Reasons for bucking:

Playful exuberance

Fear

Defiance 

Some horses buck out of fear, which commonly happens when they have something strapped around their middle, like a saddle and rider. Horse bucking can also be an act of defiance; horses that don’t go forward very well tend to buck for this reason. You can tell the difference between a fearful buck and a defiant buck because the fearful buck is lightning fast and violent while the defiant buck is somewhat premeditated and, by comparison, lazy.

Fear-Based Horse Bucking

The key to curing the problem of horses bucking depends on the reason for the behavior. For fearful horses, the key is to develop a relationship of trust with them.  Once you know how to get your horse’s trust, then you have to know how to “talk” to him, using body language – a language horses understand.

Horse Bucking As An Act of Defiance

If you have a defiant horse, you still have to get him to trust and respect you, but your strategies will be a little different from those used with a fearful horse. to motivate your horse to want to go forward without you pushing him. That’s important because these horses respond negatively when pushed, and even more so when spurred or whipped, especially when these techniques are used as punishment. The goal is to stop your horse’s bucking by not giving him a reason to buck – and that starts with his mind and emotions. Relationship and communication-based horse training will help you reach that goal and stop the horse bucking as a result.