Ford Denison, Professor
Emeritus, UC Davis
From 1993 through
R. FORD DENISON taught crop ecology and conducted research at the
Davis, on topics ranging from
sustainability to the evolution of
cooperation between microbes and plants. For most of this
time, he directed "the world's
youngest 100-year experiment" (LTRAS.ucdavis.edu),
the long-term trends that determine agricultural sustainability.
His work on symbiotic
nitrogen fixation, a possible
nitrogen fertilizers, has led to a patent and publications
journals from Nature
to Field Crops Research. One
recent paper, "Darwinian
Agriculture: When Can Humans Find Solutions Beyond the Reach of
Selection?" points out
some limitations both of agricultural biotechnology and of agriculture
that mimics natural ecosystems. He has been interviewed on National
Public Radio, Science Update (AAAS), and DeutschlandRadio and has been an
invited speaker at international meetings and at institutions
Agricultural Research Center to the Scripps Institute of
Oceanography. He was educated at Harvard, Evergreen, and
Cornell, where he earned a Ph.D. in Crop Science, with postdoctoral and
sabbatical research at UC Davis, UCLA, Queen's University (Ontario),
Welsh Plant Breeding Station (Aberystwyth), and University of
been supported by NSF, USDA, and California's
Agricultural Experiment Station. This web page was last updated
May 2005, when he moved to the University of Minnesota.
PLB 142. Ecology of Crop Systems (4) II. Denison. Lecture, 3
discussion, 1 hour. Prerequisite: Agricultural Systems and Environment
2 or Biological Sciences 1C; Math 16A or Physics 1A, or consent of
Ecological processes governing the structure and behavior of managed
Emphasis on mechanistic and systems views of the physical environment,
photosynthetic productivity, competition, adaptation, nutrient cycling,
energy relations and contemporary issues such as climate change.
PBI 225. Methods and Instrumentation for Crop and Soil Science
III. Denison, Hsiao, Hartz, Mitchell, Pettygrove, Scow & van
Kessel. Lecture, 1 hour; discussion, 1 hour; laboratory, 3 hours.
Basic knowledge of plant physiology, soil science, chemistry and
Theory and practice of in situ sampling and instrumentation methods for
crop science and related aspects of soil science (e.g. moisture and
and laboratory analysis. Not offered every year.
How does evolution based on
"selfish genes" maintain cooperation? We are trying to answer
this question for
symbiotic bacteria that infect legume plants like alfalfa or soybean
and (to varying extents) supply them with nitrogen. Fixing
nitrogen is costly for rhizobia, so why haven't rhizobia that supply
their plant hosts with nitrogen (indirectly benefiting competing
rhizobia infecting the same plant) been completely displaced by
"ineffective" rhizobia? Why are ineffective rhizobia common
enough to be a problem in some
soils but not others? This research
may lead to practical applications, such as legume
crops that selectively enrich the soil with the
local strains of rhizobia. This research may also be relevant to other
cases where symbiosis
down, as in coral bleaching. As time allows, I also hope to
explore other applications of modern evolutionary theory, pursuing some
of the ideas in our paper on Darwinian Agriculture. Steve Kaffka
has replaced me as Director
but I remain interested in scientific approaches to the problem of
that of agriculture. To pursue my research objectives, I have
had to develop new tools, including mechanistic
models and noninvasive scientific instruments, such as the nodule
oximeter or a laser-scanner (at right)
measure green leaf area index in the field.
Other recent grants on which I was principal investigator or co-PI
- Method and Apparatus for Measuring Oxygen Concentration and its
Use in Estimating Nitrogen Fixation in Plants. D.B. Layzell, S.
G. Palmer, R.F. Denison. #5,096,294.
- E.T. Kiers, S.A. West, and R.F. Denison. 2005? Maintaining
cooperation in the legume-rhizobia symbiosis: identifying selection
pressures and mechanisms. In: J.
