Hi, not usually my cup of tea, but decided to try it out anyway,
I took a Photo of my Backyard a few weeks back and so i thought it would be a good testing image to try this, While following a tutorial i found on the subject here it is:
Its not that great of a final render due to spending a hour or so on it, but for me its an achievement so to speak…
I might try again with a newer picture etc and see if i can improve on it 
Cheers
ddwagnz
Nice first test, shadows look wrong though. Thatś mainly due to a wrong indirect lighting.
You should observe your Scene, especially where the light comes from and which colours influence your object. So in your case for example, there should be some green indirect light from the bottom, due to the colour of the grass. And there are some more things to do, like making the outer line of your sphere less sharp, it looks like if it was cut out. a slight fresnel mirror should help here to blend it better to the environment.
Maybe take a ball and put it on the grass to see, how it reacts.
Most important: watch real objects! Observe the lighting and the shadows, colours reflections etc.
Your lighting doesn’t match up. If you notice in your photo, the sky appears overcast, meaning the light from the sky is diffused, giving everything soft shadows. And the light is emanating from the whole sky, not just a single point. Your specular highlights give away that you are only using 2 lights. Try a fake global illumination setup for your spotlights.
“Light wrap” is also missing which would very quickly help to blend the CG object into the scene. Light is bent as it passes close to a mass, the effect being of a slight bleeding of the background light around the edge of the ball. How you’d go about doing this in Blender I’ve no idea, i always to mine in Post with a few pixel edge mask and a bit of a blur. Really sells the shot tho