Use a Hue/Saturation adjustment layer to change the grass color.
Mask the background clouds to blend them with the ground.
step 4 of 6
Use a soft brush with low opacity to unmask some parts of the Hue/saturation adjustment layer used for the grass.
On a new layer behind the box paint and add a gradient to make the box look solid.
Add the shadows for the girl and for the box and begin to blend the background stones masking and painting over them.
step 5 of 6
Add some brush strokes and blur them with the Motion Blur filter, transform them to create the light rays.
Finish the background stones blending.
step 6 of 6
On a new layer in overlay mode add some light effects painting with a big soft brush and pale colors.
Increase a bit the brightness/contrast to finish.