Do you think that a Master's degree is the only way to be qualified to teach in a university? or an experience in the field of study would do?

The experience is more important of course, also teacher should be up to date to all new teaching techniques and strategies through the internet and attend many courses and seminars.

Whether you are getting your master’s to teach at a community college or technical school, or a Ph.D. to become a fully fledged professor, it is critical you get both research and teaching experience. You will need it for your first job. Usually such experience is gained in the form of teaching assistantships and research projects throughout your master’s or Ph.D programs. These are valuable experiences, so make the most of them. Also keep in mind that community colleges usually require more actual teaching experience to get a full-time job than a big university, which may hire fresh Ph.D. grads directly.

yes i think that master's is   a very important step to develop pe my conaissances and experiances