Development of a Wheat Model for Land Evaluation
Date
1977-09
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Degree Level
Masters
Abstract
Simulation is a new approach to rural land evaluation. Its
major advantage over more conventional methods is that it lends itself to
a consideration of a large number of alternatives. If properly used,
it can also meaningfully synthesize large amounts of varied information
to provide reliable predictions.
The prime objective of the study was to examine the possibility
of using computer simulation techniques as a means of evaluating the
biological (wheat) productivity of various land units in the prairie
provinces of Canada. The literature on crop production modelling was
discussed at length since there exists much controversy regarding why
and how such models should be developed. To ensure general applicability
of the approach, the information needed to develop and test the model,
WHTMOD, had to be readily available or obtainable.
For model development, existing data on hard red and soft spring
wheat production, moisture use and climate were used. Using a method
similar to de Wit (1958), 'm' values were calculated for the hard and
soft wheats. Different sites and years from those used in model
development were used to test WHTMOD. Data required for model testing
included daily temperatures and precipitation, tabulated astrometeorological
data, soil moisture at seeding, readily obtainable soil physical
properties, the 'm' value and seeding date.
WHTMOD simulated phenology from seeding to harvest using
Robertson's (1968) biometeorological time-scale. A moisture budget
was kept to assist in modelling transpiration and evaporation. Top and
root growth were simulated on a daily basis using de Wit's (1958)
equation modified to take account of soil nutrient status and the
nutrient-water interaction. After heading, top growth was partitioned
between grain and straw.
Yield predictions were made on a soil series basis as a larger
unit would not be sufficiently homogenous in its crop yields. However,
a method is suggested to predict yields for a tract of land of any
specified size.
The yield predictions were generally encouraging, although
there was a tendency to underpredict yields, apparently due to underprediction
of moisture use. Tests also showed considerable variation
in the nutrient factors for identical sites in different years. This
was due to different moisture conditions between test years. It was
suggested that tables of nutrient factors be calculated for a range
of moisture and nutrient conditions to simplify future use of WHTMOD.
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Citation
Degree
Master of Science (M.Sc.)
Department
Soil Science
Program
Department of Soil Science