test the hypothesis and assist indeveloping experimental conclusions. It was concluded that theexcess quantities of N fertilizer applied were not utilized to in-crease yield or grain protein content. The use of rye as a wintercover crop appeared to decrease grain yield one of two yr buthad no significant effect on residual soil N content.

GROUNDWATER is an important natural resource thatsupplies drinking water for over half of the popu-

lation and provides almost 40% of the water used in irri-gation. Nebraska ranks second in irrigated acres in theUSA and only two cities in the state do not use ground-water for municipal purposes. Thus, prevention ofgroundwater contamination is both a local and national

Department of Agronomy, 222 Keim Hall—East Campus, Universityof Nebraska, Lincoln, NE 68583.


concern. Nitrates in groundwater are objectionable forhealth reasons and their presence suggests potential forcontamination by pesticides or other chemicals.

In spite of the contamination concerns, the main in-terests in management of N in irrigated agriculture havebeen related to agronomic and economic matters. Recent-ly, there has been renewed interest by both farmers andagronomists in cropping strategies that include non-leguminous cover crops. This interest has been fueled bythe rising awareness of the need to control residual N andimprove efficiency in N management. Nonleguminouswinter cover crops are compatible with most tillagemethods. Nonleguminous cover crops offer the oppor-tunity to enhance N use efficiency and preserve waterquality by acting as a sink for residual N that might other-wise leave the soil system (Pelchat, 1986; Utomo, 1986;Hubbard et al., 1986). The objective of this research wasto determine irrigated corn (Zea mays L.) yield andresidual N as affected by N rate and rye (Secale cerealeL.) winter cover crop.

MATERIALS AND METHODS

This study was initiated in 1985 near Henderson, NE,on land irrigated by a center-pivot irrigation system.Whole plots were fertilizer N treatments of 0, 56, 112,168, 224, and 280 kg N/ha applied as ammonia nitrateat sidedress time (fourth leaf stage). Split plots were withand without a rye cover crop seeded at corn harvest.Treatments were replicated four times in a randomizedsplit block design. Subplots were 5.4 m wide (six 90-cmrows) by 7.5 m in length. The rye cover crop was incor-


porated into the soil by disking in the spring prior toplanting corn.

Soil samples taken from the root zone in October of1984 and spring of 1985-1989 were analyzed in 0.3-mincrements to a depth of 1.8 m. Nitrate-N andammonium-N concentrations (plant-available N) were de-termined on all soil samples by KCI extraction (Brem-ner, 1965) and total organic soil N (micro-Kjeldahl;Schuman et al., 1973) was determined on samples at the0 to 0.3 m depth. Nitrogen concentration was determinedin ear leaves collected at tasseling and N uptake in thegrain at harvest (Schuman et al., 1973).

RESULTS AND DISCUSSION

A yield response to rye cover crop was evident at allN rates. A reduced yield associated with winter rye covercrop existed at the 0, 56, 112, and 168 kg/ha N fertilizertreatment plots in 1987 (Table 1). A similar yield reduc-tion associated with rye was also evident at all N fertilizertreatment plots in 1988 (Table 1). The highest corn yieldassociated with rye cover in 1987 and 1988 occurred atthe 280 and 224 kg/ha fertilizer N plots, respectively. Incontrast, little yield difference was observed above 112kg N/ha without the rye cover crop for either year. Thisis substantiated by noting that the 1987 yields from highN rates were comparable with and without cover crops.The fact that yields continued to increase above the 112kg/ha N rate with the rye cover crop indicates the ryewas apparently immobilizing N at the same time N wasrequired by the crop.

Additional factors to consider when analyzing the yieldresponse to the rye cover crop include the relationshipbetween soil organic matter content, temperature, andwater. Growth of the rye cover crop would contributeto the depletion of subsoil water (Smith et al., 1987). is possible that the existence of incorporated surfaceresidues promoted soil aeration thereby increasing waterevaporation. Also, there was a consistent reduction inplant population associated with the winter rye cover cropwhen compared to plots with no cover crop (an averagepopulation reduction of 2700 plants/ha in 1988). Thepotential for an allelopathic response by the rye covercrop could also contribute to reduced yield of corn grain.Thus, rye cover crops appear to decrease crop yields overa wide range of N fertilizer rates.

Uptake of N and yield responded similarly to N ratein both 1987 and 1988 (Table 2). Although there was difference in grain N uptake attributed to the cover crop,there was a tendency for the concentration of grain Nto be greater following the rye cover crop. Apparentlythe somewhat lower plant populations associated with therye cover crop were able to take up more N per unit ofdry matter and ultimately use similar amounts of N. Itis also worth noting that N in grain increased slightly withthe increased rate of N fertilizer above 112 kg/ha. StoverN uptake was not determined, but it would be expectedto increase with N rate because of increased dry matterproduction and corn stover N concentration. While N re-


Table 1. Effect of fertlizer N rates and winter rye cover crop oncorn grain yield.

