Contemporary research and production activity require searching and collecting a variety of information, this also applies to issues in the field of agriculture. Today, the vast majority of resources are available in a digital form. FAO on the portal of the Agricultural Information Management Standards presents an AgroTagger, tool for indexing documents in the field of agriculture, which is designed for the English language. Extraction of knowledge is not very convenient in languages such as Polish language with a very extensive inflection. In Polish, the following parts of speech inflect: verbs, nouns, numerals, adjectives, and pronouns. Proper indexing requires an initial reduction of grammatical forms, to which the authors have used the dictionary of the Polish language and have developed a programme of reducing. Moreover the algorithms for determining weights corresponding to the validity of the appointments taking into account the prevalence of terms and their position in the document were developed and implemented.