Phosphorus Decision Support System (PDSS)
The Phosphorus Decision Support System is being designed to assist in the
diagnosis and correction of phosphorus (P) deficiencies in soils and crops, with
emphasis on tropical conditions.
PDSS is being developed by the Phosphorus Workgroup of the Soil Management
CRSP including Cornell University (Shaw Reid), North Carolina State University
(Fred Cox and T. Jot Smyth), Texas A&M University (Arthur Onken), and the
University of Hawaii (Russell Yost). The project is being supported by the
Agency for International Development (AID), Department of State, USA.
PDSS comprises four modules, representing steps in the overall
decision-making process of ensuring adequacy of the nutrient phosphorus.
- Diagnosis -- How to detect phosphorus deficiency using a variety of
observations and data, including crop yield, plant symptoms, associated
plants, and most definitively, soil and plant analyses. The result is a
combined probability of P deficiency ranging from 0 (certain P sufficiency) to
100 (certain P deficiency).
- P prediction -- Develops a prediction (estimate) of the P fertilizer
requirement based on soil test data, crop critical level, and soil
characteristics as represented in the P buffer coefficient. Two goals of
fertilization are offered: 1) To achieve maximum yield, and 2) Achieve both
maximum yield and a target P level in the soil after the crop, which is useful
for estimates of costs of sustaining a P level in the soil. An estimate of
prediction reliability is provided through the application of first order
- Economic analysis -- Estimating whether the benefits of P fertilization
will cover the costs of the fertilization. Factors considered include target
yield, cost of P, both current and for the next crop, and cost of borrowing
money for the fertilization. Prices of the crop are also required. The
evaluation indicates profitability and whether P is best applied to current or
to following crop, if future prices are high.
- Recommendation -- Summary of the diagnosis, P prediction, and economics
results in compact summary form.
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