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Testing and validation of an expert system for making liming decisions

Dierolf, T.S., Amien, L.I., Yost, R.S.
Nutrient cycling in agroecosystems 1999 v.54 no.1 pp. 9-20
disease diagnosis, liming, decision making, expert systems, tropical soils, acid soils, validity, calibration, aluminum, phytotoxicity, mineral soils, databases, prediction, field experimentation, Glycine max, Zea mays, Oryza sativa, Manihot esculenta, crop yield, glycine (amino acid)
Computer-based technologies are becoming increasingly important in translating the wealth of agricultural research information into forms that can be used by extension workers. The Acidity Decision Support System (ADSS) is a computer-based expert system that diagnoses and corrects Al-toxicity problems on highly-weathered mineral soils. The objectives of this work were to use published data to evaluate and provide recommendations to improve the ADSS knowledge base. The relative yield-Al saturation curves used by ADSS satisfactorily predict the results of field experiments for maize and soybean, but needs to be improved for rice and cassava. Curves used by ADSS for all four crops should, however, be updated to represent the research data better. Insufficient data were obtained to evaluate other crops satisfactorily. ADSS predicted that more lime would be needed to reduce soil Al saturation than was actually needed. This can be corrected by changing the value of the liming factor (LF) constant in ADSS to better represent the capability of liming materials to neutralize soil Al in the field. ADSS also predicted more response of rice and soybean to lime in on-farm experiments than occurred in practice, although there was a correlation between predicted and actual relative yield for soybean. ADSS should indicate the chances that the predicted relative yield response will not occur because of factors other than liming, under normal farming conditions. The Smyth and Cravo equation provides a reasonable estimate, in lieu of alternatives, of the change in soil Al saturation for up to five years after liming.