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Posted-Date: Tue, 30 Sep 1997 14:58:34 -0400 (EDT)
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From: "E. John Sadler" <[log in to unmask]>
Organization: USDA-ARS Florence SC
Subject:      The history of ag modeling.
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Greetings,
 
After the quick note the other day about historical references in ag
modeling, I read over the dissertation again and concluded that
several events and lines of work merited expansion beyond the
paragraph in the earlier e-mail.  The following is the particular
section of the dissertation, re-scanned today (I couldn't find the
old CP/M disks!). It is about 10k long.  The references are about 33k
long, and I can only send them as an attachment. Therefore, I will
send them only to those who request it.
 
EJ Sadler 1983.  Simulation of the energy, carbon, and water balance
of a fluid-roof greenhouse.  Texas A&M University, PhD Dissertation,
pg 18-24.
 
 
                           Crop Models
 
There are many models of crop growth, ranging from the fairly simple
to the extremely complex.  Unfortunately, there is a scarcity of
reviews of the subject in recent years.  The review of Loomis and
Williams (1969), and the collection of papers from the International
Biological Programme (IBP/PP) technical meeting in Trebon,
Czechoslovakia, in 1969, provided a comprehensive view of the
discipline at that time.  A brief review by Hesketh and Jones (1976)
covers the modeling of cotton.  Thornley (1976) covered the subject
of modeling and reviewed some models in his book.  Hildreth (1976)
covered several of the better-known crop models.
 
To organize the existing models for a logical discussion, the
classification of Hildreth (1976) was adopted: a) plant function
models, b) crop growth and yield models, and c) crop development and
yield models.  If physical principles are simulated throughout, the
degree of complexity generally increases from a) to c).  The plant
function models concern instantaneous processes.  The crop growth and
yield models integrate the plant function models at the plant or
plant community scale over short time periods.  The development
models extend the growth models over the growing season, including
simulation of physiological events such as flowering and maturity.
There do exist crop growth and crop development models that start
with empirical observations and that are more simple than the
integrated process type.
 
Simulation objectives of the plant function models include radiation
interception, photosynthesis rate, respiration rate, translocation or
carbohydrate partitioning, leaf energy balance, transpiration rate,
and root water uptake.  An extensive review of light interception
models was given by Lemeur and Blad (1974).  Since then, analyses
have been made by Sinclair and Lemon (1974), Anderson and Miller
(1974), Norman and Jarvis (1974, 1975), Mann et al. (1977), Kimes et
al. (1980), Denholm (1981a, 1981b), Oker-Blom and Kellomaki (1982),
and Sinclair and Knoerr (1982).  Models of photosynthesis have been
reported by Chartier (1970), Lommen et al. (1971), Van Bavel (1975),
Tenhunen et al. (1976a, 1976b), Enoch and Sacks (1978), and Thornley
et al. (1981), with a review by Thornley (1976). Respiration has
been modeled by McCree (1970, 1974), Penning de Vries (1972, 1974,
1975), Penning de Vries et al. (1974), Thornley (1976, 1977), Gay
(1981), Thornley et al. (1981), and others.  For a review and
analysis, see Gay (1981).  Leaf energy balance was simulated by
Gates (1968) and Van Bavel et al. (1973), among others.  Models of
crop evapotranspiration abound.  Thornthwaite (1948), Penman (1948),
Blaney and Criddle (1962), Jensen and Haise (1963), Monteith
(1965a), and Van Bavel (1966) are examples.  A comprehensive
comparison of water use models was made for a volume edited by Jensen
(1973).  Much work has been done on root water uptake, with Lascano
(1982) giving an extensive, recent review.
 
In the third category, there exist two major classifications of
models, based on the method of simulation.  The first is the multiple
regression or other statistical method of empirical modeling of crop
yield, development, or status, based on environmental variables,
usually temperature and rainfall.  These will not be further
discussed.  The second integrates the plant functions in some manner,
summing the individual effects to result in growth or yield.
 
A historical perspective of the evolution of crop simulation models
is useful.  One of the earlier works was by Monsi and Saeki (1953)
and Kasanaga and Monsi (1954), who studied the importance of light in
dry matter production, and introduced the idea of dividing the
canopy into layers.  Monteith (1965b), De Wit (1965) and Duncan et
al. (1967) reported models of photosynthesis that were based on
interception of radiation only, and not on temperature or CO2
concentration.  Stewart and Lemon (1969) used the light interception
models of Duncan et al. (1967) and De Wit (1965) in the
Soil-Plant-Atmosphere Model (SPAM), which considered the microclimate
in each layer of a canopy.
 
The work cited above was known at the time of the IBP/PP technical
meeting in Trebon, Czechoslovakia.  In that meeting, several papers
of note were given.  De Wit et al. (1970) described the Elementary
Crop Simulator ELCROS.  Ross (1970), Anderson (1970), and Kuroiwa
(1970) reviewed light interception and photosynthesis models. Acock
et al. (1970) discussed spatial variability of light in the canopy.
Tooming (1970) discussed net photosynthesis and plant adaptation.
Monsi and Murata (1970) discussed dry matter distribution in crops.
Denmead (1970) and Uchijima (1970) both discussed simulations of
transfer processes within canopies.  Also, the paper of McCree
(1970), listed earlier, was given.
 
