DEVELOPMENT AND TESTING OF A PHOSPHATE ROCK DECISION SUPPORT SYSTEM (PRDSS) FOR DIRECT APPLICATION

摘要

An expert system, the Phosphate Rock Decision Support System (PRDSS), was developed to provide users with the option to compare the agronomic and economic feasibility of direct application of phosphate rock (PR) with commercially available water-soluble phosphate (WSP) fertilizers. The PRDSS predicts the relative agronomic effectiveness (RAE) of PR with respect to WSP for the initial PR application. The RAE as predicted by the PRDSS depends on: (1) PR sources as quantified by PR solubility determined using the second extraction with neutral ammonium citrate (NAC_2); (2) soil pH; (3) crops as they influence the rhizosphere, root quantity and distribution, uptake of Ca, crop duration, Al toxicity/tolerance, etc.; (4) soil P-fixation capacity; (5) soil texture; (6) soil organic matter content; (7) Al saturation; (8) moisture and rainfall regime; and (9) free calcium carbonate content of the PR source. The current version as presented here is ready for future web application. The model does not predict the cumulative effect of annual PR application or the residual effect of PR. These features will be included in the next version of the PRDSS. The testing of the current version of PRDSS with available data from new and previously conducted field and greenhouse trials, in general, gave good agreement between observed and predicted RAE. As expected many of these trials were conducted with very different objectives; hence, all input information required for testing the PRDSS was not available. To further test the PRDSS with complete input data and also to generate more information for long-term PR use and residual effect, field trials are being conducted in six countries. In future, the linkage of PRDSS output with results from P simulation models would extend the applicability of the PRDSS beyond its current capability to the prediction of crop yield and P application rates for a given yield target.