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.

  1. 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).
  2. 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 uncertainty analysis.
  3. 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.
  4. Recommendation -- Summary of the diagnosis, P prediction, and economics results in compact summary form.

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