Sprent and E. James (eds.) Leguminous Symbioses. Kluwer Academic
Publishers (in press).
- Kong, A.Y., J. Six, D.C. Bryant, R.F. Denison, and C. van
2005. The relationship between carbon input, aggregation, and soil
organic carbon stabilization in sustainable cropping systems.
Science Society of America Journal (in press).
- R.F. Denison and E.T. Kiers. 2005. Sustainable crop
nutrition: constraints and opportunities. In: M. Broadley (ed.) Plant
Nutritional Genomics. Blackwell.
- Hasegawa, H., and R.F. Denison. 2005. Model
predictions of winter rainfall effects on N dynamics of winter wheat
rotation following legume cover crop or fallow. Field Crops
- R.F. Denison and E.T. Kiers. 2004. Why are
beneficial to their plant hosts, rather than parasitic? (Invited
and Infection 6:1235-1239.
- R.F. Denison and E.T. Kiers. 2004. Lifestyle
for rhizobia: mutualism, parasitism, and forgoing symbiosis.
(Invited review.) FEMS
Microbiology Letters 237:187-193.
- Denison, R.F., D.C. Bryant, and T.E.
Kearney. 2004. Crop
nine years of LTRAS, a long-term comparison of field crop systems in a
Mediterranean climate. Field
- Martini, E.A., J.S. Buyer, D.C. Bryant, T.K. Hartz, and R.F.
Denison. 2004. Yield
increases during the organic transition: improving soil quality or
Crops Research 86:255-266.
- Okano, Y., K.R. Hristova, C. Leutenegger, L. Jackson, R.F.
Gebreyesus, D. LeBauer, and
K.M. Scow. 2004. Effects of ammonium on the
size of ammonia-oxidizing bacteria in soil -- Application of real-time
and Environmental Microbiology 70:1008-1016.
- Kiers, E.T., R.A. Rousseau, S.A. West, and
sanctions and the legume-rhizobium mutualism. Nature
425:78-81. Widely covered in scientific and popular press.
- Kinraide, T.B., and R.F. Denison. 2003. Strong
American Biology Teacher 65:419-424.
- Denison, R.F., E.T. Kiers, and S.A. West. 2003. Darwinian
When can humans find solutions beyond the reach of natural
Review of Biology 78:145-168. See updates
- Denison, R.F., C. Bledsoe, M. Kahn, F. O'Gara, E.L. Simms,and
2003. Cooperation in the rhizosphere and the "free rider" problem. Ecology
- Denison, R.F., and Y. Okano. 2003. Leghemoglobin oxygenation
in alfalfa and yellow sweetclover nodules. Journal
of Experimental Botany 54:1085-1091.
- Kiers, E.T., S.A. West & R.F. Denison. 2002. Mediating
the influence of farm management practices on the evolutionary
of symbiont cooperation. Journal
of Applied Ecology 39:745-754.
- West, S.A., E.T. Kiers, I. Pen & R.F. Denison. 2002.
and mutualism stability: when should less beneficial mutualists be
of Evolutionary Biology 15:830-837.
- West, S.A., E.T. Kiers, E.L. Simms & R.F. Denison.
and mutualism stability: why do rhizobia fix nitrogen? Proceedings
of the Royal Society, London 269:685-694.
- Denison, R.F. 2001. Meeting report: ecologists and molecular
find common ground in the rhizosphere. Trends
in Ecology and Evolution
- Denison, R.F. 2000. Legume sanctions
and the evolution of
symbiotic cooperation by rhizobia.
- Hasegawa, H.,
and R.F. Denison. 2000. Testing CERES model predictions of crop growth
and N dynamics, in cropping systems with leguminous green manures in a
Mediterranean climate. Field
Crops Res. 67:239-255.
- Hasegawa, H.,J.M. Labavitch, A.M. McGuire, D.C. Bryant, and R.F.
1999. Testing CERES model predictions of N release from legume cover
Crops Res. 63:255-267.
