Site-specific farming is defined as the management of inputs on a smaller scale than the whole field. Variable-rate fertilizer, lime, and herbicide applications are examples of site-specific farming currently being used in some regions of the USA. The premises behind site-specific farming are (1) that agronomically significant variability in plant growth, yield, soil type, pest pressures, etc. exists within fields, (2) such variability can be measured, and (3) the information obtained can be used to modify management for the betterment of farm profit and the environment. Little research has been done in California's diverse irrigated cropping environment to test these ideas. The initial focus of research must be on collecting and analyzing information that in turn might provide the basis for site-specific farming practices.