Why is my image with a bump map so bad?

Hi, i would like to add some reliefs to a grass image, but the result with the bump image is really bad. Would you know what is the main problem in this picture? from left to right :

1. the grass i would like to use
   

2. the bump version of this image (in black and white, that become purple when i check "normal map")

3. the result with just the grass as a diffuse image, without reliefs

4. the result with the bump image, which is the really bad result i was talking about

5. The material that contains the diffuse image (the grass) and the bump diffuse (the black and white image that became purple)

Thanks for your help