Yields by fertilizer N rate, kg/ha

Year Cover 0 56 112 168 224 280

Mg/ha1987 Corn residue 7.33 11.04 11.23 11.27 11.50 11.80

Rye 6.13 10.38 10.88 10.46 11.77 13.011988 Corn residue 7.50 8.90 10.20 10.20 10.50 10.20

Rye 6.70 8.30 9.20 8.70 10.20 9.20

Table 2. Effect of fertllzer N rates and winter rye cover crop oncorn grain N uptake.

N uptake by fertilizer N rate, kg/ha

Year Cover 0 56 112 168 224 280

kg/ha1987 Corn residue 67.9 102.8 114.4 118.6 124.3 130.2

Rye 63.2 101.2 117.0 115.8 133.3 151.71988 Corn residue 78.5 96.9 116.9 116.5 120.1 117.9

Rye 75.1 97.3 112.8 110.2 126.6 122.3

Table 3. Effect of fertlizer N rates and winter rye cover crop onresidual soil N (nitrate-N + ammonium-N) summed to a depthof 1.8 m.

Yields by fertilizer N rate, kg/ha

Year Cover 0 56 112 168 224 280

kg/ha

1987 Corn residue 127.2 154.8 171.2 224.0 276.0 362.4Rye 129.6 184.8 160.0 241.6 357.2 366.4

1988 Corn residue 146.0 168.4 174.0 269.2 254.4 312.0Rye 116.0 149.2 163.2 180.0 310.4 338.8

1989 Corn residue 177.2 137.2 178.0 267.6 292.8 383.6Rye 133.6 144.4 162.4 212.0 352.0 562.8

moved in grain could not justify additional fertilizerabove the 112 kg/ha N rate, some of the additional fer-tilizer would likely be recycled to the soil via the residue.Residues from the plots with higher N rate (narrower C/Nratio) should mineralize more rapidly than residues fromthe N deficient plots (wider C/N ratio). Therefore, thecombination of residues with a low N concentration andcover crops that utilize N mineralized in the fall couldresult in low levels of residual soil N early in the growingseason and N deficient plants unless moderate levels offertilizer N are applied. Fertilizer placement is criticalwhere wide C/N ratio residue are present. Knifing fer-tilizer below the residue would reduce immobilization andenhance the availability of fertilizer N to the target crop,as commonly seen in high residue no-till systems (Riceand Smith, 1984).

Residual N concentrations summed over the 1.8-mdepth were similar over years for the 112 kg/ha or lowerN rates (Table 3). It is probably more than coincidentalthat yields were nearly maximized at the 112 kg/ha N rateand that residual soil inorganic N levels increased sub-stantially above that N rate. The fact that residual N wasgenerally greater in the spring with the cover crop thanwith no cover crop at the 224 and 280 kg/ha N rates sug-gests that the net effect of the cover crop was less nitrateleaching. The net effect of cover crops on N availability,

crop yield, and residual N may take several years tomanifest itself. The most detrimental economic effectscan be expected very quickly at lower fertilizer N ratesand the most obvious environmental benefits can be ex-pected at N rates in excess of those needed to attain nearmaximum yields.

CONCLUSIONS

A number of management factors should be consideredwhen designing a cropping system that includes a ryecover crop to minimize nitrate leaching and to ensure ade-quate N use efficiency and optimum crop growth. Theseinclude the stage of growth at the time of cover crop ter-mination, fertilizer N required, N fertilizer source, andtiming/method of N application. A means for estimat-ing the N fertilizer requirement of the corn crop follow-ing the winter rye cover crop is lacking. However, sincethere are both beneficial and detrimental effects from therye cover crop, this would not provide the answer. Thedifferent aspects of corn yield response to N fertilizer anda rye winter cover crop indicates a universal recommen-dation may be difficult to make. At higher N fertilizerrates the cover crop did not limit N availability and mayhave reduced N leaching over winter. Under N limitingconditions, the cover crop tended to accentuate the Navailability problem and would be less likely to affect N

leaching because of low residual N levels. In either case,stand establishment may be more difficult following awinter cover crop. Under present conditions of the study,the economic feasibility of cover crops is questionable ifthe purpose is to efficiently replace N that might other-wise be leached and since it is difficult to place a valueon the quality of groundwater.


List of Reviewers for the Journal of Agronomic Education1 January-31 December 1990

Maintaining the editorial standards of a scientific jour-nal is an important responsibility, because the publica-tions of a society are one of its major services to itsmembers. Maintaining such standards is the ultimateresponsibility of the journal editors, and this task can onlybe accomplished with the advice of associate and con-sulting editors and a large number of colleagues who areinvited to review manuscripts. Their critical commentsand helpful suggestions have played a major part in mak-ing the Journal of Agronomic Education a success. Themembers of the JAE Editorial Board want to express theirappreciation to the following individuals who helpedreview manuscripts for the 1990 issues. This list may notbe complete due to problems in collating such informa-tion from many sources. We extend our apologies to thosereviewers whose names have not been included.