After the Trebon meeting, the work started in the Netherlands by De
Wit (1965) and De Wit et al. (1970) continued.  Goudriaan and
Waggoner (1972) described an early version of a model updated and
described fully by Goudriaan (1977), and tested by Stigter et al.
(1977).  The model BACROS, for Basic Crop Simulator, evolved (De Wit
et al., 1978).  A third model simulated field water use and crop
yield (Feddes et al., 1978).
 
In the United States, Chen et al. (1969) started work that evolved
into the Nebraska corn model (Splinter, 1973; Splinter, 1974; Childs
et al., 1977).  A group in Arizona developed a cotton model
(Stapleton and Meyers, 1971; Stapleton et al., 1973).  In Ohio,
Curry (1971) and Curry and Chen (1971) described a dynamic model of
plant growth, and Curry et al. (1975) described the soybean growth
model SOYMOD I, which was used by Meyer et al. (1981) to simulate
reproductive processes and senescence.  At Purdue University in
Indiana, Miles et al. (1973) and Holt et.al. (1975) developed a model
of alfalfa, SIMED.  In Texas, Arkin et al. (1976) and Maas and Arkin
(1978) described a simulation model of grain sorghum, SORGF.
 
Other models developed in the 1970's include the CORNMOD model of
Baker and Horrocks (1974), the model of Phragmites communis reported
by Ondok and Gloser (1978a, 1978b), the barley model of Kallis and
Tooming (1974), the shortgrass prairie model of Conner et al. (1974),
the wheat model of Milthorpe and Moorby (1974), the tobacco model of
Wann et al. (1978), and corn model of Russo and Knapp (1976).
 
The descendants of the Duncan et al. (1967) model will now be
examined.  Three partial tests of their model were reported (Loomis
et al., 1968; Williams et al., 1968; and Loomis and Williams, 1969),
and an independent test was reported by Keener (1972) and Keener and
McCree (1975).  Duncan (1971) studied crop architecture and its
influence on canopy photosynthesis using the 1967 model, and included
a CO2 transport routine to study the vertical profiles of CO2 within
a canopy (Duncan and Barfield, 1970, 1971).  Duncan also
collaborated with the group at Mississippi State University to create
SIMCOT and related models of cotton (Hesketh et al., 1971, 1972;
Baker et al., 1972).  The SIMCOT model series was further documented
by Jones et al. (1974), and McKinion et al. (1975), who included the
nitrogen balance of the cotton crop. Duncan's coauthors in the 1967
paper developed a model of sugar beet growth, SUBGOL (Fick et al.,
1975; Loomis and Ng, 1977; Hunt and Loomis, 1979).
 
Meanwhile, SPAM (Stewart and Lemon, 1969). itself partially based on
the 1967 model and also De Wit (1965), was generating excitement in
modeling.  The initial journal article (Lemon et al., 1971) showed
many researchers the potential for modeling the microclimate within
crops.  Lemon et al. (1973) studied evapotranspiration with SPAM.
Shawcroft et al. (1974) described SPAM and a sensitivity analysis.
Van Bavel (1974) used part of SPAM and the leaf action model of Van
Bavel et al. (1973) to create CANLAM and study the behavior of
sunflowers with respect to soil water potential.  This combination
of SPAM and the leaf action model was used in an optimization study
of water use efficiency (Ahmed, 1974; Ahmed et al., 1976).  The CO2
assimilation equations of Van Bavel (1975) were incorporated into
their model, then named CANLAM2.  This was used in simulations of the
efficiency of field CO2 enrichment by Takami (1974) and Takami and
Van Bavel (1975), and in investigations of the effect of respiration
on crop production by McCree and Van Bavel (1977).  Takami and
Kumashiro (1982) used CANLAM2 to study the effect of canopy
architecture on rice photosynthesis.  In unrelated work, Sinclair et
al. (1977) compared the original SPAM, a simplified version of SPAM,
and a "big leaf" model similar to that of Monteith (1965b).
 
Conclusion of Literature Review
 
For the purpose of satisfying the objectives of this thesis, the SG79
greenhouse energy balance model of Van Bavel and Sadler (1979b), and
the CANLAM2 model of Takami and Van Bavel (1975) and of McCree and
Van Bavel (1977) were selected. The choice of SG79 was simple: it
was the only model that considered the energy, water, and CO2 balance
of the greenhouse together.  Of the crop models, the CANLAM2 model
was chosen, in spite of its complexity relative to SG79, because the
inputs and outputs were compatible with those in SG79's crop
calculation section.  In addition, the modification of the code,
which was in machine storage here, was more simple than either
obtaining another model and modifying it, entering a model from a
listing, or building one from the start.
 
==============================================================
E. John Sadler, Ph.D.
USDA-ARS                          [log in to unmask]
Coastal Plains Soil, Water,
   and Plant Research Center      803-669-5203x112 (voice)
2611 West Lucas St.               803-669-6970 (fax)
Florence, SC 29501-1241
U.S.A.
==============================================================