The use of standard data formats for documenting experiments and modeling crop growth and development can greatly facilitate exchange of information and software, allowing researchers to focus on fundamentals rather than on re-formatting data. The standards and ASCII file formats developed by the International Benchmark Sites Network for Agrotechnology Transfer (IBSNAT) project and used in the original Decision Support System for Agrotechnology Transfer (DSSAT) software package were of considerable value in this context, but they contained ambiguities that made them unsuitable for certain uses. The International Consortium for Agricultural Systems Applications (ICASA) revised the standards as implemented in an ASCII file format in 2000. Specific goals were to provide more complete documentation of experiments and to allow wider use of the standards in decision support tools. Experience gained in using these draft standards showed that further modifications were necessary both to permit use with crops not previously considered and to place the standards in a more general framework, necessary as software systems evolve and researchers move towards more generic mechanisms for data interchange. The ICASA standards have thus been reformulated with emphasis on standard vocabularies and sets of relations among variables. This change moves the standards closer to data ontologies being developed in other branches of plant science. The modified standards, which may be implemented in an ASCII file format, in a relational database or in XML format, are quite similar to those documented earlier. They aggregate data into a three-level hierarchy and use indices to link information both in different parts of a storage-unit and in different storage-units. This paper will provide a detailed description of the ASCII implementation of the ICASA Version 1.0 standards. Implementations for relational databases and XML will also be presented. The full implementation and description can be found on the ICASA web site www.ICASA.net.