Zakat
This is not in your knowledge, dear. The farmers take out 10th or 20th parts of their crops as Ushr and nisf ushr. You may visit any village or a farmer, and they can tell you. There are other kinds of zakat on animals. It has a different nisab. These are all in the practice of the Ummah. To learn about the practice during the time of the Prophet, please refer to the chapters on zakat in the books of Ahadith, such as Bukhari and Muslim, among others. The details of zakat are recorded in the books of Fiqh. You may consult al-Hidaya. Here is a concise book https://www.muslim-library.com/dl/books/English_Fiqh_Made_Easy.pdf