Information Technology Reference
In-Depth Information
6.3.6 Predictions
The Prediction in PDSS is usually a numerical amount of a specified amendment needed to
resolve the nutrient deficient condition identified in the Diagnostic section. There may be
additional inferences based on the additional data usually required to complete the
numerical prediction. There is a possibility that, upon analysis of the additional information,
a prediction of no requirement may occur. The Prediction was developed using a
combination of both scientific and local experiential knowledge. The preferred knowledge is
that occurring when the best scientific methodology is gleaned from the literature and tested
in the unique local soil, crop, weather, economic, and social conditions. To obtain and
ensure such knowledge clearly requires intense work by the local scientists as well as the
knowledge engineer (the person who organizes the knowledge and structures it into the
knowledge representation format of the decision-aid software). In our case, scientists have
included both international experts as well as local agricultural scientists who were in the
process of or had completed field studies of the prediction methodology.
The choice of which knowledge and how much detail needed to be recorded and
represented in order to minimize excessive detail and yet retain the essential knowledge
was and seems to be a challenging one. This aspect has been lucidly discussed in Stirzaker et
al. (2010). As Stirzaker et al. (2010) indicate, the typically detailed information resulting from
research, needs to be smoothed and simplified to be most effectively used in a working
system. Our experience has been identical and this aspect of building decision-aids seems to
us to be one that requires close interaction and discussion with the intended users to best
ascertain the appropriate level of detail. Thus it is clear that the direct transfer of algorithms
and conclusions from a research effort is seldom possible without the requisite
simplification described by Stirzaker et al. (2010). The intense and repeated contact between
the developer and the client or user group has been essential in our experience. This type of
intense interaction has come to be termed “extreme programming”(Beck, 1998; Wells, 2001).
This programming style is based on frequent viewing and discussing of the software being
developed with representative, intended users.
One of the requirements of the Prediction step that is necessary for the integration with the
subsequent components is that there be a numeric prediction. This numerical value forms
the basis of the benefit/cost analyses carried out in the subsequent Economic Analysis
section. The Prediction equation of the PDSS decision-aid is thus an equation that began
with the rather simple description given in (Yost et al., 1992a) shown in equation (2).
P requirement Soil P required - Soil P present
/Reactivity of the soil to added P
(2)
Where: P requirement is the kg/ha of fertilizer P needed to increase the soil P level (“Soil P
present”) to match the “Soil P required” and thus meet the specific crop's requirement for
nutrient P. While equation (2) gives the basic structure of the P requirement prediction
equation, there were updates to the equation which gradually increased in detail and
complexity (eq (3)).
P requirement PCL - Po / PBC 0.8 * PBC * Puptake * 0.8 * 1 / 2
* Placement factor * Application Depth / 10
(3)
Where:
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