What is demand estimation? How do I go about estimating demand? What are the necessary factors in estimating demand?

Until someone comes along who can really address your question on a personal level, you might want to check out some of the information that is on some of the websites that are listed on the following link.

Estimating Demand Agricultural Products - Google Search (http://www.google.com/search?hl=en&q=Estimating+Demand+Agricultural+Products)

If you are using a textbook for the subject, it also might behoove you to go over some of the material in it again.