Ahlrichs, J., Purdue UniversityAltman, D.W., USDA-ARS, College Station, TXAnderson, J., University of Minnesota, St. PaulAnderson, M., Wilmington College, Wilmington, OHAnderson, W., Middle Tennessee State University, Murfreesboro

Bacon, R.K., University of ArkansasBaker, D., USDA-ARS, Mississippi State UniversityBall, D.A., USDA-ARS, Fort Collins, COBeasley, J., University of GeorgiaBowen, W., University of FloridaBryant, R., Cornell University, Ithaca, NYBullock, D., University of Illinois

Campbell, A., Iowa State UniversityCollins, M., University of FloridaConklin, A., Wilmington College, Wilmington, OHCosgrove, D., University of Wisconsin-River FallsCrookston, K., University of MinnesotaCrum, J.R., Michigan State University

Davis, M., University of ArkansasDeFelice, M., University of MissouriDiPaolo, J., North Carolina State University

Elkins, D., Southern lllinois University

Fanning, C., North Dakota State UniversityFenwick, J.R., Colorado State UniversityFrancis, P., University of Arkansas, MonticelloFuess, F., Illinois State University, Normal

Gallo, K., EROS Data Center, Applications Branch, Sioux Falls, SDGrabau, L., University of KentuckyGraef, G.L., University of NebraskaGreub, L., University of Wisconsin-River Falls

Hallock, B.G., California Polytechnic University, San Luis ObispoHarpstead, M., University of Wisconsin-Stevens PointHarrison, S.A., Louisiana State UniversityHelsel, D.G., IBM, Research Triangle Park, NCHelsel, Z.R., Cook College, Rutgers University, New Brunswick, NJHildebrand, P., University of FloridaHuddleston, H., Oregon State UniversityHughes, L.B., Jr., Western Kentucky University, Bowling Green

Johnson, D., Colorado State University

Kamalay, J.C., Ohio State UniversityKarow, R., Oregon State UniversityKeim, D.L., Maxell Hybrids, Lubbock, TX

Kidder, J., University of HawaiiKiemnac, G., Eastern Oregon State College, LaGrandeKnauft, D.A., University of Florida

Larson, K.L., Iowa State UniversityLessman, G.M., University of TennesseeLogan, J., University of TennesseeLoynachan, T., Iowa State UniversityLyrene, P.M., University of Florida

Malo, D., South Dakota State UniversityMason, S., University of NebraskaMayes, M., USDA-CSRS, Washington, DCMcAlbertson, Pioneer Hi-Bred, Johnston, IAMcFee, W., Purdue UniversityMcGraw, R., University of MissouriMilford, M., Texas A&M UniversityMiller, D., University of ArkansasMiller, F.P., Ohio State UniversityMontagne, C., University of MontanaMoser, L., University of NebraskaMulla, D.J., Washington State UniversityMullen, R., Iowa State UniversityMyers, J.R., University of Idaho

Norris, R., University of California-Davis

Palmer, J., Clemson UniversityPan, W.L., Washington State UniversityParrott, W.A., University of GeorgiaPeck, T.R., University of IllinoisPennock, R., Jr., Pennsylvania State UniversityPowell, A.J., University of Kentucky

Quesenberry, K.H., University of Florida

Reed, R., Oklahoma State UniversityRichardson, J., North Dakota State UniversityRoberts, D., Washington State UniversityRogers~ T., Michigan State UniversityRothwell, D.F., University of FloridaRutledge, E.M., University of Arkansas

Sartain, J., University of FloridaScarnecchia, D.L., Washington State UniversitySchafer, J., Iowa State UniversityShroyer, J., Kansas State UniversitySikora, F., Tennessee Valley Authority, NFDC, Muscle Shoals, ALSmith, D., Colorado State UniversitySmith, E., Oklahoma State UniversitySmith, S.E., University of ArizonaSpaith, S.C., USDA-ARS, Pullman, WAStritzke, J., Oklahoma State University

Taylor, D., University of Wisconsin-River FallsTroeh, F.R., Iowa State UniversityTyler, J., University of Wisconsin-Madison

Verhalen, L., Oklahoma State University

Waldren, R., University of NebraskaWallace, S., Clemson UniversityWelsh, J., USDA-ARS, Fort Collins, COWhite, R., Colby, KSWhiting, L., Ohio State UniversityWilkens, P., Michigan State UniversityWofford, D., University of FloridaWolt, J., Dow Chemical, Midland, MIWright, F., Portageville, MO

Young, J., Oklahoma State University

Zamora, B.A., Washington State University


(1991) back matter (jnrlse)...george w. carver and booker t. washington, and self- development, hill...

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