Although the Internet is already becoming a valuable information resource in information retrieving, there are important challenges before agricultural interest groups and users for extensive accessing to this information. Indeed, there is a couple of specific search engines, directories and sites in agricultural subject domain on the web, but it seems the major public search engines could be able to response the scientific field requests as well. This paper aims to determine whether this fact is true in agricultural field domain or not? We are comparing and measuring five major public search engines in response to agricultural requests. This research examines major search engines in response to agricultural terminologies. In order to assess the recall, precision and overlap of search engines, five well-used search engines (Google, Yahoo, AltaVista, AOL, ASK) were chosen. Then five agricultural keywords which selected from CAB (consist of: Intercropping, Carnivorous plants, Soil pollution, Plant viruses, Irrigation farming) were searched in each these search engines. The best search engines in answer to the subject terms are introduced. AOL had 63% precision and 22% recall and retrieved the most relevant agricultural documents. Also, Yahoo had 43% overlap with other search engines, so Yahoo also scored the highest rank. Through this study, findings reveal that major public search engines are suitable alternative for finding agricultural information. The results of this study can also inform agricultural centers, agricultural Information Specialists and agricultural interest groups (users) seek better agricultural resources. This research is an investigation into web search engines’ recall, precision, and overlap using agricultural queries, sheds light on the uniqueness of top results retrieved by search engines. In other words, this paper indicates the signifi cant value of search engines in web retrieval even in expert areas. Search engines, recall ratio, precision ratio, overlap, agricultural information, information retrieval.