- Plant, R.E., A. Mermer, G.S. Pettygrove, M.P. Vayssieres, J.A.
Miller, L.F. Jackson, R.F.
Denison, and K. Phelps. 1999. Factors
grain yield spatial variability in three irrigated wheat fields.
- Serraj, R., V. Vadez, R.F. Denison, and T.R. Sinclair. 1999.
of ureides in nitrogen fixation inhibition in soybean. Plant
- McGuire, A.M., D.C. Bryant, and R.F. Denison. 1998. Wheat yields,
uptake, and soil moisture following winter legume cover crop vs.
- Denison, R.F. 1998. Decreased oxygen permeability: a universal
in legume root
nodules. Bot. Acta 111:191-192.
- Jacobsen, K.R., R.A. Rousseau, and R.F. Denison. 1998. Tracing
of oxygen into birdsfoot trefoil and alfalfa nodules using
111:193-203. (cover article)
- Pettygrove,G.S., S.K. Upadhyaya, M.G. Pelletier, T.K. Hartz, R.E.
and R.F. Denison. 1998. Tomato yield - color infrared photograph
Proc. 4th Intl. Conf. Precision Agric., St. Paul, MN.
- Arrese-Igor,C., A.J. Gordon, F.R. Minchin, and R.F.
entry and nitrite formation in the infected region of soybean nodules. J.
Exp. Bot. 9:41-48.
- Miller, R.O., G.S. Pettygrove, R.F. Denison, L. Jackson, M. Cahn,
Plant, T. Kearney. 1998. Site specific relationships between flag leaf
SPAD meter values and grain protein in irrigated wheat. Commun. Soil
Plant Anal. 9:1381-1382.
- Denison, R.F., and R.
Russotti. 1997. Field estimates of
area index using laser-induced chlorophyll fluorescence. Field
Crops Res. 52:143-150.
- Denison, R.F. 1997. Minimizing errors in LAI estimates from
inclined-point quadrats. Field
Crops Res. 51:231-240.
- Denison, R.F. 1997. Review of "Long-Term Experiments in
and Ecological Sciences." Field Crops Res. 54:74-75.
- Shimada, S., R. Rousseau, and R.F. Denison. 1997. Wavelength
monitoring leghemoglobin oxygenation gradients in intact legume root
Exp. Bot. 48:1251-1258. (cover article)
- Denison, R.F., R.O. Miller, D. Bryant, A. Abshahi, and W.E.
Image processing extracts more information from color infrared aerial
Agric. 50(3):9-13 (cover article)
Denison, R.F., and B.L. Harter. 1995. Nitrate effects on nodule
permeability and leghemoglobin
Nodule oximetry and computer
- Denison, R.F., and T.B. Kinraide.
in legume root nodules: possible evidence for an osmoelectrical
controlling nodule gas permeability. Plant
- Denison, R.F. 1995. Agricultural soil and crop practices.
of Science and Technology, pp. 6-9.
- Denison, R.F., J.F. Witty, and F.R. Minchin. 1992. Reversible O2-inhibition
of nitrogenase activity in attached soybean nodules. Plant
- Denison, R.F., S. Hunt, and D.B. Layzell. 1992. Nitrogenase
respiration, and O2
permeability following detopping of
and birdsfoot trefoil. Plant
- Denison, R.F. 1992. Mathematical modeling of oxygen diffusion and
in legume root nodules. Plant
- Denison, R.F., and D.B.
1991. Measurement of legume nodule respiration and O2
permeability by noninvasive spectrophotometry of leghemoglobin. Plant
- Denison, R.F., D.L. Smith, T. Legros, and D.B. Layzell. 1991.
measurement of internal oxygen concentration in field-grown soybean
- Denison, R.F., and H.D. Perry. 1990. Seasonal growth rate
orchardgrass and tall fescue on the Appalachian Plateau. Agron.
- Denison, R.F., J.M. Fedders, and C.B.S.
Tong. 1990. Amyloglucosidase digestion can overestimate starch
of plants. Agron.
- Denison, R.F. 1989. Implications of competitive inhibition in the
reduction assay for dinitrogen fixation. Ann. Bot. 64:167-169.
- Denison, R.F., and R.S. Loomis. 1989. An
Integrative Physiological Model of Alfalfa Growth and Development.
Univ. Calif. Div. Agric.
Natural Resources, Publ. 1926, 73 pp.
- Denison, R.F., and P.S. Nobel. 1988. Growth
of Agave deserti without
current photosynthesis. Photosynthetica 22:51-57.
- Denison, R.F., P.R. Weisz, and T.R. Sinclair. 1988. Oxygen supply
as a limiting factor for symbiotic nitrogen fixation. p. 767-776. In:
Summerfield (ed.) World Crops: Cool Season Food Legumes. Kluwer
- Weisz, P.R., R.F. Denison, and T.R. Sinclair. 1985. Response to
stress of nitrogen fixation (acetylene reduction) rates by field-grown
soybeans. Plant Physiol. 78:525-530.
- Sinclair, T.R., P.R. Weisz, and R.F. Denison. 1985. Oxygen
nitrogen fixation in soybean nodules. p. 797-806. In: R. Shibles (ed.)
Proceedings, World Soybean Conf. III. Westview Press, Boulder.
- Denison, R.F., and T.R. Sinclair. 1985. Diurnal and seasonal
in dinitrogen fixation (acetylene reduction) rates by field-grown
Agron. J. 77:679-684.
- Denison, R.F., P.R. Weisz, and T.R. Sinclair. 1985. Variability
in dinitrogen fixation Agron. J.77:947-950.
- Denison, R.F., P.R. Weisz, and T.R. Sinclair. 1983. Analysis of
reduction rates of soybean nodules at low acetylene concentrations. Plant
- Denison, R.F., T.R. Sinclair, R.W. Zobel, M.N. Johnson,
1983. A nondestructive field assay for soybean
nitrogen fixation by
reduction. Plant Soil 70:173-182.
- Denison, R.F. 1979. A 2K Symbolic Assembler for the
manual recently reincarnated
on the web.
- Denison, R., B. Caldwell, B. Bormann, L. Eldred, C.
Anderson. 1976. The effects of acid rain on nitrogen fixation in
Washington coniferous forests. Water Air Soil Pollut.
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Education and Employment
- Professor and Agronomist, Department of Agronomy and Range
to present (Assoc. Prof. 5/93-6/99).
- Plant Physiologist, USDA/ARS, Beckley WV. 1986 to 1993.
- Postgraduate Researcher, with P.S. Nobel, UCLA. 1985.
- Postdoctoral Research Agronomist, with R.S. Loomis, UC
- Ph.D., crop science, with T.R. Sinclair, Cornell
- B.A., with ecology emphasis, The Evergreen State College,
- Another Harvard dropout.
- Member of the Editorial Board, Field
Crops Research, 1994-present
- Invited talks: Intl. Cong. N2 Fixation, European
N2 Fixation Congress, Amer.
Soc. Agron. national meeting, Nat. Agric. Res. Center (Japan), Scripps
Bodega Marine Lab., UC Berkeley Grad School Journalism, UCD Law School,
Dept. Food & Agric., UCD Center Pop. Biol., Calif. Plant & Soil
- Annual guest lectures at UC Davis in graduate ecology and upper
crop evolution classes; departmental seminars at UC Davis and elsewhere.
- Chair of Agroecology Curriculum Review Committee, member College
Committee on Sustainable Agriculture.
- Grant reviews for USDA, NSF, NSERC, Swiss and Russian National
Foundations, IPM program, etc.
- Webmaster for Environmental
Biology and Small Farm
Ecology, Evolution and
1987 Upper Buford Circle
St. Paul, MN
E-mail: First five
letters of my last name + 036 + umn.edu (you know where to put the @)